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WO2012119361A1 - Membrane composite co-extrudée comprenant une micropoudre de caoutchouc pré-réticulé nanométrique et batterie à ion lithium la comprenant - Google Patents

Membrane composite co-extrudée comprenant une micropoudre de caoutchouc pré-réticulé nanométrique et batterie à ion lithium la comprenant Download PDF

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Publication number
WO2012119361A1
WO2012119361A1 PCT/CN2011/077074 CN2011077074W WO2012119361A1 WO 2012119361 A1 WO2012119361 A1 WO 2012119361A1 CN 2011077074 W CN2011077074 W CN 2011077074W WO 2012119361 A1 WO2012119361 A1 WO 2012119361A1
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Prior art keywords
rubber
nano
layer
extruded composite
extruded
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PCT/CN2011/077074
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English (en)
Chinese (zh)
Inventor
李鑫
李建华
陈卫
焦永军
李龙
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天津东皋膜技术有限公司
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Publication of WO2012119361A1 publication Critical patent/WO2012119361A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/494—Tensile strength
    • 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

Definitions

  • the present invention relates to a composite separator for a lithium ion battery and a method for producing the same, and particularly to a lithium ion power battery or a long life energy storage battery which is required to have high safety, cycle life and the like.
  • polyolefin microporous membrane Since the polyolefin microporous membrane has penetrating network-like submicron micropores, is resistant to high voltage oxidation, and is stable to organic electrolytes of lithium ion batteries, polyolefin microporous membranes have been widely used as separator materials in mobile phones and notebook computers. Battery, typical polyolefin microporous membrane is "dry"
  • the existing polyolefin microporous membranes currently fail to meet the high-end requirements of power batteries in terms of safety and cycle life of batteries.
  • the main technical analysis is as follows:
  • a highly crystalline polypropylene or polyethylene film having a low crystallinity is prepared, and a high crystallinity orientation is obtained after high temperature annealing.
  • the film, the film mainly forms micropores by cold stretching to form micro-cracks and continues to undergo hot tensile strengthening.
  • the process is relatively mature.
  • the main advantage of the existing "dry" PP/PE/PP three-layer separator is the manufacturing cost. Low, the main disadvantages are:
  • the diaphragm has insufficient toughness and is easy to tear in the transverse direction;
  • the intermediate microporous layer adopts PE which is turned off at a high temperature of 135-145 ° C
  • the PP microporous layer with limited melting point and hot tensile strengthening still has the disadvantages of large heat shrinkage and high temperature rupture at high temperature.
  • the other is the "wet process", the “wet process”, also known as the thermal phase separation method, which combines high molecular weight polyolefin resins with “high temperature compatibilizers” (high boiling hydrocarbons such as paraffin oil, or Other plasticizers, the solvent and the polyolefin are mutually dissolved in a thermodynamically high temperature, and can achieve molecular level mixing.
  • high temperature compatibilizer which is actually a process solvent for pore formation. The high-temperature melt which is uniformly heated and kneaded is rapidly solidified on the surface of the chill roll, phase separation occurs during the cooling process, and the sheet is stretch-strengthened by stepwise biaxial stretching or simultaneous biaxial stretching, and then the volatile cleaning solvent is used.
  • the common method is a single-layer PE film, and dry Compared with the diaphragm, the two-way tensile strengthening, the viscosity average molecular weight of the raw material is generally more than 500,000, and the wet film has improved tensile strength and elongation at break, and the existing "wet method" is separated.
  • the main disadvantages of the membrane include: 1. The extraction process must be used, and the production cost is slightly higher;
  • the heat shrinkage is too large at temperatures above 130 °C;
  • the thickness direction also lacks the stress absorption capability, which can not meet the high-end requirements of the power battery in terms of safety and battery cycle life.
  • PVDF-HFP copolymer porous gel membrane manufactured by the Bel lcore process and the pole piece can be bonded to the pole piece by a hot pressing process.
  • the pore size of the internal micropores is slightly larger, on the order of 1-2 microns, and if the thickness is controlled to be similar to the thickness of conventional commercial polyolefin membranes, such as 16-25 microns, a large number will occur.
  • the waste of internal short circuit of the battery therefore, it is required to increase the thickness of the separator (usually designed to have a thickness of 40-50 micrometers) to compensate for the lack of strength, which is disadvantageous to the rate characteristic and the energy density characteristic of the battery, and the gel membrane is usually dissolved. Produced by phase separation, the cost is high.
