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WO2018128788A1 - Supercondensateurs en forme de corde flexibles et de forme conforme - Google Patents

Supercondensateurs en forme de corde flexibles et de forme conforme Download PDF

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Publication number
WO2018128788A1
WO2018128788A1 PCT/US2017/067076 US2017067076W WO2018128788A1 WO 2018128788 A1 WO2018128788 A1 WO 2018128788A1 US 2017067076 W US2017067076 W US 2017067076W WO 2018128788 A1 WO2018128788 A1 WO 2018128788A1
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WIPO (PCT)
Prior art keywords
graphene
electrode
rope
carbon
supercapacitor
Prior art date
Application number
PCT/US2017/067076
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English (en)
Inventor
Aruna Zhamu
Bor Z. Jang
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Nanotek Instruments, Inc.
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Filing date
Publication date
Priority claimed from US15/398,416 external-priority patent/US10083799B2/en
Priority claimed from US15/398,421 external-priority patent/US10283280B2/en
Application filed by Nanotek Instruments, Inc. filed Critical Nanotek Instruments, Inc.
Priority to CN201780087514.7A priority Critical patent/CN110337753B/zh
Priority to JP2019536311A priority patent/JP7162594B2/ja
Priority to KR1020197022423A priority patent/KR102580262B1/ko
Publication of WO2018128788A1 publication Critical patent/WO2018128788A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/36—Nanostructures, e.g. nanofibres, nanotubes or fullerenes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/52—Separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/54—Electrolytes
    • H01G11/58—Liquid electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

  • the present invention relates generally to the field of supercapacitors or ultracapacitors, and more particularly to the rope-shape supercapacitors that are flexible and shape-conformal.
  • Electrochemical capacitors also known as ultracapacitors or supercapacitors
  • ECs Electrochemical capacitors
  • EVs hybrid electric vehicles
  • a battery would still be used for cruising, but supercapacitors (with their ability to release energy much more quickly than batteries) would kick in whenever the car needs to accelerate for merging, passing, emergency maneuvers, and hill climbing.
  • the EC must also store sufficient energy to provide an acceptable driving range. To be cost-, volume-, and weight-effective compared to additional battery capacity they must combine adequate energy densities (volumetric and gravimetric) and power densities with long cycle life, and meet cost targets as well.
  • ECs are also gaining acceptance in the electronics industry as system designers become familiar with their attributes and benefits. ECs were originally developed to provide large bursts of driving energy for orbital lasers.
  • CMOS complementary metal oxide semiconductor
  • a one-Farad EC having a volume of only one-half cubic inch can replace nickel-cadmium or lithium batteries and provide backup power for months.
  • the stored energy in an EC associated with a given charge is half that storable in a corresponding battery system for passage of the same charge.
  • ECs are extremely attractive power sources. Compared with batteries, they require no
  • the high volumetric capacitance density of an EC relative to conventional capacitors derives from using porous electrodes to create a large effective "plate area” and from storing energy in the diffuse double layer.
  • This double layer created naturally at a solid-electrolyte interface when voltage is imposed, has a thickness of only about 1 nm, thus forming an extremely small effective "plate separation.”
  • Such a supercapacitor is commonly referred to as an electric double layer capacitor (EDLC).
  • EDLC electric double layer capacitor
  • the double layer capacitor is based on a high surface area electrode material, such as activated carbon, immersed in a liquid electrolyte. A polarized double layer is formed at electrode-electrolyte interfaces providing high capacitance. This implies that the specific capacitance of a
  • supercapacitor is directly proportional to the specific surface area of the electrode material. This surface area must be accessible by electrolyte and the resulting interfacial zones must be sufficiently large to accommodate the so-called electric double-layer charges.
  • stored energy is further augmented by pseudo-capacitance effects, occurring again at the solid-electrolyte interface due to electrochemical phenomena such as the redox charge transfer.
  • the low mass loading is primarily due to the inability to obtain thicker electrodes (thicker than 100-200 ⁇ ) using the conventional slurry coating procedure. This is not a trivial task as one might think, and in reality the electrode thickness is not a design parameter that can be arbitrarily and freely varied for the purpose of optimizing the cell performance. Contrarily, thicker samples tend to become extremely brittle or of poor structural integrity and would also require the use of large amounts of binder resin. These problems are particularly acute for graphene material-based electrodes. It has not been previously possible to produce graphene-based electrodes that are thicker than 150 ⁇ and remain highly porous with pores remaining fully accessible to liquid electrolyte. The low areal densities and low volume densities (related to thin electrodes and poor packing density) result in relatively low volumetric capacitances and low volumetric energy density of the supercapacitor cells.
  • Nano graphene materials have recently been found to exhibit exceptionally high thermal conductivity, high electrical conductivity, and high strength. Another outstanding characteristic of graphene is its exceptionally high specific surface area.
  • a single graphene sheet provides a specific external surface area of approximately 2,675 m 2 /g (that is accessible by liquid electrolyte), as opposed to the exterior surface area of approximately 1,300 m 2 /g provided by a corresponding single-wall CNT (interior surface not accessible by electrolyte).
  • the electrical conductivity of graphene is slightly higher than that of CNTs.
  • graphene sheets as a supercapacitor electrode active material
  • a solid current collector e.g. Al foil
  • the graphene electrode typically requires a large amount of a binder resin (hence, significantly reduced active material proportion vs. non-active or overhead materials/components).
  • any electrode prepared in this manner that is thicker than 50 ⁇ is brittle and weak. There has been no effective solution to these problems.
  • thick electrodes in conventional supercapacitors are also mechanically rigid, not flexible, not bendable, and not conformal to a desired shape. As such, for conventional supercapacitors, high volumetric/gravimetric energy density and mechanical flexibility appear to be mutually exclusive.
  • the present invention provides a rope-shape supercapacitor containing filamentary or rod-like anode and cathode electrodes that are combined to form a braid or twist yarn shape (e.g. twist 2-ply, 3-ply, 4-ply, 5-ply yarn or braid, etc.).
  • the supercapacitor can be an electric double layer capacitor (EDLC, symmetric or asymmetric), pseudo-capacitor, lithium-ion capacitor, or sodium-ion capacitor.
  • EDLC electric double layer capacitor
  • pseudo-capacitor lithium-ion capacitor, or sodium-ion capacitor.
  • a lithium-ion capacitor or sodium-ion capacitor contains a pre-lithiated or pre-sodiated anode active material (i.e. a battery-type anode) and a cathode that contains a high surface area carbon material, such as activated carbon or graphene sheets (i.e. an EDLC type cathode).
  • the supercapacitor comprises: (a) a first electrode comprising a first electrically conductive porous rod (or filament) having pores and a first mixture of a first electrode active material and a first electrolyte, wherein the first mixture resides in pores of the first porous rod (e.g. foam of a filamentary shape); (b) a porous separator wrapping around or encasing the first electrode to form a separator-protected first electrode; (c) a second electrode comprising a second electrically conductive porous rod (e.g.
  • foam of a filamentary shape having pores and a second mixture of a second electrode active material and a second electrolyte, wherein the second mixture resides in the pores of the second porous rod; wherein the separator-protected first electrode and the second electrode are combined in a spiral manner to form a braid or twist yarn; and (d) a protective casing or sheath wrapping around or encasing the braid or twist yarn.
  • the second electrolyte may be the same as or different than the first electrolyte.
  • the pores in the first or second electrode preferably contain interconnected pores and the porous rod/filament is preferably open-cell foam.
  • the first active material and/or the second active material contains multiple particles of a carbon material and/or multiple isolated graphene sheets, wherein multiple graphene sheets contain single-layer graphene or few-layer graphene each having from 1 to 10 graphene planes and said multiple particles of carbon material or graphene sheets have a specific surface area no less than 500 m 2 /g when measured in a dried state (preferably > 1,000 m 2 /g and more preferably > 2,000 m 2 /g). These isolated graphene sheets are not part of a graphene foam (if the porous rod is a graphene-based foam structure). These isolated graphene sheets are the true electrode active material, separate from or in addition to the porous rod.
  • the first or the second electrode active material contains particles of activated carbon or isolated graphene sheets having a length or width smaller than 1 ⁇ to readily impregnate into the pores of the first or the second electrode, wherein the graphene sheets are selected from pristine graphene, graphene oxide, reduced graphene oxide, fluorinated graphene, nitrogenated or nitrogen-doped graphene, hydrogeneated or hydrogen-doped graphene, boron-doped graphene, chemically functionalized graphene, or a combination thereof
  • the first or second electrode may further contain a redox pair partner material selected from a metal oxide, a conducting polymer, an organic material, a non- graphene carbon material, an inorganic material, or a combination thereof.
  • the partner material in combination with graphene or activated carbon, forms a redox pair for providing pseudo- capacitance.
  • the first or second electrode contains the following materials as the only electrode active material in the first or second electrode: (a) graphene sheets alone; (b) graphene sheets mixed with a porous carbon material (e.g. activated carbon); (c) graphene sheets mixed with a partner material that forms a redox pair with the graphene sheets to develop pseudo-capacitance; or (d) graphene sheets and a porous carbon material mixed with a partner material that forms a redox pair with the graphene sheets or the porous carbon material to develop pseudo-capacitance, and wherein there is no other electrode active material present in the first or second electrode.
  • a porous carbon material e.g. activated carbon
  • the invented supercapacitor may further comprise a porous separator wrapping around or encasing the second electrode to form a separator-protected second electrode.
  • both the first and second electrodes (each having an active material -electrolyte mixture pre-impregnated into pores of the porous rod) are encased by a porous separator prior to being braided or interlaced together to form a braid or twist yarn.
  • the two electrodes are as closely packed as possible to maximize the contact or interfacial areas between the electrodes.
  • the rope-shape supercapacitor further comprises a third electrolyte disposed between the braid or yarn and the protective sheath.
  • the third electrolyte may be the same as or different than the first electrolyte or the second electrolyte.
  • the first electrode can be a negative electrode (or anode) and the second electrode a positive electrode (or cathode).
  • the second electrode is a negative electrode or anode and the first electrode is a positive electrode or cathode.
  • the supercapacitor can comprise a plurality of the first electrodes and/or a plurality of the second electrodes.
  • the supercapacitor can have multiple anode and/or multiple cathode filaments/rods combined together to form a braid or twist yarn structure.
  • At least one of the electrodes is an anode and at least one of the electrodes is a cathode.
  • the rope-shaped supercapacitor has a length and a diameter or thickness with a length-to-diameter or length-to-thickness aspect ratio being at least 5, preferably at least 10, and more preferably at least 20.
  • the supercapacitor comprises: (a) a first electrode comprising a first electrically conductive rod (not a porous foam) and a first mixture of a first electrode active material and a first electrolyte, wherein the first mixture is deposited on or in the first rod; (b) a porous separator wrapping around or encasing the first electrode to form a separator-protected first electrode; (c) a second electrode comprising a second electrically conductive rod that is porous and has pores and a second mixture of a second electrode active material and a second electrolyte, wherein the second mixture resides in the pores of the second rod that is porous; wherein the separator-protected first electrode and the second electrode are interlaced or combined in a spiral or twist manner to form a braid or yarn; and (d) a protective casing or sheath wrapping around or encasing the yarn or braid.
  • the first active material and/or the second active material may contain multiple particles of a carbon material and/or multiple isolated graphene sheets, having a high specific surface area (no less than 500 m 2 /g, preferably > 1,000 m 2 /g, and more preferably > 2,000 m 2 /g). Again, these isolated graphene sheets are not part of a graphene foam (if the porous rod is a graphene-based foam structure). These isolated graphene sheets are the true electrode active material, separate from or in addition to the porous rod.
