WO2018101308A1 - Electrode for energy storage devices, and energy storage device - Google Patents

Abstract

Provided is an electrode for energy storage devices which is provided with a collector substrate, an undercoat layer formed on at least one surface of the collector substrate, and an active material layer formed on the undercoat layer, wherein, when the two-dimensional distribution of K absorption edge energy of metal atoms other than lithium included in the active material in the electrode of an energy storage device, which has been prepared using the electrode, activated, and subsequently discharged from a fully charged state to a depth of discharge of 20%, is measured by way of X-ray absorption fine structure analysis using an angle resolution of 10-50 µm, the half-value width of the resultant histogram when A represents the K absorption edge energy in the fully charged state, and B represents the K absorption edge energy in a fully discharged state, is |A-B|÷8.4 or lower.

Description

Electrode for energy storage device and energy storage device

The present invention relates to an electrode for an energy storage device and an energy storage device.

In recent years, development of high-performance batteries has been actively promoted in response to demands for portable electronic devices such as smartphones, digital cameras, and portable game machines that are smaller and lighter and have higher functionality. Demand for energy storage devices such as secondary batteries and electric double layer capacitors is growing significantly. Among them, a lithium ion secondary battery is a secondary battery that is currently being most vigorously developed due to its high energy density, high voltage, and lack of a memory effect during charging and discharging. In addition, the development of electric vehicles has been actively promoted due to recent efforts to deal with environmental problems, and higher performance has been demanded for secondary batteries as a power source.

In a lithium ion secondary battery, a positive electrode and a negative electrode that can occlude and release lithium, and a separator interposed therebetween are accommodated in a container, and an electrolyte solution (in the case of a lithium ion polymer secondary battery, liquid electrolysis is included). It has a structure filled with a gel or an all-solid electrolyte instead of a liquid. For the positive electrode and the negative electrode, an active material capable of inserting and extracting lithium, a conductive material mainly composed of a carbon material, and a composition containing a polymer binder are generally applied on a current collector such as a copper foil or an aluminum foil. It is manufactured by doing. This binder is used to bond the active material and the conductive material, and further to the metal foil, and is a fluorine-based resin soluble in N-methyl-2-pyrrolidone (NMP) such as polyvinylidene fluoride (PVdF), Aqueous dispersions of olefin polymers are commercially available.

The active material generally has low conductivity, and the conductivity of the electrodes such as the positive electrode and the negative electrode is mainly borne by the conductive material contained in the electrode. On the other hand, in order to increase the capacity of the battery, it is necessary to increase the proportion of the active material in the electrode. Therefore, the ratio of the conductive material in the electrode is reduced, and the current flowing through the electrode flows through a part of the electrode. Since the active material and the conductive material are greatly different in weight, shape, size, specific gravity and the like, the electrodes are likely to be non-uniform, and the current flow tends to be non-uniform.

Non-Patent Documents 1 and 2 are examples of evaluating the two-dimensional non-uniformity of charge / discharge of such an electrode, but the charge / discharge of the electrode is extremely non-uniform because the conductivity of the electrode is low. It has been shown. Such non-uniformity indicates that the electrode is easily charged and discharged locally, and is considered to cause deterioration of the battery. In order to improve such non-uniformity, it is necessary to increase the amount of the conductive additive added. However, as described above, since the ratio of the active material is decreased as a result, the capacity of the battery is decreased. There was a problem.

This invention is made | formed in view of the said situation, and aims at providing the electrode for energy storage devices and energy storage device which can perform charging / discharging uniformly.

As a result of intensive studies from the viewpoint of uniformly charging and discharging while maintaining the active material density of the electrode, the present inventors have a conductive undercoat layer between the current collector substrate and the active material layer. By using an electrode that exhibits a predetermined X-ray absorption distribution when an X-ray absorption fine structure (XAFS) analysis is performed, an energy storage device that can be charged and discharged uniformly is obtained. The headline and the present invention were completed.

Specifically, the present invention provides the following electrode for energy storage device and energy storage device.
1. An electrode for an energy storage device, comprising: a current collecting substrate; an undercoat layer formed on at least one surface of the current collecting substrate; and an active material layer formed on the undercoat layer,
After activating the energy storage device produced using the electrode, the device was discharged from a fully charged state to a discharge depth of 20%.
A two-dimensional distribution of K absorption edge energy of metal atoms other than lithium contained in the active material in the electrode is measured by X-ray absorption fine structure analysis with a resolution of 10 to 50 μm square;
An electrode for an energy storage device in which the half width of a histogram obtained by setting the K absorption edge energy in a fully charged state as A and the K absorption edge energy in a fully discharged state as B is | AB− ÷ 8.4 or less.
2. 1. The electrode for an energy storage device according to 1, wherein discharge is performed at 0.5 to 50 C from the fully charged state to a discharge depth of 20%.
3. The electrode for 1 or 2 energy storage devices whose said active material contains an iron atom.
4). 3. The electrode for an energy storage device according to 3, wherein the active material is lithium iron phosphate.
5). The electrode for an energy storage device according to any one of 1 to 4, wherein the undercoat layer contains a conductive material.
6). 5. The electrode for an energy storage device according to 5, wherein the conductive material contains carbon nanotubes.
7). 6. The electrode for an energy storage device according to 6, wherein the undercoat layer contains a carbon nanotube dispersant.
8). 7. The electrode for an energy storage device according to 7, wherein the carbon nanotube dispersant is a triarylamine hyperbranched polymer or a vinyl polymer containing an oxazoline group in a side chain.
9. The electrode for an energy storage device according to any one of 1 to 8, wherein the undercoat layer contains a matrix polymer.
10. The electrode for an energy storage device according to any one of 1 to 9, wherein the current collecting substrate is an aluminum foil or a copper foil.
11. An energy storage device comprising an electrode for an energy storage device according to any one of 11.1 to 10.

By using the electrode for energy storage device of the present invention, an energy storage device that can be charged and discharged uniformly is obtained.

It is an imaging XAFS image of the positive electrode measured in Example 2 and Comparative Example 2. It is a histogram of absorption edge energy about all the measured areas.

[Electrodes for energy storage devices]
The electrode for energy storage devices of this invention is equipped with a current collection board | substrate, the undercoat layer formed in the at least one surface of this current collection board | substrate, and the active material layer formed on the undercoat layer. In addition, the electrode for energy storage device of the present invention is discharged from a fully charged state to a discharge depth of 20% after activation of the energy storage device manufactured using the electrode, and is included in the active material in the electrode of the device. The two-dimensional distribution of the K absorption edge energy of metal atoms other than lithium is measured by XAFS analysis with a resolution of 10 to 50 μm square, the K absorption edge energy in the fully charged state is A, and the K absorption edge energy in the fully discharged state is B. The half width of the histogram obtained as follows is | AB | ÷ 8.4 or less.

Here, in the present invention, “activation” means that complete charge / discharge is repeated for 1 to 5 cycles at 0.1 to 0.5 C.

When the device is activated and discharged from a fully charged state to a discharge depth of 20%, it is preferable to discharge at 0.5 to 50 C, more preferably 0.5 to 10 C, and more preferably 0.5 to 1 C. It is even more preferable to discharge at. The charging is preferably performed at 0.01 to 10C, and more preferably at 0.1 to 0.5C.

The half width of the obtained histogram is preferably | AB | ÷ 8.4 or less, more preferably | AB | ÷ 8.5 or less, and more preferably | AB | ÷ 8.6 or less. , | AB | ÷ 8.7 or less is more preferable, and | AB | ÷ 8.9 or less is most preferable. The lower limit of the full width at half maximum is not particularly limited, but is usually a value greater than zero.

The full width at half maximum is the same as the sample of the device electrode (hereinafter referred to as the first cycle sample) when the device is not charged / discharged after activation and the device is fully charged and then discharged to a discharge depth of 20%. It is preferable that it is a value measured as. If the half width of the sample in the first cycle is within the above range, charging and discharging can be performed uniformly. Therefore, even if the charging and discharging cycle is repeated, the electrode is not easily deteriorated, and a device having a long life can be obtained.

Specific examples of the electrode for an energy storage device of the present invention will be described below, but the present invention is not limited thereto.