  • the diaphragm is required to have the following characteristics:
  • 130-20CTC has fused shutdown characteristics at high temperatures and low heat shrinkage
  • the separator and the pole piece have good bonding strength. When the battery is overcharged and internal heat is generated, the local current density is prevented from rising sharply, resulting in thermal runaway.
  • the above patents only provide the manufacturing technology of the thermal shutdown diaphragm, and the cycle life of the diaphragm to the lithium ion power battery.
  • Technical solutions were not provided for improvement in reliability.
  • the Chinese invention patent application 200880003493. 7, 200880000072. 9 reported on the polyolefin microporous membrane A composite membrane technology in which a ceramic micropowder such as alumina is bonded to a porous coating by a bonding agent; Chinese Patent Application No. 200510086061. 5 reports that a polyamide having a high melting point of 180 ° C or higher is used on the surface of the polyolefin microporous membrane.
  • a technical solution for forming a porous coating layer such as polyamideimide, polyimide, etc.; Chinese Patent Application No. 200480034190.
  • the existing polyolefin separator is basically an inert material, the adhesion between the coating and the coating is insufficient, the coating is thick and easy to peel off, and the heat shrinkage effect of the polyolefin membrane is not obvious;
  • the colloid and its slurry in the slurry will enter the micropores of the polyolefin membrane during the implementation of the above coating scheme, which may affect the membrane after the solvent is evaporated and dried to form a membrane.
  • the pore size distribution and gas permeability, the consistency of the coating method for mass production is difficult to control, and the coating method composite membrane is expensive to manufacture.
  • Chinese Patent Application No. 01 112218.8 proposes mixing and adding a monomer which can be thermally crosslinked to form a gel in the electrolyte.
  • the gel is used to increase the bonding strength between the separator and the positive electrode tab.
  • the gel forms a gel in the micropores of the separator during the thermal crosslinking formation, thereby affecting the permeability of the separator.
  • the monomer with incomplete reaction may also oxidize, gas, etc. on the positive electrode side, and may even affect the cycle performance of the battery.
  • thermoplastic olefin elastomer diethylene propylene rubber, ternary B in polyolefin matrix
  • the thermoplastic polyolefin elastomer used in this method has good compatibility with polyolefin substrates such as PP and PE, but the proportion of thermoplastic olefin elastomer mixed therein is too Low and no cross-linking treatment, so the elastic properties of the separator are limited. If the proportion of thermoplastic polyolefin elastomer is higher than 10%, it will affect the ability of the polyolefin matrix to "dry" into pores. To the appropriate porosity.
  • the safety is easy to fail; usually the battery is used before the injection is 85-90 °C
  • the normal use temperature is between _1 (T+60 °C), so the diaphragm is required to adapt to the elastic properties under normal charge and discharge conditions in this temperature range.
  • the "wet method" polyolefin composite membrane is also reported by the co-extrusion process.
  • the Chinese invention patent application 200680035668. 3, 200780005795. 3 , 200510029794. 5 etc. mainly adopts the adjustment of the solid content of the inter-layer polyolefin raw material.
  • the co-extrusion composite membrane is improved by different methods such as different ratios of polyethylene/polypropylene materials and controlling the molecular weight of different membrane materials to obtain different porosity and pore size distribution between layers and different melting points between membrane layers.
  • the high temperature membrane rupture temperature and compression resistance of the separator and the elastic properties are still insufficient.
  • the current multilayer polyolefin microporous membrane or battery separator whether produced by "wet method” or “dry method”, has the above characteristics and can improve the safety performance and cycle performance of the lithium ion battery.
  • Layer or multilayer polyolefin microporous separators the disclosed technical solutions have not yet been seen; the present invention has been proposed based on various deficiencies of existing diaphragm and lithium ion battery designs.
  • the object of the present invention is to provide a co-extruded composite diaphragm having the following comprehensive characteristics and a lithium ion battery using the same.
  • the specific invention is as follows:
  • a co-extruded composite membrane comprising nano-pre-crosslinked rubber micropowder, characterized in that the co-extruded composite membrane material comprises pre-crosslinked rubber micropowder having a particle size of 25-300 nm and a gel content of more than 80%, co-extruded composite
  • the separator comprises at least two layers of microporous membranes A and B, wherein the layer A microporous membrane is mainly composed of polyethylene having a melting point of 118-145 ° C and nanometer pre-crosslinked rubber micropowder having a weight percentage of 30% or less, wherein the layer B microporous membrane It is mainly composed of polyolefin and nano pre-crosslinked rubber micropowder.