  • the first or second electrode may further contain a redox pair partner material selected from a metal oxide, a conducting polymer, an organic material, a non-graphene carbon material, an inorganic material, or a combination thereof. The partner material, in combination with graphene or activated carbon, forms a redox pair for providing pseudo-capacitance.
  • the invented supercapacitor may further comprise a porous separator wrapping around or encasing the second electrode to form a separator-protected second electrode.
  • the supercapacitor further comprises a third electrolyte disposed between the braid or yarn and the protective sheath.
  • the third electrolyte may be the same as or different than the first electrolyte or the second electrolyte.
  • the first or second electrode (but not both) comprises a conductive rod (not a foam) and the first or second mixture is coated or deposited on the surface of this conductive rod.
  • This rod can be as simple as a metal wire, a conductive polymer fiber or yarn, a carbon or graphite fiber or yarn, or multiple wires, fibers, or yarns.
  • the rope-shaped supercapacitor has a first end and a second end and the first electrode contains a first terminal connector comprising at least one metallic wire, conductive carbon/graphite fiber, or conductive polymer fiber that is embedded in, connected to, or integral with the first electrode.
  • the at least one metallic wire, conductive carbon/graphite fiber, or conductive polymer fiber runs approximately from the first end to the second end. This wire or fiber preferably is protruded out of the first end or second end to become a terminal tab for connecting to an electronic device or external circuit or load.
  • the rope-shaped supercapacitor has a first end and a second end and the second electrode contains a second terminal connector comprising at least one metallic wire, conductive carbon/graphite fiber, or conductive polymer fiber that is embedded in, connected to, or integral with the second electrode.
  • at least one metallic wire, conductive carbon/graphite fiber, or conductive polymer fiber runs approximately from the first end to the second end. This wire or fiber preferably is protruded out of the first end or second end to become a terminal tab for connecting to an electronic device or external circuit or load.
  • the first or second electrically conductive porous rod may contain a porous foam selected from a metal foam, metal web, metal fiber mat, metal nanowire mat, metal wire braid, conductive polymer fiber mat, conductive polymer foam, conductive polymer fiber braid, conductive polymer-coated fiber foam, carbon foam, graphite foam, carbon aerogel, graphene aerogel, carbon xerogel, graphene foam, graphene oxide foam, reduced graphene oxide foam, carbon fiber foam, graphite fiber foam, exfoliated graphite foam, or a combination thereof.
  • a porous foam selected from a metal foam, metal web, metal fiber mat, metal nanowire mat, metal wire braid, conductive polymer fiber mat, conductive polymer foam, conductive polymer fiber braid, conductive polymer-coated fiber foam, carbon foam, graphite foam, carbon aerogel, graphene aerogel, carbon xerogel, graphene foam, graphene oxide foam, reduced graphene oxide foam, carbon fiber foam, graphite fiber foam, exfoliated
  • foam structures can be readily made into a porosity level > 50%, typically and desirably > 70%, more typically and preferably > 80%, still more typically and preferably > 90%), and most preferably > 95% (graphene aerogel can exceed a 99% porosity level).
  • the skeleton structure (pore walls) in these foams forms a 3D network of electron-conducting pathways while the pores can accommodate a large proportion of an electrode active material (anode active material in the anode or cathode active material in the cathode) without using any conductive additive or a binder resin.
  • the foam rod/filament can have a cross-section that is circular, elliptic, rectangular, square, hexagon, hollow, or irregular in shape.
  • the supercapacitor has a rope shape that has a length and a diameter or thickness and an aspect ratio (length/thickness or length/diameter ratio) greater than 10, preferably greater than 15, more preferably greater than 20, further preferably greater than 30, even more preferably greater than 50 or 100.
  • the thickness or diameter is typically and preferably from 100 nm to 10 cm, more preferably and typically from 1 ⁇ to 1 cm, and most typically from 10 ⁇ to 1 mm.
  • the length can run from 1 ⁇ to tens of meters or even hundreds of meters (if so desired).
  • the supercapacitor is a lithium-ion capacitor or sodium-ion capacitor having an anode active material selected from the group consisting of pre- lithiated or pre-sodiated versions of (a) particles of natural graphite, artificial graphite, meso- carbon microbeads (MCMB), and carbon; (b) silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium (Cd); (c) alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd with other elements, wherein the alloys or compounds can be stoichiometric or non-stoichiometric; (d) oxides, carbides, nitrides, s
  • the lithium-ion capacitor or sodium-ion capacitor may contain pre-lithiated or pre- sodiated graphene sheets as an anode active material, selected from pre-lithiated or pre-sodiated versions of pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, a physically or chemically activated or etched version thereof, or a combination thereof.
  • pre-lithiated or pre- sodiated graphene sheets as an anode active material, selected from pre-lithiated or pre-sodiated versions of pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated
  • the second or first electrode active material contains a lithium intercalation compound or lithium absorbing compound selected from the group consisting of lithium cobalt oxide, doped lithium cobalt oxide, lithium nickel oxide, doped lithium nickel oxide, lithium manganese oxide, doped lithium manganese oxide, lithium vanadium oxide, doped lithium vanadium oxide, lithium mixed-metal oxides, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium mixed-metal phosphates, metal sulfides, lithium selenide, lithium polysulfide, and combinations thereof.
  • a lithium intercalation compound or lithium absorbing compound selected from the group consisting of lithium cobalt oxide, doped lithium cobalt oxide, lithium nickel oxide, doped lithium nickel oxide, lithium manganese oxide, doped lithium manganese oxide, lithium vanadium oxide, doped lithium vanadium oxide, lithium mixed-metal oxides, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium mixed-metal phosphates
  • the second or first electrode active material contains a sodium intercalation compound or a potassium intercalation compound selected from NaFeP0 4 , Na ( i. x) K x P0 4 , KFeP0 4 , Na 0 7 FeP0 4 , Nai 5 VOPO 4 F 0 5 , Na 3 V 2 (P0 4 ) 3 , Na 3 V 2 (P0 4 ) 2 F 3 , Na 2 FeP0 F, NaFeF 3 , NaVP0 4 F, KVP0 4 F, Na 3 V 2 (P0 4 ) 2 F 3 , Nai 5 VOPO 4 F 0 5 , Na 3 V 2 (P0 4 ) 3 , NaV 6 0i 5 , Na x V0 2 , Na 0 .
  • a sodium intercalation compound or a potassium intercalation compound selected from NaFeP0 4 , Na ( i. x) K x P0 4 , KFeP0 4 , Na 0 7 FeP
  • Nii /3 Mni /3 Coi /3 0 2 , Cu 0.56 Ni 0 . 44 HCF, NiHCF, Na x Mn0 2 , NaCr0 2 , KCr0 2 , Na 3 Ti 2 (P0 4 ) 3 , C02O4, Ni 3 S 2 /FeS 2 , Sb 2 0 4 , Na 4 Fe(CN) 6 /C, NaVi -x Cr x P0 4 F, Se z S y , y/z 0.01 to 100, Se, sodium polysulfide, sulfur, Alluaudites, or a combination thereof, wherein x is from 0.1 to 1.0.
  • the first electrolyte and/or the second electrolyte may contain a lithium salt or sodium salt dissolved in a liquid solvent and wherein the liquid solvent is water, an organic solvent, an ionic liquid, or a mixture of an organic solvent and an ionic liquid.
  • the liquid solvent may be mixed with a polymer to form a polymer gel.
  • the first electrolyte and/or second electrolyte preferably contains a lithium salt or sodium salt dissolved in a liquid solvent having a salt concentration greater than 2.5 M (preferably > 3.0 M, further preferably > 3.5 M, even more preferably > 5.0 M, still more preferably > 7.0 M, and most preferably > 10 M, up to 15 M).
  • the first or second electrically conductive porous rod has at least 90% by volume of pores
  • the first or second electrode has a diameter or thickness no less than 200 ⁇ or has an active mass loading (anode or cathode active material) occupying at least 30%) by weight or by volume of the entire battery cell
  • the first and second electrode active materials combined occupies at least 50 % by weight or by volume of the entire battery cell.
  • the first or second electrically conductive porous rod has at least 95% by volume of pores
  • the first or second electrode has a diameter or thickness no less than 300 ⁇ or has an active mass loading occupying at least 35% by weight or by volume of the entire battery cell, or the first and second electrode active materials combined occupies at least 60 % by weight or by volume of the entire battery cell.
  • the first or second electrode active material comprises an alkali metal intercalation compound or alkali metal-absorbing compound selected from an inorganic material, an organic or polymeric material, a metal oxide/phosphate/sulfide, or a combination thereof.
  • This compound can be an anode active material (e.g. lithium titanate or lithiated graphite) in a lithium-ion capacitor, wherein the cathode is an EDLC type having a high specific surface area (e.g. activated carbon).
  • the metal oxide/phosphate/sulfide contains a vanadium oxide selected from the group consisting of V0 2 , Li x V0 2 , V 2 0 5 , Li x V 2 0 5 , V 3 0 8 , Li x V 3 07, V4O9, Li x V40 , V 6 0i 3 , Li x V 6 0i 3 , their doped versions, their derivatives, and combinations thereof, wherein 0.1 ⁇ x ⁇ 5.
  • This compound can be an inorganic material selected from a transition metal
  • the inorganic material is selected from TiS 2 , TaS 2 , MoS 2 , NbSe 3 , Mn0 2 , Co0 2 , an iron oxide, a vanadium oxide, or a combination thereof.
  • the inorganic material is selected from: (a) bismuth selenide or bismuth telluride, (b) transition metal dichalcogenide or trichalcogenide, (c) sulfide, selenide, or telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a transition metal; (d) boron nitride, or (e) a combination thereof.
  • Redox pair partner materials may be selected from an alkali metal intercalation compound or alkali metal -absorbing compound selected from a metal carbide, metal nitride, metal boride, metal dichalcogenide, or a combination thereof.
  • the cathode contains an alkali metal intercalation compound or alkali metal-absorbing compound selected from an oxide, dichalcogenide, trichalcogenide, sulfide, selenide, or telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in a nanowire, nano-disc, nano-ribbon, or nano platelet form.
  • the redox pair partner material contains nano discs, nano platelets, nano-coating, or nano sheets of an inorganic material selected from: (a) bismuth selenide or bismuth telluride, (b) transition metal dichalcogenide or trichalcogenide, (c) sulfide, selenide, or telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a transition metal; (d) boron nitride, or (e) a combination thereof; wherein the discs, platelets, or sheets have a thickness less than 100 nm (preferably ⁇ 10 nm and more preferably ⁇ 3 nm) to ensure a high specific surface area.
  • an inorganic material selected from: (a) bismuth selenide or bismuth telluride, (b) transition metal dichalcogenide or trichalcogenide, (c) s
  • FIG.1(A) Schematic of a prior art supercapacitor composed of an anode current collector (e.g.
  • anode electrode e.g. a layer of activated carbon particles and conductive additive bonded by a resin binder
  • a porous separator e.g. a layer of activated carbon particles and conductive additive bonded by a resin binder
  • a cathode current collector e.g. Al foil
  • FIG.1(B) Schematic of a process for producing a rope-shaped, flexible and shape-conformable supercapacitor
  • FIG.1(C) Four examples of the procedure for producing an electrode (rod-shaped anode or cathode) in a continuous and automated manner;
  • FIG.1(D) Schematic of a presently invented process for continuously producing an alkali metal- ion battery electrode.
  • FIG.2 An electron microscopic image of isolated graphene sheets.
  • FIG.3(C) Examples of conductive porous layers: graphite foam and Ni foam.
  • FIG.3(D) Examples of conductive porous layers: Cu foam and stainless steel foam.