[Collector board]
The said current collection board | substrate can use what was conventionally used as a current collection board | substrate of the electrode for energy storage devices. For example, thin films of copper, aluminum, nickel, gold, silver and alloys thereof, carbon materials, metal oxides, conductive polymers, etc. can be used, but electrode structures are applied by applying welding such as ultrasonic welding. When producing a body, it is preferable to use a metal foil made of copper, aluminum, nickel, gold, silver and alloys thereof. The thickness of the current collector substrate is not particularly limited, but is preferably 1 to 100 μm in the present invention.

[Undercoat layer]
The undercoat layer preferably contains a conductive material. Examples of the conductive material include carbon nanotube (CNT), carbon black, ketjen black, acetylene black, carbon whisker, carbon fiber, natural graphite, artificial graphite, titanium oxide, ITO, ruthenium oxide, aluminum, nickel and the like. Among these, CNT is preferable from the viewpoint of forming a uniform thin film.

CNTs are generally produced by arc discharge, chemical vapor deposition (CVD), laser ablation, etc., but the CNTs used in the present invention may be obtained by any method. . In addition, a single-walled CNT (SWCNT) in which a single carbon film (graphene sheet) is wound in a cylindrical shape, and a double-walled CNT (DWCNT) in which two graphene sheets are wound in a concentric shape There are multi-layer CNTs (MWCNT) in which a plurality of graphene sheets are concentrically wound. In the present invention, SWCNT, DWCNT, and MWCNT can be used alone or in combination. From the viewpoint of cost, multilayer CNT is most advantageous.

In addition, when producing SWCNT, DWCNT or MWCNT by the above method, catalyst metals such as nickel, iron, cobalt, yttrium may remain, and thus purification for removing these impurities may be required. is there. In order to remove impurities, ultrasonic treatment is effective together with acid treatment with nitric acid, sulfuric acid and the like. However, acid treatment with nitric acid, sulfuric acid, or the like destroys the π-conjugated system constituting CNT and may impair the original characteristics of CNT. Therefore, it is desirable to purify and use under appropriate conditions.

Specific examples of CNTs that can be used in the present invention include a spar gloss CNT (manufactured by Shinsei Energy and Industrial Technology Development Organization) and eDIPS-CNT (manufactured by Shinshin Energy and Industrial Technology Development Organization). ], SWNT series [made by Meijo Nanocarbon Co., Ltd .: trade name], VGCF series [made by Showa Denko KK: trade name], FloTube series [made by CNano Technology Co., Ltd .: trade name], AMC [Ube Industries, Ltd.] Manufactured: trade name], NANOCYL NC7000 series [produced by Nanocyl SA: trade name], Baytubes [produced by Bayer: trade name], GRAPHISTRENGTH [produced by Arkema: trade name], MWNT7 (made by Hodogaya Chemical Co., Ltd.): Product name], Hyperion CNT [manufactured by Hypeprion Catalysis International: trade name], and the like.

The undercoat layer is preferably produced using a conductive material-containing composition (dispersion) containing the conductive material described above and a solvent.

The solvent is not particularly limited as long as it is conventionally used for the preparation of a conductive material-containing composition such as CNT. For example, water; tetrahydrofuran (THF), diethyl ether, 1,2-dimethoxyethane (DME), etc. Ethers; halogenated hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane; N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone ( Amides such as NMP); Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; Alcohols such as methanol, ethanol, isopropanol and n-propanol; Aliphatic hydrocarbons such as n-heptane, n-hexane and cyclohexane Benzene, toluene, xylene, ethyl Examples include aromatic hydrocarbons such as benzene; glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether; organic solvents such as glycols such as ethylene glycol and propylene glycol. These solvent can be used individually by 1 type or in mixture of 2 or more types. In particular, when CNT is used as the conductive material, water, NMP, DMF, THF, methanol, and isopropanol are preferable because the ratio of isolated dispersion of CNT can be improved. These solvent can be used individually by 1 type or in mixture of 2 or more types.

Further, the conductive material-containing composition may contain a matrix polymer as necessary. Matrix polymers include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer (P (VDF-HFP)), fluoride Fluorine-based resins such as vinylidene-chlorotrifluoroethylene copolymer (P (VDF-CTFE)), polyvinylpyrrolidone, ethylene-propylene-diene terpolymer, polyethylene (PE), polypropylene (PP), ethylene- Polyolefin resins such as vinyl acetate copolymer (EVA) and EEA (ethylene-ethyl acrylate copolymer); polystyrene (PS), high impact polystyrene (HIPS), acrylonitrile-styrene copolymer (AS), acrylonitrile- Butadiene Polystyrene resins such as Tylene Copolymer (ABS), Methyl Methacrylate-Styrene Copolymer (MS), Styrene-Butadiene Rubber; Polycarbonate Resin; Vinyl Chloride Resin; Polyamide Resin; Polyimide Resin; Sodium Polyacrylate, Polymethyl (Meth) acrylic resins such as methacrylate (PMMA); polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polylactic acid (PLA), poly-3-hydroxybutyric acid, polycaprolactone, polybutylene succin Polyester resins such as polyethylene succinate / adipate; polyphenylene ether resins; modified polyphenylene ether resins; polyacetal resins; polysulfone resins; Resin; Polyvinyl alcohol resin; Polyglycolic acid; Modified starch; Cellulose acetate, carboxymethyl cellulose, cellulose triacetate; Chitin, chitosan; Thermoplastic resin such as lignin, emeraldine base that is polyaniline and its half oxide; Polythiophene; Polypyrrole; Polyphenylene vinylene; polyphenylene; conductive polymer such as polyacetylene; and epoxy resin; urethane acrylate; phenol resin; melamine resin; urea resin; thermosetting resin such as alkyd resin; In the conductive material-containing composition, since it is preferable to use water as a solvent, the matrix polymer is also water-soluble, such as sodium polyacrylate, sodium carboxymethylcellulose, water-soluble cellulose ether, sodium alginate. Polyvinyl alcohol, polystyrene sulfonic acid, polyethylene glycol and the like are preferable, and sodium polyacrylate, sodium carboxymethyl cellulose and the like are particularly preferable.

The matrix polymer can also be obtained as a commercial product. For example, Aron A-10H (polyacrylic acid, manufactured by Toagosei Co., Ltd., solid content concentration 26 mass%, aqueous solution), Aron A-30 (polyacrylic acid) Ammonium, manufactured by Toagosei Co., Ltd., solid concentration 32% by mass, aqueous solution), sodium polyacrylate (manufactured by Wako Pure Chemical Industries, Ltd., degree of polymerization 2,700-7,500), sodium carboxymethylcellulose (Wako Pure) Yakuhin Kogyo Co., Ltd.), sodium alginate (manufactured by Kanto Chemical Co., Ltd., deer grade 1), Metroles (registered trademark) SH series (hydroxypropylmethylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd.), Metroses SE series (hydroxyethyl) Methyl cellulose, manufactured by Shin-Etsu Chemical Co., Ltd.), JC-25 (completely saponified polyvinyl alcohol, manufactured by Nihon Ventures & Poval), JM-17 (intermediate saponified poly) Vinyl alcohol, manufactured by Nippon Vinegar-Poval Co., Ltd.), JP-03 (partially saponified polyvinyl alcohol, manufactured by Nippon Vinegar-Poval Co., Ltd.), polystyrene sulfonic acid (manufactured by Aldrich, solid content concentration 18% by mass) , Aqueous solution) and the like.

The content of the matrix polymer is not particularly limited, but is preferably about 0.0001 to 99% by mass, more preferably about 0.001 to 90% by mass in the composition.

Furthermore, the conductive material-containing composition may contain a dispersant in order to improve the dispersibility of the conductive material in the composition. Although it does not specifically limit as said dispersing agent, It can select from a well-known thing suitably, For example, carboxymethylcellulose (CMC), polyvinylpyrrolidone (PVP), an acrylic resin emulsion, a water-soluble acrylic polymer, a styrene emulsion, silicon | silicone Emulsion, acrylic silicon emulsion, fluororesin emulsion, EVA emulsion, vinyl acetate emulsion, vinyl chloride emulsion, urethane resin emulsion, triarylamine hyperbranched polymer described in International Publication No. 2014/04280, International Publication No. 2015/029949 And vinyl polymers having an oxazoline group in the side chain. In the present invention, a triarylamine hyperbranched polymer described in International Publication No. 2014/04280 and a vinyl polymer having an oxazoline group in the side chain described in International Publication No. 2015/029949 are suitable.

