JP2017149920A - Conductive composition, collector with base layer for power storage device, electrode for power storage device and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive composition for forming a power storage device, which gives excellent conductivity and safety function to a power storage device, the power storage device having excellent conductivity in a normal operation and thereby having excellent output characteristics and long-term reliability, as well as having a function of increasing an internal resistance when an inner temperature of the power storage device elevates.SOLUTION: The conductive composition comprises a conductive carbon material (A), water-dispersed resin fine particles (B) comprising olefin resin fine particles which are neutralized with an amine compound having a boiling point of 100°C or higher and are modified with a compound containing a carbonyl group, and an aqueous liquid medium (C). In the solid content of the conductive composition, the conductive carbon material (A) is included by 20 to 70 mass% and the water-dispersed resin fine particles (B) are included by 20 to 60 mass%; and a water dispersion containing the water-dispersed resin fine particles (B) by 10 to 60 mass% in terms of a solid content shows a pH of 5.0 to 8.5.SELECTED DRAWING: None

Description

  The present invention relates to a conductive composition, an electrode for an electricity storage device obtained using the composition, and an electricity storage device obtained using the electrode. Specifically, the present invention relates to a conductive composition, a power storage device electrode, and a power storage device having a function of increasing the internal resistance of the power storage device when the temperature of the power storage device rises.

  In recent years, small portable electronic devices such as digital cameras and mobile phones have been widely used. These electronic devices have always been required to minimize the volume and reduce the weight, and in the installed power storage device, it is required to realize a small, lightweight and large capacity power storage device. Yes. In particular, lithium-ion secondary batteries have a higher energy density than water-based secondary batteries such as lead-acid batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. In addition, it is expected to be preferably used as a high-output power source mounted on a vehicle.

  Lithium ion secondary batteries, while having the advantage of high energy density, use a non-aqueous electrolyte, so a sufficient countermeasure for safety is required. In recent years, ensuring the safety has become a major issue as the size and capacity of batteries increase. For example, if the battery temperature rises abnormally and suddenly due to overcharging or a short circuit inside the battery, it is difficult to control the heat generation with only the safety mechanism provided outside the battery, and it ignites. There is a risk.

  Patent Document 1 describes a method of joining an electron conductive material having a function of a positive temperature coefficient resistor (hereinafter referred to as PTC) to a current collector. However, since the thickness of the electron conductive material is as thick as 50 μm, there is a problem that the energy density of the whole battery is lowered.

  Patent Document 2 discloses that any of a positive electrode, a negative electrode, and a non-aqueous electrolyte has PTC characteristics. However, in order to impart PTC characteristics to these, it is necessary to add a large amount of additives that do not contribute to battery capacity, resulting in a decrease in energy density.

  Patent Document 3 describes a method of providing a conductive layer made of a crystalline thermoplastic resin, a conductive agent, and a binder on the surface of a current collector. In this conductive layer, when the temperature in the battery exceeds the melting point of the crystalline thermoplastic resin, the resistance of the conductive layer increases and the current between the current collector and the active material is interrupted. However, there is a problem in that the internal resistance during normal operation of the battery increases, and the output characteristics of the battery deteriorate.

  Patent Document 4 describes a method in which a conductive layer made of polyvinylidene fluoride and a conductive agent is provided on the current collector surface, and the current collector provided with the conductive layer is heated at a temperature exceeding 120 ° C. However, in addition to an additional heat treatment step, there is a problem that the resistance rise when the temperature in the battery rises is not sufficient.

  Patent Document 5 describes a method for producing a current collector provided with a conductive layer made of conductive carbon and a fine particle binder neutralized with a neutralizing agent. However, since the content of the particulate binder with respect to the conductive carbon is small, it tends to result in insufficient PTC characteristics.

JP-A-10-241665 JP 11-329503 A JP 2001-357854 A JP 2012-104422 A JP 2014-137915 A

As a result of intensive studies, the present inventors have found that when a neutralized fine particle binder as in Patent Document 5 is used, the conductivity and long-term reliability of the electricity storage device are reduced depending on the type of the neutralizing agent. I understood.
For example, it was found that when a fine particle binder neutralized with sodium hydroxide is used, the internal resistance increases due to the high hygroscopic property unique to sodium hydroxide, and the output characteristics of the electricity storage device deteriorate. On the other hand, when a fine particle binder neutralized with an amine compound having a boiling point of 100 ° C. or less, such as ammonia, is used, the ammonia is volatilized, so that the fine particle binder aggregates, and the conductive composition has long-term storage stability. It turns out that it gets worse. Further, when a fine particle binder neutralized with an amine compound having a boiling point of 100 ° C. or higher, such as dimethylaminoethanol, is used, the storage degradation of the electricity storage device may occur due to oxidative decomposition of the amine remaining in the underlayer. I understood.

  The purpose of the present invention is excellent in the electrical conductivity during normal operation, so that the output characteristics of the electricity storage device are excellent, and since there is no influence of the amine compound remaining in the underlayer, the long-term reliability of the electricity storage device is excellent. Furthermore, when the internal temperature of the electricity storage device rises, a conductive composition for forming an electricity storage device (for example, a lithium ion secondary battery) having a function of increasing the internal resistance, An object is to provide a conductive composition having excellent conductivity, long-term reliability, and safety function.

A conductive carbon material (A), water-dispersed resin fine particles (B) containing olefin resin fine particles modified with a compound containing a carbonyl group neutralized with a neutralizing agent, and an aqueous liquid medium (C) The conductive composition is included, and when the electricity storage device generates heat, the resistance of the current collector increases and the current is interrupted to avoid ignition of the electricity storage device.
Furthermore, by controlling the solid content of the water-dispersed resin fine particles (B) in the conductive composition, the neutralizing agent, and the pH, an increase in resistance when the temperature in the electricity storage device rises can be effectively expressed, and In addition to reducing the internal resistance during normal operation and improving the output characteristics, the electrode underlayer contains almost no amine compound, so that an electricity storage device with excellent long-term reliability can be provided.
In addition, the amine compound can be removed from the electrode underlayer by appropriately controlling the drying temperature of the current collector with the underlayer formed from the conductive composition, and the battery has excellent output characteristics and long-term reliability. A device can be provided.

That is, the present invention relates to water-dispersed resin fine particles comprising conductive carbon material (A) and olefin resin fine particles neutralized with an amine compound having a boiling point of 100 ° C. or higher and modified with a compound containing a carbonyl group ( A conductive composition comprising B) and an aqueous liquid medium (C),
In the solid content of the conductive composition, the conductive carbon material (A) is 20 to 70% by mass, and the water-dispersed resin fine particles (B) are 20 to 60% by mass,
Furthermore, it is related with the electroconductive composition characterized by the pH of the aqueous dispersion which is solid content 10-60 mass% of water dispersion resin microparticles | fine-particles (B) being 5.0-8.5.
In addition, the present invention relates to the conductive composition, wherein the compound containing a carbonyl group contains at least a carboxylic acid or a carboxylic acid ester.
Further, the present invention relates to the conductive composition, further comprising 10 to 50% by mass of a water-soluble resin (D) with respect to 100% by mass of the solid content of the conductive composition.
Further, the present invention relates to the conductive composition, which is used for forming a base layer of an electrode for an electricity storage device.
Further, the present invention relates to a current collector with an underlayer for an electricity storage device, which includes a current collector and an underlayer formed from the conductive composition.
Further, the present invention relates to an electrode for an electricity storage device having a current collector, an underlayer formed from the conductive composition, and a composite layer formed from an electrode forming composition containing an electrode active material and a binder.
The present invention also relates to an electricity storage device including a positive electrode, a negative electrode, and an electrolytic solution, wherein at least one of the positive electrode or the negative electrode is the electrode for the electricity storage device.
Further, the conductive carbon material (A), water-dispersed resin fine particles (B) containing olefin resin fine particles neutralized with an amine compound having a boiling point of 100 ° C. or more and modified with a compound containing a carbonyl group, A method for producing a current collector with an underlayer for an electricity storage device, wherein the drying temperature of the current collector with an underlayer formed from a conductive composition containing an aqueous liquid medium (C) is 130 to 250 ° C About.