  • the nano-pre-crosslinked rubber micropowder accounts for 30-75% by weight of the B-layer material, and the Gurley value of the co-extruded composite membrane at room temperature is 30-400S/100CC, A.
  • the peel strength between the two layers is greater than 10gf/cm, and the co-extruded composite diaphragm has the following characteristics:
  • the compressive deformation of the coextruded composite diaphragm in the thickness direction It is greater than 5% of the thickness before compression and less than 25%.
  • the compression set of the co-extruded composite diaphragm is less than 10%.
  • the diaphragm still maintains compressive elasticity.
  • the shrinkage permanent deformation is not more than 10% of the initial thickness, and the Gurley value is still less than 500S/100CC;
  • the co-extruded composite membrane is applied with a static compressive stress of 0.35 MPa in the thickness direction and kept for 60 minutes, then cooled to room temperature, the membrane remains intact, and its thermal shrinkage in both the longitudinal and transverse directions is less than 10%.
  • 1. 3. Apply a static compressive stress of 0.35 MPa in the thickness direction, and heat the co-extruded composite diaphragm at a rate of 1 °C/min from 100_200 °C. The thermal shutdown temperature of the diaphragm is not higher than 150 °C to 200 °. C and keep it for 5 minutes After cooling to room temperature, the separator remained intact with a thermal shrinkage of less than 15% in both the machine and cross directions and a Gurley value greater than 2000 S/100 cc.
  • the weight percentage of the material is preferably from 10 to 30%.
  • the material of the nano-pre-crosslinked rubber fine powder is selected from the group consisting of styrene-butadiene rubber SBR (ie, styrene-butadiene rubber) and butyl rubber IIR ( Isobutylene-isoprene rubber, isoprene rubber IR (isoprene-butadiene rubber), styrene-butadiene rubber PSBR
  • A-layer microporous membrane is mainly composed of a high-density polyethylene material having a weight average molecular weight of 3 to 3,000,000, preferably a weight average molecular weight of 60-300. Ten thousand high density polyethylene.
  • a method for manufacturing a co-extruded composite membrane comprising nano-pre-crosslinked rubber micropowder characterized in that it mainly comprises the following steps: 1. Ingredients: Firstly mechanically mixing raw materials of layer A and layer B, respectively, including polyethylene or poly Olefin composition, nano pre-crosslinked rubber micropowder, high temperature compatibilizer; 2.
  • Co-extruded cast, hot drawing Premixed slurry of layer A and layer B are separately metered into two or three twin-screw extrusions Machine, co-extruded and quenched at a high temperature, and the cooled composite sheet is preheated at 100-118 ° C for the first step of hot stretching;
  • the second hot drawing and heat setting treatment, the semi-finished film after the above extraction is preheated at 100-118 ° C, and the second step is hot stretching, heat The stretched film is heat set at 100-118 ° C for 5-30 seconds. 5. Cooling and winding, the above heat-set film is cooled, trimmed, wound, and cut to obtain a co-extruded composite membrane. .
  • a lithium ion battery comprising a nano-pre-crosslinked rubber micropowder, comprising: a positive electrode tab, a negative electrode tab, an electrolyte, and the nanopre-crosslinked rubber micropowder according to claims 1-8 Co-extruded composite membrane.
  • the co-extruded composite separator is preferably a B/A/B three-layer co-extruded structure, wherein the nano-pre-crosslinked rubber fine powder
  • the co-extruded composite separator and the positive and negative pole pieces are subjected to 85-100 ° C /0. 7 MPa hot pressing for 5 minutes and stripping between the pole pieces.
  • the strength is greater than 3gf/cm.
  • the co-extruded composite diaphragm has thermal shutdown capability at high temperatures. After heating, the micropores in the diaphragm are closed, and at least one layer can be closed to prevent the internal electrochemical reaction of the lithium ion battery from continuing under the condition of overheating, and the lithium ion battery is internally There is also thermal inertia when overheating. It is also expected that after the separator is turned off, even if the inside of the battery continues to heat up, the diaphragm does not exhibit high heat shrinkage. The electronic insulation of the diaphragm to the positive and negative electrodes should be maintained. This is to prevent the battery from being out of control early.
  • At least one microporous membrane contains a relatively high content of nano-pre-crosslinked rubber micropowder, and at least one microporous membrane contains relatively few nano-pre-crosslinked rubber micropowders, and contains relatively high poly
  • the ethylene content microporous layer provides thermal shutdown capability at elevated temperatures.