  • FIG.4(A) Schematic of a commonly used process for producing exfoliated graphite, expanded graphite flakes (thickness > 100 nm), and graphene sheets (thickness ⁇ 100 nm, more typically ⁇ 10 nm, and can be as thin as 0.34 nm).
  • FIG.4 (B) Schematic drawing to illustrate the processes for producing exfoliated graphite
  • FIG.5 Ragone plots (gravimetric and volumetric power density vs. energy density) of symmetric supercapacitor (EDLC) cells containing reduced graphene oxide (RGO) sheets as the electrode active material and EMF BF 4 ionic liquid electrolyte. Data were obtained from both the rope-shape supercapacitors and, for comparison, prior art supercapacitors prepared by the conventional slurry coating of electrodes.
  • EDLC symmetric supercapacitor
  • RGO reduced graphene oxide
  • FIG.6 Ragone plots (gravimetric and volumetric power density vs. energy density) of symmetric supercapacitor (EDLC) cells containing activated carbon (AC) particles as the electrode active material and organic liquid electrolyte.
  • EDLC symmetric supercapacitor
  • AC activated carbon
  • FIG.7(A) Ragone plots (gravimetric and volumetric power density vs. energy density) of lithium ion capacitor (LIC) cells containing pristine graphene sheets as the electrode active material and lithium salt-PC/DEC organic liquid electrolyte
  • FIG.7(B) Ragone plots (gravimetric and volumetric power density vs. energy density) of sodium ion capacitor (NIC) cells containing pristine graphene sheets as the electrode active material and sodium salt-PC/DEC organic liquid electrolyte.
  • FIG.8 The cell-level gravimetric and volumetric energy densities plotted over the achievable electrode diameter range of the AC -based EDLC supercapacitors prepared via the conventional method and the presently invented method. With the presently invented method, there is no theoretical limit on the electrode diameter that can be achieved.
  • the practical electrode thickness is from 10 ⁇ to 5,000 ⁇ , more typically from 100 ⁇ to 1,000 ⁇ , and most typically from 200 ⁇ to 800 ⁇ .
  • FIG.9 The cell-level gravimetric and volumetric energy densities plotted over the achievable electrode thickness range of the RGO-based EDLC supercapacitors (organic liquid electrolyte) prepared via the conventional method and the rope-shape cells prepared by the presently invented method (easily achieved electrode tap density of approximately 0.75 g/cm 3 ).
  • FIG.10 The cell-level gravimetric and volumetric energy densities plotted over the achievable electrode thickness range of the pristine graphene-based EDLC supercapacitors (organic liquid electrolyte) prepared via the conventional method and those rope-shape cells by the presently invented method (electrode tap density of approximately 0.85 g/cm 3 ).
  • FIG.11 The cell-level gravimetric and volumetric energy densities plotted over the achievable electrode thickness range of the pristine graphene-based EDLC supercapacitors (ionic liquid electrolyte) prepared via the conventional method and those rope-shape cells by the presently invented method (electrode tap density of approximately 0.85 g/cm 3 ).
  • FIG.12 The cell-level gravimetric energy densities plotted over the achievable active material proportion (active material weight/total cell weight) for activated carbon-based EDLC supercapacitors (with organic liquid electrolyte).
  • FIG.13 The cell-level gravimetric energy densities plotted over the achievable active material proportion (active material weight/total cell weight) in a supercapacitor cell for two series of pristine graphene-based EDLC supercapacitors (all with organic liquid electrolyte).
  • This invention is directed at a flexible and shape-conformable rope-like supercapacitor exhibiting an exceptionally high volumetric energy density and high gravimetric energy density compared to conventional supercapacitors.
  • This supercapacitor can be an EDLC supercapacitor (symmetric or asymmetric), a redox or pseudo-capacitor, a lithium-ion capacitor (not lithium-ion battery), or sodium-ion capacitor (not sodium-ion battery).
  • the supercapacitor is based on an aqueous electrolyte, a non-aqueous or organic electrolyte, a gel electrolyte, an ionic liquid electrolyte, or a mixture of organic and ionic liquid.
  • a prior art supercapacitor cell is typically composed of an anode current collector 202 (e.g. Al foil 12-15 ⁇ thick), an anode active material layer 204 (containing an anode active material, such as activated carbon particles 232 and conductive additives that are bonded by a resin binder, such as PVDF) coated on the current collector, a porous separator 230, a cathode active material layer 208 (containing a cathode active material, such as activated carbon particles 234, and conductive additives that are all bonded by a resin binder, not shown), a cathode current collector 206 (e.g.
  • anode active material layer 204 also simply referred to as the "anode layer”
  • cathode active material layer 208 or simply “cathode layer”
  • the entire cell is encased in a protective housing, such as a thin plastic-aluminum foil laminate-based envelop.
  • the prior art supercapacitor cell is typically made by a process that includes the following steps:
  • the first step is mixing particles of the anode active material (e.g. activated carbon), a conductive filler (e.g. graphite flakes), a resin binder (e.g. PVDF) in a solvent (e.g. MP) to form an anode slurry.
  • particles of the cathode active material e.g. activated carbon
  • a conductive filler e.g. acetylene black
  • a resin binder e.g. PVDF
  • a solvent e.g. NMP
  • the second step includes coating the anode slurry onto one or both primary surfaces of an anode current collector (e.g. Cu or Al foil), drying the coated layer by vaporizing the solvent (e.g. NMP) to form a dried anode electrode coated on Cu or Al foil. Similarly, the cathode slurry is coated and dried to form a dried cathode electrode coated on Al foil.
  • the third step includes laminating an anode/ Al foil sheet, a porous separator layer, and a cathode/ Al foil sheet together to form a 3-layer or 5-layer assembly, which is cut and slit into desired sizes and stacked to form a rectangular structure (as an example of shape) or rolled into a cylindrical cell structure.
  • a liquid electrolyte is then injected into the laminated structure to make a supercapacitor cell.
  • An electrode of 100 ⁇ thickness typically requires a heating zone of 30-50 meters long in a slurry coating facility, which is too time consuming, too energy intensive, and not cost-effective.
  • the actual mass loadings of the electrodes and the apparent densities for the active materials are too low.
  • the active material mass loadings of the electrodes (areal density) is significantly lower than 10 mg/cm 2 and the apparent volume density or tap density of the active material is typically less than 0.75 g/cm 3 (more typically less than 0.5 g/cm 3 and most typically less than 0.3 g/cm 3 ) even for relatively large particles of activated carbon.
  • non-active materials e.g. conductive additive and resin binder
  • These low areal densities and low volume densities result in relatively low volumetric capacitances and low volumetric energy density.
  • the conventional process requires dispersing electrode active materials (anode active material and cathode active material) in a liquid solvent (e.g. NMP) to make a slurry and, upon coating on a current collector surface, the liquid solvent has to be removed to dry the electrode layer.
  • a liquid solvent e.g. NMP
  • the anode and cathode layers, along with a separator layer, are laminated together and packaged in a housing to make a supercapacitor cell, one then injects a liquid electrolyte into the cell. In actuality, one makes the two electrodes wet, then makes the electrodes dry, and finally makes them wet again. Such a wet-dry-wet process does not sound like a good process at all.
  • NMP is not an environmentally friendly solvent; it is known to potentially cause birth defects.
  • EDLC EDLC capacitors
  • experimental supercapacitors exhibit large volumetric electrode capacitances (100 to 200 F/cm 3 in most cases) at the electrode level (not the cell level), their typical active mass loading of ⁇ 1 mg/cm 2 , tap density of ⁇ 0.1 g/cm "3 , and electrode thicknesses of up to tens of micrometers remain significantly lower than those used in most commercially available electrochemical capacitors, resulting in energy storage devices with relatively low areal and volumetric capacities and low volumetric energy densities based on the cell (device) weight.
  • the present invention provides a process for producing a flexible and shape-conformable supercapacitor having a rope shape, high active material mass loading, low overhead weight and volume, high gravimetric energy density, and high volumetric energy density.
  • the manufacturing costs of the supercapacitors produced by the presently invented process can be significantly lower than those by conventional processes and are much more environmentally benign.
  • the present rope- shaped supercapacitor, containing braid- or yarn-shape electrodes can be made by a process that includes a first step of supplying a first electrode 11, which is composed of an electrically conductive porous rod (e.g. carbon foam, graphene foam, metal nanowire mat, etc.) having pores that are partially or fully loaded with a mixture of a first electrode active material (e.g. activated carbon particles or isolated/separated graphene sheets, having a size smaller than the pore size of the porous rod) and a first electrolyte.
  • a first electrode active material e.g. activated carbon particles or isolated/separated graphene sheets, having a size smaller than the pore size of the porous rod
  • a conductive additive or a resin binder may be optionally added into the mixture, but this is not required or even desired.
  • This first electrode 11 can optionally contain an active material-free and electrolyte-free end section 13 that can serve as a terminal tab for connecting the supercapacitor to an external load.
  • This first electrode can assume a cross-section that is of any shape; e.g. circular, rectangular, elliptic, square, hexagonal, hollow, or irregular in shape.
  • the first electrode comprises a conductive rod (not a porous foam) and the first mixture is coated or deposited on the surface of this conductive rod.
  • This rod can be as simple as a metal wire, conductive polymer fiber or yarn, carbon or graphite fiber or yarn, or multiple thin wires, fibers, or yarns.
  • the second electrode must contain a porous foam structure.
  • the second step involves wrapping around or encasing the first electrode 11 with a thin layer of porous separator 15 (e.g. porous plastic film, paper, fiber mat, non-woven, glass fiber cloth, etc.) that is permeable to ions in the electrolyte.
  • porous separator 15 e.g. porous plastic film, paper, fiber mat, non-woven, glass fiber cloth, etc.
  • This step can be as simple as wrapping the first electrode with a thin, porous plastic tape in one full circle or slightly more than one full circle, or in a spiral manner.
  • the main purpose is to electronically separate the anode and the cathode to prevent internal shorting.
  • the porous separator layer can be simply deposited all around the first electrode by spraying, printing, coating, dip casting, etc.
  • the third step involves preparing a second electrode 17 that comprises a mixture of second active material and second electrolyte and, optionally, a conductive additive or resin binder (although not necessary and not desirable).
  • This second electrode 17 can optionally contain an active material-free and electrolyte-free end section that can serve as a terminal tab for connecting to an external load.
  • the second electrode may be optionally but desirably encased or wrapped around by a porous separator layer 18.
  • This second electrode is then combined with the first electrode using a braiding or yarn-making procedure to make a 2-ply twist yarn or braid. If the first electrode is an anode, then the second electrode is a cathode; or vice versa.
  • a yarn or braid can contain multiple anodes (i.e. multiple filaments or rods each containing an anode active material and an electrolyte) combined with one single cathode or multiple cathodes.
  • a yarn or braid can contain multiple cathodes (i.e. multiple filaments or rods each containing a cathode active material and an electrolyte) combined with one single anode or multiple anode filaments.
  • this braid or yarn structure is encased or protected by a protective casing or sheath 19 that is electrically insulating (e.g. a plastic sheath or rubber shell). It may be noted that some additional electrolyte may be incorporated between the n-ply braid/yarn (n > 2) and the protective sheath. However, this is not a requirement since all the electrode rods or filaments already contain an active material and an electrolyte in their pores.
  • one of the electrodes comprises a porous rod having pores to accommodate an active material-electrolyte mixture and at least one of the electrodes is a non- porous rod (filament, fiber, wire, etc.) having an active material-electrolyte mixture coated on its surface.
  • the electrodes of the instant supercapacitor may be produced in a roll-to-roll manner.
