JP6683028B2 - Conductive composition, current collector with underlayer for power storage device, electrode for power storage device, and power storage device - Google Patents

Description

  The present invention provides a conductive composition, and an electrode for an electricity storage device (for example, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, an electric double layer capacitor, a lithium ion capacitor) obtained by using the composition, and The present invention relates to an electricity storage device obtained by using the electrode. More specifically, the present invention relates to a conductive composition having a function of increasing the internal resistance of an electricity storage device when the temperature of the electricity storage device rises, an electrode for an electricity storage device, and an electricity storage device.

  In recent years, small portable electronic devices such as digital cameras and mobile phones have been widely used. For these electronic devices, it has been constantly required to minimize the volume and reduce the weight, and it is also required to realize a small-sized, lightweight and large-capacity battery as a battery to be mounted. Lithium-ion secondary batteries, in particular, have a greater energy density than water-based secondary batteries such as lead-acid batteries, nickel-cadmium batteries, and nickel-hydrogen batteries, so their importance as power sources for personal computers and mobile terminals has increased. In addition, it is expected to be preferably used as a high-output power source mounted on a vehicle.

  The lithium-ion secondary battery has the advantage of high energy density, but uses a non-aqueous electrolyte, and therefore requires a sufficient safety countermeasure. In recent years, ensuring the safety has become a major issue in accordance with the increase in size and capacity of batteries. For example, if the battery temperature rises abnormally and suddenly due to overcharging or a short circuit inside the battery, it will be difficult to control heat generation with only the safety mechanism provided outside the battery, and it will ignite. 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 entire battery is low.

  Patent Document 2 discloses that any one of the positive electrode, the negative electrode, and the 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 the battery capacity, and there is a problem that the energy density is low.

  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 the current collector. In this conductive layer, when the temperature inside 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 cut off. However, there is a problem that the internal resistance of the battery during normal operation becomes high and the output characteristic of the battery is low.

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

  Patent Document 5 describes a method of providing a current collector provided with a conductive layer composed of conductive particles, carboxymethyl cellulose, a water-dispersed olefin resin, and a dispersant. However, the resistance increases when the temperature inside the battery rises. Is not enough.

JP, 10-241665, A JP-A-11-329503 JP, 2001-357854, A JP, 2012-104422, A International Publication No. 2015/046469

  The problem to be solved by the present invention is to provide a power storage device (for example, a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery, an electric double layer capacitor, a lithium ion capacitor, etc.) without impairing the energy density during normal operation. , Which has excellent output characteristics of the electricity storage device and can suppress excessive heat generation and ignition by increasing the internal resistance even when the internal temperature of the electricity storage device rises, and an electrode for forming the electricity storage device , A current collector and a conductive composition.

The present invention is a conductive composition containing a conductive carbon material (A), a water-soluble resin (B), and water-dispersed resin fine particles (C) containing at least olefin-based resin fine particles. At times, the resistance of the current collector increases and the current is cut off to prevent the electric storage device from firing.
Appropriately controlling the solid content ratio of the conductive composition and the total specific surface area of the conductive carbon material (A), the present inventors surprisingly reduced the internal resistance during normal operation, and stored electricity devices. The inventors have found that a dramatic increase in resistance occurs when the internal temperature rises, and completed the present invention.

That is, the present invention relates to an electrode for an electricity storage device containing a conductive carbon material (A), a water-soluble resin (B), water-dispersed resin fine particles (C) and an aqueous liquid medium (D). A conductive composition for forming an underlayer, wherein the water-dispersed resin fine particles contain at least olefinic resin fine particles, and the conductive carbon material (A) is contained in 100% by mass of the total solid content of the conductive composition. The content is 30 to 70% by mass, the content of the water-soluble resin (B) is 1 to 40% by mass, and the content of the water-dispersed resin fine particles (C) is 20 to 60% by mass, The present invention relates to a conductive composition for forming an underlayer of an electrode for an electricity storage device, wherein the conductive carbon material (A) has a total specific surface area of 30 m ² / g or less.

  In the present invention, the conductive carbon material (A) contains at least graphite, and the content of graphite in the conductive carbon material (A) is 60 to 100% by mass. Sex composition.

Further, in the present invention, the olefin resin fine particles contained in the water-dispersible resin fine particles (C) are polyolefin resin fine particles having a carbonyl group, and the infrared absorption spectrum of the polyolefin resin fine particles has a maximum peak at 2800 to 3000 cm ⁻¹ . The ratio (Y) / (X) between the height (maximum absorbance) (X) and the maximum peak height (maximum absorbance) (Y) at 1690 to 1740 cm ⁻¹ is 0.05 to 1.0. The present invention relates to a conductive composition for forming an underlayer.

Further, the present invention is a current collector with an underlayer for an electricity storage device, which has a current collector and an underlayer formed from the above-mentioned underlayer-forming conductive composition for an electrode for an electricity storage device. The present invention relates to a current collector with an underlayer having a density of 1.4 g / cm ³ or more.

  Further, the present invention is formed from a current collector, an underlayer formed from the conductive composition for forming an underlayer of the electrode for an electricity storage device, and an electrode forming composition containing an electrode active material and a binder. And a composite material layer.

  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 and the negative electrode is the electrode for the electricity storage device.

  The present invention also relates to the above-mentioned electricity storage device, which is either a non-aqueous electrolyte secondary battery, an electric double layer capacitor or a lithium ion capacitor.

  INDUSTRIAL APPLICABILITY According to the present invention, an electric storage device which has excellent output characteristics and the like of an electric storage device during normal operation and which can suppress excessive heat generation and ignition when the internal temperature of the electric storage device rises (for example, a lithium ion secondary battery) Non-aqueous electrolyte secondary batteries, electric double layer capacitors, lithium ion capacitors, etc.) are now available.

<Conductive composition>
The conductive composition of the present invention can be used for forming a base layer of an electrode for a power storage device. The conductive composition contains a conductive carbon material (A), a water-soluble resin binder (B), water-dispersible resin particles (C) containing at least olefin resin particles, and an aqueous liquid medium (D). To do.

  The content of the conductive carbon material (A) in the total solid content of the conductive composition of 100% by mass is 30 to 70% by mass, preferably 40 to 60% by mass, from the viewpoint of conductivity and internal resistance. %.

  The content of the water-soluble resin (B) in the total solid content of 100% by mass of the conductive composition is from 1 to 40 mass from the viewpoint of the adhesion and conductivity of the electrodes and the increase of the internal resistance of the battery at the time of heat generation. %, And preferably 5 to 30 mass%. If the content of the water-soluble resin (B) is 1 to 40% by mass, it is confirmed that the water-soluble resin (B) has an effect of preventing re-contact between carbons even when the polyolefin resin fine particles are melted by heating. It is preferable because it dramatically improves the safety of.

  The content of the water-dispersed resin fine particles (C) in the total solid content of 100% by mass of the conductive composition is 20 to 60% by mass from the viewpoint of internal resistance and conductivity, and increase in internal resistance of the battery during heat generation. And preferably 30 to 50% by mass. When the content of the water-dispersed resin fine particles (C) is within 20 to 60% by mass, the volume expansion of the polyolefin resin (the water-dispersed resin fine particles (C)) is sufficiently exhibited, and when the internal temperature of the battery is increased. This is preferable because the internal resistance is effectively increased.

  The total amount of the conductive composition (A), the water-soluble resin (B), and the water-dispersed resin fine particles (C) is 100% by mass of the total solid content of the conductive composition. From the viewpoint of increasing the internal resistance of, it is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. Any component may be added to the composition as needed.