  • the main function of the A-layer microporous membrane design of the co-extruded composite membrane is to achieve high temperature shutdown and high machine Mechanical strength; effective closing of the membrane micropores at high temperatures is very important to prevent thermal runaway ignition and explosion in the case of internal heating of lithium ion batteries.
  • the A-layer microporous membrane material of the co-extruded composite membrane is mainly made of polyethylene, polyethylene material.
  • the co-extruded composite separator can be provided with thermal shutdown performance at high temperature; wherein the nano-pre-crosslinked rubber micropowder is less than 30% by weight, in the A-layer microporous membrane material
  • the nano-pre-crosslinked rubber micropowder having a content of 10-30% can appropriately increase the elasticity of the co-extruded composite separator without affecting the thermal shutdown capability, and can also appropriately increase the pore size and permeability of the A-layer microporous membrane, especially It is possible to properly coordinate the elastic deformation of the A/B layer under pressure.
  • the deformation uncoordinated diaphragm is prone to wrinkle and wavy, and the pore size distribution may be inconsistent and affect the uniform distribution of charge and discharge of the battery; nano-pre-crosslinking in the A layer material
  • the proportion of rubber micropowder should not be too high, otherwise it will affect its melting and shutting off performance; the polyethylene in the A layer material can be provided by co-extrusion composite diaphragm after hot tensile strengthening.
  • the tensile strength preferably the coextruded composite separator has a longitudinal tensile strength of 50-150 MPa, a longitudinal elongation at break of more than 50%, and a needling strength of more than 300 gf/20 ⁇ m; the high longitudinal strength can satisfy the tension of the battery winding Dimensional stability and micropore stability under action and prevention of foreign particles puncturing the separator.
  • the A-layer microporous membrane main material is preferably composed of a high-density polyethylene material having a weight average molecular weight of 3 to 3 million, especially using a weight average molecular weight of 60.
  • the coextruded composite separator has a transverse tensile strength of 20 to 75 MPa and a transverse elongation at break of more than 100%; and the excessively high molecular weight of the polyethylene is disadvantageous in melt viscosity during extrusion processing.
  • polyethylene includes high density polyethylene, linear low density polyethylene, low density polyethylene, maleic anhydride grafted polyethylene or combinations thereof.
  • the core idea of the B-layer microporous membrane design is to use a high proportion of rubber micropowder at the expense of the microporous membrane layer. Under the condition of mechanical strength, the co-extruded composite membrane mainly contributes to elastic properties and high temperature resistance.
  • the B-layer microporous membrane is mainly composed of polyolefin and nano-pre-crosslinked rubber micropowder blended, in which high content of nano-pre-crosslinked rubber micropowder is dispersed. Distributed in a continuous polyolefin matrix, the polyolefin matrix serves as a skeleton and a retaining action, and fixes the nano-pre-crosslinked rubber micropowder.
  • the polyolefin comprises a copolymer of polyethylene, polypropylene, ethylene- ⁇ -olefin or a combination thereof, preferably weight average High molecular weight high density polyethylene having a molecular weight of 6 to 3 million.
  • the co-extruded composite diaphragm is properly elastically deformed in the thickness direction and the diaphragm has an appropriate thickness.
  • the graphite active material of the negative electrode or the silicon negative electrode and the alloy negative electrode have a volume expansion ratio. Above 5%, the thickness direction of the negative electrode tab is expanded by 3-10%, and if the coextrusion composite diaphragm has a compressive elastic deformation amount of less than 5% or a too thin thickness in the thickness direction, it is disadvantageous for releasing the compressive stress of the negative electrode tab.
  • the thickness of the coextruded composite membrane is preferably At 20-40 microns, the proper thickness can provide the necessary elastic deformation ability under the condition of ensuring the strength.
  • the negative electrode When the negative electrode is charged and expanded, it can absorb and reduce the compressive stress. After the lithium ion battery discharges, the negative electrode shrinks and the diaphragm has a suitable elastic recovery.
  • the separator When the lithium battery is charged and discharged, the cycle between the negative electrode and the diaphragm is accompanied by compression and stress release. Therefore, it is desirable that the separator has good elastic recovery ability, and the conventional commercial polyolefin separator has poor elastic deformation ability in the thickness direction, after the negative electrode is expanded.
  • the discharge process due to the uneven fluctuation of the distance between the positive and negative electrodes, the local large gap existing after the deformation of the pole piece often cannot be restored to the original uniform small gap state, which may cause a large gap between the pole pieces. It may cause local internal resistance to increase or even local poor liquid state, which leads to battery capacity attenuation and uniformity, and poor cycle performance.