A conductive carbon material (A), water-dispersed resin fine particles (B) containing olefin resin fine particles modified with a compound containing a carbonyl group neutralized with a neutralizing agent, and an aqueous liquid medium (C) By including, the electrical storage device provided with the function to raise internal resistance when the internal temperature of an electrical storage device rises can be provided.
Furthermore, since the base layer formed on the current collector contains almost no amine compound, it is possible to provide a power storage device that improves output characteristics without impairing the long-term reliability of the power storage device.

<Conductive composition>
As described above, the conductive composition of the present invention can be used for forming a base layer of an electricity storage device. The conductive composition contains a conductive carbon material (A), water-dispersed resin fine particles (B) containing modified olefin resin fine particles neutralized with a neutralizing agent, and an aqueous liquid medium (C). .
In the case where the conductive carbon material (A) in the conductive composition is dispersed, it is preferable to use a surfactant from the viewpoint of the solid content of the conductive composition. It is more preferable to use a water-soluble resin (D) from the viewpoint of increasing resistance.
In the total 100% by mass of the solid content of the conductive composition, the content of the conductive carbon material (A) is 20 to 70 from the viewpoint of conductivity and internal resistance, and increase in internal resistance of the electricity storage device during heat generation. It is 20 mass%, Preferably it is 20-50 mass%.
The content of the water-dispersed resin fine particles (B) including the modified olefin resin fine particles neutralized with a neutralizing agent in the total solid content of 100% by mass of the conductive composition is determined by internal resistance, conductivity, and heat generation. From the viewpoint of increasing the internal resistance of the electricity storage device, the content is 20 to 60% by mass, preferably 30 to 60% by mass.
The total amount of the water-dispersed resin fine particles (B) containing the conductive carbon material (A) and the modified olefin resin fine particles neutralized with the neutralizing agent in the total 100 mass% of the solid content of the conductive composition is: From the viewpoint of internal resistance and conductivity, and increase in internal resistance of the electricity storage device during heat generation, it is preferably 50% or more, and more preferably 70% or more.
The content of the water-soluble resin (D) in the total solid content of 100% by mass of the conductive composition is preferably 10 from the viewpoints of electrode adhesion and conductivity, and an increase in internal resistance of the electricity storage device during heat generation. It is -50 mass%, More preferably, it is 10-40 mass%, More preferably, it is 15-35 mass%.
The pH of the conductive composition is preferably 5.0 to 9.0, more preferably 6.0 to 8.5, from the viewpoint of corrosion of the current collector and deterioration due to redox of the electricity storage device.
Moreover, although the appropriate viscosity of an electroconductive composition is based on the coating method of an electroconductive composition, generally it is preferable to set it as 10 mPa * s or more and 30,000 mPa * s or less.

First, the conductive carbon material (A) will be described.
The conductive carbon material (A) in the present invention is not particularly limited as long as it is a conductive carbon material, but graphite, carbon black, conductive carbon fiber (carbon nanotube, carbon nanofiber, carbon Fiber), fullerene, etc. can be used alone or in combination of two or more. From the viewpoint of conductivity, availability, and cost, it is preferable to use carbon black.

  Carbon black is a furnace black produced by continuously pyrolyzing a gas or liquid raw material in a reactor, especially ketjen black using ethylene heavy oil as a raw material. Channel black that has been rapidly cooled and precipitated, thermal black obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, and particularly various types such as acetylene black using acetylene gas as a raw material, or 2 More than one type can be used in combination. Ordinarily oxidized carbon black, hollow carbon and the like can also be used.

  The oxidation treatment of carbon is performed by treating carbon at a high temperature in the air or by secondary treatment with nitric acid, nitrogen dioxide, ozone, etc., for example, such as phenol group, quinone group, carboxyl group, carbonyl group. This is a treatment for directly introducing (covalently bonding) an oxygen-containing polar functional group to the carbon surface, and is generally performed to improve the dispersibility of carbon. However, it is preferable to use carbon that has not been oxidized from the viewpoint of conductivity.

As the specific surface area of the carbon black used in the present invention is larger, the number of contact points between the carbon black particles increases, which is advantageous in reducing the internal resistance of the electrode. Specifically, from the viewpoint of conductivity and easy availability, the specific surface area (BET) determined from the amount of nitrogen adsorption is preferably 20 to 1500 m ² / g, more preferably 40 to 1500 m ² / g. It is desirable to use something. Further, the particle size of the carbon black to be used is preferably 0.005 to 1 μm, particularly preferably 0.01 to 0.2 μm in terms of primary particle size. However, the primary particle diameter here is an average of the particle diameters measured with an electron microscope or the like.

The dispersed particle diameter of the conductive carbon material (A) in the conductive composition is 0.03 μm or more from the viewpoint of difficulty in preparing the composition, variation in the material distribution of the coating film, and variation in the resistance distribution of the electrode, It is desirable to reduce the size to 5 μm or less.
The dispersed particle size referred to here is a particle size (D50) that is 50% when the volume ratio of the particles is integrated from the fine particle size distribution in the volume particle size distribution. A particle size distribution meter such as a dynamic light scattering type particle size distribution meter ("Microtrack UPA" manufactured by Nikkiso Co., Ltd.).

Examples of commercially available carbon black include Toka Black # 4300, # 4400, # 4500, # 5500 (Tokai Carbon Co., Furnace Black), Printex L and the like (Degussa Co., Furnace Black), Raven 7000, 5750, 5250, 5000 ULTRA III, 5000 ULTRA, etc., Conductex SC ULTRA
, Conductex 975 ULTRA, etc., PUER BLACK100, 115, 2
05, etc. (Colombian, Furnace Black), # 2350, # 2400B, # 2600B, # 30050B, # 3030B, # 3230B, # 3350B, # 3400B, # 5400B, etc. (Mitsubishi Chemical Corporation, Furnace Black), MONARCH1400, 1300, 900, Vulcan XC-72R, BlackPearls 2000, etc. (Cabot, Furnace Black), Ensaco 250G, Ensaco 260G, Ensaco 350G, SuperP-Li (manufactured by TIMCAL), Ketjen Black EC-300J, EC-600JD (manufactured by Akzo) Examples of graphite such as Denka Black, Denka Black HS-100, FX-35 (manufactured by Denki Kagaku Kogyo Co., Ltd., acetylene black) include artificial graphite and flakes Lead, massive graphite, there may be mentioned natural graphite such as earthy graphite, is not limited thereto, it may be used in combination of two or more.
As the conductive carbon fibers, those obtained by firing from petroleum-derived raw materials are preferable, but those obtained by firing from plant-derived raw materials can also be used. For example, VGCF manufactured by Showa Denko Co., Ltd. manufactured with petroleum-derived raw materials can be mentioned.

Next, the water-dispersed resin fine particles (B) containing the modified olefin resin fine particles neutralized with the neutralizing agent will be described.
The water-dispersed resin fine particles (B) used in the present invention are generally called water-based emulsions, meaning that the resin particles are not dissolved in water but are dispersed in the form of fine particles.
The water-dispersed resin fine particles include at least olefin-based resin fine particles, and the ratio of the olefin-based resin fine particles contained in the water-dispersed resin fine particles is preferably 50 to 100% by mass, more preferably 60 to 100% by mass as the solid content. Yes, more preferably 70 to 100% by mass. If necessary, water-dispersed resin fine particles other than the olefin resin fine particles may be combined. Water-dispersed resin fine particles other than olefin resin fine particles are not particularly limited, but (meth) acrylic emulsions, nitrile emulsions, urethane emulsions, diene emulsions (SBR, etc.), fluorine emulsions (PVDF, PTFE, etc.), etc. These may be used in combination of two or more.