  Although the optional component is not particularly limited, for example, a material that adsorbs or consumes an acid generated by a reaction of an electrolytic solution, a material that generates a gas when a temperature exceeds a predetermined temperature, an inorganic PTC material, or a polyolefin resin fine particle expands in volume. You may add the material etc. which hold | maintain the electrically conductive path after doing.

Examples of the material that adsorbs the acid generated by the reaction of the electrolytic solution include magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), boron oxide (B ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), Examples thereof include indium oxide (In ₂ O ₃ ).

  Materials that consume the acid generated by the reaction of the electrolytic solution include metal carbonates such as magnesium carbonate and calcium carbonate, sodium carboxylate, potassium carboxylate, sodium sulfonate, potassium sulfonate, sodium benzoate, and potassium benzoate. And organic silicates, sodium silicate, potassium silicate, aluminum silicate, magnesium silicate, silicates such as silicon dioxide, and alkaline hydroxides such as magnesium hydroxide.

  Examples of materials that generate gas at a predetermined temperature or higher include lithium carbonate, zinc carbonate, lead carbonate, carbonates such as strontium carbonate, and expanded graphite.

Examples of the inorganic PTC material include BaTiMO ₃ (M is at least one element selected from the group consisting of Cr, Pb, Ca, Sr, Ce, Mn, La, Y, Nb, and Nd).

  Examples of the material that holds the conductive path after the volume expansion of the polyolefin resin fine particles include inorganic fine particles such as cellulose nanofibers, silica, and alumina.

  The appropriate viscosity of the conductive composition depends on the method of applying the conductive composition, but it is generally preferable to be 10 mPa · s or more and 30,000 mPa · s or less.

<Conductive carbon material (A)>
The conductive carbon material (A) in the present invention is not particularly limited as long as it is a carbon material having conductivity, but graphite (graphite), carbon black, conductive carbon fibers (carbon nanotube, carbon nano). Fiber, carbon fiber), fullerene and the like can be used alone or in combination of two or more kinds. In particular, graphite is preferably used from the viewpoint of increasing the internal resistance of the battery during heat generation. When graphite is contained in the conductive carbon material (A), the olefin resin fine particles are expanded in volume, and at the same time, the graphite is expanded in volume, and the contact points between the conductive carbon materials are changed from surface contact to point contact or disconnection. Therefore, it is considered that the effect of cutting the contact between the conductive carbon materials is enhanced.

  Graphite is a hexagonal plate-like crystal of carbon, and examples of the present invention include natural graphite such as earth graphite, lump graphite, and scaly graphite, and artificial graphite. In addition, expanded graphite, exfoliated graphite with exfoliation to improve moldability and conductivity, exfoliated graphite with reduced orientation due to spheroidizing and crushing, and molten pig iron to reduce temperature due to hot metal pretreatment Also included is quiche graphite, which is planarly crystallized carbon that is precipitated along with it. The expanded graphite is, for example, natural graphite or the like is immersed in a strong oxidizing solution of a mixed solution of concentrated sulfuric acid and nitric acid or a mixed solution of concentrated sulfuric acid and hydrogen peroxide to form a graphite intercalation compound. It is a powder obtained by subjecting the graphite crystal to washing in water and then rapidly heating to expand the graphite crystal in the C-axis direction, or a powder obtained by once rolling it into a sheet and crushing it. In particular, exfoliated graphite or natural graphite is preferably used from the viewpoint of the energy density of the electricity storage device and the conductivity of the underlayer.

  Examples of commercially available graphite include SCMG-AH, SCMG-AR, SCMG-AR-H, SCMG-AF, SCMG-AFC, UF-G10, UF-G30, KS-6 and SFG manufactured by Timcal. -6, CPB, UCP, AP, P # 1, PAG-5, HAG-10W, ACP, ACB-150, SP-10, SP-20, J-SP, GR-15, UP manufactured by Nippon Graphite Industry Co., Ltd. -5N, UP-15N, CGC-20, CGB-20, J-SP-α, UP-5-α, SP-5030-α, EXP-SM, UF-2, BF-3A manufactured by Fuji Graphite Industry Co., Ltd. , BF-5A, BF-8A, BF-10A, BF-20A, CNG-44N, BSP-5A, BSP-20A, A-0, FAG-1C, JSG-25, JSG-75, WF-10, WF. -20, WF- 0, CX-3000, BF-1AT, FBF, BF, CBR, G-6S, WF-15C, CPB-6S, BSP-10AK, HF-80, HF-48, Ito Graphite Industry manufactured by Chuetsu Graphite Industry Co., Ltd. Z-5F, CNP-7, CNP-15, CNP-35, Z + 80, Z-25, Z-50, X-10, X-20, SRP7, SRP10, CP2000M, EC1500, SG-BH8, SG manufactured by the same company. -BH, SNO-20 manufactured by SEC Carbon Co., SNO-10, SNO-5, SNE-20, SNE-10, SNE-5, and the like, but are not limited to these, two or more types. You may combine.

  As carbon black, furnace black produced by continuously thermally decomposing a gas or liquid raw material in a reaction furnace, especially Ketjen black made from ethylene heavy oil, burning raw material gas, and burning the flame, channel steel bottom Channel blacks that have been rapidly cooled and deposited, and thermal blacks obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, especially various types such as acetylene black using acetylene gas as a raw material, or 2 More than one type can be used together. Further, commonly used oxidation-treated carbon black, hollow carbon and the like can also be used.

  As the conductive carbon fiber, one obtained by firing from a petroleum-derived raw material is preferable, but one obtained by firing from a plant-derived raw material can also be used. For example, VGCF manufactured by Showa Denko KK, which is manufactured from petroleum-derived raw materials, can be mentioned.

Further, from the viewpoint of the conductivity of the electricity storage device during normal use and the increase in resistance when the temperature rises, the total specific surface area of the conductive carbon material (A) in the present invention is 30 m ² / g or less. It is preferably 1.0 m ² / g or more and 30 m ² / g or less, more preferably 5.0 m ² / g or more and 30 m ² / g or less. Further, it is considered that when the total specific surface area of the conductive carbon material (A) is 30 m ² / g or less, the effect of the water-soluble resin (B) for preventing recontact of carbons can be enhanced.
The total specific surface area of the conductive carbon material (A) of the present invention is the BET specific surface area measured by JIS K6217-2 using a gas adsorption measuring device and mixed with the BET specific surface area of each conductive carbon material. The weighted average value of the ratio is calculated.

<Water-soluble resin (B)>
The water-soluble resin (B) in the present specification means 1 g of the water-soluble resin (B) in 99 g of water at 25 ° C., stirring the mixture, and leaving it at 25 ° C. for 24 hours, and then separating the resin in water without precipitation. Is soluble.

  The water-soluble resin (B) is not particularly limited as long as it is a water-soluble resin as described above. For example, acrylic resin, polyurethane resin, polyester resin, polyamide resin, polyimide resin, polyallylamine resin, Examples of the polymer compound include a phenol resin, an epoxy resin, a phenoxy resin, a urea resin, a melamine resin, an alkyd resin, a formaldehyde resin, a silicone resin, a polyvinyl alcohol resin, a fluororesin, and a polysaccharide resin such as carboxymethyl cellulose. Further, if it is water-soluble, a modified product, a mixture, or a copolymer of these resins may be used. These water-soluble resins may be used alone or in combination of two or more. By including a predetermined amount of the water-soluble resin (B) in the conductive composition, the water-soluble resin (B) prevents re-contact between carbons even when the polyester-based resin particles or the polyurethane-based resin particles are dissolved. Is confirmed, and the safety of the battery can be improved. Furthermore, since the water-soluble resin (B) is chemically stable in the conductive composition (slurry), it is less likely to change with time and has excellent coating properties when forming the underlayer.