Specifically, it is obtained by condensation polymerization of triarylamines and aldehydes and / or ketones under acidic conditions, and is highly branched having a repeating unit represented by the following formula (1) or (2) A polymer is preferably used.

In the formulas (1) and (2), Ar ¹ to Ar ³ each independently represents any divalent organic group represented by the formulas (3) to (7). A substituted or unsubstituted phenylene group represented by

In formulas (2) to (7), R ¹ to R ³⁸ each independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, or a branched structure. And an optionally substituted alkoxy group having 1 to 5 carbon atoms, a carboxyl group, a sulfo group, a phosphoric acid group, a phosphonic acid group or a salt thereof.

Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the alkyl group having 1 to 5 carbon atoms which may have a branched structure include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n -Pentyl group and the like.

Examples of the alkoxy group having 1 to 5 carbon atoms which may have a branched structure include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, and n-pentyloxy group.

As salts of carboxyl group, sulfo group, phosphoric acid group and phosphonic acid group, alkali metal salts such as sodium and potassium; Group 2 metal salts such as magnesium and calcium; ammonium salts; propylamine, dimethylamine, triethylamine, ethylenediamine, etc. Aliphatic amine salts of the following: alicyclic amine salts such as imidazoline, piperazine and morpholine; aromatic amine salts such as aniline and diphenylamine; pyridinium salts and the like.

In formulas (1) and (2), Z ¹ and Z ² are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, or formulas (8) to (11 ) Represents any monovalent organic group. However, Z ¹ and Z ² do not simultaneously become the alkyl group.

In formulas (8) to (11), R ³⁹ to R ⁶² each independently have a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms which may have a branched structure, or a branched structure. A haloalkyl group having 1 to 5 carbon atoms, a phenyl group, —OR ⁶³ , —COR ⁶³ , —NR ⁶³ R ⁶⁴ , or —COOR ⁶⁵ (wherein R ⁶³ and R ⁶⁴ are each independently a hydrogen atom, alkyl group having 1 carbon atoms which may 5 have a branched structure, carbon atoms 1 may have a branched structure 1-5 haloalkyl group, or a phenyl group, R ⁶⁵ is An alkyl group having 1 to 5 carbon atoms which may have a branched structure, a haloalkyl group having 1 to 5 carbon atoms which may have a branched structure, or a phenyl group), or a carboxyl group or a sulfo group Represents a phosphoric acid group, a phosphonic acid group or a salt thereof.

Here, the haloalkyl group having 1 to 5 carbon atoms which may have a branched structure includes a difluoromethyl group, a trifluoromethyl group, a bromodifluoromethyl group, a 2-chloroethyl group, a 2-bromoethyl group, and 1,1. -Difluoroethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 2-chloro-1,1,2-trifluoroethyl group, pentafluoroethyl group, 3 -Bromopropyl group, 2,2,3,3-tetrafluoropropyl group, 1,1,2,3,3,3-hexafluoropropyl group, 1,1,1,3,3,3-hexafluoropropane Examples include -2-yl group, 3-bromo-2-methylpropyl group, 4-bromobutyl group, perfluoropentyl group and the like. In addition, examples of the alkyl group having 1 to 5 carbon atoms which may have a halogen atom or a branched structure include the same groups as those exemplified in the formulas (2) to (7).

Of these, Z ¹ and Z ² are each independently preferably a hydrogen atom, a 2- or 3-thienyl group, or a group represented by the formula (8), and particularly any ^one of Z ¹ and Z ² Is more preferably a hydrogen atom, the other being a hydrogen atom, a 2- or 3-thienyl group, a group represented by the formula (8), particularly those in which R ⁴¹ is a phenyl group, or R ⁴¹ is a methoxy group. When R ⁴¹ is a phenyl group, an acidic group may be introduced onto the phenyl group when a method for introducing an acidic group after polymer production is used in the acidic group introduction method described later. Examples of the alkyl group having 1 to 5 carbon atoms which may have a branched structure include those described above.

In particular, in consideration of further improving the adhesion to the current collector substrate, the hyperbranched polymer has a carboxyl group in at least one aromatic ring of the repeating unit represented by the formula (1) or (2), Those having at least one acidic group selected from a sulfo group, a phosphoric acid group, a phosphonic acid group, and salts thereof are preferred, and those having a sulfo group or a salt thereof are more preferred.

The hyperbranched polymer having a repeating unit represented by the formula (1) is, for example, a triarylamine compound represented by the following formula (A) and, for example, the following formula (B) as shown in the following scheme 1. It is obtained by condensation polymerization of an aldehyde compound and / or a ketone compound as shown in the presence of an acid catalyst.

(In the formula, Ar ¹ to Ar ³ , Z ¹ and Z ² are the same as described above.)

As shown in the following scheme 2, the hyperbranched polymer having a repeating unit represented by the formula (2) includes a triarylamine compound represented by the formula (A) and an aldehyde compound such as phthalate such as terephthalaldehyde. It can be obtained by condensation polymerization of a bifunctional compound represented by the following formula (C) such as aldehydes in the presence of an acid catalyst.

(In the formula, Ar ¹ to Ar ³ and R ¹ to R ⁴ are the same as described above.)

In the condensation polymerization reaction, an aldehyde compound and / or a ketone compound can be used at a ratio of 0.1 to 10 equivalents with respect to 1 equivalent of the aryl group of the triarylamine compound.

Examples of the acid catalyst include mineral acids such as sulfuric acid, phosphoric acid and perchloric acid; organic sulfonic acids such as p-toluenesulfonic acid and p-toluenesulfonic acid monohydrate; carboxylic acids such as formic acid and oxalic acid. Etc. can be used. The amount of the acid catalyst to be used is variously selected depending on the kind thereof, but is usually preferably 0.001 to 10,000 parts by mass, more preferably 0.01 to 1,000 parts per 100 parts by mass of the triarylamines. Part by mass, more preferably 0.1 to 100 parts by mass.

Examples of the aldehyde compound include formaldehyde, paraformaldehyde, acetaldehyde, propylaldehyde, butyraldehyde, isobutyraldehyde, valeraldehyde, capronaldehyde, 2-methylbutyraldehyde, hexylaldehyde, undecylaldehyde, 7-methoxy-3,7-dimethyl. Saturated aliphatic aldehydes such as octyl aldehyde, cyclohexane carboxaldehyde, 3-methyl-2-butyraldehyde, glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, adipine aldehyde; unsaturated aliphatic aldehydes such as acrolein and methacrolein Heterocyclic aldehydes such as furfural, pyridine aldehyde, thiophene aldehyde; benzaldehyde, tolylaldehyde Hydride, trifluoromethylbenzaldehyde, phenylbenzaldehyde, salicylaldehyde, anisaldehyde, acetoxybenzaldehyde, terephthalaldehyde, acetylbenzaldehyde, formylbenzoic acid, methyl formylbenzoate, aminobenzaldehyde, N, N-dimethylaminobenzaldehyde, N, N-diphenyl Aromatic aldehydes such as aminobenzaldehyde, naphthyl aldehyde, anthryl aldehyde and phenanthryl aldehyde, aralkyl aldehydes such as phenylacetaldehyde and 3-phenylpropionaldehyde, and the like. Of these, aromatic aldehydes are preferred.

The ketone compounds are alkyl aryl ketones and diaryl ketones, and examples thereof include acetophenone, propiophenone, diphenyl ketone, phenyl naphthyl ketone, dinaphthyl ketone, phenyl tolyl ketone, and ditolyl ketone.

The condensation reaction can be performed without a solvent, but is usually performed using a solvent. Any solvent that does not inhibit the reaction can be used. Examples thereof include cyclic ethers such as tetrahydrofuran and 1,4-dioxane; N, N-dimethylformamide (DMF), N, N-dimethylacetamide ( DMAc), amides such as N-methyl-2-pyrrolidone (NMP); ketones such as methyl isobutyl ketone and cyclohexanone; halogenated hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane and chlorobenzene; benzene, And aromatic hydrocarbons such as toluene and xylene. Of these, cyclic ethers are particularly preferable. These solvent can be used individually by 1 type or in mixture of 2 or more types.