  The water-dispersed resin fine particles are particularly limited as long as the resin expands in volume within a range of 80 to 180 ° C. and can peel the contact between the conductive carbon materials dispersed in the conductive layer. Is not to be done. Examples of the olefin component of the polyolefin resin include ethylene, propylene, isobutylene, isobutene, 1-butene, 2-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-hexene, Examples thereof include 1-octene and norbonene. A single polymer of these olefin components may be used, and a copolymer of two or more components may be used.

  In the present invention, the olefin resin fine particles contained in the water-dispersed resin fine particles (B) contain at least one modified with a carboxylic acid or a carboxylic acid ester. Since the melting resistance of the resin can be imparted by modification, the volume expansion of the polyolefin resin can be maintained when the internal temperature of the electricity storage device rises due to an internal short circuit or the like, and the cutting effect between the carbon materials can be maintained. Conceivable.

  Although it does not specifically limit as a component of carboxylic acid or carboxylic acid ester, Acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic anhydride, itaconic acid, fumaric acid, crotonic acid, methyl acrylate, (meth) acrylic acid Methyl, ethyl (meth) acrylate, propyl (meth) acrylate, butyl acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, (meth ) Dodecyl acrylate, stearyl (meth) acrylate, vinyl formate, vinyl acetate, vinyl propionate, vinyl piperate.

The amount of modification of the polyolefin resin fine particles modified as described above can be determined by a total reflection measurement method (ATR) using a Fourier transform infrared spectrometer (FT-IR: Spectrum One / 100 manufactured by PerkinElmer), and can be determined from 2800 to 3000 cm. ^-1 olefin-derived maximum peak height (maximum absorbance) (X) and the carbonyl-derived maximum peak height (maximum absorbance) (Y) of 1690-1740 cm ^-1 (Y) / (X) It is preferable that it is 0.05-1.0. In the resin fine particles made of polyethylene, the above (Y) / (X) is 0.3 to 0.8, and in the resin fine particles made of polypropylene, the above (Y) / (X) is 0.05 to 0.8. More preferably, it is 0.5.
The peak height referred to here is a value obtained by measuring a solid obtained by removing the dispersion medium from the water-dispersed resin fine particles (C) and finally drying at 120 ° C. by FT-IR. The amount of modification of the polyolefin resin fine particles was determined by using a spectrum in which the absorbance was plotted against the wave number, and a line connecting the two points of the absorbance at 2700 m ^{−1 and} the absorbance at 3000 cm ⁻¹ was defined as the baseline BX. Among the two or four derived from olefins observed at 2800 to 3000 cm ⁻¹ , the height (maximum absorbance) (X) from the maximum peak to the baseline BX, and the point indicating the absorbance at 1650 m ⁻¹ Height from the maximum peak derived from the carbonyl of 1690 to 1740 cm ^-1 to the baseline BY (maximum absorbance) when the straight line connecting the two points with the point indicating the absorbance at 1850 cm ^-1 is defined as the baseline BY (Y) And the ratio (Y) / (X). In general, two polyethylene resins and four polypropylene resins are observed, and the maximum peak is observed in the vicinity of 2915 cm ^{-1 in} both cases.

In the present invention, the water-dispersed resin fine particles (B) include water-dispersed resin fine particles neutralized with a neutralizing agent. The neutralization in the present invention means that at least a part of an acidic group such as carboxylic acid or carboxylic acid ester is reacted with a basic compound. By neutralizing, it becomes possible to exist in the state of an emulsion in a solvent such as water, and good dispersion stability can be obtained.
Examples of the amine compound having a boiling point of 100 ° C. or higher used as the neutralizing agent include hexylamine (130 ° C.), 2-ethylhexylamine (169 ° C.), 3-ethoxypropylamine (132 ° C.), 3-lauryloxypropylamine, 3 -Methoxypropylamine (120 ° C), 3-aminopropanol (188 ° C), 2-piperidineethanol (131 ° C), dimethylaminoethanol (133 ° C), aminomethylpropanol (165 ° C), ethanolamine (170 ° C), Examples include triethanolamine (208 ° C.) and morpholine (129 ° C.).
When using an amine compound having a high boiling point, it is important to control the pH of the water-dispersed resin fine particles (B) during neutralization, and the pH is 5.0 to 8.5. When the pH is 8.5 or less, almost no amine remains in the coating film, so that good electricity storage device storage characteristics can be obtained. Moreover, if pH is 5.0 or more, the dispersion stability of water-dispersed resin microparticles | fine-particles can be hold | maintained by electrostatic repulsion of an anion.
In the case of neutralization, an amine compound having a boiling point of 100 ° C. or more may be added from the beginning so that the pH is 5.0 to 8.5, and after adding an excessive amount, the pH is 5.0 to 8. You may remove so that it may be set to 5. Further, after removing an excessive amount of the amine compound having a boiling point of 100 ° C. or higher, a neutralizing agent may be newly added so that the pH becomes 5.0 to 8.5. An amine compound or an alkali metal hydroxide having a boiling point of 100 ° C. or less may be added as a neutralizing agent.
Examples of the amine compound having a boiling point of 100 ° C. or lower include ammonia, diethylamine, triethylamine, trimethylamine, butylamine, isopropylamine, isoamylamine, isobutylamine, 2-methoxyethylamine, 2-ethylhexylpropylamine and the like.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and examples of the alkaline earth metal hydroxide include beryllium hydroxide, magnesium hydroxide, and calcium hydroxide.
The method for removing the amine compound can be removed by washing by ultrafiltration, an ion exchange method, or the like, but is not limited thereto.

  The dispersion medium of the water-dispersed resin fine particles (B) of the present invention is an aqueous dispersion medium, and it is preferable to use water. However, in order to stabilize the resin fine particles, a liquid medium compatible with water is used. Also good. Liquid media compatible with water include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, and phosphoric acid esters , Ethers, nitriles and the like, and may be used as long as they are compatible with water. The content of the liquid medium compatible with water is preferably 50% by mass or less, more preferably 30% by mass or less, and still more preferably in 100% by mass of the total dispersion medium of the water-dispersed resin fine particles (B). It is 20 mass% or less.

  The pH of the neutralized water-dispersed resin fine particles (B) means a value measured with a pH meter. Specifically, a dispersion obtained by dispersing the water-dispersed resin fine particles (B) at a solid content of 10 to 60% by mass in the above-mentioned aqueous dispersion medium is prepared in a pH meter (Horiba, Ltd.) in an environment at a liquid temperature of 25 ° C. Measured with D-54). When using a liquid medium that is compatible with water as the dispersion medium of the water-dispersed resin fine particles (B), from the viewpoint of pH measurement, the water-dispersed resin fine particles (B) are dispersed in a total of 100% by weight of the dispersion medium. The content of the dissolved liquid medium is measured at 50% or less.

  Commercially available products can be used as the olefin-based resin fine particles contained in the water-dispersed resin fine particles (B) as described above. As commercial products, Arrow Base SB-1200, SD-1200, SE- manufactured by Unitika Co., Ltd. are used. Chemipearls S100, S200, S300, V100, V200, V300 manufactured by Mitsui Chemicals, Inc. , Harden NZ-1004, NZ-1015 manufactured by Toyobo Co., Ltd., Hitech S-3121 manufactured by Toho Chemical Co., Ltd., etc., but are not limited to these and may be used in combination of two or more. The amine compound may be added or removed accordingly.