  The molecular weight of the water-soluble resin (B) is not particularly limited, but the weight average molecular weight is preferably 5,000 to 2,000,000. The mass average molecular weight (Mw) indicates a polyethylene oxide-equivalent molecular weight in gel permeation chromatography (GPC).

  Further, in the present invention, it is preferable to use carboxymethyl cellulose as the water-soluble resin (B), and the above-mentioned mass average molecular weight is 10,000 to 70, from the viewpoint of resistance increase when the internal temperature of the electricity storage device rises. More preferably, the degree of etherification is 0.3 to 1.0. Etherification is determined by boiling an ashed sample in sulfuric acid, adding phenolphthalein indicator, and back titrating excess acid with potassium hydroxide.

  Furthermore, it is more preferable that the viscosity of a 1 mass% aqueous solution obtained by putting 1 g of carboxymethyl cellulose in 99 g of water at 25 ° C. and stirring is 0.01 to 0.1 Pa · s. The viscosity of the aqueous solution was measured by a rheometer (AR-G2 manufactured by TA Instruments Co., Ltd.) using a cone plate (60 mm, 1 °) at a measurement temperature of 25 ° C. and a shear rate of 360 (1 / s). is there.

  Commercial products can be used as the carboxymethyl cellulose as described above, and examples of the commercially available products include # 1110, # 1120, # 1130, # 1140. Examples include # 1170, # 1210, # 1240, # 1250, # 1260, and # 1270, but are not limited to these.

<Water-dispersed resin fine particles (C)>
The water-dispersed resin fine particles (C) of the present invention are generally called an aqueous emulsion, and the resin fine particles are not dissolved in water but are dispersed in the form of fine particles. Since they are water-dispersed resin particles, the conductivity of the carbon material (A) is not impaired, the internal resistance during normal operation can be reduced, and the output characteristics can be improved.

The water-dispersed resin fine particles contain at least olefin-based resin fine particles, and the proportion of the olefin-based resin fine particles contained in the water-dispersed resin fine particles is preferably 50 to 100% by mass. Further, two or more kinds of olefin resin fine particles may be contained, and if necessary, water dispersed resin fine particles other than the olefin resin fine particles may be contained. The water-dispersed resin fine particles other than the olefin resin fine particles are not particularly limited, but (meth) acrylic emulsion, nitrile emulsion, urethane emulsion, diene emulsion (SBR, etc.), fluorine emulsion (PVDF, PTFE, etc.), etc. Can be mentioned.

The water-dispersed resin fine particles are resins capable of interrupting the contact between the conductive carbon materials dispersed in the conductive layer by volume expansion of the olefin resin fine particles in the range of 80 to 180 ° C. It is preferable. As a result, the resistance of the electrode itself is increased, so that it is considered that the current flowing to the short-circuited portion is reduced, Joule heat generation is suppressed, and the safety of the battery is maintained.
As the olefin component in the polyolefin resin fine particles, for example, ethylene, propylene, isobutylene, isobutene, 1-butene, 2-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1- Hexene, 1-octene, norbornene and the like can be mentioned. These olefin components may be one type or two or more types. In addition, modification or copolymerization with a carboxylic acid or a carboxylic acid ester may be performed in order to maintain the volume expansion of the olefin resin fine particles when the temperature inside the electricity storage device rises.

  In the present invention, the olefin resin fine particles contained in the water dispersed resin fine particles (C) preferably have a certain amount or more of carbonyl groups (—CO—). Further, it is preferable that the olefin resin fine particles are modified with a carboxylic acid or a carboxylic acid ester. Having a carbonyl group can impart resistance to melting of the resin fine particles, so that when the internal temperature of the electricity storage device rises due to an internal short circuit, the volume expansion of the polyolefin resin fine particles can be maintained, and the cutting effect between the carbon materials can be maintained. I think we can continue.

  For example, carboxylic acid or carboxylic acid ester is not particularly limited, but 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 pipariate and the like can be mentioned.

The content of a carbonyl group in the polyolefin resin fine particles having a carbonyl group can be determined by a total reflection measurement method (ATR) using a Fourier transform infrared spectroscope (FT-IR: Spectrum One / 100 manufactured by PerkinElmer) and can be determined by 2800. Ratio (Y) / (of maximum peak height (maximum absorbance) (X) derived from olefin of ˜3000 cm ⁻¹ (X) and maximum peak height (maximum absorbance) (Y) derived from carbonyl group of 1690 to 1740 cm ^−1. X) is preferably 0.05 to 1.0. In the resin fine particles made of polyethylene, the (Y) / (X) is 0.3 to 0.8, and in the resin fine particles made of polypropylene, the (Y) / (X) is 0.05 to 0.8. More preferably, it is 0.5.

The peak height referred to here is a solid substance obtained by removing the dispersion medium from the water-dispersed resin fine particles (C) and finally drying at 120 ° C., and measuring the solid substance by FT-IR. The content of carbonyl group in the polyolefin resin fine particles is based on a straight line connecting two points, that is, the absorbance at 2700 m ^{-1 and} the absorbance at 3000 cm ^-1 by using the spectrum in which the absorbance is plotted against the wave number. Of the two or four olefin-derived ones found in 2800 to 3000 cm ⁻¹ when the line BX is used, the height from the maximum peak to the baseline BX (maximum absorbance) (X) and the absorbance at 1650 m ⁻¹ When the straight line connecting the two points of the point indicating the and the point indicating the absorbance at 1850 cm ⁻¹ is used as the baseline BY, the height from the maximum peak derived from the carbonyl group at 1690 to 1740 cm ⁻¹ to the baseline BY (maximum Absorbance) (Y) and ratio (Y) / (X). In general, two peaks are observed for polyethylene resin and four peaks for polypropylene resin, and the maximum peaks of both peaks are observed near 2915 cm ⁻¹ .

  As the polyolefin resin fine particles as described above, commercially available products can be used, and as commercially available products, Arrow Base SB-1200, SD-1200, SE-1200, TC-4010, TD-4010 manufactured by Unitika Ltd., Aquapetro DP-2401, DP-2502 manufactured by Toyo Adre, Saixen AC, A, AC-HW-10, L, NC, N manufactured by Sumitomo Seika Co., Ltd., Chemipearl A100, A400, M200 manufactured by Mitsui Chemicals, Inc. , S100, S200, S300, V100, V200, V300, W100, W200, W300, W400, W4005, WP100, HARDREN NZ-1004, NZ-1015 manufactured by Toyobo Co., Ltd., Hitec E-6500, P-9018 manufactured by Toho Kagaku. , S-3121, etc., but are not limited to these. , It may be used in combination of two or more thereof.

  Water is preferably used as the dispersion medium for the water-dispersed resin fine particles (C), but for the purpose of stabilizing the resin fine particles, the following aqueous liquid medium (D) compatible with water is used. Is also good. Examples of the liquid medium that is 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. Examples thereof include ethers, ethers, nitriles, etc., and may be used in a range compatible with water.

  The average particle diameter of the water-dispersed resin fine particles (C) is preferably 0.01 to 5 μm, more preferably 0.05 to 1 μm. If the particle size is too small, it will be difficult to manufacture stably, while if the particle size is too large, it will be difficult to keep the conductivity of the conductive layer uniform, and the internal resistance during normal operation will increase, and the output Performance etc. deteriorates.