  • the coextruded composite membrane of the present invention still has suitable elasticity, which is controlled to be no more than 10% of the initial thickness on the compression set, and the Gurley value is still less than 500S/100CC;
  • the uniform spacing between the pole pieces can accommodate and maintain a sufficient electrolyte, and it is necessary to ensure that the different parts of the pole piece can perform electrochemical reaction in a balanced manner. Therefore, the present invention particularly pays attention to the realization of the function, and the co-extruded composite diaphragm of the present invention is The optimum design of the compression characteristics in the normal operating temperature range of T+60°C is as follows: After the first 0.
  • 35MPa static compressive stress is applied to the coextruded composite diaphragm in the thickness direction and held for 5 minutes, the coextruded composite diaphragm is in the thickness direction.
  • the amount of compressive deformation is greater than 5% of the thickness value before compression, less than 25%, more preferably less than 20%, and the compression set of the coextruded composite membrane is less than 10% after the pressure is released for 5 minutes, and the membrane is still after the compression/release cycle 2000 times. Maintaining compressive elasticity, the compression set is not more than 10% of the initial thickness, and the Gurley value is still less than 500S/100CC.
  • the coextrusion composite separator is mainly provided by a highly elastic nano-pre-crosslinked rubber micropowder. Therefore, when the material system of the B layer is designed, the proportion of the nano-pre-crosslinked rubber micropowder is 30% or more and 75% or less. It should be high enough, preferably 50-65%; but the proportion of too high above 75% is not conducive to co-extrusion, the surface quality of the membrane is deteriorated, the pore size distribution is easy to be uneven; the proportion of high rubber micropowder and rubber micropowder are high.
  • the degree of bonding is the requirement to ensure the elasticity of the co-extruded composite membrane.
  • the nano-pre-crosslinked rubber micropowder can maintain its physical stability at a high temperature of 100-20 CTC. Dispersion distribution on a continuous polyolefin matrix can hinder the aggregation in the A and B layers.
  • the heat shrinkage of ethylene and polyolefin melts is advantageous for improving the high temperature rupture of the coextruded composite separator and preventing the high temperature short circuit of the positive/negative electrode sheets.
  • the pre-crosslinked rubber micropowder has a gel content of 80% or more, preferably 90% or more, and a high gel content indicates that the degree of crosslinking (or degree of vulcanization) of the rubber micropowder is high, and the degree of crosslinking directly affects the elasticity of the rubber micropowder.
  • Resilience compared with raw rubber powder that has not been cross-linked, the cross-linked rubber powder does not It is easily dissolved in the electrolyte and has good compatibility with the electrolyte; the cross-linking treatment is completed in advance and the independent nano-powder can prevent the agglomeration phenomenon of the raw rubber powder, which is convenient for the polyethylene or polyolefin. Mix evenly.
  • the particle size of the pre-crosslinked rubber micropowder is controlled at the nanometer scale.
  • the micropores of the co-extruded composite membrane are directly related in the submicron order.
  • the particle size of the nano rubber micropowder is too large.
  • the particle size is not conducive to providing elasticity, and thus the nano-pre-crosslinked rubber fine powder has a particle diameter of 25 to 300 nm, preferably 50 to 150 nm.
  • Maleic anhydride grafted polyethylene is also known as a viscous resin. Polyethylene itself is inert and chemically grafted with polar maleic anhydride groups. It has a certain polarity and adhesion at high temperatures. It has been widely used in the field of membranes and the like, and an appropriate amount of the raw material in the A/B layer of the co-extruded composite separator of the present invention can improve the interface between the polyethylene or polyolefin matrix and the nano-pre-crosslinked rubber micropowder and the electrode sheet. The force is more conducive to the elastic recovery of the co-extruded composite membrane.
  • the maleic anhydride grafted polyethylene and the pre-crosslinked rubber micropowder are preferably selected from the strong polar styrene-butadiene rubber PSBR (ie vinylpyridine-styrene-butadiene rubber).
  • PSBR strong polar styrene-butadiene rubber
  • the positive and negative pole pieces of the battery can also be blended into 0-8% polar nano-pre-crosslinked rubber.
  • Micro powder preferably positive
  • the negative electrode tab is mixed with 3-8% of the highly polar nano-pre-crosslinked rubber micropowder; the co-extruded composite separator of the present invention and the positive and negative pole pieces are subjected to 85-100 ° C / 0. 7MP hot pressing for 5 minutes.