  The average particle diameter of the water-dispersed resin fine particles (B) used in the present invention is preferably 0.01 to 5 μm from the viewpoints of productivity, stability with time of the resin fine particles or the conductive composition, and internal resistance of the electricity storage device. Furthermore, 0.05-1 micrometer is further more preferable.

  In addition, the average particle diameter in this invention represents a volume average particle diameter (D50), and can be measured by the dynamic light scattering method. The average particle diameter can be measured by the dynamic light scattering method as follows. The water-dispersed resin fine particle dispersion is diluted with water 200 to 1000 times depending on the solid content. About 5 ml of the diluted solution is injected into a cell of a measuring device [Nanotrack manufactured by Nikkiso Co., Ltd.], and after inputting the refractive index conditions of the solvent (water in the present invention) and the resin according to the sample, the measurement is performed.

Next, the aqueous liquid medium (C) will be described.
As the aqueous liquid medium (C) used in the present invention, it is preferable to use water, but if necessary, for example, a liquid medium compatible with water in order to improve the coating property to the current collector. May be used.

  Liquid media compatible with water include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, and phosphoric acid esters , Ethers, nitriles and the like, and may be used as long as they are compatible with water.

  Furthermore, a surfactant, a film forming aid, an antifoaming agent, a leveling agent, a preservative, a pH adjusting agent, a viscosity adjusting agent, and the like can be added to the conductive composition as necessary.

  The surfactant used in the present invention is not particularly limited as long as it can disperse a conductive carbon material. For example, nonionic surfactants include ester types such as glycerin fatty acid esters, polyoxygens, and the like. Examples include ether types such as ethylene alkylphenyl ether, and ionic surfactants such as anionic surfactants such as monoalkyl sulfates and alkylbenzene sulfonates, and cationic surfactants such as dialkyldimethylammonium. Examples thereof include salts and alkylbenzyldimethylammonium salts, but are not limited to these, and two or more kinds may be used in combination.

Next, water-soluble resin (D) is demonstrated.
The water-soluble resin (D) of the present invention is a mixture of 1 g of water-soluble resin (D) in 99 g of water at 25 ° C., stirred, and allowed to stand at 25 ° C. for 24 hours. It can be dissolved.

The water-soluble resin (D) is not particularly limited as long as it is a water-soluble resin as described above. For example, an acrylic resin, a polyurethane resin, a polyester resin, a polyamide resin, a polyimide resin, a polyallylamine resin, Examples include phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, formaldehyde resins, silicone resins, fluororesins, and polymer compounds containing polysaccharide resins such as carboxymethylcellulose. In view of the stability of the slurry and the cost, the use of carboxymethyl cellulose is preferred.
Moreover, if it is water-soluble, the modified substance, mixture, or copolymer of these resin may be sufficient. These water-soluble resins can be used alone or in combination.
Although the molecular weight of water-soluble resin (D) is not specifically limited, Preferably a mass mean molecular weight is 5,000-2,000,000. The mass average molecular weight (Mw) indicates a molecular weight in terms of polystyrene in gel permeation chromatography (GPC).

(Disperser / Mixer)
As an apparatus used when obtaining the conductive composition of the present invention or a composite ink described later, a disperser or a mixer that is usually used for pigment dispersion or the like can be used.
For example, mixers such as dispersers, homomixers, or planetary mixers; homogenizers such as “Clearmix” manufactured by M Technique, or “fillmix” manufactured by PRIMIX; paint conditioner (manufactured by Red Devil), ball mill, sand mill (Shinmaru Enterprises "Dynomill", etc.), Attritor, Pearl Mill (Eirich "DCP Mill", etc.), or Coball Mill, etc .; Media type dispersers; Wet Jet Mill (Genus, "Genus PY", Sugino Media-less dispersers such as “Starburst” manufactured by Machine, “Nanomizer” manufactured by Nanomizer, etc., “Claire SS-5” manufactured by M Technique, or “MICROS” manufactured by Nara Machinery; or other roll mills, etc. Although The present invention is not limited to these. Moreover, as the disperser, it is preferable to use a disperser that has been subjected to a metal contamination prevention treatment from the disperser.
For example, when using a media-type disperser, a disperser in which the agitator and vessel are made of a ceramic or resin disperser, or the surface of the metal agitator and vessel is treated with tungsten carbide spraying or resin coating. Is preferably used. As the media, it is preferable to use glass beads, ceramic beads such as zirconia beads or alumina beads. Moreover, also when using a roll mill, it is preferable to use a ceramic roll. Only one type of dispersion device may be used, or a plurality of types of devices may be used in combination. Further, in the case of a positive or negative electrode active material in which particles are easily broken or crushed by a strong impact, a medialess disperser such as a roll mill or a homogenizer is preferable to a media type disperser.

(Current collector with base layer for electricity storage device, electrode for electricity storage device)
The current collector with an underlayer for an electricity storage device of the present invention has an underlayer formed from the conductive composition of the present invention on the current collector.
The electrode for an electricity storage device of the present invention has, on a current collector, an underlayer formed from the conductive composition of the present invention and a composite layer formed from a composite ink described later.

(Current collector)
The material and shape of the current collector used for the electrode are not particularly limited, and those suitable for various power storage devices can be appropriately selected.
For example, examples of the material for the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. In the case of a lithium ion battery, aluminum is particularly preferable as the positive electrode material, and copper is preferable as the negative electrode material. In general, a flat foil is used as the shape, but a roughened surface, a perforated foil, or a mesh current collector can also be used.

  There is no restriction | limiting in particular as a method of apply | coating an electroconductive composition on a collector, A well-known method can be used. Specific examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method, and an electrostatic coating method.

  As the drying method, standing drying, blower dryer, hot air dryer, infrared heater, far infrared heater, vacuum dryer, and the like can be used, but are not particularly limited thereto.

The drying temperature should just be a temperature which can remove the aqueous liquid medium (C) in the electrically conductive composition apply | coated to the electrical power collector, and is generally 50-300 degreeC as drying temperature.
When the pH of the water-dispersed resin fine particles (B) is 8.5 or less, the drying temperature is not particularly limited as long as the aqueous liquid medium (C) can be removed.
On the other hand, when the pH of the water-dispersed resin fine particles (B) neutralized with the amine compound is 8.5 or more, the drying temperature is 130 to 250 ° C, preferably 150 to 200 ° C. If the drying temperature is 130 ° C. or higher, excess amine contained in the conductive underlayer volatilizes and the content is greatly reduced, so that an electricity storage device having excellent storage characteristics can be obtained. Further, from the viewpoint of battery characteristics and productivity, the drying temperature is 250 ° C. or lower. The method for removing the aqueous liquid medium (C) and the amine compound by drying is not particularly limited, but it may be a one-step process in which the aqueous liquid medium (C) and the amine compound are simultaneously removed at 130 to 250 ° C. After removing the aqueous liquid medium (C), the amine compound may be removed at 130 to 250 ° C.
As described above, the amine can be removed from the water-dispersed resin fine particles (B) by ultrafiltration or ion exchange, or by high-temperature drying during formation of the conductive underlayer. Ultrafiltration and ion exchange methods enable stable quality control, but the manufacturing process is complicated. On the other hand, high-temperature drying of the conductive base layer may impose restrictions on the drying equipment. From the viewpoint of cost, quality control, etc., these can be used properly as necessary.

  The thickness of the underlayer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm. If the thickness of the underlayer is too thin, a bypass portion where the current collector and the active material are in direct contact is locally formed, and when the electricity storage device generates heat, the current blocking effect due to the increase in resistance of the underlayer portion is insufficient. Become. On the other hand, if the thickness of the underlayer is too thick, the ratio of the underlayer to the electrodes increases, the active material content ratio decreases, and the capacity of the electricity storage device decreases.