  In addition, the average particle diameter in this specification represents a volume average particle diameter (D50), and indicates a value measured by a dynamic light scattering method. The average particle size can be measured by the dynamic light scattering method as follows. The water-dispersed resin 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 the cell of a measuring device [Nanotrack manufactured by Nikkiso Co., Ltd.], and the solvent (water in the present invention) and the refractive index condition of the resin according to the sample are input, and then the measurement is performed.

<Aqueous liquid medium (D)>
As the aqueous liquid medium (D), it is preferable to use water, but if necessary, for example, a liquid medium compatible with water may be used to improve coatability on the current collector. good.

  Examples of the liquid medium that is 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. Examples thereof include ethers, ethers, nitriles, etc., and may be used in a range compatible with water.

<Other additives>
Further, a surfactant, a film forming aid, a defoaming 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 required.

<Disperser / Mixer>
As a device used for obtaining the conductive composition of the present invention and the composite ink described below, a disperser or a mixer which is usually used for pigment dispersion can be used.
For example, mixers such as a disperser, a homomixer, or a planetary mixer; a homogenizer such as "Clearmix" manufactured by M Technique Co., Ltd. or a "Fillmix" manufactured by PRIMIX; a paint conditioner (manufactured by Red Devil), a ball mill, a sand mill Media type disperser such as (Dimino Mill manufactured by Shinmaru Enterprises Co., Ltd.), attritor, pearl mill (“DCP mill” manufactured by Eirich, etc.), or coball mill; wet jet mill (“Genus PY” manufactured by Genus, Sugino) Machineless "Starburst", Nanomizer "Nanomizer" etc.), M Technique "Clear SS-5" or Nara Machinery "MICROS" medialess disperser; or other roll mills etc. Can be mentioned, The present invention is not limited to these. Further, as the disperser, it is preferable to use a disperser that has been subjected to a metal mixing prevention treatment.

  For example, when using a media type disperser, a method in which the agitator and vessel use a ceramic or resin disperser, or a metal agitator and a disperser in which the vessel surface is treated with tungsten carbide spraying or resin coating, etc. Is preferably used. Then, as the medium, it is preferable to use glass beads, or ceramic beads such as zirconia beads or alumina beads. 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 underlayer 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. Moreover, the electrode for an electricity storage device of the present invention refers to an electrode forming composition (mixture) containing a base layer formed from the conductive composition of the present invention on a collector and an electrode active material and a binder. Ink) and a composite material layer formed from the ink.

(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 of the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless. In the case of a lithium ion battery, aluminum is particularly preferable as the positive electrode material, and copper is particularly preferable as the negative electrode material. Further, as the shape, a flat foil is generally used, but a roughened surface, a perforated foil-shaped one, and a mesh-shaped current collector can also be used.

  There is no particular limitation on the method of applying the conductive composition or the mixture ink described below on the current collector, and a known method can be used. Specific examples thereof include die coating method, dip coating method, roll coating method, doctor coating method, knife coating method, spray coating method, gravure coating method, screen printing method or electrostatic coating method, and drying. As the method, standing drying, blow dryer, warm air dryer, infrared heater, far infrared heater and the like can be used, but are not particularly limited thereto, and rolling treatment by a lithographic press or calendar roll after coating is performed. You may go.

  The thickness of the underlayer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and further preferably 0.5 to 3 μm. When the thickness of the underlayer is 0.1 μm or more, the bypass portion where the current collector and the active material are in direct contact is uniformly formed, and when the battery heats up, the current blocking effect due to the increase in the resistance of the underlayer portion is sufficient. Becomes On the other hand, when the thickness of the underlayer is 10 μm or less, the capacity of the electricity storage device does not easily decrease, which is preferable.

And a conductive electric storage device in normal use, from the viewpoint of resistance increase at the time of temperature rise, the density of the base layer is preferably 1.4 g / cm ³ or more, more preferably, 1.4 g / cm ³ or more It is 2.2 g / cm ³ or less. When the density of the underlayer is 1.4 g / cm ³ or more, it is considered that the effect of cutting the contact between the carbon materials due to the volume expansion of the olefin resin fine particles is enhanced, and it is particularly preferable to use graphite as the carbon material. preferable.

  The underlayer can be provided on one side or both sides of the current collector, but it is preferably provided on both sides of the current collector from the viewpoint of increasing the resistance due to heat and reducing the internal resistance of the electricity storage device.

<Compound ink>
As described above, a general mixture ink for a power storage device essentially contains an active material and a solvent, and optionally contains a conductive auxiliary agent and a binder.
The active material is preferably contained as much as possible, and for example, the ratio of the active material in the solid content of the mixture ink is preferably 80 to 99% by mass. When the conductive additive is contained, the ratio of the conductive additive in the solid content of the mixture ink is preferably 0.1 to 15% by mass. When a binder is included, the proportion of the binder in the mixture ink solid content is preferably 0.1 to 15% by mass.

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

  The solvent (dispersion medium) of the composite material ink is not particularly limited, but can be properly selected according to the binder used. For example, when a resin type binder is used, a solvent capable of dissolving the resin is used, and when an emulsion type binder is used, it is preferable to use a solvent capable of maintaining the dispersion of the emulsion. Examples of the solvent include amides such as dimethylformamide, dimethylacetamide and methylformamide, amines such as N-methyl-2-pyrrolidone (NMP) and dimethylamine, ketones such as methyl ethyl ketone, acetone and cyclohexanone, alcohols, Examples thereof include glycols, cellosolves, amino alcohols, sulfoxides, carboxylic acid esters, phosphoric acid esters, ethers, nitriles, water and the like. Moreover, you may use the said solvent in combination of 2 or more types as needed. For example, when polyvinylidene fluoride (PVDF) is used as a binder, NMP capable of dissolving PVDF is preferably used, and when carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) are used as binders, CMC is dissolved to obtain SBR. Water that can maintain dispersion is preferably used.

The active material used in the composite ink will be described below.
The positive electrode active material for the lithium-ion secondary battery is not particularly limited, but metal oxides capable of doping or intercalating lithium ions, metal compounds such as metal sulfides, and conductive polymers are used. be able to.

For example, oxides of transition metals such as Fe, Co, Ni, and Mn, complex oxides with lithium, inorganic compounds such as transition metal sulfides, and the like can be given. Specifically, MnO, V ₂ O ₅ , V ₆ O ₁₃ ,
Transition metal oxide powder such as TiO ₂ ; layered structure lithium nickel oxide, lithium cobalt oxide, lithium manganate, complex oxide powder of lithium and transition metal such as spinel structure lithium manganate, olivine structure phosphoric acid compound Examples include lithium iron phosphate-based materials, transition metal sulfide powders such as TiS ₂ and FeS, and the like.

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

The negative electrode active material for a lithium ion secondary battery is not particularly limited as long as it can dope or intercalate lithium ions. For example, metallic Li, alloys thereof such as tin alloy, silicon alloy, lead alloy, Li _X Fe ₂ O ₃ , Li _X Fe ₃ O ₄ , Li _X WO ₂ , lithium titanate, lithium vanadate, and silicon. Metal oxides such as lithium oxide, conductive polymers such as polyacetylene and poly-p-phenylene, amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon materials, or natural Carbonaceous materials such as carbonaceous powders such as graphite, carbon black, mesophase carbon black, resin-fired carbon materials, vapor-grown carbon fibers, carbon fibers and the like can be mentioned. These negative electrode active materials may be used alone or in combination of two or more.