  • the invented process comprises continuously feeding an electrically conductive porous rod/filament (e.g. 304, 310, 322, or 330), from a feeder roller (not shown), into an active material impregnation zone where a wet active material-electrolyte mixture (e.g. slurry, suspension, or gel-like mass, such as 306a, 306b, 312a, 312b) containing an electrode active material (e.g.
  • a wet active material-electrolyte mixture e.g. slurry, suspension, or gel-like mass, such as 306a, 306b, 312a, 312b
  • an electrode active material e.g.
  • the wet active material- electrolyte mixture (306a, 306b) is forced to impregnate into the porous layer from both sides using one or two pairs of rollers (302a, 302b, 302c, and 302d) to form an impregnated active electrode 308 (an anode or cathode).
  • the conductive porous layer contains interconnected electron-conducting pathways and preferably at least 70% by volume (preferably > 80%, more preferably > 90%) of pores.
  • the foam rods/filaments typically have a pore volume from 50% to approximately 99%.
  • two feeder rollers 316a, 316b are used to continuously pay out two protective films 314a, 314b that support wet active material-electrolyte mixture rods/filaments 312a, 312b.
  • These wet active material-electrolyte mixture rods/filaments 312a, 312b can be delivered to the protective (supporting) films 314a, 314b using a broad array of procedures (e.g. printing, spraying, casting, coating, etc., which are well known in the art).
  • the wet active material-electrolyte mixture is impregnated into the pores of the porous rods or filaments 310 to form an active material electrode 320 (an anode or cathode electrode) tentatively covered by two protective films 314a, 314b.
  • two spraying devices 324a, 324b are used to dispense the wet active material -electrolyte mixture (325a, 325b) to the two opposed porous surfaces of the conductive porous layer 322.
  • the wet active material-electrolyte mixture is forced to impregnate into the porous rod from both sides using one or two pairs of rollers to form an impregnated active electrode 326 (an anode or cathode).
  • two spraying devices 332a, 332b are used to dispense the wet active material-electrolyte mixture (333a, 333b) to the porous surfaces of the conductive porous rod 330.
  • the wet active material-electrolyte mixture is forced to impregnate into the porous rod using one or two pairs of rollers to form an impregnated active electrode 338 (an anode or cathode).
  • the electrode production process begins by continuously feeding a conductive porous rod 356 from a feeder roller 340.
  • the porous rod 356 is directed by a roller 342 to get immersed into a wet active material- electrolyte mixture mass 346 (slurry, suspension, gel, etc.) in a container 344.
  • the active material-electrolyte mixture begins to impregnate into pores of the porous rod 356 as it travels toward roller 342b and emerges from the container to feed into the gap between two rollers
  • Two protective films 350a, 350b are concurrently fed from two respective rollers 352a, 352b to cover the impregnated porous rod 354, which may be continuously collected on a rotating drum (a winding roller 355).
  • the process is applicable to both the anode and the cathode electrodes.
  • the resulting electrode rod or filament can have a thickness or diameter from 100 nm to several centimeters (or thicker, if so desired).
  • the electrode thickness or diameter is from 100 nm to 100 ⁇ , more typically from 1 ⁇ to 50 ⁇ , and most typically from 10 ⁇ to 30 ⁇ .
  • a macroscopic, flexible and conformal cable battery e.g.
  • the electrode typically and desirably has a thickness no less than 100 ⁇ (preferably > 200 ⁇ , further preferably > 300 ⁇ , more preferably > 400 ⁇ ; further more preferably > 500 ⁇ , 600 ⁇ , or even > 1,000 ⁇ ; no theoretical limitation on the electrode thickness.
  • the electrically conductive porous rods or filaments may be selected from metal foam, metal web or screen, perforated metal sheet-based structure, metal fiber mat, metal nanowire mat, conductive polymer nano-fiber mat, conductive polymer foam, conductive polymer-coated fiber foam, carbon foam, graphite foam, carbon aerogel, carbon xerogel, graphene aerogel, graphene foam, graphene oxide foam, reduced graphene oxide foam, carbon fiber foam, graphite fiber foam, exfoliated graphite foam, or a combination thereof.
  • the porous rods or filaments must be made of an electrically conductive material, such as a carbon, graphite, metal, metal- coated fiber, conductive polymer, or conductive polymer-coated fiber, which is in a form of highly porous mat, screen/grid, non-woven, foam, etc. Examples of conductive porous layers are presented in FIG.3(A), FIG. 3(B), FIG. 3(C), and FIG. 3(D).
  • the porosity level must be at least 50% by volume, preferably greater than 70%, further preferably greater than 90%, and most preferably greater than 95% by volume.
  • the backbone of the foam or the foam walls forms an integral 3D network of electron-conducting pathways.
  • the graphene or graphene oxide material in a graphene foam, graphene oxide foam, or graphene aerogel foam structure constitutes the pore walls of the foam.
  • This graphene or graphene oxide material in the form does not contain isolated or separated graphene sheets.
  • This graphene or graphene oxide material in the foam is not part of the active material-electrolyte mixture that is impregnated into pores of the foam.
  • This mixture can contain activated carbon particles or isolated graphene sheets that are not part of the foam structure.
  • These activated carbon particles or isolated graphene sheets are the primary electrode active material of a supercapacitor.
  • These foam structures can be readily made into any cross-sectional shape. They also can be very flexible; typically, non-metallic foams being more flexible than metallic foams.
  • metal nano-fibers can be made into highly flexible foams. Since the electrolyte is in either a liquid or gel state, the resulting cable battery can be very flexible and can be made to be conformal to essentially any odd shape. Even when the salt concentration in a liquid solvent is high (e.g. from 2.5 M to 15 M), the foam structure containing electrolyte inside their pores remains deformable, bendable, twistable, and conformable to even an odd shape.
  • the electrically conductive porous rod in the first or second electrode contains a conductive polymer fiber mat, a carbon/graphite fiber mat, a fiber tow with pores between fibers, conductive fiber knit structure or nonwoven structure having multiple fibers and pores.
  • These multiple fibers can contain conductive polymer fibers, metal-coated fibers, carbon-coated polymer fibers, carbon fibers, or graphite fibers.
  • substantially all of the pores in the original conductive porous rods or filaments are filled with the electrode active material (anode or cathode), electrolyte, and optional conductive additive (no binder resin needed). Since there are great amounts of pores
  • the graphene electrode active material (in place of activated carbon) is selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, or a combination thereof.
  • the starting graphitic material for producing any one of the above graphene materials may be selected from natural graphite, artificial graphite, meso-phase carbon, meso-phase pitch, meso- carbon micro-bead, soft carbon, hard carbon, coke, carbon fiber, carbon nano-fiber, carbon nano- tube, or a combination thereof.
  • the present invention also provides a lithium-ion capacitor (LIC) or a sodium-ion capacitor (NIC), wherein at least one of the two electrodes in a cell is produced by the presently invented process. More preferably, both the anode electrode and the cathode electrode for the presently invented LIC or NIC are made by the presently invented process described above.
  • This inventive process includes (A) Continuously feeding an electrically conductive porous rod/filament to an anode material impregnation zone, wherein the conductive porous
  • the rod/filament has porous surfaces and contain interconnected electron-conducting pathways and, preferably, at least 70% by volume of pores; and (B) Impregnating a wet anode active material- electrolyte mixture into the electrically conductive porous rod from at least one porous surface to form an electrode.
  • the wet anode active material mixture contains a liquid electrolyte and an anode active material preferably selected from pre-lithiated or pre-sodiated versions of graphite particles, carbon particles, Si nano particles, Sn nano particles, or any other commonly used anode active materials for lithium-ion batteries or sodium-ion batteries.
  • anode active materials can be made into a fine particle form and multiple particles, along with conductive additive particles, can be readily mixed with a liquid electrolyte to form a wet anode active material mixture (e.g. in a slurry form) for impregnation into a conductive porous layer.
  • the corresponding cathode can contain an EDLC-type active material (e.g. activated carbon or isolated graphene sheets), with or without a redox pair partner material (such as an intrinsically conducting conjugate polymer or a transition metal oxide).
  • the anode active material may be selected from the group consisting of: (a) Pre-lithiated particles of natural graphite, artificial graphite, meso-carbon microbeads (MCMB), and carbon; (b) Pre-lithiated particles or coating of Silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium (Cd); (c) Pre- lithiated alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd with other elements, wherein said alloys or compounds are stoichiometric or non-stoichiometric; (d) Pre- lithiated oxides, carbides, nitrides, sulfides,
  • Pre-lithiation can be accomplished electrochemically by using a compact mass of graphene sheets as the working electrode and lithium metal as the counter electrode. Pre-lithiation may also be accomplished by adding lithium powder or chips along with the anode active material (e.g. Si particles) and conductive additive particles into a liquid electrolyte.
  • anode active material e.g. Si particles
  • the anode active material contains a sodium intercalation compound selected from the following groups of materials: (a) Sodium-doped silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti), cobalt (Co), nickel (Ni), manganese (Mn), cadmium (Cd), and mixtures thereof; (b) Sodium-containing alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni, Mn, Cd, and their mixtures; (c) Sodium-containing oxides, carbides, nitrides, sulfides, phosphides, selenides, tellurides, or antimonides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd, and mixtures
  • Pre-sodiation can be accomplished electrochemically by using a compact mass of graphene sheets as the working electrode and sodium metal as the counter electrode. Pre-sodiation may also be accomplished by adding lithium powder or chips along with the anode active material (e.g. Sn particles) and conductive additive particles into a liquid electrolyte.
  • the anode active material e.g. Sn particles
  • conductive additive particles into a liquid electrolyte.
  • Bulk natural graphite is a 3-D graphitic material with each graphite particle being composed of multiple grains (a grain being a graphite single crystal or crystallite) with grain boundaries (amorphous or defect zones) demarcating neighboring graphite single crystals. Each grain is composed of multiple graphene planes that are oriented parallel to one another.
  • a graphene plane in a graphite crystallite is composed of carbon atoms occupying a two- dimensional, hexagonal lattice.
  • the graphene planes are stacked and bonded via van der Waal forces in the crystallographic c-direction (perpendicular to the graphene plane or basal plane).
  • the graphene planes in one grain are parallel to one another, typically the graphene planes in one grain and the graphene planes in an adjacent grain are inclined at different orientations. In other words, the orientations of the various grains in a graphite particle typically differ from one grain to another.
  • the constituent graphene planes of a graphite crystallite in a natural or artificial graphite particle can be exfoliated and extracted or isolated to obtain individual graphene sheets of hexagonal carbon atoms, which are single-atom thick, provided the inter-planar van der Waals forces can be overcome.
  • An isolated, individual graphene plane of carbon atoms is commonly referred to as single-layer graphene.
  • a stack of multiple graphene planes bonded through van der Waals forces in the thickness direction with an inter-graphene plane spacing of approximately 0.3354 nm is commonly referred to as a multi-layer graphene.
  • a multi-layer graphene platelet has up to 300 layers of graphene planes ( ⁇ 100 nm in thickness), but more typically up to 30 graphene planes ( ⁇ 10 nm in thickness), even more typically up to 20 graphene planes ( ⁇ 7 nm in thickness), and most typically up to 10 graphene planes (commonly referred to as few-layer graphene in scientific community).
  • Single-layer graphene and multi-layer graphene sheets are collectively called “nano graphene platelets" (NGPs), as shown in FIG. 2.
  • NTPs nano graphene platelets
  • NGPs are a new class of carbon nano material (a 2-D nano carbon) that is distinct from the 0-D fullerene, the 1-D CNT or CNF, and the 3-D graphite.