If the acid catalyst used is a liquid such as formic acid, for example, the acid catalyst can also serve as a solvent.

The reaction temperature during the condensation is usually 40 to 200 ° C. The reaction time is variously selected depending on the reaction temperature, but is usually about 30 minutes to 50 hours.

When introducing an acidic group into a hyperbranched polymer, it is introduced in advance on the aromatic ring of the triarylamine compound, aldehyde compound or ketone compound, which is the polymer raw material, and is introduced by a method for producing a hyperbranched polymer using this. However, the obtained hyperbranched polymer may be introduced by a method of treating with a reagent capable of introducing an acidic group on the aromatic ring, but the latter method may be used in consideration of the ease of production. preferable. In the latter method, the method for introducing the acidic group onto the aromatic ring is not particularly limited, and may be appropriately selected from conventionally known various methods according to the type of the acidic group. For example, when a sulfo group is introduced, a technique of sulfonation using an excessive amount of sulfuric acid can be used.

The average molecular weight of the hyperbranched polymer is not particularly limited, but the weight average molecular weight (Mw) is preferably 1,000 to 2,000,000, more preferably 2,000 to 1,000,000. In the present invention, Mw is a value measured by gel permeation chromatography (in terms of polystyrene).

Specific examples of the hyperbranched polymer include, but are not limited to, those represented by the following formula.

On the other hand, as a vinyl polymer having an oxazoline group in the side chain (hereinafter referred to as oxazoline polymer), an oxazoline monomer having a polymerizable carbon-carbon double bond-containing group at the 2-position as represented by the formula (13): A polymer having a repeating unit bonded to a polymer main chain or a spacer group at the 2-position of the oxazoline ring, which is obtained by radical polymerization of is preferably used.

In formula (13), X represents a polymerizable carbon-carbon double bond-containing group, and R ¹⁰⁰ to R ¹⁰³ each independently represent a hydrogen atom, a halogen atom, or a carbon number that may have a branched structure. An alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms is represented.

The polymerizable carbon-carbon double bond-containing group is not particularly limited as long as it contains a polymerizable carbon-carbon double bond, but is preferably a chain hydrocarbon group containing a polymerizable carbon-carbon double bond, For example, alkenyl groups having 2 to 8 carbon atoms such as vinyl group, allyl group, isopropenyl group and the like are preferable.

Examples of the halogen atom and the alkyl group having 1 to 5 carbon atoms which may have a branched structure include those described above.

Specific examples of the aryl group having 6 to 20 carbon atoms include phenyl group, xylyl group, tolyl group, biphenyl group, naphthyl group and the like.

Specific examples of the aralkyl group having 7 to 20 carbon atoms include benzyl group, phenylethyl group, phenylcyclohexyl group and the like.

Specific examples of the oxazoline monomer represented by the formula (13) include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl Vinyl-4-propyl-2-oxazoline, 2-vinyl-4-butyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-5-ethyl-2-oxazoline, 2-vinyl- 5-propyl-2-oxazoline, 2-vinyl-5-butyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-4-ethyl -2-oxazoline, 2-isopropenyl-4-propyl-2-oxazoline, 2-isopropenyl-4-butyl-2-oxazoly 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-5-propyl-2-oxazoline, 2-isopropenyl-5-butyl-2 -Oxazoline and the like. Of these, 2-isopropenyl-2-oxazoline is preferable from the viewpoint of availability.

In consideration of preparing the conductive material-containing composition using an aqueous solvent, the oxazoline polymer is preferably water-soluble. Such a water-soluble oxazoline polymer may be a homopolymer of the oxazoline monomer represented by the formula (13), but has a (meth) having a hydrophilic functional group with the oxazoline monomer in order to further improve the solubility in water. It is preferable that it is obtained by radical polymerization of at least two monomers with an acrylate monomer.

Specific examples of the (meth) acrylic monomer having a hydrophilic functional group include (meth) acrylic acid, 2-hydroxyethyl acrylate, methoxypolyethylene glycol acrylate, monoesterified product of acrylic acid and polyethylene glycol, acrylic acid 2-aminoethyl and its salt, 2-hydroxyethyl methacrylate, methoxypolyethylene glycol methacrylate, monoesterified product of methacrylic acid and polyethylene glycol, 2-aminoethyl methacrylate and its salt, sodium (meth) acrylate, Examples include ammonium (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, sodium styrenesulfonate, and the like. These may be used alone or in combination of two or more. Among these, methoxypolyethylene glycol (meth) acrylate and monoesterified products of (meth) acrylic acid and polyethylene glycol are preferable.

In addition, other monomers other than the oxazoline monomer and the (meth) acrylic monomer having a hydrophilic functional group can be used in combination within a range that does not adversely affect the conductive material dispersibility of the oxazoline polymer. Specific examples of other monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, (meth) acrylic. (Meth) acrylic acid ester monomers such as perfluoroethyl acid and phenyl (meth) acrylate; α-olefin monomers such as ethylene, propylene, butene and pentene; haloolefins such as vinyl chloride, vinylidene chloride and vinyl fluoride Monomers; Styrene monomers such as styrene and α-methylstyrene; Vinyl ester monomers such as vinyl acetate and vinyl propionate; Vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether. These may be used alone or in combination of two or more.

In the monomer component used in the production of the oxazoline polymer used in the present invention, the content of the oxazoline monomer is preferably 10% by mass or more, more preferably 20% by mass or more from the viewpoint that the conductive material dispersibility of the obtained oxazoline polymer is further increased. Preferably, 30% by mass or more is even more preferable. In addition, the upper limit of the content rate of the oxazoline monomer in a monomer component is 100 mass%, and the homopolymer of an oxazoline monomer is obtained in this case. On the other hand, the content of the (meth) acrylic monomer having a hydrophilic functional group in the monomer component is preferably 10% by mass or more, more preferably 20% by mass or more from the viewpoint of further improving the water solubility of the obtained oxazoline polymer. 30% by mass or more is even more preferable. In addition, as described above, the content of other monomers in the monomer component is in a range that does not affect the conductive material dispersibility of the obtained oxazoline polymer. What is necessary is just to set suitably in the range of 5-95 mass%, Preferably it is 10-90 mass%.

The average molecular weight of the oxazoline polymer is not particularly limited, but Mw is preferably 1,000 to 2,000,000, more preferably 2,000 to 1,000,000.

The oxazoline polymer that can be used in the present invention can be synthesized by the conventional radical polymerization of the above-mentioned monomers, but can also be obtained as a commercial product, and as such a commercial product, for example, Epocross (registered trademark) ) WS-300 (manufactured by Nippon Shokubai Co., Ltd., solid concentration 10 mass%, aqueous solution), Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd., solid content concentration 25 mass%, aqueous solution), Epocross WS-500 (( Manufactured by Nippon Shokubai Co., Ltd., solid content: 39% by mass, water / 1-methoxy-2-propanol solution), Poly (2-ethyl-2-oxazoline) (Aldrich), Poly (2-ethyl-2-oxazoline) ) (Manufactured by Alfa Aesar), Poly (2-ethyl-2-oxazoline) (manufactured by VWR International), and the like. In addition, when it is marketed as a solution, it may be used as it is, or it may be used after substituting with the target solvent.

The mixing ratio of the conductive material and the dispersant in the conductive material-containing composition can be about 1,000: 1 to 1: 100 in terms of mass ratio.

The concentration of the dispersing agent is not particularly limited as long as the conductive material can be dispersed in the solvent, but is preferably about 0.001 to 30% by mass, and about 0.002 to 20% by mass in the composition. More preferably.

The concentration of the conductive material changes in the weight of the target undercoat layer and the required mechanical, electrical, thermal characteristics, etc., and at least a part of the conductive material is isolated and dispersed, Although it is optional as long as the undercoat layer can be produced with an appropriate basis weight, it is preferably about 0.0001 to 30% by mass in the composition, more preferably about 0.001 to 20% by mass, More preferably, it is about 0.001 to 10% by mass.