The electrode active material for the electric double layer capacitor is not particularly limited, but examples thereof include activated carbon, polyacene, carbon whiskers, graphite and the like, and powders or fibers thereof. A preferred electrode active material for electric double layer capacitors is activated carbon, specifically, activated carbon activated with phenolic, coconut husk, rayon, acrylic, coal / petroleum pitch coke, mesocarbon microbeads (MCMB), etc. Can be mentioned. It is preferable that the specific surface area is large so that an interface having a larger area can be formed even with the same weight. Specifically, the specific surface area is preferably 30 m ² / g or more, preferably 500 to 5000 m ² / g, more preferably 1000 to 3000 m ² / g.

  These electrode active materials can be used alone or in combination of two or more kinds, and may be used in combination of two or more kinds of carbon having different volume average particle diameter (D50) or particle size distribution.

  The positive electrode active material for a lithium ion capacitor is not particularly limited as long as it is a material capable of reversibly doping / dedoping lithium ions and anions, and examples thereof include activated carbon powder. The volume average particle diameter (D50) of the activated carbon is preferably 0.1 μm to 20 μm. The volume average particle diameter (D50) here is as described above.

  The negative electrode active material for a lithium ion capacitor is not particularly limited as long as it is a material capable of reversibly doping / dedoping lithium ions, and examples thereof include graphite-based materials such as artificial graphite and natural graphite. Can be mentioned. The volume average particle diameter (D50) of the graphite material is preferably 0.1 μm to 20 μm. The volume average particle diameter (D50) here is as described above.

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

  The binder in the composite ink is used to bind particles of the active material or the conductive carbon material to each other, or to bind the conductive carbon material and the current collector.

As the binder used in the mixture ink, for example, acrylic resin, polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicone 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, 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 may be used alone or in combination of two or more.
The binder preferably used in the aqueous mixture ink is preferably an aqueous medium, and examples of the binder form of the aqueous medium include water-soluble type, emulsion type, hydrosol type, etc., and are appropriately selected. be able to.

  Further, a film forming aid, a defoaming agent, a leveling agent, a preservative, a pH adjusting agent, a viscosity adjusting agent and the like can be added to the mixture ink as required.

<Method of manufacturing electrode>
The conductive composition of the present invention can be applied on a current collector and dried to form an underlayer, whereby an underlayer electrode for an electricity storage device can be obtained.

  Alternatively, the conductive composition of the present invention may be applied on a current collector and dried to form an underlayer, and a mixture layer may be provided on the underlayer to obtain an electrode for a power storage device. The composite material layer provided on the base layer can be formed using the composite material ink described above.

<Power storage device>
By using the above electrode for at least one of the positive electrode and the negative electrode, a power storage device such as a secondary battery or a capacitor can be obtained.

  Examples of the secondary battery include a lithium-ion secondary battery, a sodium-ion secondary battery, a magnesium-ion secondary battery, an alkaline secondary battery, a lead storage battery, a sodium-sulfur secondary battery, a lithium-air secondary battery, and the like. An electrolytic solution, a separator, or the like conventionally known in each secondary battery can be appropriately used.

  Examples of the capacitor include an electric double layer capacitor, a lithium ion capacitor, and the like, and an electrolytic solution, a separator, or the like conventionally known for each capacitor can be appropriately used.

<Electrolyte>
A case of a lithium ion secondary battery will be described as an example. As the electrolytic solution, a solution containing an electrolyte containing lithium dissolved in a non-aqueous solvent is used.

Examples of the electrolyte include 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, LiBPh _{4 and the} like, but are not limited thereto.

The non-aqueous solvent is not particularly limited, but examples thereof include 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;
Examples thereof include nitriles such as acetonitrile. Further, these solvents may be used alone or in combination of two or more kinds.

  Further, the above electrolyte solution may be held in a polymer matrix to form a gel polymer electrolyte. 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 polyethylene non-woven fabric, polypropylene non-woven fabric, polyamide non-woven fabric, and those obtained by subjecting them to hydrophilic treatment, but are not particularly limited thereto.

  The structure of the lithium ion secondary battery, the electric double layer capacitor, the lithium ion capacitor using the composition of the present invention is not particularly limited, but is usually composed of a positive electrode and a negative electrode, and a separator provided as necessary, Various shapes such as a paper type, a cylinder type, a button type, and a laminated type can be used according to the purpose of use.

(Example 1)
<Conductive composition>
1. 60 parts by mass of graphite (A-1: TIMREX KS-6, manufactured by Timcal) as a conductive carbon material, carboxymethyl cellulose (B-1: CMC Daicel # 1240, manufactured by Daicel Chemical Industries, Ltd.) which is a water-soluble resin 2. 200 parts by mass of a 5% aqueous solution (5 parts by mass as a solid content) and 500 parts by mass of water as an aqueous liquid medium (D) were put in a mixer and mixed for 30 minutes, and further put in a sand mill and dispersed for 30 minutes. Next, 140 parts by mass of polyolefin-based resin particles (C-1: Arrow Base SB-1200, manufactured by Unitika Ltd., 25% aqueous dispersion liquid (average particle diameter 0.10 μm)) which are water-dispersed resin particles (35 parts by mass as solid content). Part) and mixed for 10 minutes with a mixer to obtain a conductive composition (1).

The materials used in Examples and Comparative Examples were evaluated as follows.
(Total specific surface area of conductive carbon material)
The specific surface area of the conductive carbon material was measured according to JIS K6217-2 using a gas adsorption amount measuring device (BELSORP-mini manufactured by Bell Japan Ltd.). For the total specific surface area, the weighted average value of the specific surface area of each conductive carbon material and the mixing ratio was used as the total specific surface area.

(Viscosity of carboxymethyl cellulose aqueous solution)
An aqueous solution was prepared by mixing 1 g of carboxymethyl cellulose and 99 g of water. Then, the viscosity of the aqueous solution was measured by a rheometer (AR-G2 manufactured by TA Instruments Co., Ltd.) using a cone plate (60 mm, 1 °) at a measurement temperature of 25 ° C. and a shear rate of 360 (1 / s).

(Volume average particle diameter of water-dispersed resin particles)
The water-dispersed resin fine particle dispersion is diluted with water 200 to 1000 times according to the solid content, and about 5 ml of the diluted solution is injected into the cell of Nanotrac (Wave-EX150 manufactured by Nikkiso Co., Ltd.) to refract water and resin. After inputting the rate conditions, measurement was performed to determine the D50 volume average particle diameter. The "volume average particle diameter" may be abbreviated as "average particle diameter".

(Carbonyl group content in polyolefin resin fine particles (Y) / (X))
The dispersion liquid containing the water-dispersed resin fine particles (C) was 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 solid was measured by a total reflection measurement method (ATR) using a Fourier transform infrared spectroscope (FT-IR: Spectrum One / 100 manufactured by PerkinElmer) to obtain an infrared absorption spectrum. Carbonyl group content in the resin fine particles, using an infrared absorption spectrum obtained by plotting absorbance against wave number, 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 The height (maximum absorbance) (X) from the maximum peak derived from olefin at 2800 to 3000 cm ^-1 to the baseline BX when the baseline BX is set (X), the point indicating the absorbance at 1650 m ^{-1 and} the absorbance at 1850 cm ^-1 When the straight line connecting two points with the point indicating is the baseline BY, the ratio from the maximum peak derived from the carbonyl group at 1690 to 1740 cm ⁻¹ to the baseline BY (maximum absorbance) (Y) ( Y) / (X) was calculated.