  • the peel strength between the pole pieces can be made 3gf/cm or more, which is advantageous for the battery to prevent the pole pieces from being misaligned and to keep the insulation when overheated.
  • the composite membrane is manufactured by a co-extrusion processing method, and the co-extruded composite membrane has a simple production process and a low production cost compared with the various coating methods described above, and polyethylene and polyolefin in the A/B two-layer semi-finished product during co-extrusion processing.
  • the high temperature melt has a certain interdiffusion entanglement at the interface, which can ensure high bond strength/peel strength between the two layers.
  • the peel strength of lOgf/cm or more between A/B layers can be utilized with high content of nano pre-crosslinked rubber.
  • the B layer of the fine powder effectively suppresses the heat shrinkage of the polyethylene-based A layer at a high temperature.
  • the appropriate pore size and porosity of the co-extruded composite membrane are integrated in the Gurley value of the gas permeability index.
  • the excessive Gurley value means that the membrane pore resistance is large, the membrane permeability is poor, especially the permeability after compression is worse, the battery capacity.
  • the initial low Gurley value means that the diaphragm has large pores, high porosity, easy battery short-circuit, and poor safety. Therefore, it is preferred in the present invention that the co-extruded composite membrane has a Gurley value of 30-400 S/100 cc at room temperature.
  • the embodiment of the present invention will be described in detail. Further, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.
  • the weighed nano pre-crosslinked rubber micropowder W1 is boiled in dilute toluene for more than 8 hours. After filtration through a membrane, the residue W2 is weighed and compared with the initial n.
  • the toluene insoluble matter is defined as a gel, which also refers to the chemical gel content. .
  • microporous membrane was tested for gas permeability in accordance with JIS P8117.
  • the measuring instrument was tested by MTS's CMT4000 electronic tester, and the maximum load when the needle was inserted into the polyolefin porous film at a speed of 2 mm/s with a 1 ⁇ diameter needle with a spherical surface (curvature radius R: 0.5 mm) at the front end was measured. .
  • a long strip of film sample having a width of 20 inches was used and measured using an MTS CMT4000 electronic tester.
  • the strip After the pole piece and the diaphragm are hot pressed, the strip has a width of 20 ⁇ and a length of 50 ,.
  • the two clamps of the peel strength tester are clamped to the pole piece and the diaphragm, respectively, and the pole piece and the diaphragm are separated. The maximum force required.
  • the slurry was applied on one side to an aluminum foil having a thickness of 20 ⁇ m by a coater, dried at 130 ° C for 30 minutes, and then compression-molded by a roll press at a pressure of 5 MPa, and the areal density of the positive electrode active material was 200g / m 2, bulk density of active material is compressed to 2. 5g / cm 3.
  • the concentration of LiFP 6 is 1.0 mol/L.
  • the concentration of LiFP 6 is 1.0 mol/L.
  • the concentration of LiFP 6 is 1.0 mol/L.
  • a film having a shear size of 55 mm X 55 mm was placed between a positive electrode piece cut into 50 mm ⁇ 50 mm and a negative electrode piece cut into 52 mm ⁇ 52 mm , and pressed with a smooth teflon plate, and the periphery was bolted and placed.
  • the slurry was coated on both sides onto a 20 ⁇ m aluminum current collector and rolled, and the areal density of the active material was 400 g/m 2 .
  • the positive electrode piece was cut into a size of 270 ⁇ X 100 mm, a total of 20 pieces.
  • the slurry was coated on both sides of a 12 ⁇ m copper current collector and rolled, and the surface density of the active material was 220 g/m 2 .
  • the negative electrode tab was cut into a size of 275 mm X 105 mm, a total of 21 pieces.
  • the ratio of the electrolyte is the same as described in (9) c.
  • the double-sided coating material of each of the positive pole pieces having a width of 100 mm and a 20-inch wide edge area is cleaned; the same method is to make the negative pole piece width of 105 ⁇ on one side, and the 20 mm wide edge area on both sides
  • the coating material is cleaned up.
  • the cleaned positive electrode piece, the diaphragm, and the cleaned negative electrode piece are stacked in sequence, wherein the positive electrode piece has a cleaning area on one side and a negative side has a cleaning area in opposite directions, the negative electrode
  • the active material material region of the pole piece is completely covered with the active material portion of the positive electrode tab, and the separator is located between the positive and negative materials, and completely covers the active material region of the negative electrode.