The conductive material-containing composition may contain a crosslinking agent that causes a crosslinking reaction with the dispersant to be used, or a crosslinking agent that self-crosslinks. These crosslinking agents are preferably dissolved in the solvent used.

Examples of the crosslinking agent for the triarylamine-based hyperbranched polymer include melamine-based, substituted urea-based, and these polymer-based crosslinking agents. These crosslinking agents can be used alone or in combination of two or more. Preferably, it is a cross-linking agent having at least two cross-linking substituents, specifically, CYMEL (registered trademark), methoxymethylated glycoluril, butoxymethylated glycoluril, methylolated glycoluril, methoxymethyl. Melamine, butoxymethylated melamine, methylolated melamine, methoxymethylated benzoguanamine, butoxymethylated benzoguanamine, methylolated benzoguanamine, methoxymethylated urea, butoxymethylated urea, methylolated urea, methoxymethylated thiourea, methoxymethylated thio Examples thereof include compounds such as urea and methylolated thiourea, and condensates of these compounds.

As the cross-linking agent of the oxazoline polymer, for example, a compound having two or more functional groups having reactivity with an oxazoline group such as a carboxyl group, a hydroxy group, a thiol group, an amino group, a sulfinic acid group, and an epoxy group is particularly preferable. Although not limited, the compound which has 2 or more of carboxyl groups is preferable. In addition, a compound having a functional group that causes a crosslinking reaction by heating during the formation of a thin film or in the presence of an acid catalyst such as a sodium salt, potassium salt, lithium salt, or ammonium salt of a carboxylic acid is also crosslinked. It can be used as an agent.

Specific examples of compounds that cause a crosslinking reaction with an oxazoline group include metal salts of synthetic polymers such as polyacrylic acid and copolymers thereof and natural polymers such as carboxymethylcellulose and alginic acid that exhibit crosslinking reactivity in the presence of an acid catalyst. Examples thereof include ammonium salts of the above synthetic polymers and natural polymers that exhibit crosslinking reactivity upon heating. In particular, sodium polyacrylate, lithium polyacrylate, ammonium polyacrylate, sodium carboxymethylcellulose, lithium carboxymethylcellulose, carboxymethylcellulose ammonium and the like that exhibit crosslinking reactivity in the presence of an acid catalyst or under heating conditions are preferred.

Such a compound that causes a crosslinking reaction with an oxazoline group can also be obtained as a commercial product. Examples of such a commercial product include sodium polyacrylate (manufactured by Wako Pure Chemical Industries, Ltd., degree of polymerization: 2, 700-7,500), sodium carboxymethylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.), sodium alginate (manufactured by Kanto Chemical Co., Ltd., deer grade 1), Aron A-30 (polyammonium acrylate, Toagosei Co., Ltd.) ), Solid concentration 32% by mass, aqueous solution), DN-800H (carboxymethylcellulose ammonium, manufactured by Daicel Finechem Co., Ltd.), ammonium alginate (manufactured by Kimika Co., Ltd.), and the like.

Examples of the crosslinking agent that self-crosslinks include, for example, an aldehyde group for an hydroxy group, an epoxy group, a vinyl group, an isocyanate group or an alkoxy group, an aldehyde group for a carboxyl group, an amino group, an isocyanate group or an epoxy group, an isocyanate group or an aldehyde for an amino group. Compounds that have crosslinkable functional groups that react with each other in the same molecule, such as groups, hydroxy groups that react with the same crosslinkable functional groups (dehydration condensation), mercapto groups (disulfide bonds), ester groups (Claisen) (Condensation), silanol group (dehydration condensation), vinyl group, acryl group and the like. Specific examples of the crosslinking agent that self-crosslinks include at least one of a polyfunctional acrylate, a tetraalkoxysilane, a monomer having a blocked isocyanate group, a hydroxy group, a carboxylic acid, and an amino group that exhibit crosslinking reactivity in the presence of an acid catalyst. A block copolymer of a monomer having

Such a self-crosslinking cross-linking agent can also be obtained as a commercial product, and as such a commercial product, for example, polyfunctional acrylate, A-9300 (ethoxylated isocyanuric acid triacrylate, Shin-Nakamura Chemical Co., Ltd. ( Co., Ltd.), A-GLY-9E (Ethoxylated glycerine triacrylate (EO9mol), Shin-Nakamura Chemical Co., Ltd.), A-TMMT (pentaerythritol tetraacrylate, Shin-Nakamura Chemical Co., Ltd.), etc. Examples of tetraalkoxysilane include tetramethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.), tetraethoxysilane (manufactured by Toyoko Chemical Co., Ltd.), etc., and polymers having a blocked isocyanate group include Elastron series E-37, H-3, H38, BAP, NEW BAP-15, C-52, F-29, W-11P, MF-9, MF-25K (Daiichi Kogyo Seiyaku Co., Ltd.) and the like.

The amount of these crosslinking agents to be added varies depending on the solvent used, the substrate used, the required viscosity, the required film shape, etc., but is 0.001 to 80% by mass with respect to the dispersant, preferably 0.00. The amount is from 01 to 50% by mass, more preferably from 0.05 to 40% by mass. These cross-linking agents may cause a cross-linking reaction due to self-condensation, but they cause a cross-linking reaction with the dispersant. If a cross-linkable substituent is present in the dispersant, the cross-linking reaction is caused by these cross-linkable substituents. Is promoted.

In the present invention, as a catalyst for accelerating the crosslinking reaction, p-toluenesulfonic acid, trifluoromethanesulfonic acid, pyridinium p-toluenesulfonic acid, salicylic acid, sulfosalicylic acid, citric acid, benzoic acid, hydroxybenzoic acid, naphthalenecarboxylic acid And / or a thermal acid generator such as 2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyl tosylate, and organic sulfonic acid alkyl ester can be added. .

The addition amount of the catalyst is 0.0001 to 20% by mass, preferably 0.0005 to 10% by mass, and more preferably 0.001 to 3% by mass with respect to the conductive material dispersant.

The method for preparing the conductive material-containing composition is not particularly limited. For example, a conductive material such as CNT and a solvent, and a dispersant, a matrix polymer, and a crosslinking agent used as necessary are mixed in any order. can do.

At this time, it is preferable to disperse the mixture, and this treatment can further improve the dispersion ratio of the conductive material such as CNT. Examples of the dispersion treatment include mechanical treatment, wet treatment using a ball mill, bead mill, jet mill, or the like, and ultrasonic treatment using a bath type or probe type sonicator. Of these, wet processing and ultrasonic processing using a jet mill are preferred.

The time for the dispersion treatment is arbitrary, but is preferably about 1 minute to 10 hours, more preferably about 5 minutes to 5 hours. At this time, heat treatment may be performed as necessary. In addition, when using a crosslinking agent and / or matrix polymer, you may add these, after preparing the mixture which consists of electrically conductive materials, such as a dispersing agent, CNT, and a solvent.

The undercoat layer can be formed by applying the conductive material-containing composition to at least one surface of the current collecting substrate and drying it naturally or by heating. At this time, it is preferable to apply the conductive material-containing composition to the entire surface of the current collector substrate and form an undercoat layer on the entire surface of the current collector substrate. In addition, in this invention, what formed the undercoat layer in the at least one surface of the current collection board | substrate is also called undercoat foil.

In the present invention, the basis weight of the undercoat layer per one surface of the current collector substrate is set to 0 in order to efficiently join the undercoat foil and a metal tab described later by welding such as ultrasonic welding at the undercoat layer portion of the foil. .1g / m ² or less, preferably 0.09 g / m ² or less, and more preferably less than 0.05 g / m ^2.

On the other hand, in order to ensure the function of the undercoat layer and to obtain a battery having excellent characteristics with good reproducibility, the basis weight of the undercoat layer per surface of the current collecting substrate is preferably 0.001 g / m ² or more, more preferably 0.005 g / m ² or more, even more preferably 0.01 g / m ² or more, further preferably 0.015 g / m ² or more.

The thickness of the undercoat layer is not particularly limited as long as the weight per unit area is satisfied. However, in consideration of reducing the welding efficiency and the internal resistance of the obtained device, 0.01 to 10 μm is preferable, and 0.02 to 5 μm. Is more preferable, and 0.03 to 1 μm is even more preferable.