(Examples 2-15, Comparative Examples 2-3, Reference Example 1)
Conductive compositions (2) to (15) and (17) to (19) were obtained in the same manner as in Example 1 except that the materials and composition ratios shown in Table 1 were changed.

The materials used in Examples and Comparative Examples are shown below.
(Conductive carbon material (A))
A-1: TIMREX KS-6 (manufactured by Timcal, graphite, specific surface area 20 m ² / g)
A-2: J-SP-α (manufactured by Nippon Graphite Co., Ltd., graphite, specific surface area 10 m ² / g, average particle size 6 μm)
A-3: SNO-5 (made by SEC Carbon Co., graphite, specific area 15 m ² / g, average particle size 5 μm)
-A-4: Denka Black HS-100 (manufactured by Denka Co., acetylene black, average particle diameter 48 nm, specific surface area 45 m ² / g)
(Water-soluble resin) (B))
B-1: CMC Daicel # 1240 (manufactured by Daicel Chemical Industries, carboxymethyl cellulose, viscosity 0.02 Pa · s)
B-2: sodium polyacrylate (Wako Pure Chemical Industries, Ltd., average molecular weight 5000)
B-3: Kuraray Poval PVA235 (Kuraray's polyvinyl alcohol)
(Water-dispersed resin fine particles (C))
C-1: Saixen AC (30% solid content aqueous dispersion, average particle size 0.04 μm, modification amount (Y) / (X) 0.64, carbonyl group-containing polyethylene resin fine particles) (Sumitomo Seika Chemicals Ltd.) Made)
C-2: Arrow base SB-1200 (solid content 25% aqueous dispersion, average particle size 0.10 μm, modification amount (Y) / (X) 0.58, carbonyl group-containing polyethylene resin fine particles) (Unitika) (Made by the company)
C-3: Chemipearl W4005 (solid content 40% aqueous dispersion, average particle size 0.57 μm, unmodified, polyethylene resin fine particles) (manufactured by Mitsui Chemicals, Inc.)

<Current collector with underlayer> (Examples 1 to 14, Comparative examples 2 to 3, Reference example 1)
The conductive compositions (1) to (14) and (17) to (19) were formed into aluminum foil having a thickness of 20 μm (hereinafter, referred to as a current collector) so that the thickness after drying would be the thickness shown in Table 1. (Although abbreviated as "aluminum") is applied using a bar coater, then dried by heating at 80 ° C., and current collectors (1) to (14) and (17) to (19) with a base layer. ) Respectively.

<Current collector with underlayer> (Example 15)
The conductive composition (15) was applied using a bar coater on a copper foil having a thickness of 20 μm to serve as a current collector so that the thickness after drying was 3 μm, and then dried by heating at 80 ° C. A collector (15) with a base layer was obtained.

  Table 1 shows the obtained conductive composition and current collector with an underlayer.

<Compound 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, which is a kind of 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. And mixed to prepare a positive electrode mixture ink which is a kind of electrode forming composition.

<Lithium-ion secondary battery negative electrode mixture ink>
As a negative electrode active material, which is a kind of electrode active material, 98 parts by mass of artificial graphite and 66.7 parts by mass of 1.5% aqueous solution of carboxymethyl cellulose (1 part by mass as solid content) were put into a planetary mixer and kneaded, and 33 parts of water was added. Part, and 2.08 parts by mass of a styrene-butadiene emulsion 48% by mass aqueous dispersion (1 part by mass as a solid content) were mixed to obtain a negative electrode secondary battery electrode mixture ink which is a kind of electrode forming composition. .

<Positive Electrode for Lithium Ion Secondary Battery with Underlayer> (Examples 1 to 14, Comparative Examples 2 to 3, Reference Example 1)
The above-mentioned lithium ion secondary battery positive electrode mixture ink is dried on the surface of the current collectors (1) to (14) and (17) to (19) with an underlayer for a secondary battery on which the underlayer is formed. It was applied using a doctor blade so that the subsequent basis weight would be 20 mg / cm ^2, and dried by heating at 80 ° C. Further, a rolling treatment was performed by a roll press to produce positive electrodes (1) to (14) and (17) to (19) having a composite material layer density of 3.1 g / cm ³ .

<Cathode for Lithium Ion Secondary Battery without Underlayer> (Cathode for Example 15 and Comparative Example 1)
The above-mentioned lithium ion secondary battery positive electrode mixture ink was used on a 20 μm thick aluminum foil as a current collector using a doctor blade so that the basis weight after drying would be 20 mg / cm ^2. And then dried by heating at 80 ° C. Further, a rolling treatment was performed by a roll press to produce positive electrodes (15) and (16) having a composite material layer density of 3.1 g / cm ³ .

<Anode for Lithium Ion Secondary Battery without Underlayer> (Anodes for Examples 1-14, Comparative Examples 1-3, and Reference Example 1)
The above-mentioned lithium ion secondary battery negative electrode mixture ink was applied using a doctor blade so that the basis weight after drying was 12 mg / cm ^2, and was heated and dried at 80 ° C. Further, a rolling process was performed by a roll press to produce negative electrodes (1) to (14) and (16) to (19) having a composite material layer density of 1.5 g / cm ³ .

<Anode for Lithium Ion Secondary Battery with Underlayer> (Example 15)
A doctor blade was applied to the surface of the current collector (15) having a base layer on which the base layer was formed, so that the basis weight of the lithium ion secondary battery negative electrode composite material ink was 12 mg / cm ^2. It was applied, and dried by heating at 80 ° C. Further, a rolling treatment was performed by a roll press to prepare a negative electrode (15) having a composite material layer density of 1.5 g / cm ³ .

<Laminate type lithium ion secondary battery> (Examples 1 to 15, Comparative examples 1 to 3, Reference example 1)
The positive electrode and the negative electrode shown in Table 2 were punched out into 45 mm × 40 mm and 50 mm × 45 mm, respectively, and a separator (porous polypropylene film) inserted between them was inserted into an aluminum laminate bag, vacuum-dried, and then an electrolytic solution. After injecting (a non-aqueous electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1M into a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio of 1: 1 (volume ratio)), the aluminum laminate was sealed. A laminate type lithium ion battery was produced. The laminate type lithium ion type battery is manufactured in a glove box in which argon gas is replaced. After the laminate type lithium ion type battery is manufactured, the initial resistance, resistance increase, rate characteristics and cycle characteristics of the battery characteristics are measured by the following methods. An evaluation was made.

(Resistance measurement)
The resistance of the laminate type battery, which was subjected to constant current discharge at a discharge end voltage of 3.0 V at a discharge current of 12 mA (0.2 C), at 500 kHz by an impedance analyzer (SP-50 manufactured by biologic).
The above-mentioned laminated battery was heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min all at once, and the resistance was measured. The resistance measured at 25 ° C. was taken as the initial resistance, and the value calculated by the following (formula 1) was taken as the resistance increase.
(Equation 1) Resistance increase = resistance value at 180 ° C./resistance value at 25 ° C. Table 2 shows the results of evaluation of initial resistance and resistance increase based on the following criteria.
-Initial resistance ◯: "Initial resistance is smaller than the initial resistance of Comparative Example 1 without the underlayer. Excellent."
Δ: “Initial resistance is equivalent to that of Comparative Example 1 without the underlayer.”
X: "Initial resistance is larger than the initial resistance of Comparative Example 1 without the underlayer. Inferior."
・ Increase in resistance ○ ○: “Increase in resistance is 10 times or more of initial resistance. Particularly excellent.”
◯: “Increase in resistance is 5 times or more and less than 10 times the initial resistance. Excellent.”
Δ: “Increase in resistance is 3 times or more and less than 5 times the initial inefficiency. A practical level”
X: "Increase in resistance is less than three times the initial resistance. Current cutoff effect is low. Poor."