(Composite ink)
A general ink mixture (electrode-forming composition) for an electricity storage device essentially contains an active material and a solvent, and contains a conductive additive and a binder as necessary.
The active material is preferably contained as much as possible. For example, the proportion of the active material in the solid material ink solid content is preferably 80 to 99% by mass. When the conductive assistant is included, the proportion of the conductive assistant in the solid ink solid content is preferably 0.1 to 15% by mass. When the binder is included, the ratio of the binder to the solid material ink solid content is preferably 0.1 to 15% by mass.

  Although it depends on the coating method, the viscosity of the composite ink is preferably 100 mPa · s or more and 30,000 mPa · s or less in the range of 30 to 90% by mass of the solid content.

  There is no restriction | limiting in particular as a method of apply | coating mixed-material ink to a collector, A well-known method can be used. Specific examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method, or an electrostatic coating method. As drying methods, standing drying, blow dryer, hot air dryer, infrared heater, far-infrared heater, vacuum dryer, etc. can be used. However, the drying method is not particularly limited. You may perform the rolling process by a roll etc.

(Active material)
The active material used in the composite ink will be described below.
The positive electrode active material is not particularly limited, and metal oxides that can be doped or intercalated with lithium ions, metal compounds such as metal sulfides, conductive polymers, and conductive carbon can be used. .

Examples thereof include transition metal oxides such as Fe, Co, Ni, and Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides. Specifically, transition metal oxide powders such as MnO, V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , layered structure lithium nickelate, lithium cobaltate, lithium manganate, spinel structure lithium manganate, etc. Examples thereof include composite oxide powders of lithium and transition metals, lithium iron phosphate materials that are phosphate compounds having an olivine structure, and transition metal sulfide powders such as TiS ₂ and FeS.

  In addition, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Moreover, you may mix and use said inorganic compound and conductive polymer.

  Also, conductive carbon such as activated carbon and graphite can be used.

  The negative electrode active material is not particularly limited as long as it can be doped or intercalated with lithium ions. For example, metal Li, alloys thereof such as tin alloys, silicon alloys, lead alloys, etc., metal oxides such as lithium titanate, lithium vanadate, lithium siliconate, and conductive such as polyacetylene, poly-p-phenylene, etc. Polymers, soft carbon and hard carbon, such as amorphous carbonaceous materials, artificial graphite such as highly graphitized carbon materials, carbonaceous powder such as natural graphite, activated carbon, carbon black, mesophase carbon black, resin-fired carbon Examples thereof include carbon-based materials such as materials, air-growth carbon fibers, and carbon fibers. These negative electrode active materials can be used alone or in combination.

  The conductive assistant in the composite ink is not particularly limited as long as it is a carbon material having conductivity, and the same conductive carbon material (A) as described above can be used.

  The binder in the composite ink is used for binding particles such as an active material or a conductive carbon material, or a conductive carbon material and a current collector.

Examples of binders used in the composite ink include acrylic resin, polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicon resin, fluorine resin, Cellulose resins such as carboxymethyl cellulose, synthetic rubbers such as styrene-butadiene rubber and fluororubber, conductive resins such as polyaniline and polyacetylene, and polymer compounds containing fluorine atoms such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene Is mentioned. Further, a modified product, a mixture, or a copolymer of these resins may be used. These binders can be used alone or in combination.
The binder suitably used in the water-based composite ink is preferably an aqueous medium, and examples of the aqueous medium binder include water-soluble type, emulsion type, hydrosol type, and the like. be able to.

  The solvent in the composite ink is not particularly limited, but amides such as dimethylformamide, dimethylacetamide, methylformamide, amines such as N-methyl-2-pyrrolidone (NMP) dimethylamine, methyl ethyl ketone, acetone, cyclohexane, etc. Ketones, alcohols, glycols, cellosolves, amino alcohols, sulfoxides, carboxylic acid esters, phosphoric acid esters, ethers, nitriles, water and the like.

  Furthermore, a film forming aid, an antifoaming agent, a leveling agent, a preservative, a pH adjuster, a viscosity adjuster, and the like can be blended in the composite ink as necessary.

(Method for manufacturing electrode)
The conductive composition of the present invention can be applied and dried on a current collector to form a base layer, whereby a base layer electrode for an electricity storage device can be obtained.
Alternatively, the conductive composition of the present invention can be applied to a current collector and dried to form a base layer, and a composite layer can be provided on the base layer to obtain an electrode for an electricity storage device. The composite material layer provided on the base layer can be formed using the above-described composite ink.

(Electrolyte)
A case of a lithium ion secondary battery will be described as an example. As the electrolytic solution, an electrolyte containing lithium dissolved in a non-aqueous solvent is used.
As electrolytes, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₃ C , LiI, LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, or LiBPh _4, but are not limited thereto.

Although it does not specifically limit as a non-aqueous solvent, For example, carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate;
Lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone;
Glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane;
Esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and
Nitriles such as acetonitrile are exemplified. These solvents may be used alone or in combination of two or more.
Furthermore, the electrolyte solution may be a polymer electrolyte that is held in a polymer matrix and made into a gel. Examples of the polymer matrix include, but are not limited to, an acrylate resin having a polyalkylene oxide segment, a polyphosphazene resin having a polyalkylene oxide segment, and a polysiloxane having a polyalkylene oxide segment.

(separator)
Examples of the separator include, but are not limited to, a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyamide nonwoven fabric and those obtained by subjecting them to a hydrophilic treatment.

(Power storage device structure / configuration)
Examples of the electricity storage device using the composition of the present invention include, but are not limited to, a lithium ion secondary battery, an electric double layer capacitor, a lithium ion capacitor, and a lithium air battery. Usually, it is comprised from the positive electrode and negative electrode, and the separator provided as needed, and can be made into various shapes according to the purpose to use, a paper type, a cylindrical type, a button type, a lamination type.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. The materials used in Examples and Comparative Examples are shown below.
(Conductive carbon material)
A-1: Denka Black HS-100 (manufactured by Denki Kagaku Kogyo)
A-2: Ketjen Black EC-300J (Lion Corporation)
(Water-dispersed resin fine particles)
B-1: Syxen L (24% solid content aqueous dispersion, modified amount (Y) / (X) 0.64, pH 9.0, modified polyethylene) (manufactured by Sumitomo Seika Co., Ltd.)
B-2: Arrow Base TD-4010 (25% solid content aqueous dispersion, modified amount (Y) / (X) 0.08, pH 9.5, modified polypropylene) (manufactured by Unitika)
* (Y) is derived from carboxylic acid or carboxylic acid ester.
(Water-soluble resin)
D-1: CMC Daicel # 1240 (manufactured by Daicel Chemical Industries)
D-2: sodium polyacrylate, average molecular weight 10,000 (manufactured by Wako Pure Chemical Industries, Ltd.)
D-3: Kuraray Poval PVA235 (manufactured by Kuraray)

(Conductive composition)
Example 1
Zyxen L (B-1: manufactured by Sumitomo Seika Co., Ltd., modified amount (Y) / (X) 0.64, pH 9.0, polyethylene) which is water-dispersed resin fine particles containing olefin resin fine particles neutralized with dimethylaminoethanol ) While concentrating the 24 mass% aqueous dispersion using an ultrafiltration device (Nippon Pole Ultrafiltration Device, fractional molecular weight 300K), ion-exchanged water was added, and the solid content of the olefin resin fine particles was 20 Washing was performed within a range of ˜25% by mass until pH 8.0 and a solid content of 25% by mass were achieved.
40 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 970 parts by mass of ion-exchanged water as an aqueous liquid medium (C), and ether type non-ion 0.4 parts by mass of a surfactant (Triton X, manufactured by Roche Life Science) was mixed in a mixer, and further dispersed in a sand mill. Next, 240 mass parts (60 mass parts as a solid content) of 25 mass% water-dispersed resin fine particles obtained by the ultrafiltration washing was added and mixed with a mixer to obtain a conductive composition (1).