  • a graphene material isolated graphene sheets
  • CNT carbon nanotube
  • CNF carbon nano-fiber
  • graphene materials are obtained by intercalating natural graphite particles with a strong acid and/or an oxidizing agent to obtain a graphite intercalation compound (GIC) or graphite oxide (GO), as illustrated in FIG. 4(A) and FIG. 4(B) (schematic drawings).
  • GIC graphite intercalation compound
  • GO graphite oxide
  • FIG. 4(A) and FIG. 4(B) schematic drawings.
  • the presence of chemical species or functional groups in the interstitial spaces between graphene planes in a GIC or GO serves to increase the inter-graphene spacing (i3 ⁇ 402, as determined by X- ray diffraction), thereby significantly reducing the van der Waals forces that otherwise hold graphene planes together along the c-axis direction.
  • the GIC or GO is most often produced by immersing natural graphite powder (100 in FIG.
  • GIC graphite oxide
  • oxidizing agent e.g. potassium permanganate or sodium perchlorate
  • the resulting GIC (102) is actually some type of graphite oxide (GO) particles if an oxidizing agent is present during the intercalation procedure.
  • This GIC or GO is then repeatedly washed and rinsed in water to remove excess acids, resulting in a graphite oxide suspension or dispersion, which contains discrete and visually discernible graphite oxide particles dispersed in water.
  • Route 1 involves removing water from the suspension to obtain "expandable graphite,” which is essentially a mass of dried GIC or dried graphite oxide particles.
  • expandable graphite essentially a mass of dried GIC or dried graphite oxide particles.
  • the GIC undergoes a rapid volume expansion by a factor of 30-300 to form "graphite worms" (104), which are each a collection of exfoliated, but largely un-separated graphite flakes that remain interconnected.
  • these graphite worms can be re-compressed to obtain flexible graphite sheets or foils (106) that typically have a thickness in the range of 0.1 mm (100 ⁇ ) - 0.5 mm (500 ⁇ ).
  • NGPs single-layer and multi-layer graphene sheets
  • Single-layer graphene can be as thin as 0.34 nm
  • multi -layer graphene can have a thickness up to 100 nm, but more typically less than 10 nm (commonly referred to as few-layer graphene).
  • Multiple graphene sheets or platelets may be made into a sheet of NGP paper using a paper-making process. This sheet of NGP paper is an example of the porous graphene structure layer utilized in the presently invented process.
  • Route 2 entails ultrasonicating the graphite oxide suspension (e.g. graphite oxide particles dispersed in water) for the purpose of separating/isolating individual graphene oxide sheets from graphite oxide particles.
  • the inter-graphene plane separation bas been increased from 0.3354 nm in natural graphite to 0.6-1.1 nm in highly oxidized graphite oxide, significantly weakening the van der Waals forces that hold neighboring planes together.
  • Ultrasonic power can be sufficient to further separate graphene plane sheets to form fully separated, isolated, or discrete graphene oxide (GO) sheets.
  • NGPs or graphene materials include discrete sheets/platelets of single-layer and multi-layer (typically less than 10 layers) pristine graphene, graphene oxide, reduced graphene oxide (RGO), graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, doped graphene (e.g.
  • Pristine graphene has essentially 0% oxygen.
  • RGO typically has an oxygen content of 0.001%-5% by weight.
  • Graphene oxide (including RGO) can have 0.001%-50% by weight of oxygen.
  • all the graphene materials have 0.001%-50% by weight of non-carbon elements (e.g. O, H, N, B, F, CI, Br, I, etc.). These materials are herein referred to as non-pristine graphene m ateri al s .
  • Pristine graphene in smaller discrete graphene sheets (typically 0.3 ⁇ to 10 ⁇ ), may be produced by direct ultrasonication (also known as liquid phase exfoliation or production) or supercritical fluid exfoliation of graphite particles. These processes are well-known in the art.
  • the graphene oxide (GO) may be obtained by immersing powders or filaments of a starting graphitic material (e.g. natural graphite powder) in an oxidizing liquid medium (e.g. a mixture of sulfuric acid, nitric acid, and potassium permanganate) in a reaction vessel at a desired temperature for a period of time (typically from 0.5 to 96 hours, depending upon the nature of the starting material and the type of oxidizing agent used).
  • an oxidizing liquid medium e.g. a mixture of sulfuric acid, nitric acid, and potassium permanganate
  • the resulting graphite oxide particles may then be subjected to thermal exfoliation or ultrasonic wave-induced exfoliation to produce isolated GO sheets.
  • These GO sheets can then be converted into various graphene materials by substituting -OH groups with other chemical groups (e.g. -Br, H 2 , etc.).
  • Fluorinated graphene or graphene fluoride is herein used as an example of the halogenated graphene material group.
  • fluorination of pre-synthesized graphene This approach entails treating graphene prepared by mechanical exfoliation or by CVD growth with fluorinating agent such as XeF 2 , or F-based plasmas;
  • Exfoliation of multilayered graphite fluorides Both mechanical exfoliation and liquid phase exfoliation of graphite fluoride can be readily accomplished.
  • the process of liquid phase exfoliation includes ultrasonic treatment of a graphite fluoride in a liquid medium.
  • the nitrogenation of graphene can be conducted by exposing a graphene material, such as graphene oxide, to ammonia at high temperatures (200-400°C). Nitrogenated graphene could also be formed at lower temperatures by a hydrothermal method; e.g. by sealing GO and ammonia in an autoclave and then increased the temperature to 150-250°C. Other methods to synthesize nitrogen doped graphene include nitrogen plasma treatment on graphene, arc- discharge between graphite electrodes in the presence of ammonia, ammonolysis of graphene oxide under CVD conditions, and hydrothermal treatment of graphene oxide and urea at different temperatures.
  • a graphene material such as graphene oxide
  • Nitrogenated graphene could also be formed at lower temperatures by a hydrothermal method; e.g. by sealing GO and ammonia in an autoclave and then increased the temperature to 150-250°C.
  • Other methods to synthesize nitrogen doped graphene include nitrogen plasma treatment on graphene,
  • a graphite particle (e.g. 100) is typically composed of multiple graphite crystallites or grains.
  • a graphite crystallite is made up of layer planes of hexagonal networks of carbon atoms. These layer planes of hexagonally arranged carbon atoms are substantially flat and are oriented or ordered so as to be substantially parallel and equidistant to one another in a particular crystallite.
  • These layers of hexagonal-structured carbon atoms commonly referred to as graphene layers or basal planes, are weakly bonded together in their thickness direction (crystallographic c-axis direction) by weak van der Waals forces and groups of these graphene layers are arranged in crystallites.
  • the graphite crystallite structure is usually characterized in terms of two axes or directions: the c-axis direction and the a-axis (or b-axis) direction.
  • the c- axis is the direction perpendicular to the basal planes.
  • the a- or ⁇ -axes are the directions parallel to the basal planes (perpendicular to the c-axis direction).
  • a highly ordered graphite particle can consist of crystallites of a considerable size, having a length of L a along the crystallographic a-axis direction, a width of 3 ⁇ 4 along the crystallographic ⁇ -axis direction, and a thickness L c along the crystallographic c-axis direction.
  • the constituent graphene planes of a crystallite are highly aligned or oriented with respect to each other and, hence, these anisotropic structures give rise to many properties that are highly directional.
  • the thermal and electrical conductivity of a crystallite are of great magnitude along the plane directions ⁇ a- or ⁇ -axis directions), but relatively low in the perpendicular direction (c-axis).
  • different crystallites in a graphite particle are typically oriented in different directions and, hence, a particular property of a multi-crystallite graphite particle is the directional average value of all the constituent crystallites.
  • natural graphite can be treated so that the spacing between the graphene layers can be appreciably opened up so as to provide a marked expansion in the c-axis direction, and thus form an expanded graphite structure in which the laminar character of the carbon layers is substantially retained.
  • the process for manufacturing flexible graphite is well-known in the art.
  • flakes of natural graphite e.g. 100 in FIG. 4(B)
  • the GICs are washed, dried, and then exfoliated by exposure to a high temperature for a short period of time.
  • the exfoliated graphite flakes are vermiform in appearance and, hence, are commonly referred to as graphite worms 104.
  • These worms of graphite flakes which have been greatly expanded can be formed without the use of a binder into cohesive or integrated sheets of expanded graphite, e.g. webs, papers, strips, tapes, foils, mats or the like (typically referred to as "flexible graphite" 106) having a typical density of about 0.04-2.0 g/cm 3 for most applications.
  • Acids such as sulfuric acid
  • intercalating agent intercalant
  • Many other types of intercalating agents such as alkali metals (Li, K, Na, Cs, and their alloys or eutectics), can be used to intercalate graphite to stage 1, stage 2, stage 3, etc.
  • Stage n implies one intercalant layer for every n graphene planes.
  • a stage-1 potassium-intercalated GIC means there is one layer of K for every graphene plane; or, one can find one layer of K atoms inserted between two adjacent graphene planes in a G/K/G/K/G/KG ....
  • G is a graphene plane and K is a potassium atom plane.
  • a stage-2 GIC will have a sequence of GG/K/GG/K/GG/K/GG .... and a stage-3 GIC will have a sequence of GGG/K/GGG/K/GGG ...., etc.
  • These GICs can then be brought in contact with water or water-alcohol mixture to produce exfoliated graphite and/or separated/isolated graphene sheets.
  • Exfoliated graphite worms may be subjected to high -intensity mechanical
  • NGPs nano graphene platelets
  • An NGP is composed of a graphene sheet or a plurality of graphene sheets with each sheet being a two-dimensional, hexagonal structure of carbon atoms.
  • a mass of multiple NGPs including discrete sheets/platelets of single-layer and/or few-layer graphene or graphene oxide may be made into a graphene film/paper (114 in FIG.
  • graphite worms tend to be separated into the so-called expanded graphite flakes (108 in FIG. 4(B) having a thickness > 100 nm. These flakes can be formed into graphite paper or mat 106 using a paper- or mat-making process, with or without a resin binder.
  • graphene sheets have an exceptionally high specific surface area
  • graphene sheets have a great tendency to re-stack together or to overlap with one another, thereby dramatically reducing the specific capacitance due to the significantly reduced specific surface area that is accessible by the electrolyte.
  • This tendency to re-stack is particularly acute during the supercapacitor cell electrode production process.
  • graphene sheets, along with other conductive additive and resin binder e.g. PVDF
  • a solvent typically NMP
  • the solvent is then removed (vaporized) to form a dried layer of active material electrode, which is then fed through a pair of rollers in a compression machine to consolidate the electrode layer.
  • These drying and compressing procedures induce severe graphene re-stacking.
  • the maximum specific capacitance of a single-layer graphene-based supercapacitor is as high as 550 F/g (based on an EDLC structure, no redox pair or pseudo-capacitance), but experimentally achieved values have been in the range of mere 90-170 F/g.
  • the present invention provides a highly innovative and elegant process to overcome this graphene sheet re-stacking issue.
  • This invented process completely eliminates the need to go through slurry coating, drying, and compressing procedures. Instead of forming a slurry containing an environmentally undesirable solvent (i.e. NMP), the process entails dispersing graphene sheets in a liquid electrolyte to form a slurry of electrode active material-liquid electrolyte mixture. This mixture slurry is then injected into pores of a conductive foam-based current collector; no subsequent drying and compressing are required and no or little possibility of graphene sheets re-stacking together.
  • NMP environmentally undesirable solvent
  • graphene sheets are already pre-dispersed in a liquid electrolyte, implying that essentially all graphene surfaces are naturally accessible to the electrolyte, leaving behind no "dry pockets". This process also enables us to pack graphene sheets (with electrolyte in between) in a highly compact manner, giving rise to an unexpectedly high electrode active material tap density.