(Rate characteristics)
The above-mentioned laminated battery was subjected to charge / discharge measurement using a charge / discharge device (SM-8 manufactured by Hokuto Denko KK).
Constant current constant voltage charge with charge end voltage 4.2V at charge current 12mA (0.2C) (cutoff current 0.6mA, then discharge end at discharge currents 12mA (0.2C) and 120mA (2C). Constant-current discharge was performed until the voltage reached 3.0 V, and the respective discharge capacities were obtained.The rate characteristics are represented by the ratio of 0.2 C discharge capacity and 2 C discharge capacity, that is, (Formula 2) below.
(Equation 2) Rate characteristic = 2C discharge capacity / 0.2C discharge capacity × 100 (%)
The results evaluated according to the following criteria are shown in Table 2.
-Rate characteristic ◯: "Rate characteristic is 80% or more. Excellent."
Δ: “Rate characteristic is 70 or more and less than 80%. Equivalent to the rate characteristic of Comparative Example 1 without the underlayer.”
X: "Rate characteristic is less than 70%. Inferior."

(Cycle characteristics)
After performing constant-current constant-voltage charging (cut-off 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 end voltage reaches 3.0 V at a discharge current of 60 mA. The constant current discharge was performed up to and the initial discharge capacity was determined. This charging / discharging cycle was performed 200 times, and the discharge capacity retention ratio (percentage of the discharge capacity at the 200th time with respect to the initial discharge capacity) was calculated. The results evaluated according to the following criteria are shown in Table 2.
・ Cycle characteristics ○: "Discharge capacity maintenance rate is 85% or more. Excellent."
Δ: “Discharge capacity retention rate is 80% or more and less than 85%. Equivalent to the discharge capacity retention rate of Comparative Example 1 without the underlayer.”
X: "Discharge capacity retention rate is less than 80%. Inferior."

  As shown in Table 2, it was confirmed that by using the underlayer formed of the conductive composition of the present invention, the internal resistance of the battery was increased when the internal temperature of the battery was increased. From this, for example, when the battery abnormally generates heat due to an internal short circuit or the like, it is considered that the resistance of the current collector increases and the current is cut off to prevent the battery from igniting.

  On the other hand, Comparative Example 1 in which an underlayer is not formed, and Comparative Examples 2 to 3 in which graphite is not included or the ratio of graphite is small, the specific surface area of the conductive carbon material (A) is high, and the density of the underlayer is low. In Reference Example 1, no noticeable increase in the internal resistance of the battery was observed even if the internal temperature of the battery increased.

  Since Comparative Example 1 does not form the underlayer, it has no effect of increasing the resistance during heat generation, and in Comparative Examples 2-3 and Reference Example 1, the volume expansion of graphite accompanying the volume expansion of the resin during heat generation is insufficient. Therefore, it is considered that the effect of blocking the conductivity between the carbon materials was small.

<Compound ink for positive and negative electrodes for electric double layer capacitors>
85 parts of activated carbon (specific surface area 1800 m ² / g) as an active material, 5 parts of conduction aid (acetylene black: Denka Black HS-100, manufactured by Denka), 8 parts of carboxymethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd.), binder ( Polytetrafluoroethylene 30-J: Mitsui DuPont Fluorochemical Co., 60% aqueous dispersion 3.3 parts (2 parts as solid content) and 220 parts of water are mixed to prepare a composite ink for positive and negative electrodes. did.

<Positive Electrode for Electric Double Layer Capacitor without Underlayer, Negative Electrode (Comparative Example 4, and Counter Electrode for Evaluation)>
The mixture ink for electric double layer capacitors described above was applied onto an aluminum foil having a thickness of 20 μm, which is a current collector, using a doctor blade, followed by heating and drying, followed by rolling treatment by a roll press to obtain an electrode thickness. A positive electrode and a negative electrode having a thickness of 50 μm were produced.

<Positive electrode, negative electrode for electric double layer capacitor with underlayer>
(Example 16)
The composite ink for electric double layer capacitors described above was applied to the surface of the current collector (1) with an underlayer of Example 1 on which the underlayer was formed by using a doctor blade and then dried by heating at 80 ° C. After that, rolling treatment was performed by a roll press to produce a positive electrode having a thickness of 50 μm.

(Examples 17 to 29, Comparative Examples 5 and 6, Reference Example 2)
A positive electrode and a negative electrode were produced in the same manner as in Example 16, except that the current collector with underlayer (1) was changed to the current collector shown in Table 3.

<Electric double layer capacitor>
Each of the positive electrode and the negative electrode shown in Table 3 was punched out to a diameter of 16 mm, and a separator (porous polypropylene film) inserted between them and an electrolytic solution (propylene carbonate solvent TEMABF ₄ (boron tetrafluoride triethylmethylammonium)) at a concentration of 1M. An electric double layer capacitor composed of the non-aqueous electrolyte solution dissolved in. The electric double layer capacitor was carried out in a glove box in which argon gas was replaced, and after the electric double layer capacitor was manufactured, predetermined electric characteristics were evaluated.

(Charge / discharge cycle characteristics)
The obtained electric double layer capacitor was subjected to charge / discharge measurement using a charge / discharge device.
After charging to a charge end voltage of 2.0 V at a charge current of 10 C rate, constant current discharge was performed at a discharge current of 10 C until a discharge end voltage of 0 V was reached. These charging / discharging cycles were set as one cycle, charging / discharging was repeated for 5 cycles, and the discharging capacity at the 5th cycle was defined as the initial discharging capacity. (The initial discharge capacity is 100% maintenance rate). The charging / discharging current rate was set such that the amount of current capable of discharging the cell capacity in 1 hour was 1C.
Next, after charging at a charge current of 10 C at a charge end voltage of 2.0 V in a 50 ° C. constant temperature bath, constant current discharge was performed at a discharge current of 10 C until a discharge end voltage of 0 V was reached. This charge / discharge cycle was repeated 500 times to calculate the change rate of the discharge capacity retention rate (the closer to 100%, the better).
◯: “The change rate is 85% or more. Excellent.”
Δ: “The rate of change is 80% or more and less than 85%. Equivalent to the discharge capacity retention rate of Comparative Example 1 without the underlayer.”
X: "The change rate is less than 80%. Inferior."

(Resistance measurement)
The resistance of the laminate type battery charged at a charge current of 10 C to a charge end voltage of 2.0 V was measured at 500 kHz with an impedance analyzer (SP-50 manufactured by biologic).
The above-mentioned laminated battery was heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min all at once, and the resistance was measured. 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 represented by the following (Equation 1).
(Equation 1) Resistance increase = resistance value at 180 ° C./resistance value at 25 ° C. Table 2 shows the results of evaluation of initial resistance and resistance increase based on the following criteria.
-Initial resistance ◯: "Initial resistance is smaller than the initial resistance of Comparative Example 1 without the underlayer. Excellent."
Δ: “Initial resistance is equivalent to that of Comparative Example 1 without the underlayer.”
X: "Initial resistance is larger than the initial resistance of Comparative Example 1 without the underlayer. Inferior."
・ Increase in resistance ○ ○: “Increase in resistance is 10 times or more of initial resistance. Particularly excellent.”
◯: “Increase in resistance is 5 times or more and less than 10 times the initial resistance. Excellent.”
Δ: “Increase in resistance is 3 times or more and less than 5 times the initial inefficiency. A practical level”
X: "Increase in resistance is less than three times the initial resistance. Current cutoff effect is low. Poor."