(PH of water-dispersed resin fine particles (B))
An aqueous dispersion obtained by dispersing 25% by mass of the water-dispersed resin fine particles (B) containing the neutralized olefin-based resin fine particles in an environment at a liquid temperature of 25 ° C. with a pH meter (D-54 manufactured by Horiba Seisakusho). It was measured.

(Modification amount of water-dispersed resin fine particles (B) (Y) / (X))
The water-dispersed resin fine particles (B) containing the water-dispersed olefin resin fine particles were placed in an oven at 80 ° C. to remove the dispersion medium, and then dried at 120 ° C. for 30 minutes to obtain a solid. This was measured by a total reflection measurement method (ATR) using a Fourier transform infrared spectrometer (FT-IR: Spectrum One / 100 manufactured by PerkinElmer).
Modification amount using spectral plotting absorbance against wave numbers, when used as a baseline BX a straight line connecting two points of the point indicating the absorbance at a point and 3000 cm ^-1 indicating the absorbance at 2700 cm ^-1, 2800 The height (maximum absorbance) (X) from the maximum peak derived from the olefin of ˜3000 cm ⁻¹ to the baseline BX is connected to the point indicating the absorbance at 1650 m ⁻¹ and the point indicating the absorbance at 1850 cm ⁻¹ . The ratio (Y) / (X) to the height (maximum absorbance) (Y) from the maximum peak derived from the carbonyl of 1690 to 1740 cm ⁻¹ to the baseline BY when the straight line was taken as the baseline BY was determined.

(Example 2, Example 3, Example 5, Example 6)
The conductive compositions (2), (3), (5), and (6) of the examples were changed in the same manner as the conductive composition (1) except that the materials and conditions shown in Table 1 were changed. Obtained.

Example 4
Recycled cation exchange resin (Amberlite IR120B manufactured by Organo Co., Ltd.) was packed into a column, and this column was neutralized with dimethylaminoethanol diluted to 5% by mass with ion exchange water (B-1: Sumitomo Sumitomo). Ion exchange was carried out. The obtained water-dispersed resin fine particles containing the olefin-based resin fine particles were concentrated by ultrafiltration until the solid content became 25% by mass and pH 5.5.
40 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 970 parts by mass of ion-exchanged water as an aqueous liquid medium (C), and ether type non-ion 0.4 parts by mass of a surfactant (Triton X, manufactured by Roche Life Science) was mixed in a mixer, and further dispersed in a sand mill. Next, 240 mass parts (60 mass parts as a solid content) of 25 mass% water-dispersed resin fine particles obtained by the ultrafiltration washing were added and mixed with a mixer to obtain a conductive composition (4).

(Example 7)
Recycled cation exchange resin (Amberlite IR120B manufactured by Organo Co., Ltd.) was packed into a column, and this column was neutralized with dimethylaminoethanol diluted to 5% by mass with ion exchange water (B-1: Sumitomo Sumitomo). Ion exchange was performed until pH 4.0 was achieved. Immediately after the ion exchange, 3-ethoxypropylamine was added to the olefin resin fine particles as a neutralizing agent so as to have a pH of 8.0. The obtained water-dispersed resin fine particles containing the olefin resin fine particles were concentrated by ultrafiltration until the solid content became 25% by mass.
40 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 970 parts by mass of ion-exchanged water as an aqueous liquid medium (C), and ether type non-ion 0.4 parts by mass of a surfactant (Triton X, manufactured by Roche Life Science) was mixed in a mixer, and further dispersed in a sand mill. Next, 240 mass parts (60 mass parts as a solid content) of 25 mass% water-dispersed resin fine particles obtained by the ultrafiltration washing were added and mixed with a mixer to obtain a conductive composition (7).

(Example 8)
A conductive composition (8) was obtained in the same manner as in Example 7 except that the neutralizing agent after ion exchange was changed to hexylamine.

Example 9
Arrow base TD-4010 (B-2: manufactured by Unitika Co., Ltd., modified amount (Y) / (X) 0.08, pH 9.5, which is water-dispersed resin fine particles containing olefin-based resin fine particles neutralized with dimethylaminoethanol Polypropylene) While concentrating a 25% by mass aqueous dispersion using an ultrafiltration device (Nippon Pole Ultrafiltration Device, fractional molecular weight 300K), adding ion-exchanged water and water dispersion containing olefin resin fine particles The resin fine particles were washed within a range of 20 to 25% by mass, and washed until pH 8.0 and the solid content was 25% by mass.
25 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 25 parts by mass of ion-exchanged water as an aqueous liquid medium (C), and a water-soluble resin Carboxymethylcellulose (D-1: CMC Daicel # 1240, manufactured by Daicel Chemical Industries) 2.5 parts aqueous solution 1000 parts by weight (solid part 25 parts by weight) is mixed in a mixer, and further placed in a sand mill for dispersion. It was. Next, 200 parts by mass (50 parts by mass as a solid content) of 25% by mass water-dispersed resin fine particles obtained by the above ultrafiltration washing were added and mixed with a mixer to obtain a conductive composition (9).

(Examples 10 to 14, Comparative Example 5 and Comparative Example 6)
Except having changed into the material and conditions shown in Table 1, according to the method similar to electroconductive composition (9), electroconductive composition (10)-(14), (19), (19) of (Example) and a comparative example, respectively ( 20) was obtained.

(Comparative Example 2)
As a conductive carbon material, 40 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) and carboxymethyl cellulose (D-1: CMC Daicel # 1240, Daicel Chemical Industries) as a water-soluble resin are used. 2400 parts by mass of a 2.5% aqueous solution (60 parts by mass as solid content) was mixed in a mixer, and further dispersed in a sand mill to obtain a conductive composition (16).

(Comparative Example 3)
40 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 960 parts by mass of ion-exchanged water as an aqueous liquid medium (C), and ether type non-ion 0.4 parts by mass of a surfactant (Triton X, manufactured by Roche Life Science) was mixed in a mixer, and further dispersed in a sand mill. Next, Zyxen L (B-1: manufactured by Sumitomo Seika Co., Ltd., modified amount (Y) / (X) 0.64, pH 9, polyethylene) which is a water-dispersed resin fine particle containing olefin-based resin fine particles neutralized with dimethylaminoethanol ) 250 parts by mass of a 24% by mass aqueous dispersion (60 parts by mass as a solid content) was added and mixed with a mixer to obtain a conductive composition (17).

(Comparative Example 4)
Recycled cation exchange resin (Amberlite IR120B manufactured by Organo Corporation) is packed in a column, and this column is neutralized with dimethylaminoethanol diluted to 5% by mass with ion exchange water (B-1: Sumitomo Seiyu). The water-dispersed resin fine particles containing the resulting olefin resin fine particles were concentrated by ultrafiltration to a solid content of 25% by mass and a pH of 4.0.
40 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 970 parts by mass of ion-exchanged water as an aqueous liquid medium (C), and ether type non-ion 0.4 parts by mass of a surfactant (Triton X, manufactured by Roche Life Science) was mixed in a mixer, and further dispersed in a sand mill. Next, 240 parts by mass (60 parts by mass as a solid content) of 25% by mass water-dispersed resin fine particles obtained by the ultrafiltration washing were added and mixed with a mixer to obtain a conductive composition (18).

(Example 15)
40 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 960 parts by mass of ion-exchanged water as an aqueous liquid medium (C), and ether type non-ion 0.4 parts by mass of a surfactant (Triton X, manufactured by Roche Life Science) was mixed in a mixer, and further dispersed in a sand mill. Next, 240 parts by mass of an aqueous dispersion TD-4010 (B-2: manufactured by Unitika Co., Ltd.) 25% by mass of an aqueous dispersion resin fine particle containing dimethylaminoethanol-neutralized olefin resin fine particles (60 mass as a solid content) Part) and mixed with a mixer to obtain a conductive composition (21).