  • the graphene sheets used in the aforementioned process may be subjected to the following treatments, separately or in combination:
  • Useful surface functional groups may include quinone, hydroquinone, quaternized aromatic amines, mercaptans, or disulfides. This class of functional groups can impart pseudo-capacitance to graphene-based supercapacitors.
  • activation treatment analogous to activation of carbon black materials
  • the activation treatment can be accomplished through C0 2 physical activation, KOH chemical activation, or exposure to nitric acid, fluorine, or ammonia plasma.
  • 2D inorganic materials can be used in the presently invented supercapacitors prepared by the invented active material- electrolyte mixture impregnation process.
  • Layered materials represent a diverse source of 2D systems that can exhibit unexpected electronic properties and high specific surface areas that are important for supercapacitor applications.
  • graphite is the best known layered material, transition metal dichalcogenides (TMDs), transition metal oxides (TMOs), and a broad array of other compounds, such as BN, Bi 2 Te 3 , and Bi 2 Se 3 , are also potential sources of 2D materials.
  • Non-graphene 2D nano materials single-layer or few-layer (up to 20 layers), can be produced by several methods: mechanical cleavage, laser ablation (e.g. using laser pulses to ablate TMDs down to a single layer), liquid phase exfoliation, and synthesis by thin film techniques, such as PVD (e.g. sputtering), evaporation, vapor phase epitaxy, liquid phase epitaxy, chemical vapor epitaxy, molecular beam epitaxy (MBE), atomic layer epitaxy (ALE), and their plasma-assisted versions.
  • PVD e.g. sputtering
  • evaporation vapor phase epitaxy
  • liquid phase epitaxy liquid phase epitaxy
  • chemical vapor epitaxy molecular beam epitaxy
  • ALE atomic layer epitaxy
  • the supercapacitance values are exceptionally high when these 2D nano materials are used in combination with a small amount of nano graphene sheets (particularly single-layer graphene).
  • the required single-layer graphene can be from 0.1% to 50% by weight, more preferably from 0.5% to 25%, and most preferably from 1%) to 15%) by weight.
  • electrolytes that can be used in the supercapacitor: aqueous, organic, gel, and ionic liquid.
  • electrolytes for supercapacitors consist of solvent and dissolved chemicals (e.g. salts) that dissociate into positive ions (cations) and negative ions (anions), making the electrolyte electrically conductive.
  • ions positive ions
  • anions negative ions
  • the electrolyte provides the molecules for the separating monolayer in the Helmholtz double-layer (electric double layer) and delivers the ions for pseudo- capacitance.
  • Water is a relatively good solvent for dissolving inorganic chemicals.
  • acids such as sulfuric acid (H 2 SO 4 ), alkalis such as potassium hydroxide (KOH), or salts such as quaternary phosphonium salts, sodium perchlorate (NaC10 4 ), lithium perchlorate (L1CIO 4 ) or lithium hexafluoride arsenate (LiAsF 6 )
  • water offers relatively high conductivity values.
  • Aqueous electrolytes have a dissociation voltage of 1.15 V per electrode and a relatively low operating temperature range. Water electrolyte-based supercapacitors exhibit low energy density.
  • electrolytes may contain organic solvents, such as acetonitrile, propylene carbonate, tetrahydrofuran, diethyl carbonate, ⁇ -butyrolactone, and solutes with quaternary ammonium salts or alkyl ammonium salts such as tetraethylammonium tetrafluorob orate
  • organic solvents such as acetonitrile, propylene carbonate, tetrahydrofuran, diethyl carbonate, ⁇ -butyrolactone, and solutes with quaternary ammonium salts or alkyl ammonium salts such as tetraethylammonium tetrafluorob orate
  • Organic electrolytes are more expensive than aqueous electrolytes, but they have a higher dissociation voltage of typically 1.35 V per electrode (2.7 V capacitor voltage), and a higher temperature range.
  • the lower electrical conductivity of organic solvents (10 to 60 mS/cm) leads to a lower power density, but a higher energy density since the energy density is proportional to the square of the voltage.
  • the ionic liquid is composed of ions only.
  • Ionic liquids are low melting temperature salts that are in a molten or liquid state when above a desired temperature. For instance, a salt is considered as an ionic liquid if its melting point is below 100°C. If the melting temperature is equal to or lower than room temperature (25°C), the salt is referred to as a room temperature ionic liquid (RTIL).
  • RTIL room temperature ionic liquid
  • the IL salts are characterized by weak interactions, due to the combination of a large cation and a charge-delocalized anion. This results in a low tendency to crystallize due to flexibility (anion) and asymmetry (cation).
  • a typical and well-known ionic liquid is formed by the combination of a l-ethyl-3- methylimidazolium (EMI) cation and an N,N-bis(trifluoromethane)sulphonamide (TFSI) anion.
  • EMI l-ethyl-3- methylimidazolium
  • TFSI N,N-bis(trifluoromethane)sulphonamide
  • Ionic liquids are basically composed of organic ions that come in an essentially unlimited number of structural variations owing to the preparation ease of a large variety of their components.
  • various kinds of salts can be used to design the ionic liquid that has the desired properties for a given application. These include, among others, imidazolium, pyrrolidinium and quaternary ammonium salts as cations and bis(trifluoromethanesulphonyl) imide, bis(fluorosulphonyl)imide, and hexafluorophosphate as anions.
  • ionic liquids come in different classes that basically include aprotic, protic and zwitterionic types, each one suitable for a specific application.
  • RTILs room temperature ionic liquids
  • RTILs include, but not limited to, tetraalkylammonium, di-, tri-, and tetra-alkylimidazolium, alkylpyridinium, dialkyl- pyrrolidinium, dialkylpiperidinium, tetraalkylphosphonium, and trialkylsulfonium.
  • RTILs include, but not limited to, BF 4 " , B(CN) 4 “ , CH3BF3 “ , CH2CHBF 3 “ , CF 3 BF 3 “ , C 2 F 5 BF 3 " , «-C 3 F 7 BF 3 “ , «-C 4 F 9 BF 3 “ , PF 6 " , CF 3 C0 2 “ , CF 3 S0 3 “ , N(S0 2 CF 3 ) 2 " , N(COCF 3 )(S0 2 CF 3 ) “ , N(S0 2 F) 2 “ , N(CN) 2 “ , C(CN) 3 “ , SCN “ , SeCN “ , CuCl 2 “ , A1C1 4 “ , F(HF) 2.3 “ , etc.
  • RTILs can possess archetypical properties such as high intrinsic ionic conductivity, high thermal stability, low volatility, low (practically zero) vapor pressure, non-flammability, the ability to remain liquid at a wide range of temperatures above and below room temperature, high polarity, high viscosity, and wide electrochemical windows. These properties, except for the high viscosity, are desirable attributes when it comes to using an RTIL as an electrolyte ingredient (a salt and/or a solvent) in a supercapacitor.
  • the anode active material or cathode active material may be designed to contain graphene sheets and a redox pair partner material selected from a metal oxide, a conducting polymer, an organic material, a non-graphene carbon material, an inorganic material, or a combination thereof.
  • a redox pair partner material selected from a metal oxide, a conducting polymer, an organic material, a non-graphene carbon material, an inorganic material, or a combination thereof.
  • graphene fluoride graphene hydrogenide
  • nitrogenated graphene can work with a wide variety of partner materials to form a redox pair for developing pseudo-capacitance.
  • the metal oxide or inorganic materials that serve in such a role include Ru0 2 , Ir0 2 , NiO, Mn0 2 , V0 2 , V 2 0 5 , V 3 0 8 , Ti0 2 , Cr 2 0 3 , Co 2 0 3 , Co 3 0 4 , Pb0 2 , Ag 2 0, MoC x , Mo 2 N, or a combination thereof.
  • the inorganic material may be selected from a metal carbide, metal nitride, metal boride, metal dichalcogenide, or a combination thereof.
  • the desired metal oxide or inorganic material is selected from an oxide, dichalcogenide, trichalcogenide, sulfide, selenide, or telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in a nanowire, nano-disc, nano-ribbon, or nano platelet form.
  • These materials can be in the form of a simple mixture with sheets of a graphene material, but preferably in a nano particle or nano coating form that that is physically or chemically bonded to a surface of the graphene sheets prior to being formed into a wet active material mixture (e.g. in a slurry form) and impregnated into the pores of the conductive porous layers.
  • a rope shape supercapacitor means a supercapacitor that contains at least a rod-shape or filament-shape anode and a rod-shape or filament-shape cathode combined into a braid or twist yarn.
  • the supercapacitor has a length and a diameter or thickness wherein the aspect ratio (length-to-diameter or length-to-thickness ratio) is at least 10 and preferably at least 20.
  • the rope-shaped supercapacitor can have a length greater than 1 m, or even greater than 100 m. The length can be as short as 1 ⁇ , but typically from 10 ⁇ to 10 m and more typically from micrometers to a few meters. Actually, there is no theoretical limitation on the length of this type of rope-shape supercapacitor.
  • the invented rope-shaped supercapacitor is so flexible that the supercapacitor can be easily bent to have a radius of curvature greater than 10 cm.
  • the supercapacitor is bendable to substantially conform to the shape of a void or interior compartment in a vehicle.
  • the void or interior compartment may be a trunk, door, hatch, spare tire compartment, area under seat or area under dashboard.
  • the supercapacitor is removable from a vehicle and is bendable to conform to the shape of a different void or interior compartment.
  • One or more units of instant rope-shape supercapacitor can be incorporated into a garment, belt, carrying strap, luggage strap, weaponry strap, musical instrument strap, helmet, hat, boot, foot covering, glove, wrist covering, watch band, jewelry item, animal collar or animal harness.
  • One or more units of instant rope-shaped supercapacitor can be removably incorporated a garment, belt, carrying strap, luggage strap, weaponry strap, musical instrument strap, helmet, hat, boot, foot covering, glove, wrist covering, watch band, jewelry item, animal collar or animal harness.
  • the invented rope supercapacitor conforms to the interior radius of a hollow bicycle frame.
  • EXAMPLE 1 Illustrative examples of electronically conductive porous rods or filaments as a porous current collector to accommodate an active material -electrolyte mixture
  • conductive porous rods serving as a current collector
  • anode or cathode e.g. Ni foam, Cu foam, Al foam, Ti foam, Ni mesh/web, stainless steel fiber mesh, etc.
  • Metal -coated polymer foams and carbon foams can also be used as current collectors.
  • the most desirable thickness/diameter ranges for these conductive porous rods are 50-1000 ⁇ , preferably 100-800 ⁇ , more preferably 200-600 ⁇ .
  • microscopic rope-shape supercapacitors having a diameter from 100 nm to 100 ⁇ , for instance
  • graphene foams graphene aerogel foam
  • porous carbon fibers e.g. made by electro-spinning polymer fibers, carbonizing the polymer fibers, and activating the resulting carbon fibers
  • porous graphite fibers can be used to accommodate an electrode active material-electrolyte mixture.
  • EXAMPLE 2 Ni foam and CVD graphene foam -based porous rods supported on Ni foam templates
  • Ni frame was etched away.
  • a thin layer of poly (methyl methacrylate) (PMMA) was deposited on the surface of the graphene films as a support to prevent the graphene network from collapsing during nickel etching. After the PMMA layer was carefully removed by hot acetone, a fragile graphene foam sample was obtained.
  • the use of the PMMA support layer was considered critical to preparing a free-standing film of graphene foam. Instead, a conducting polymer was used as a binder resin to hold graphene together while Ni was etched away.
  • the graphene foam or Ni foam thickness/diameter range was from 35 ⁇ to 600 ⁇ .