  • 20 positive electrode sheets, 21 separators, and 21 negative electrode sheets are laminated in turn, and then all the positive electrode sheets are cleaned on one side and 60 mm X 100 mm positive electrode polymer batteries are used by an ultrasonic welding machine.
  • the tabs are welded together, and all the negative electrode polymer cells on the side of the negative electrode tab are soldered to the poles of 60 mm X 100 mm, and then the battery is sealed with an aluminum plastic film, and a liquid injection hole is left on one side.
  • 85 ° C vacuum is 0. O lMpa, after baking for 12 hours, take out the electrolyte and seal it.
  • the battery is charged at a temperature of 8 ° C (about 0.5 ° C) to a voltage of 4. 2 V, and maintained at a voltage of 4. 2 V, when the current is less than 0.8 A, the charging is completed, after being left for 30 minutes, The current of 8A discharges the battery to 3.0V.
  • the current is discharged to 3. 0V, and the current is discharged to 3. 0V, and the current is discharged to 3. 0V, when the current is less than 1. 6A, the charging is completed, after being left for 30 minutes, discharged with a current of 16A to 3. 0V,
  • the discharge capacity at this time was 1 C discharge capacity (Ah).
  • Example 1 The charge and discharge cycle test was carried out in accordance with the above method, and the ratio of the discharge capacity after the predetermined cycle to the discharge capacity at the first cycle was 70% as the end life, thereby judging the battery cycle performance.
  • Example 1 The charge and discharge cycle test was carried out in accordance with the above method, and the ratio of the discharge capacity after the predetermined cycle to the discharge capacity at the first cycle was 70% as the end life, thereby judging the battery cycle performance.
  • Co-extruded composite membrane material formulation Formula A: Weight average molecular weight (Mw) 1.5 million ultra-high molecular weight polyethylene (UHMWPE): 10 parts; Maleic anhydride grafted high-density polyethylene: 15 parts; Irradiation cross-linked with particle size of 100-150 nm 5 parts of benzene rubber micropowder, dioctyl sebacate (DOS): 70 parts; antioxidant 1010: 0.3 parts;
  • Ultra-high molecular weight polyethylene with a weight average molecular weight (Mw) of 2.5 million: 10 parts; Maleic anhydride grafted high density polyethylene: 10 parts; Irradiation crosslinked with a particle size of 100-150 nm Benzene rubber micropowder PSBR: 28 parts; dioctyl sebacate (DOS): 120 parts; antioxidant 1010: 0.2 parts;
  • Co-extruded cast piece The above A and B raw materials are separately swelled and mixed in a different stainless steel stirred tank at 90 ° C for 24 hours to prepare a uniform slurry; then the slurry is equally equivalent by a metering pump
  • the conveyance amount was melt-kneaded in parallel co-rotating twin-screw extruders A and B having a length to diameter ratio of 1:68.
  • the temperature setting range of the extruder is between 190 °C and 210 °C.
  • the melts of layers A and B pass through the mixer and are extruded into the same co-extrusion flat die and quenched and cast.
  • the thickness of the cast piece is controlled to 1.0 mm and the width is 800 ⁇ .
  • High-pressure extraction cleaning using pentafluoroacetamidine, hexafluoroacetic acid or its combination for extraction and dissolution.
  • the composite rolled product is placed in a supercritical extraction kettle for cleaning.
  • the cleaning process is: Cleaning temperature: 75 °C, cleaning pressure: 5.5MPa, separation pressure is 1.5MPa, separation temperature is 65 °C, extraction solvent is circulated throughout the system to clean the product.
  • the stepwise hot stretching, the longitudinal heat stretching of the semi-finished film after the extraction is 1.6 times, the transverse heat stretching is 2 times, and the stretching temperature is 120 ° C;
  • the compressive deformation amount of the coextruded composite diaphragm in the thickness direction is 5-value of the thickness before compression.
  • the compression set of the co-extruded composite membrane was tested to be less than 5%. After the compression/release cycle 2000 times, the diaphragm still maintains compressive elasticity, the compression set is not more than 12% of the initial thickness, and the Gurley value is finally 95S. /100CC;
  • the co-extruded composite separator was applied at a temperature of 130 ° C in a thickness direction of 0. 35 MPa static compressive stress and held for 60 minutes and then cooled to room temperature, the separator remained intact, and the heat shrinkage ratio in both the longitudinal and transverse directions was less than 10%; 0. 35MPa static compressive stress, heated from 100-200 °C to the co-extruded composite membrane at a rate of 1 °C / min, the membrane thermal shutdown temperature of 139 ° C, to 200 ° C for 5 minutes and then cooled to room temperature, diaphragm It remains intact with a thermal shrinkage of less than 12% in both the machine and cross directions and a Gurley value greater than 2600 S/100 cc.