(Examples 16 to 19, Comparative Example 7)
Except having changed into the material and conditions shown in Table 1, according to the method similar to electroconductive composition (21), the electroconductive compositions (22)-(25) and (26) of an Example and a comparative example were obtained, respectively. It was.

With respect to the conductive compositions (1) to (14) and (16) to (26), the stability of the coating liquid was evaluated. The evaluation results are shown in Table 2.
(Coating solution stability)
The conductive composition prepared above was stored at 50 ° C., and the solids were observed for aggregation, sedimentation, and separation from the solvent, and judged by visual judgment. The evaluation criteria are shown below.
A: “The above phenomenon was not observed for more than four weeks. Excellent.”
○: “The above-mentioned phenomenon was observed in two to four weeks. Excellent.”
○ △: “The above phenomenon was observed during one to two weeks. (Actually usable level)”
X: “The above phenomenon was observed within one week. Inferior”

<Current collector with underlayer>
(Examples 1-14, Comparative Examples 2-7)
The conductive compositions (1) to (14), (16) to (20), and (26) were coated on a 20 μm thick aluminum foil serving as a current collector using a bar coater, and then 80 ° C. It dried in 10 minutes and obtained collector (1)-(14), (16)-(20), (26) with a base layer so that the thickness of a base layer might be 2 micrometers.

(Example 15)
The conductive composition (21) was applied onto a 20 μm thick aluminum foil serving as a current collector using a bar coater, dried at 80 ° C. for 10 minutes, then dried at 130 ° C. for 30 seconds, A current collector (21) with an underlayer was obtained so that the thickness of the base layer was 2 μm.

(Examples 16 to 19)
Except having changed into the drying temperature shown in Table 1, the collectors (22)-(25) with a foundation layer of an Example were each obtained by the method similar to the collector (21) with a foundation layer, respectively.

<Composite ink for lithium ion secondary battery positive electrode>
93 parts by mass of LiNi _0.5 Mn _0.3 Co _0.2 O ₂ as a positive electrode active material, 4 parts by mass of acetylene black as a conductive agent, 3 parts by mass of polyvinylidene fluoride as a binder, and 45 parts by mass of N-methylpyrrolidone are mixed and mixed. A composite ink was prepared.

<Composite ink for negative electrode of lithium ion secondary battery>
As a negative electrode active material, 98 parts by mass of artificial graphite and 66.7 parts by mass of a carboxymethyl cellulose 1.5% aqueous solution (1 part by mass as a solid content) were put in a planetary mixer and kneaded, 33 parts by mass of water, 48 parts by mass of a styrene butadiene emulsion. % Aqueous dispersion 2.08 parts by mass (1 part by mass as solid content) was mixed to obtain a negative electrode mixture ink.

<Positive electrode for lithium ion secondary battery with underlayer>
(Examples 1-19, Comparative Examples 2-7)
After applying the above-mentioned ink mixture for lithium ion secondary battery positive electrode on the collectors (1) to (14) and (16) to (26) with the underlayer using a doctor blade, the mixture ink is dried at 80 ° C. Thus, the basis weight per unit area of the electrode was adjusted to 20 mg / cm ² . Furthermore, the rolling process by roll press was performed and the positive electrode (1)-(14) and (16)-(26) from which the density of a compound-material layer became 3.1 g / cm < ³ > were produced.
(Comparative Example 8)
The positive electrode (26) for a lithium ion secondary battery with an underlayer produced in Comparative Example 7 was vacuum-heated and dried at 200 ° C. for 12 hours to produce a positive electrode (27).

<Positive electrode for lithium ion secondary battery without base layer> (Comparative Example 1)
The above-mentioned ink mixture for lithium ion secondary battery positive electrode was applied onto a 20 μm thick aluminum foil serving as a current collector using a doctor blade, and then dried by heating, so that the basis weight per unit area of the electrode was 20 mg. It adjusted so that it might become / cm < ² >. Furthermore, the rolling process by a roll press was performed and the positive electrode (15) from which the density of a compound-material layer became 3.1 g / cm < ³ > was produced.

<Negative Electrode for Lithium Ion Secondary Battery Without Underlayer> (Examples 1 to 19, Comparative Examples 1 to 8)
After applying the above-mentioned ink mixture for lithium ion secondary battery negative electrode on a copper foil having a thickness of 20 μm as a current collector using a doctor blade, it is dried at 80 ° C., and the basis weight per unit area of the electrode Was adjusted to 12 mg / cm ² . Furthermore, the rolling process by a roll press was performed and the negative electrodes (1)-(27) from which the density of a compound-material layer became 1.5 g / cm < ³ > were produced.

<Laminated Lithium Ion Secondary Battery> (Examples 1 to 19, Comparative Examples 1 to 8)
The positive electrode and negative electrode shown in Table 2 are punched into 45 mm × 40 mm and 50 mm × 45 mm, respectively, and a separator (porous polypropylene film) inserted between them is inserted into an aluminum laminated bag, and after vacuum drying, an electrolytic solution ( After injecting LiPF ₆ at a concentration of 1M) into a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a ratio of 1: 1 (volume ratio), the aluminum laminate is sealed and laminated. Type lithium ion battery was produced. Laminate type lithium ion batteries are manufactured in a glove box substituted with argon gas, and after making laminated type lithium ion batteries, the following initial resistance, resistance increase, rate characteristics, cycle characteristics and storage characteristics are shown. Evaluation was performed.

(Resistance measurement)
A laminate type battery that was discharged at a constant discharge current of 3.0 V at a discharge current of 12 mA (0.2 C) was subjected to resistance measurement at 500 kHz with an impedance analyzer (SP-50 manufactured by biologic).
The laminate type battery described above was heated from 25 ° C. to 180 ° C., and resistance measurement was performed at each temperature. The resistance measured at 25 ° C. was taken as the initial resistance, and the quotient of the resistance value measured at 180 ° C. and the resistance value measured at 25 ° C. was taken as the resistance increase. That is, the increase in resistance is expressed by the following (formula 1).
(Equation 1) Resistance increase = resistance value at 180 ° C./resistance value at 25 ° C. The results of evaluating the initial resistance and the resistance increase according to the following criteria are shown in Table 2.
Initial resistance ○: “The initial resistance is smaller than the initial resistance of Comparative Example 1 without an underlayer. Excellent.”
Δ: “The initial resistance is equivalent to the initial resistance of Comparative Example 1 without the underlayer”
X: “The initial resistance is larger than the initial resistance of Comparative Example 1 without the underlayer. Inferior”
・ Resistance increase ◎: “Resistance increase is more than 5 times the initial resistance. Excellent”
○: “Increased resistance is 3 times or more and less than 5 times the initial resistance.
Δ: “Increase in resistance is less than three times the initial resistance. Current blocking effect is low. Inferior”

(Rate characteristics)
About the laminated battery mentioned above, charging / discharging measurement was performed using the charging / discharging apparatus (SM-8 by Hokuto Denko).
Constant current and constant voltage charge with a charge current of 12 mA (0.2 C) and a charge end voltage of 4.2 V (after a cut-off current of 0.6 mA, the discharge was terminated at a discharge current of 12 mA (0.2 C) and 120 mA (2 C). The constant current discharge was performed until the voltage reached 3.0 V, and the discharge capacity was obtained, respectively, and the rate characteristic is expressed by the ratio of 0.2 C discharge capacity to 2 C discharge capacity, that is, the following (Equation 2).
(Equation 2) Rate characteristics = 2C discharge capacity / 0.2C discharge capacity × 100 (%)
Table 2 shows the results of evaluation based on the following criteria.
・ Rate characteristic ○: “Rate characteristic is 80% or more. Particularly excellent.”
○ △: “Rate characteristic is 75% or more and less than 80%. Excellent”
Δ: “The rate characteristic is 70 or more and less than 75%. Equivalent to the rate characteristic of Comparative Example 1 without a base layer.”
X: “Rate characteristic is less than 70%. Inferior”