The basis weight of the undercoat layer in the present invention is the ratio of the mass (g) of the undercoat layer to the area (m ² ) of the undercoat layer. When the undercoat layer is formed in a pattern, the area is The area is only the undercoat layer and does not include the area of the current collector substrate exposed between the undercoat layers formed in a pattern.

For the mass of the undercoat layer, for example, a test piece of an appropriate size was cut out from the undercoat foil, and its mass W ⁰ was measured. Thereafter, the undercoat layer was peeled off from the undercoat foil, and the undercoat layer was peeled off. The subsequent mass W ¹ is measured and calculated from the difference (W ⁰ −W ¹ ), or the mass W ² of the current collecting substrate is measured in advance, and then the undercoat foil mass on which the undercoat layer is formed W ³ can be measured and calculated from the difference (W ³ −W ² ).

Examples of the method for peeling the undercoat layer include a method of immersing the undercoat layer in a solvent in which the undercoat layer is dissolved or swelled and wiping the undercoat layer with a cloth or the like.

The basis weight can be adjusted by a known method. For example, when the undercoat layer is formed by coating, the solid content concentration of the coating liquid (conductive material-containing composition) for forming the undercoat layer, the number of coatings, the clearance of the coating liquid inlet of the coating machine, etc. It can be adjusted by changing To increase the weight per unit area, increase the solid content concentration, increase the number of coatings, or increase the clearance. When it is desired to reduce the basis weight, the solid content concentration is decreased, the number of coatings is decreased, or the clearance is decreased.

Examples of the method for applying the conductive material-containing composition include spin coating, dip coating, flow coating, ink jet, spray coating, bar coating, gravure coating, slit coating, roll coating, and flexographic printing. Method, transfer printing method, brush coating, blade coating method, air knife coating method and the like. Of these, the inkjet method, casting method, dip coating method, bar coating method, blade coating method, roll coating method, gravure coating method, flexographic printing method, and spray coating method are preferable from the viewpoint of work efficiency and the like.

The temperature for heating and drying is arbitrary, but is preferably about 50 to 200 ° C, more preferably about 80 to 150 ° C.

[Active material layer]
As the active material, various active materials conventionally used for electrodes for energy storage devices can be used. For example, in the case of a lithium secondary battery or a lithium ion secondary battery, a chalcogen compound capable of adsorbing / leaving lithium ions or a lithium ion-containing chalcogen compound, a polyanion compound, a simple substance of sulfur and a compound thereof may be used as a positive electrode active material. it can.

Examples of the chalcogen compound that can adsorb and desorb lithium ions include FeS ₂ , TiS ₂ , MoS ₂ , V ₂ O ₆ , V ₆ O ₁₃ , and MnO ₂ .

Examples of the lithium ion-containing chalcogen compound include LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiMo ₂ O ₄ , LiV ₃ O ₈ , LiNiO ₂ , Li _x Ni _y M _1-y O ₂ (where M is Co Represents at least one metal element selected from Mn, Ti, Cr, V, Al, Sn, Pb, and Zn, 0.05 ≦ x ≦ 1.10, 0.5 ≦ y ≦ 1.0) Etc.

Examples of the polyanionic compound include lithium iron phosphate (LiFePO ₄ ). Examples of the sulfur compound include Li ₂ S and rubeanic acid.

On the other hand, as the negative electrode active material constituting the negative electrode, at least one element selected from alkali metals, alkali alloys, and elements of Groups 4 to 15 of the periodic table that occlude / release lithium ions, oxides, sulfides, nitrides Or a carbon material capable of reversibly occluding and releasing lithium ions can be used.

Examples of the alkali metal include Li, Na, K, and the like, and examples of the alkali metal alloy include Li—Al, Li—Mg, Li—Al—Ni, Na—Hg, Na—Zn, and the like.

Examples of the simple substance of at least one element selected from Group 4 to 15 elements of the periodic table that occlude and release lithium ions include silicon, tin, aluminum, zinc, and arsenic.

Similarly, examples of the oxide include tin silicon oxide (SnSiO ₃ ), lithium bismuth oxide (Li ₃ BiO ₄ ), lithium zinc oxide (Li ₂ ZnO ₂ ), and lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ). Can be mentioned.

Similarly, examples of the sulfide include lithium iron sulfide (Li _x FeS ₂ (0 ≦ x ≦ 3)) and lithium copper sulfide (Li _x CuS (0 ≦ x ≦ 3)).

Similarly as the nitrides, lithium-containing transition metal nitrides and the like, _{specifically, Li x M y N (M} = Co, Ni, Cu, 0 ≦ x ≦ 3,0 ≦ y ≦ 0.5), Examples thereof include lithium iron nitride (Li ₃ FeN ₄ ).

Examples of the carbon material capable of reversibly occluding and releasing lithium ions include graphite, carbon black, coke, glassy carbon, carbon fiber, carbon nanotube, and a sintered body thereof.

The thickness of the active material layer is preferably 10 to 500 μm, more preferably 10 to 300 μm, and even more preferably 20 to 100 μm in consideration of the balance between the capacity and resistance of the battery.

As the active material used in the present invention, those containing heavy atoms are preferable from the viewpoint of the sensitivity of XAFS measurement. In the present invention, the heavy atom means a metal atom heavier than scandium. As said active material, what contains heavy atoms, such as iron, nickel, lead, titanium, manganese, cobalt, tin, chromium, vanadium, zinc, ruthenium, is preferable. Of these, those containing iron atoms are preferred, and lithium iron phosphate is more preferred.

The active material layer can be formed by applying the electrode slurry containing the active material, the binder polymer, and, if necessary, the solvent described above on the undercoat layer and naturally or by heating and drying.

The formation part of the active material layer may be appropriately set according to the cell form of the device to be used, and may be all or part of the surface of the undercoat layer. Is used as an electrode structure joined by welding such as ultrasonic welding, it is preferable to form an active material layer by applying electrode slurry to a part of the surface of the undercoat layer in order to leave a weld. In particular, in a laminate cell application, it is preferable to form an active material layer by applying an electrode slurry to the remaining part of the undercoat layer other than the periphery.

The binder polymer can be appropriately selected from known materials and used, for example, PVdF, polyvinylpyrrolidone, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, P (VDF-HFP), P ( VDF-CTFE), polyvinyl alcohol, polyimide, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, CMC, polyacrylic acid (PAA), polyaniline, and other conductive polymers.

In addition, the addition amount of the binder polymer is preferably 0.1 to 20 parts by mass, particularly 1 to 10 parts by mass with respect to 100 parts by mass of the active material.

Examples of the solvent include the solvents exemplified in the conductive material-containing composition, and may be appropriately selected according to the type of the binder, but NMP is preferable in the case of a water-insoluble binder such as PVdF. In the case of a water-soluble binder such as PAA, water is preferable.

Note that the electrode slurry may contain a conductive additive. Examples of the conductive assistant include carbon black, ketjen black, acetylene black, carbon whisker, carbon fiber, natural graphite, artificial graphite, titanium oxide, ruthenium oxide, aluminum, nickel and the like.

As a method for applying the electrode slurry, the same method as that for the conductive material-containing composition described above can be used. The temperature for drying by heating is arbitrary, but is preferably about 50 to 400 ° C, more preferably about 80 to 150 ° C.

Also, the electrode can be pressed as necessary. As the pressing method, a generally adopted method can be used, but a die pressing method and a roll pressing method are particularly preferable. The press pressure in the roll press method is not particularly limited, but is preferably 0.2 to 3 ton / cm.

[Energy storage device]
The energy storage device of the present invention includes the above-described electrode for energy storage device, and more specifically, includes at least a pair of positive and negative electrodes, a separator interposed between these electrodes, and an electrolyte. And at least one of the positive and negative electrodes is composed of the above-described electrode for an energy storage device.

Examples of the energy storage device of the present invention include various energy storage devices such as a lithium ion secondary battery, a hybrid capacitor, a lithium secondary battery, a nickel hydride battery, and a lead storage battery.

Since this energy storage device is characterized by the use of the above-mentioned electrode for energy storage device as an electrode, other device constituent members such as separators and electrolytes may be appropriately selected from known materials and used. it can.