  • the composite separator is used, the A side thereof is in contact with the positive electrode tab, and the B side is in contact with the above negative electrode tab.
  • the pole group is pressurized at 100 ° C / 1.5 MPa for 10 min, and then dried and injected. Electrolysis The liquid was made into a lithium ion battery and tested at 150 ° C for hot box, acupuncture, short circuit, and 1 C cycle at room temperature of 25 ° C. The battery safety test was all qualified, and the cycle life was 2,900 times.
  • the battery manufacturing process is the same as in the first embodiment.
  • the diaphragm is made of a dry PP/PE/PP film from a foreign company, with a thickness of 25 ⁇ m, a porosity of 40%, a Gurley value of 600-630 S/100 CC, and a tensile strength of 165 MPa in the MD direction.
  • the TD direction is 13 MPa, and the transverse elongation at break is 12%.
  • Battery safety test 150 ° C hot box, acupuncture, short circuit are unqualified, cycle life: 835 times.
  • the battery manufacturing process is the same as in the first embodiment.
  • the diaphragm is made of a wet single-layer PE separator from a foreign company.
  • the thickness is 23 micrometers, the porosity is 49%, the Gurley value is 95S/100CC, and the tensile strength is 143 MPa in the MD direction and 21 MPa in the TD direction.
  • the longitudinal elongation at break was 42% and the transverse elongation at break was 344%.
  • Battery safety test 150 ° C hot box, acupuncture, short circuit are unqualified, cycle life: 1376 times.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Cell Separators (AREA)
  • Laminated Bodies (AREA)

Abstract

L'invention concerne une membrane composite co-extrudée comprenant une micropoudre de caoutchouc pré-réticulé nanométrique, et une batterie à ion lithium la comprenant. La membrane possède de bonnes propriétés d'élasticité, de résistance mécanique et de résistance aux hautes températures, et permet d'améliorer efficacement les propriétés de cyclage et de sécurité de la cellule. La micropoudre de caoutchouc pré-réticulé possède une taille de particules de 25 à 300 nm, et un contenu en gel ne dépassant pas 80%. La cellule à ion lithium comprenant la micropoudre de caoutchouc pré-réticulé nanométrique comprend une pièce de pôle positif, une pièce de pôle négatif, un électrolyte et une membrane composite co-extrudée modifiée par la micropoudre de caoutchouc pré-réticulé nanométrique.
PCT/CN2011/077074 2011-03-09 2011-07-12 Membrane composite co-extrudée comprenant une micropoudre de caoutchouc pré-réticulé nanométrique et batterie à ion lithium la comprenant WO2012119361A1 (fr)

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CN201110055620.1 2011-03-09
CN201110055620.1A CN102683628B (zh) 2011-03-09 2011-03-09 含有纳米预交联橡胶微粉的共挤复合隔膜以及使用其的锂离子电池

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CN105449140A (zh) * 2014-08-27 2016-03-30 宁德时代新能源科技股份有限公司 隔离膜及锂离子二次电池
CN105406004A (zh) * 2015-12-05 2016-03-16 江苏天鹏电源有限公司 锂离子电池卷芯用隔膜
CN106769845A (zh) * 2016-12-27 2017-05-31 深圳市星源材质科技股份有限公司 一种聚合物涂覆锂电池隔膜与极片之间粘结力的表征方法
CN108832061B (zh) 2018-06-06 2021-11-23 宁德新能源科技有限公司 隔离膜和电化学装置
CN113809469B (zh) * 2018-07-19 2024-06-18 河南天工膜材新能源科技有限公司 电池隔膜铸片及其制造方法、电池隔膜及其制造方法
CN111628133B (zh) * 2020-05-25 2022-10-04 大连中比能源科技有限公司 一种锂离子电池复合隔膜及其制备方法
CN111809739A (zh) * 2020-07-15 2020-10-23 柳州东方工程橡胶制品有限公司 一种超高阻尼橡胶支座及其制备方法
CN112993490B (zh) * 2021-03-03 2023-06-09 广州鹏辉能源科技股份有限公司 锂电池隔膜及其制备方法和应用
WO2024192595A1 (fr) * 2023-03-17 2024-09-26 宁德时代新能源科技股份有限公司 Séparateur, batterie secondaire et dispositif électrique

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