(Cycle characteristics)
After performing constant current and constant voltage charging (cutoff current 0.6 mA) at a charge current of 60 mA and a charge end voltage of 4.2 V in a 50 ° C. constant temperature bath, the discharge current reaches 60 V at a discharge current of 60 mA. The initial discharge capacity was obtained by performing constant current discharge until. This charge / discharge cycle was performed 200 times, and the discharge capacity maintenance ratio (percentage of the 200th discharge capacity with respect to the initial discharge capacity) was calculated. Table 2 shows the results of evaluation based on the following criteria.
Cycle characteristics ○: “Discharge capacity maintenance rate is 90% or more. Particularly excellent.”
○ △: “Discharge capacity maintenance ratio is 85% or more and less than 90%. Excellent”
Δ: “Discharge capacity maintenance ratio is 80% or more and less than 85%. Equivalent to the discharge capacity maintenance ratio of Comparative Example 1 without a base layer.”
×: “Discharge capacity maintenance rate is less than 80%. Inferior”

(Storage characteristics)
[Initial capacity]
After performing a constant current and constant voltage charge (cutoff current 0.6 mA) at a charge current of 30 mA and a charge end voltage of 4.2 V in a 50 ° C. constant temperature bath, the discharge end voltage reaches 3.0 V at a discharge current of 30 mA. A constant current discharge was performed until the initial discharge capacity was obtained and used as the initial capacity.
[Storage capacity]
The battery whose initial discharge capacity was obtained was subjected to constant current and constant voltage charge (cutoff current 0.6 mA) at a charge current of 30 mA and a charge end voltage of 4.2 V in a 50 ° C. constant temperature bath, and then 50 ° C. And stored for 7 days.
The battery stored for 7 days is discharged in a constant temperature bath at 50 ° C. with a discharge current of 30 mA until the discharge end voltage reaches 3.0 V (discharge 1-1), the charge current is 30 mA and the charge end voltage is 4. After performing constant current and constant voltage charge (cutoff current 0.6 mA) at 2 V, constant current discharge is performed at a discharge current of 30 mA until the discharge end voltage reaches 3.0 V (discharge 2-1). The discharge capacity was defined as the storage capacity (discharge 2-1).
The above test was repeated 4 times, and the storage capacity retention rate was calculated based on the storage capacity (discharge 2-4) after conducting a storage test at 50 ° C. for 28 days in a 4.2 V charged state.
The storage characteristics are represented by the ratio between the initial capacity and the discharge capacity (discharge 2-4) after the storage test for 28 days, that is, the storage capacity maintenance ratio shown below (Formula 3).
(Formula 3) Storage capacity retention rate = 28 days storage capacity (discharge 2-4) / initial capacity × 100 (%)
Table 2 shows the results of evaluation based on the following criteria.
Storage characteristics ○: “Storage capacity retention rate is 80% or more. Excellent.”
○ △: “Storage capacity maintenance rate is 70% or more and less than 80%.
Δ: “Storage capacity retention ratio is 60 or more and less than 70%. Equivalent to the storage capacity retention ratio of Comparative Example 1 without the underlayer”
×: “Storage capacity retention rate is less than 60%. Inferior”

As shown in Table 2, by using the underlayer formed from the conductive composition of the present invention, the internal resistance of the electricity storage device is reduced at the normal operating temperature, and the output characteristics, cycle characteristics and storage characteristics are improved. Further, it was confirmed that the internal resistance increases when the internal temperature of the electricity storage device increases. From this, it is considered that when the power storage device abnormally heats up due to an internal short circuit or the like, the resistance of the current collector increases and the current is cut off to avoid ignition of the power storage device.
On the other hand, in Comparative Example 1 in which the underlayer is not formed and in Comparative Example 2 in which the underlayer containing no olefin-based resin fine particles is formed, even if the internal temperature of the electricity storage device rises, a noticeable increase in internal resistance is observed. I couldn't. Since Comparative Example 1 has no base layer formed, it has no effect of increasing resistance during heat generation. In Comparative Example 2, the volume expansion of the resin during heat generation is insufficient, so that the conductive material dispersed in the conductive layer is not present. This is thought to be due to the fact that the active carbon materials could not be peeled apart.
Further, in Comparative Examples 3 and 7 in which the pH of the olefin resin fine particles is high and in Comparative Example 6 in which the composition ratio of the olefin resin fine particles is large, storage deterioration of the electricity storage device was confirmed. This is probably because the amine compound remained in the underlayer and the amine was oxidatively decomposed.
Further, in the case of using olefin resin fine particles containing an amine compound having a boiling point of 100 ° C. or higher in excess, good storage characteristics were obtained in Examples 15 to 19 which were dried at 130 to 250 ° C. In Comparative Example 8 in which the composite material layer was applied and then dried at a high temperature, the storage deterioration of the electricity storage device was confirmed. It is considered that the amine compound can be effectively removed by drying the current collector with the underlayer at 130 to 250 ° C., which led to improvement in characteristics.
In Comparative Example 4 where the pH of the water-dispersed resin fine particles containing the olefin resin fine particles was low, aggregation of olefin and carbon was observed, and initial resistance, rate characteristics, and cycle characteristics deteriorated. It is thought that the electrostatic repulsion of anions was insufficient, the olefin dispersion state could not be maintained, and the underlayer could not be formed.
From the above results, according to the present invention, it is excellent in the output characteristics of the electricity storage device, and excellent in long-term reliability such as cycle characteristics and storage characteristics, and when the internal temperature of the electricity storage device rises due to an internal short circuit, By suppressing the flowing current by increasing the internal resistance, it is possible to provide a conductive composition for forming an electricity storage device having a function of improving safety.

Claims (8)

A conductive carbon material (A), water-dispersed resin fine particles (B) containing olefin-based resin fine particles neutralized with an amine compound having a boiling point of 100 ° C. or more and modified with a compound containing a carbonyl group, and an aqueous liquid A conductive composition comprising a medium (C),
In the solid content of the conductive composition, the conductive carbon material (A) is 20 to 70% by mass, and the water-dispersed resin fine particles (B) are 20 to 60% by mass,
Furthermore, pH of the aqueous dispersion which is solid content 10-60 mass% of water dispersion resin microparticles | fine-particles (B) is 5.0-8.5, The electrically conductive composition characterized by the above-mentioned. The conductive composition according to claim 1, wherein the compound containing a carbonyl group contains at least a carboxylic acid or a carboxylic acid ester. The conductive composition according to claim 1 or 2, further comprising 10 to 50% by mass of a water-soluble resin (D) with respect to 100% by mass of the solid content of the conductive composition. The conductive composition according to claim 1, wherein the conductive composition is used for forming a base layer of an electrode for an electricity storage device. The electrical power collector with a base layer for electrical storage devices which has a collector and the base layer formed from the electrically conductive composition in any one of Claims 1-4. A current collector, an underlayer formed from the conductive composition according to claim 1, and a composite layer formed from an electrode-forming composition containing an electrode active material and a binder. An electrode for an electricity storage device. 7. An electricity storage device comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein at least one of the positive electrode or the negative electrode is the electrode for an electricity storage device according to claim 6. A conductive carbon material (A), water-dispersed resin fine particles (B) containing olefin-based resin fine particles neutralized with an amine compound having a boiling point of 100 ° C. or more and modified with a compound containing a carbonyl group, and an aqueous liquid A method for producing a current collector with an underlayer for an electricity storage device, wherein the drying temperature of the current collector with an underlayer formed from a conductive composition containing the medium (C) is 130 to 250 ° C.