Examples of the separator include a cellulose separator and a polyolefin separator. The electrolyte may be either liquid or solid, and may be either aqueous or non-aqueous. The electrode for an energy storage device of the present invention is practically sufficient even when applied to a device using a non-aqueous electrolyte. Performance can be demonstrated.

Examples of the non-aqueous electrolyte include a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous organic solvent. Examples of electrolyte salts include lithium salts such as lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, and lithium trifluoromethanesulfonate; tetramethylammonium hexafluorophosphate, tetraethylammonium hexafluorophosphate, tetrapropylammonium Quaternary ammonium salts such as hexafluorophosphate, methyltriethylammonium hexafluorophosphate, tetraethylammonium tetrafluoroborate, tetraethylammonium perchlorate, lithium imides such as lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide, etc. Can be mentioned.

Examples of the non-aqueous organic solvent include alkylene carbonates such as propylene carbonate, ethylene carbonate, and butylene carbonate; dialkyl carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; nitriles such as acetonitrile; and amides such as dimethylformamide. .

The form of the energy storage device is not particularly limited, and it is possible to adopt various types of cells known in the art such as a cylindrical type, a flat wound rectangular type, a laminated square type, a coin type, a flat wound laminated type, and a laminated laminated type. it can.

When applied to a coin type, the above-described electrode for an energy storage device of the present invention may be used by punching it into a predetermined disk shape. For example, in a lithium ion secondary battery, a predetermined number of lithium foils punched into a predetermined shape are placed on a lid to which a coin cell washer and spacer are welded, and a separator of the same shape impregnated with an electrolyte is stacked thereon. Further, from above, the electrode for an energy storage device of the present invention can be overlaid with the active material layer down, and a case and a gasket can be placed thereon and sealed with a coin cell caulking machine.

When applied to the laminated laminate type, the electrode in which the active material layer is formed on a part of the surface of the undercoat layer has a metal in the portion (welded part) where the undercoat layer is formed and the active material layer is not formed. An electrode structure obtained by welding with a tab may be used. In this case, one or a plurality of electrodes constituting the electrode structure may be used, but generally a plurality of positive and negative electrodes are used. It is preferable that the plurality of electrodes for forming the positive electrode are alternately stacked one by one with the plurality of electrode plates for forming the negative electrode, and the separator described above is interposed between the positive electrode and the negative electrode. It is preferable to make it.

Even if the metal tab is welded at the welded portion of the outermost electrode of the plurality of electrodes, the metal tab is welded with the metal tab sandwiched between the welded portions of any two adjacent electrodes among the plurality of electrodes. Also good. The material of the metal tab is not particularly limited as long as it is generally used for energy storage devices, for example, metals such as nickel, aluminum, titanium, copper; stainless steel, nickel alloy, aluminum alloy, titanium alloy, Examples include alloys such as copper alloys. Among these, in consideration of welding efficiency, those including at least one metal selected from aluminum, copper and nickel are preferable. The shape of the metal tab is preferably a foil shape, and the thickness is preferably about 0.05 to 1 mm.

As the welding method, a known method used for metal-to-metal welding can be used. Specific examples thereof include TIG welding, spot welding, laser welding, ultrasonic welding, and the like. Since the undercoat layer has a basis weight particularly suitable for ultrasonic welding, it is preferable to join the electrode and the metal tab by ultrasonic welding.

As a technique of ultrasonic welding, for example, a plurality of electrodes are arranged between an anvil and a horn, a metal tab is arranged in a welded portion, and ultrasonic welding is applied to collect a plurality of electrodes. A technique of welding first and then welding a metal tab is exemplified.

In the present invention, in any method, not only the metal tab and the electrode are welded at the welded portion, but also the plurality of electrodes are formed with an undercoat layer and no active material layer is formed. The parts will be ultrasonically welded together. The pressure, frequency, output, processing time, and the like during welding are not particularly limited, and may be set as appropriate in consideration of the material used, the basis weight of the undercoat layer, and the like.

The electrode structure produced as described above is accommodated in a laminate pack, and after injecting the above-described electrolyte solution, heat sealing is performed to obtain a laminate cell.

The energy storage device thus obtained has at least one electrode structure including a metal tab and one or a plurality of electrodes, and the electrode includes a current collector substrate and the current collector. When an undercoat layer formed on at least one surface of the electric substrate and an active material layer formed on a part of the surface of the undercoat layer and a plurality of electrodes are used, The undercoat layer is formed and ultrasonically welded to each other at the portion where the active material layer is not formed, at least one of the electrodes is formed with the undercoat layer, and the active material layer is It has a configuration in which a metal tab is ultrasonically welded at a portion that is not formed.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example. The measuring devices and reagents used are as follows.
(1) Probe-type ultrasonic irradiation device (dispersion processing)
Device: Hielscher Ultrasonics UIP1000
(2) Wire bar coater (thin film production)
Equipment: PM-9050MC manufactured by SMT Co., Ltd.
(3) Charge / discharge measuring device (rechargeable battery evaluation)
Device: HJ1001SD8 manufactured by Hokuto Denko Corporation
(4) Micrometer (Binder and active layer thickness measurement)
Equipment: IR54 manufactured by Mitutoyo Corporation
(5) Homodisper (mixing of electrode slurry)
Apparatus: TK Robomix (with Homodisper 2.5 type (φ32)) (manufactured by Primics Co., Ltd.)
(6) Thin film swirl type high speed mixer (mixing of electrode slurry)
Equipment: Filmics type 40 manufactured by Primics Co., Ltd. (7) Rotating / revolving mixer (defoaming electrode slurry)
Equipment: Shintaro Awatori Ryotaro ARE-310
(8) Roll press device (electrode compression)
Equipment: Hosen Co., Ltd. ultra-compact desktop heat roll press HSR-60150H
(9) Scanning electron microscope (SEM)
Equipment: JEOL JSM-7400F

[1] Production of undercoat foil [Production Example 1]
As a dispersant, 0.50 g of PTPA-PBA-SO ₃ H represented by the following formula was dissolved in 43 g of 2-propanol as a dispersion medium and 6.0 g of water, and MWCNT (NC7000 manufactured by Nanocyl, outer diameter: 10 nm) was added to this solution. ) 0.50 g was added. PTPA-PBA-SO ₃ H was synthesized by the same method as in Synthesis Example 2 of International Publication No. 2014/042080. This mixture was subjected to ultrasonic treatment at room temperature (approximately 25 ° C.) for 30 minutes using a probe-type ultrasonic irradiation device to obtain a black MWCNT-containing dispersion liquid in which MWCNT was uniformly dispersed without a precipitate.
To 50 g of the obtained MWCNT-containing dispersion, 3.88 g of Aron A-10H (manufactured by Toagosei Co., Ltd., solid content concentration 25.8 mass%), which is an aqueous solution containing polyacrylic acid (PAA), and 2-propanol 46 .12 g was added and stirred to obtain an undercoat solution A.
The undercoat solution A is uniformly spread on an aluminum foil (thickness 15 μm) as a current collecting substrate with a wire bar coater (OSP30 manufactured by Matsuo Sangyo Co., Ltd., wet film thickness 30 μm), and then dried at 120 ° C. for 20 minutes to form an undercoat. A coat layer was formed to prepare an undercoat foil A. When the undercoat foil was torn and the cross section was observed by SEM, the thickness of the undercoat layer was about 250 nm.

[2] Production of electrode and lithium ion secondary battery using lithium iron phosphate (LFP) as an active material [Example 1]
17.3 g of LFP (manufactured by TATUNG FINE CHEMICALS) as an active material, 12.8 g of NMP solution of polyvinylidene fluoride (PVdF) as a binder (12% by mass, Kureha Co., Ltd., KF polymer L # 1120), as a conductive auxiliary agent Acetylene black (0.384 g) and NMP (9.54 g) were mixed with a homodisper at 3,500 rpm for 5 minutes. Next, the slurry was mixed for 60 seconds at a peripheral speed of 20 m / sec using a thin film swirl type high-speed mixer, and further defoamed at 2,200 rpm for 30 seconds with a rotating / revolving mixer, so that an electrode slurry (solid content concentration 48) was obtained. Mass%, LFP: PVdF: AB = 90: 8: 2 (mass ratio)).
After the obtained electrode slurry is uniformly spread on the undercoat foil A (wet film thickness 200 μm), it is dried at 80 ° C. for 30 minutes and then at 120 ° C. for 30 minutes to form an active material layer on the undercoat layer, Furthermore, an electrode having an active material layer thickness of 50 μm was produced by pressure bonding with a roll press.