  • the Ni foam or the CVD graphene foam used herein is intended as conductive porous rods (CPR) to accommodate the ingredients (anode or cathode active material + optional conductive additive + liquid electrolyte) for the anode or cathode or both.
  • CPR conductive porous rods
  • pre- lithiated Si nano particles as an anode active material for a lithium-ion capacitor
  • an organic liquid electrolyte e.g. 1-5.5 M of LiPF 6 dissolved in PC-EC
  • Graphene sheets (300-750 nm long) dispersed in the same liquid electrolyte were made into cathode slurry, which was sprayed over porous surfaces of a continuous Ni foam rod to form a cathode electrode.
  • EXAMPLE 3 Graphitic foam -based conductive porous rods from pitch-based carbon foams Pitch powder, granules, or pellets are placed in a aluminum mold with the desired final shape of the foam. Mitsubishi ARA-24 meso-phase pitch was utilized. The sample is evacuated to less than 1 torr and then heated to a temperature approximately 300°C. At this point, the vacuum was released to a nitrogen blanket and then a pressure of up to 1,000 psi was applied. The temperature of the system was then raised to 800°C. This was performed at a rate of 2 degree C/min. The temperature was held for at least 15 minutes to achieve a soak and then the furnace power was turned off and cooled to room temperature at a rate of approximately 1.5 degree C/min with release of pressure at a rate of approximately 2 psi/min. Final foam
  • EXAMPLE 4 Preparation of graphene oxide (GO) and reduced graphene oxide (RGO) nano sheets from natural graphite powder Natural graphite from Huadong Graphite Co. (Qingdao, China) was used as the starting material.
  • GO was obtained by following the well-known modified Hummers method, which involved two oxidation stages.
  • the first oxidation was achieved in the following conditions: 1100 mg of graphite was placed in a 1000 mL boiling flask. Then, 20 g of K 2 S 2 0 8 , 20 g of P 2 0 5 , and 400 mL of a concentrated aqueous solution of H 2 S0 4 (96%) were added in the flask. The mixture was heated under reflux for 6 hours and then let without disturbing for 20 hours at room temperature. Oxidized graphite was filtered and rinsed with abundant distilled water until neutral pH. A wet cake-like material was recovered at the end of this first oxidation.
  • the previously collected wet cake was placed in a boiling flask that contains 69 mL of a concentrated aqueous solution of H 2 S0 4 (96%).
  • the flask was kept in an ice bath as 9 g of KMn0 4 was slowly added. Care was taken to avoid overheating.
  • the resulting mixture was stirred at 35°C for 2 hours (the sample color turning dark green), followed by the addition of 140 mL of water. After 15 min, the reaction was halted by adding 420 mL of water and 15 mL of an aqueous solution of 30 wt % H 2 0 2 . The color of the sample at this stage turned bright yellow.
  • the mixture was filtered and rinsed with a 1 : 10 HC1 aqueous solution.
  • the collected material was gently centrifuged at 2700g and rinsed with deionized water.
  • the final product was a wet cake that contained 1.4 wt % of GO, as estimated from dry extracts. Subsequently, liquid dispersions of GO sheets were obtained by lightly sonicating wet-cake materials, which were diluted in deionized water.
  • RGO-BS Surfactant-stabilized RGO
  • Sonication was performed using a Branson Sonifier S-250A equipped with a 13 mm step disruptor horn and a 3 mm tapered micro-tip, operating at a 20 kHz frequency. For instance, 10 mL of aqueous solutions containing 0.1 wt.
  • % of GO was sonicated for 10 min and subsequently centrifuged at 2700g for 30 min to remove any non-dissolved large particles, aggregates, and impurities.
  • Chemical reduction of as-obtained GO to yield RGO was conducted by following the method, which involved placing 10 mL of a 0.1 wt. % GO aqueous solution in a boiling flask of 50 mL. Then, 10 ⁇ ⁇ of a 35 wt. % aqueous solution of N 2 H 4 (hydrazine) and 70 mL of a 28 wt. % of an aqueous solution of H 4 OH (ammonia) were added to the mixture, which was stabilized by surfactants. The solution was heated to 90°C and refluxed for 1 h. The pH value measured after the reaction was approximately 9. The color of the sample turned dark black during the reduction reaction.
  • RGO was used as an electrode active material (alone or with a redox pair partner material) in either or both of the anode and cathode in several of presently invented
  • the wet anode active-electrolyte mixture and cathode active material-electrolyte mixtures were separately delivered to surfaces of graphite foams for forming an anode and a cathode, respectively.
  • a rope-shape battery was then fabricated, wherein one filamentary electrode (e.g. an anode) and one filamentary electrode (a cathode) were combined to form a braid, twist yarn, and the like.
  • Electrodes and a separator disposed between two dried electrodes were then assembled and encased in an Al-plastic laminated packaging envelop, followed by liquid electrolyte injection to form a conventional supercapacitor cell.
  • Product was collected by centrifugation at 8000 rpm for 5 min, washed with DI water and recollected by centrifugation. The washing step was repeated for at least 5 times to ensure that most DMF was removed. Finally, product was dried, mixed with liquid electrolyte to produce active cathode mixture slurry for impregnation into carbon foam.
  • Example 7 Preparation of graphene fluoride (GF) sheets as a supercapacitor active material
  • GF graphene fluoride
  • HEG highly exfoliated graphite
  • FHEG fluorinated highly exfoliated graphite
  • Pre-cooled Teflon reactor was filled with 20-30 mL of liquid pre-cooled C1F 3 , the reactor was closed and cooled to liquid nitrogen temperature. Then, no more than 1 g of HEG was put in a container with holes for C1F 3 gas to access and situated inside the reactor. In 7-10 days a gray -beige product with approximate formula C 2 F was formed.
  • FHEG FHEG
  • an organic solvent methanol and ethanol, separately
  • an ultrasound treatment 280 W
  • Example 8 Preparation of nitrogenataed graphene sheets as a supercapacitor electrode active material
  • Graphene oxide (GO), synthesized in Example 2 was finely ground with different proportions of urea and the pelletized mixture heated in a microwave reactor (900 W) for 30 s. The product was washed several times with deionized water and vacuum dried. In this method graphene oxide gets simultaneously reduced and doped with nitrogen.
  • the products obtained with graphene : urea mass ratios of 1 : 0.5, 1 : 1 and 1 : 2 are designated as NGO-1, NGO-2 and NGO-3 respectively and the nitrogen contents of these samples were 14.7, 18.2 and 17.5 wt% respectively as found by elemental analysis. These nitrogenataed graphene sheets remain dispersible in water.
  • the resulting suspensions were then dried to obtain nitrogenated graphene powder.
  • the powder was mixed in a liquid electrolyte to form a slurry for impregnation into pores of conductive porous rods/filaments.
  • EXAMPLE 9 Preparation of two-dimensional (2D) layered Bi 2 Se 3 chalcogenide nanoribbons
  • the preparation of (2D) layered Bi 2 Se 3 chalcogenide nanoribbons is well-known in the art.
  • Bi 2 Se 3 nanoribbons were grown using the vapor-liquid-solid (VLS) method.
  • Nanoribbons herein produced are, on average, 30-55 nm thick with widths and lengths ranging from hundreds of nanometers to several micrometers. Larger nanoribbons were subjected to ball- milling for reducing the lateral dimensions (length and width) to below 200 nm.
  • Nanoribbons prepared by these procedures (with or without the presence of graphene sheets or exfoliated graphite flakes) were used as a supercapacitor electrode active material.
  • EXAMPLE 10 MXenes powder + chemically activated RGO Selected MXenes, were produced by partially etching out certain elements from layered structures of metal carbides such as T1 3 AIC 2 . For instance, an aqueous 1 M H 4 FIF 2 was used at room temperature as the etchant for Ti 3 AlC 2 .
  • the MXene materials investigated include Ti 2 CT x , Nb 2 CT x , V 2 CT X , Ti 3 CNT x , and Ta 4 C 3 T x .
  • 35-95% MXene and 5-65% graphene sheets were mixed in a liquid electrolyte and impregnated into pores of conductive porous filaments.
  • EXAMPLE 11 Preparation of Mn0 2 -graphene redox pairs as a pseudo-capacitance active material
  • the Mn0 2 powder was synthesized by two methods (each with or without the presence of graphene sheets).
  • a 0.1 mol/L KMn0 4 aqueous solution was prepared by dissolving potassium permanganate in deionized water.
  • 13.32 g surfactant of high purity sodium bis(2-ethylhexyl) sulfosuccinate was added in 300mL iso-octane (oil) and stirred well to get an optically transparent solution.
  • 32.4mL of 0.1 mol/L KMn0 4 solution and selected amounts of GO solution were added in the solution, which was ultrasonicated for 30 min to prepare a dark brown precipitate.
  • the product was separated, washed several times with distilled water and ethanol, and dried at 80°C for 12 h.
  • the sample is graphene-supported Mn0 2 in a powder form, which was dispersed in a liquid electrolyte to form a slurry and impregnated into pores of a foamed current collector.
  • an electrode cathode or anode
  • an electrode active material e.g. graphene, activated carbon, inorganic nano discs, etc.
  • Super-P acetylene black-based conductive additive
  • the specific capacitance (C) of the cell is represented by the slope at each point of the voltage vs. specific capacity plot,
  • FIG.5 Shown in FIG.5 are Ragone plots (gravimetric and volumetric power density vs. energy density) of two sets of symmetric supercapacitor (EDLC) cells containing reduced graphene oxide (RGO) sheets as the electrode active material and EMEVIBF4 ionic liquid as the electrolyte.
  • EDLC symmetric supercapacitor
  • RGO reduced graphene oxide
  • EMEVIBF4 ionic liquid as the electrolyte.
  • One of the two series of supercapacitors was prepared according to an embodiment of instant invention and the other was by the conventional slurry coating of electrodes.
  • supercapacitor cells prepared by the presently invented method are significantly higher than those of their counterparts prepared via the conventional method (denoted as "conventional”).
  • the differences are highly dramatic and are mainly due to the high active material mass loading (> 20 mg/cm 2 ) associated with the presently invented cells, reduced proportion of overhead (non-active) components relative to the active material weight/volume, no need to have a binder resin, the ability of the inventive method to more effectively pack graphene sheets into pores of the foamed current collector.
  • volumetric energy densities and volumetric power densities are significantly lower than those of their gravimetric energy densities and gravimetric power densities, due to the very low tap density (packing density of 0.25 g/cm 3 ) of RGO-based electrodes prepared by the conventional slurry coating method.
  • volumetric energy densities (23.8 Wh/L) and volumetric power densities (9, 156 W/L) are higher than those of their gravimetric energy densities and gravimetric power densities, due to the relatively high tap density (packing density of 1.05 g/cm 3 ) of RGO-based electrodes prepared by the presently invented method.
  • supercapacitors prepared by the conventional process are 3.1 Wh/L and 1, 139 W/L, respectively, which are one order of magnitude lower. These are dramatic and unexpected.
  • FIG. 6 shows the Ragone plots (both gravimetric and volumetric power density vs. energy density) of symmetric supercapacitor (EDLC) cells containing activated carbon (AC) particles as the electrode active material and organic liquid electrolyte.
  • EDLC symmetric supercapacitor
  • AC activated carbon
  • the presently invented methods still surprisingly enables the AC particles to be packed with a significantly higher tap density (0.75 g/cm 3 ) than what is achieved with the conventional slurry coating process (0.55 g/cm 3 ) in the present study.
  • FIG. 7(A) Shown in FIG. 7(A) are Ragone plots of lithium ion capacitor (LIC) cells containing pristine graphene sheets as the cathode active material, prelithiated graphite particles as the anode active material, and lithium salt (LiPF 6 )-PC/DEC as organic liquid electrolyte.