The obtained electrode was punched into a disk shape having a diameter of 13 mm, and the mass was measured. Then, the electrode was vacuum-dried at 100 ° C. for 8 hours and transferred to a glove box filled with argon.
A lithium foil having a diameter of 15 mm and a thickness of 0.2 mm was installed in an HS type test cell (Hosen Co., Ltd.), and an electrolytic solution (manufactured by Kishida Chemical Co., Ltd., ethylene carbonate: diethyl carbonate = 1: 1). A separator (Selgard Co., Ltd., 2500) punched to a diameter of 16 mm, which was impregnated with (volume ratio), 1 mol / L of lithium hexafluorophosphate as an electrolyte, was stacked one by one. Further, the electrodes were stacked from the top with the surface coated with the active material facing down. Further, 0.2 mL of the electrolytic solution was dropped, and then the HS type test cell was sealed, and then allowed to stand for 24 hours to obtain a lithium ion secondary battery A for testing.

[Comparative Example 1]
An electrode was produced in the same manner as in Example 1 except that a solid aluminum foil without an undercoat layer was used, and a test lithium ion secondary battery B was produced using the electrode.

[3] Evaluation of lithium ion secondary battery [Example 2, Comparative Example 2]
Regarding the lithium ion secondary batteries A and B produced in Example 1 and Comparative Example 1, 0.5C (LFP capacity was set to 170 mAh / g) using a charge / discharge measuring apparatus, and a cutoff voltage of 4.50 V− After being activated by charging and discharging for 4 cycles at 2.00 V and room temperature, the battery was fully charged at 0.5 C, and further discharged to a discharge depth of 20% at 0.5 C.
The obtained lithium ion secondary battery was disassembled in a glove box, and the taken-out positive electrode was washed with diethyl carbonate and dried, and then sealed in an aluminum laminate bag. After activation, for imaging XAFS in the first cycle Samples of

In addition, three lithium ion secondary batteries were produced in the same manner as in Example 1 and Comparative Example 1, and 0.5C (the capacity of LFP was set to 170 mAh / g) using a charge / discharge measuring device. The battery was activated by charging and discharging for 5 cycles at a cutoff voltage of 4.50 to 2.00 V and room temperature. Subsequently, a full charge at 0.5C was performed for one cycle of complete discharge at 5C, and a sample that was further fully charged at 0.5C and discharged to a discharge depth of 20% at 5C was taken as a second cycle sample. In addition, after activation, a sample that was fully charged at 0.5C and fully discharged at 5C for 3 cycles, and further charged at 0.5C and discharged at 5C to a discharge depth of 20% was taken as a sample for the fourth cycle. In addition, after activation, a sample that was fully charged at 0.5 C and completely discharged at 5 C for 5 cycles, and further fully charged at 0.5 C and discharged to a discharge depth of 20% at 5 C was taken as a sample for the sixth cycle. About these samples, the sample for imaging XAFS was produced similarly to the above.

Imaging XAFS measurements were performed at the Ritsumeikan University SR Center BL-4. For the measurement, a two-dimensional detector for X-rays was used as a transmission intensity monitor in a transmission arrangement. Incident X-ray intensity was measured with an ion chamber. The spatial resolution was 26 μm. The area that can be observed by one measurement is 13 mm × 3 mm, and in order to grasp the reaction in the entire electrode having a diameter of 13 mm, three samples were measured for each sample. The measurement energy range is in the vicinity of the K absorption edge of iron (7,076 to 7,181 eV), the absorption spectrum is calculated with each element from the obtained transmission image of each energy, and the element of the detector corresponding to the position on the sample Each chemical state was determined. For discrimination of the chemical state, the K absorption edge energy of iron was used, and LiFePO ₄ and FePO ₄ were used as standard samples. The absorption edge energy of LiFePO ₄ was 718.6 eV, and the absorption edge energy of FePO ₄ was 713.6 eV. The absorption edge energy of FePO ₄ corresponds to the K absorption edge energy in the fully charged state, and the absorption edge energy of LiFePO ₄ corresponds to the K absorption edge energy in the fully discharged state.

FIG. 1 shows an imaging XAFS image of the positive electrode after disassembly, FIG. 2 shows a histogram of the absorption edge energy for all the measured regions, and Table 1 shows the half width of the histogram obtained from FIG.

As shown in FIG. 1, in the lithium ion secondary battery using the undercoat foil as the current collecting substrate manufactured in Example 1, the surface distribution of the valence of iron contained in the active material is extremely flat, It was found that the discharge progressed uniformly. On the other hand, in the lithium ion secondary battery using solid aluminum foil as the current collecting substrate produced in Comparative Example 1, spot-like reaction channels were observed, and it was found that charging and discharging proceeded unevenly. .

Furthermore, as shown in FIG. 2, in the lithium ion secondary battery using the undercoat foil as the current collecting substrate produced in Example 1, the histogram did not widen even after repeated cycles, whereas Comparative Example 1 In the lithium ion secondary battery using solid aluminum foil as the current collecting substrate manufactured in step 1, the histogram spreads. In the half width of the histogram shown in Table 1, in the lithium ion secondary battery using the solid aluminum foil, the half width of the initial histogram is as large as 0.60 eV, and the half width is increased with each cycle. However, in the lithium ion secondary battery using the undercoat foil, the half-value width of the initial histogram was as small as 0.56 eV, and the half-value width did not change greatly even when the cycle was repeated. This is because when the solid aluminum foil is used, the initial charge / discharge reaction is non-uniform, so repeating the cycle increases the non-uniformity and leads to deterioration of the battery. In the case of using the battery, the initial charge / discharge reaction is uniform, so that the uniformity is maintained even when the cycle is repeated, and the battery has a long life. In other words, by using an undercoat foil and having activated, the full width at half maximum in the first cycle of the discharge from the fully charged state to the discharge depth of 20% is set to | A−B | ÷ 8.4 or less, thereby extending the life. It was found that a lithium ion secondary battery can be obtained.

Claims (11)

1. An electrode for an energy storage device, comprising: a current collecting substrate; an undercoat layer formed on at least one surface of the current collecting substrate; and an active material layer formed on the undercoat layer,
   After activating the energy storage device produced using the electrode, the device was discharged from a fully charged state to a discharge depth of 20%.
   A two-dimensional distribution of K absorption edge energy of metal atoms other than lithium contained in the active material in the electrode is measured by X-ray absorption fine structure analysis with a resolution of 10 to 50 μm square;
   An electrode for an energy storage device in which the half width of a histogram obtained by setting the K absorption edge energy in a fully charged state as A and the K absorption edge energy in a fully discharged state as B is | AB− ÷ 8.4 or less.
2. The electrode for an energy storage device according to claim 1, wherein discharge is performed at 0.5 to 50 C from the fully charged state to a discharge depth of 20%.
3. The electrode for an energy storage device according to claim 1 or 2, wherein the active material contains an iron atom.
4. The electrode for an energy storage device according to claim 3, wherein the active material is lithium iron phosphate.
5. The electrode for an energy storage device according to any one of claims 1 to 4, wherein the undercoat layer contains a conductive material.
6. The electrode for an energy storage device according to claim 5, wherein the conductive material includes carbon nanotubes.
7. The electrode for an energy storage device according to claim 6, wherein the undercoat layer contains a carbon nanotube dispersant.
8. The electrode for an energy storage device according to claim 7, wherein the carbon nanotube dispersant is a triarylamine hyperbranched polymer or a vinyl polymer containing an oxazoline group in a side chain.
9. The electrode for an energy storage device according to any one of claims 1 to 8, wherein the undercoat layer contains a matrix polymer.
10. The electrode for an energy storage device according to any one of claims 1 to 9, wherein the current collecting substrate is an aluminum foil or a copper foil.
11. An energy storage device comprising the energy storage device electrode according to any one of claims 1 to 10.

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