  • the data are for both LICs prepared by the presently invented method and those by the conventional slurry coating of electrodes. These data indicate that both the gravimetric and volumetric energy densities and power densities of the LIC cells prepared by the presently invented method are significantly higher than those of their counterparts prepared via the conventional method.
  • the absolute magnitudes of the volumetric energy densities and volumetric power densities are significantly lower than those of their gravimetric energy densities and gravimetric power densities, due to the very low tap density (average packing density of 0.75 g/cm 3 ) of pristine graphene-based cathodes prepared by the conventional slurry coating method.
  • the absolute magnitudes of the volumetric energy densities and volumetric power densities are higher than those of their gravimetric energy densities and gravimetric power densities, due to the relatively high tap density of pristine graphene-based cathodes prepared by the presently invented method.
  • FIG. 7(B) Shown in FIG. 7(B) are Ragone plots of sodium-ion capacitor (NIC) cells containing pristine graphene sheets as the cathode active material, pre-sodiated graphite particles as the anode active material, and sodium salt (NaPF 6 )-PC/DEC as organic liquid electrolyte.
  • the data are for both LICs prepared by the presently invented method and those by the conventional slurry coating of electrodes. These data indicate that both the gravimetric and volumetric energy densities and power densities of the NIC cells prepared by the presently invented method (rope- shape cells) are significantly higher than those of their counterparts prepared via the
  • the weight of the active material i.e. activated carbon
  • the weight of the active material accounts for about 25%-30% of the total mass of the packaged cell.
  • a factor of 3 to 4 is frequently used to extrapolate the energy or power densities of the device (cell) from the properties based on the active material weight alone.
  • the properties reported are typically based on the active material weight alone and the electrodes are typically very thin ( « 100 ⁇ , and mostly « 50 ⁇ ).
  • the active material weight is typically from 5% to 10% of the total device weight, which implies that the actual cell (device) energy or power densities may be obtained by dividing the corresponding active material weight-based values by a factor of 10 to 20. After this factor is taken into account, the properties reported in these papers do not really look any better than those of commercial supercapacitors. Thus, one must be very careful when it comes to read and interpret the performance data of supercapacitors reported in the scientific papers and patent applications.
  • EXAMPLE 13 Achievable electrode thickness and its effect on electrochemical performance of supercapacitor cells
  • the electrode thickness of a supercapacitor is a design parameter that can be freely adjusted for optimization of device performance; but, in reality, the supercapacitor thickness is manufacturing-limited and one cannot produce electrodes of good structural integrity that exceed certain thickness level. Our studies further indicate that this problem is even more severe with graphene-based electrode. The instant invention solves this critically important issue associated with supercapacitors.
  • FIG.8 Shown in FIG.8 are the cell-level gravimetric (Wh/kg) and volumetric energy densities (Wh/L) plotted over the achievable electrode thickness range of the activated carbon-based symmetric EDLC supercapacitors prepared via the conventional method and those rope-shape cells prepared by the presently invented method.
  • the activated carbon-based electrodes can be fabricated up to a thickness of 100-200 ⁇ using the conventional slurry coating process.
  • the practical electrode thickness is from 10 ⁇ to 5000 ⁇ , more typically from 50 ⁇ to 2,000 ⁇ , further more typically from 100 ⁇ to 1,000 ⁇ , and most typically from 200 ⁇ to 800 ⁇ .
  • ultra-thick supercapacitor electrodes not previously achievable.
  • These ultra-thick electrodes lead to exceptionally high active material mass loading, typically significantly > 10 mg/cm 2 (more typically > 15 mg/cm 2 , further typically > 20 mg/cm 2 , often > 25 mg/cm 2 , and even > 30 mg/cm 2 ).
  • These high active material mass loadings have not been possible to obtain with conventional supercapacitors made by the slurry coating processes.
  • the typical cell-level energy densities of commercial AC -based supercapacitors are from 3 to 8 Wh/kg and from 1 to 4 Wh/L.
  • the presently invented method enables supercapacitors containing the same type of electrode active material (AC) to deliver an energy density up to 19.5 Wh/kg or 14.6 Wh/L. Such an increase in energy density has not been considered possible in the supercapacitor industry.
  • FIG.9 Also highly significant and unexpected are the data summarized in FIG.9 for reduced graphene oxide-based EDLC supercapacitors.
  • the gravimetric ( ⁇ ) and volumetric (A) energy density of the conventional supercapacitors are based on the highest achieved electrode tap density of approximately 0.25 g/cm 3
  • the gravimetric ( ⁇ ) and volumetric (X) energy density of the presently invented rope-shape supercapacitors are from those having an electrode tap density of approximately 0.75 g/cm 3 , by no means the highest. No one else has previously reported such a high tap density for un-treated, non-activated RGO electrodes.
  • EDLC supercapacitor cells produced by the conventional slurry coating method is approximately 12 Wh/kg, but those prepared by the presently invented method exhibit a gravimetric energy density as high as 25.6 Wh/kg at room temperature. This is an unprecedentedly high energy density value for EDLC supercapacitors (based on the total cell weight, not the electrode weight or active material weight alone). Even more impressive is the observation that the volumetric energy density of the presently invented supercapacitor cell is as high as 19.2 Wh/L, which is more than 6 times greater than the 3.0 Wh/L achieved by the conventional counterparts.
  • FIG.10 Summarized in FIG.10 are the data of the cell-level gravimetric and volumetric energy densities plotted over the achievable electrode thickness range of the pristine graphene-based EDLC supercapacitors (organic liquid electrolyte) prepared via the conventional method and those rope-shape cells prepared by the presently invented method.
  • the legends include the gravimetric ( ⁇ ) and volumetric (A) energy density of the conventional supercapacitors (highest achieved electrode tap density of approximately 0.25 g/cm 3 ) and the gravimetric ( ⁇ ) and volumetric (X) energy density of the presently invented supercapacitors (electrode tap density of approximately 0.85 g/cm 3 ).
  • these EDLC supercapacitors deliver a gravimetric energy density as high as 32.3 Wh/kg, which are already in the energy densities (20-40 Wh/kg) of advanced lead-acid batteries.
  • This is of high utility value since an EDLC supercapacitor can be charged and discharged for 250,000-500,000 cycles, as opposed to the typical 100-400 cycles of lead-acid batteries.
  • This achievement is very dramatic and totally unexpected in the art of supercapacitors.
  • carbon- or graphene-based EDLC supercapacitors can be re-charged in seconds, in contrast to the typically hours of recharge time required of lead-acid batteries. Lead-acid batteries are notorious for their highly negative environmental impact, yet the instant supercapacitors are environmentally benign.
  • FIG.11 Further significant examples include those data summarized in FIG.11 for the cell -level gravimetric and volumetric energy densities plotted over the achievable electrode thickness range of the pristine graphene-based EDLC supercapacitors (ionic liquid electrolyte) prepared via the conventional method and those rope-shape cells fabricated by the presently invented method.
  • the gravimetric ( ⁇ ) and volumetric (A) energy density are for those conventional supercapacitors (highest achieved electrode tap density of approximately 0.25 g/cm 3 ) and the gravimetric ( ⁇ ) and volumetric (X) energy density are for those inventive supercapacitors having an electrode tap density of approximately 0.85 g/cm 3 .
  • the presently invented pristine graphene- based EDLC supercapacitors are capable of storing a cell-level energy density of 38.6 Wh/kg, which is 6 times greater than what could be achieved by conventional AC -based EDLC supercapacitors.
  • the volumetric energy density value of 32.8 Wh/L is also unprecedented and is 10-fold greater than the 3-4 Wh/L of commercial AC -based supercapacitors.
  • EXAMPLE 14 Achievable active material weight percentage in a cell and its effect on electrochemical performance of supercapacitor cells Because the active material weight accounts for up to about 30% of the total mass of the packaged commercial supercapacitors, a factor of 30% must be used to extrapolate the energy or power densities of the device from the performance data of the active material alone. Thus, the energy density of 20 Wh/kg of activated carbon (i.e. based on the active material weight alone) will translate to about 6 Wh/kg of the packaged cell. However, this extrapolation is only valid for electrodes with thicknesses and densities similar to those of commercial electrodes (150 ⁇ or about 10 mg/cm 2 of the carbon electrode).
  • An electrode of the same active material that is thinner or lighter will mean an even lower energy or power density based on the cell weight.
  • the instant invention makes it possible to elevate the active material proportion above 90% if so desired; but typically from 15%> to 85%>, more typically from 30%> to 80%>, even more typically from 40% to 75%, and most typically from 50% to 70%.
  • the cell-level gravimetric energy densities of the activated carbon- based EDLC supercapacitors are plotted over the achievable active material proportion (active material weight/total cell weight), which are from 4.2% to 33.3%) resulting in an energy density from 1.3 to 8.4 Wh/kg.
  • the instant invention allows us to achieve a pristine graphene content in a supercapacitor cell from 17.5% to 79% by weight, resulting in a gravimetric energy density from 4.9 to 19.5 Wh/kg.
  • FIG.13 shows the cell-level gravimetric energy densities plotted over the achievable active material proportion (active material weight/total cell weight) in a supercapacitor cell for two series of pristine graphene-based EDLC supercapacitors (all with organic liquid electrolyte).
  • the presently invented rope-shape cells containing filamentary electrodes pre-impregnated with an active material-electrolyte mixture can be made to contain an exceptionally high active material proportion and, hence, extraordinarily high energy density.
  • EXAMPLE 15 The electrochemical performance of supercapacitor cells based on various electrode active materials and/or different porous or foamed structures as current collectors
  • RGO electrode active material
  • metal foam e.g. Ni and Ti foam
  • metal web e.g. stainless steel web
  • perforated metal sheet-based 3-D structure metal fiber mat (steel fibers), metal nanowire mat (Cu nanowires), conductive polymer nano-fiber mat (polyaniline), conductive polymer foam (e.g.
  • PEDOT conductive polymer-coated fiber foam
  • carbon foam from Ni-supported CVD graphene
  • graphene oxide foam obtained via fireeze- drying GO-water solution
  • reduced graphene oxide foam RGO mixed with a polymer and then carbonized
  • carbon fiber foam graphite fiber foam
  • exfoliated graphite foam exfoliated graphite worms bonded by a carbonized resin
  • the electrical conductivity of the foam material is an important parameter with a higher conductivity tending to result in a higher power density and faster supercapacitor response time.
  • the porosity level is also an important parameter with a higher pore content resulting in a larger amount of active material given the same volume, leading to a higher energy density.
  • a higher porosity level can lead to slower response time possibly due to a lower electron-conducting capability.
  • metal foam enables more ready formation of or connection to a tab (terminal lead). Two leads are required in each cell.

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Abstract

L'invention concerne un supercondensateur en forme de corde comprenant : (a) une première électrode comprenant une première tige poreuse conductrice ayant des pores et un premier mélange d'un premier matériau actif d'électrode (par exemple du charbon actif ou des feuilles de graphène isolées) et un premier électrolyte se trouvant dans les pores de la première tige poreuse; (b) un séparateur poreux entourant la première électrode pour former une première électrode protégée par une séparateur; (c) une seconde électrode comprenant une seconde tige poreuse conductrice ayant des pores et un second mélange d'un second matériau actif d'électrode et d'un second électrolyte se trouvant dans les pores de la seconde tige poreuse; la première électrode protégée par un séparateur et la seconde électrode étant combinées pour former un fil tressé ou torsadé; et (d) une gaine protectrice enveloppant ou entourant la tresse ou le fil.
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