<Compound ink for positive electrode for lithium ion capacitor>
85 parts of activated carbon (specific surface area 1800 m ² / g) as an active material, 5 parts of conduction aid (acetylene black: Denka Black HS-100, manufactured by Denka), 8 parts of carboxymethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd.), binder ( Polytetrafluoroethylene 30-J: manufactured by Mitsui DuPont Fluorochemical Co., Ltd., 60% aqueous dispersion 3.3 parts (2 parts as solid content) were mixed to prepare a positive electrode material mixture ink.

<Negative electrode mixture ink for lithium-ion capacitors>
90 parts of graphite as a negative electrode active material, 5 parts of a conductive additive (acetylene black: Denka Black HS-100, manufactured by Denka), 175 parts of a 2 wt% aqueous solution of hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd.) (as a solid content of 3. 5 parts) are put into a mixer and mixed, and 26.3 parts of water and 3.75 parts of binder (SBR: 40% aqueous dispersion of styrene butadiene latex) (1.5 parts as solid content) are mixed to form a negative electrode. A mixed material ink was prepared.

<Positive Electrode for Lithium Ion Capacitor without Underlayer (Example 41, Comparative Example 7)>
The positive electrode mixture ink for a lithium ion capacitor described above was applied onto a 20 μm thick aluminum foil serving as a current collector using a doctor blade, dried under reduced pressure and subjected to rolling treatment by a roll press. A positive electrode having a thickness of 60 μm was produced.

<Positive electrode for lithium-ion capacitor with underlayer>
(Example 30)
The positive electrode mixture ink for a lithium ion capacitor described above was applied to the surface of the current collector (1) with an underlayer of Example 1 on which the underlayer was formed using a doctor blade, followed by heating under reduced pressure and drying. After performing rolling treatment by a roll press, a positive electrode having a thickness of 60 μm was produced.

(Examples 31 to 40, 42, 43, Comparative Examples 8, 9 and Reference Example 3)
A positive electrode was obtained in the same manner as in Example 30, except that the collector (1) with the underlayer was changed to the collector shown in Table 4.

<Negative Electrode for Lithium Ion Capacitor without Underlayer (Examples 30 to 40, 42, 43, Comparative Examples 7 to 9 and Reference Example 3)>
The above-mentioned negative electrode mixture ink for lithium ion capacitors was applied onto a copper foil having a thickness of 20 μm to be a current collector using a doctor blade, followed by drying under reduced pressure and rolling treatment by a roll press, A negative electrode having a thickness of 45 μm was produced.

<Negative electrode for lithium ion capacitor with underlayer>
(Example 41)
The above negative electrode mixture ink for lithium ion capacitors was applied onto the current collector (1) with an underlayer of Example 1 by using a doctor blade, followed by drying under reduced pressure and rolling treatment by a roll press. After that, a negative electrode having a thickness of 45 μm was manufactured.

<Lithium-ion capacitor>
A positive electrode shown in Table 4 and a negative electrode half-doped with lithium ions were prepared in a size of 16 mm in diameter, and a separator (porous polypropylene film) inserted between them and an electrolytic solution (ethylene carbonate and dimethyl) were prepared. A lithium ion capacitor composed of a mixed solvent of carbonate and diethyl carbonate in a ratio of 1: 1: 1 (volume ratio) and a non-aqueous electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1 M was produced. Half-doping of lithium ions was performed by sandwiching a separator between a negative electrode and lithium metal in a beaker cell and doping the negative electrode with lithium ions so that the amount of the lithium ions would be about half the negative electrode capacity. Further, the lithium ion capacitor was carried out in a glove box whose atmosphere was replaced with argon gas, and after the lithium ion capacitor was produced, predetermined electric characteristics were evaluated.

(Charge / discharge cycle characteristics)
The obtained lithium ion capacitor was subjected to charge / discharge measurement using a charge / discharge device.
After charging to a charge end voltage of 4.0 V at a charge current of 10 C, constant current discharge was performed at a discharge current of 10 C until a discharge end voltage of 2.0 V was reached. These charging / discharging cycles were set as one cycle, charging / discharging was repeated for 5 cycles, and the discharging capacity at the 5th cycle was defined as the initial discharging capacity. (The initial discharge capacity is 100% maintenance rate).
Next, after charging at a charge current of 10 C at a charge end voltage of 4.0 V in a 50 ° C. constant temperature bath, constant current discharge was performed at a discharge current of 10 C until a discharge end voltage of 2.0 V was reached. This charge / discharge cycle was repeated 500 times to calculate the change rate of the discharge capacity retention rate (the closer to 100%, the better).
◯: “The change rate is 85% or more. Excellent.”
Δ: “The rate of change is 80% or more and less than 85%. Equivalent to the discharge capacity retention rate of Comparative Example 1 without the underlayer.”
X: "The change rate is less than 80%. Inferior."

(Resistance measurement)
The resistance of the laminate type battery charged at a charge current of 10 C to a charge end voltage of 4.0 V was measured at 500 kHz with an impedance analyzer (SP-50 manufactured by biologic).
The above-mentioned laminated battery was heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min all at once, and the resistance was measured. 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 represented by the following (Equation 1).
(Equation 1) Resistance increase = resistance value at 180 ° C./resistance value at 25 ° C. Table 2 shows the results of evaluation of initial resistance and resistance increase based on the following criteria.
-Initial resistance ◯: "Initial resistance is smaller than the initial resistance of Comparative Example 1 without the underlayer. Excellent."
Δ: “Initial resistance is equivalent to that of Comparative Example 1 without the underlayer.”
X: "Initial resistance is larger than the initial resistance of Comparative Example 1 without the underlayer. Inferior."
・ Increase in resistance ○ ○: “Increase in resistance is 10 times or more of initial resistance. Particularly excellent.”
◯: “Increase in resistance is 5 times or more and less than 10 times the initial resistance. Excellent.”
Δ: “Increase in resistance is 3 times or more and less than 5 times the initial inefficiency. A practical level”
X: "Increase in resistance is less than three times the initial resistance. Current cutoff effect is low. Poor."

  Further, as shown in Tables 3 and 4, it was confirmed that the electric double layer capacitor and the lithium ion capacitor had the same effects as those of the examples of the lithium ion secondary battery.

  From the above results, according to the present invention, it is possible to suppress the current flowing by increasing the internal resistance when the internal temperature of the electricity storage device rises due to overcharge, internal short-circuiting, etc. It is possible to provide a conductive composition for forming a power storage device such as a non-aqueous electrolyte secondary battery having a function of enhancing battery safety.

Claims (7)

Conductivity for forming an underlayer of an electrode for an electricity storage device, which contains a conductive carbon material (A), a water-soluble resin (B), water-dispersed resin fine particles (C), and an aqueous liquid medium (D) In the composition, the water-dispersed resin fine particles contain at least olefin-based resin fine particles, and the content of the conductive carbon material (A) is 30 to 70 in the total solid content of 100% by mass of the conductive composition. The content of the water-soluble resin (B) is 1 to 40 mass%, the content of the water-dispersed resin fine particles (C) is 20 to 60 mass%, and the conductive carbon material ( A total specific surface area of A) is 30 m ² / g or less, a conductive composition for forming an underlayer of an electrode for an electricity storage device. The conductive carbon material (A) contains at least graphite, and the content ratio of graphite in the conductive carbon material (A) is 60 to 100% by mass. Composition. The olefin resin fine particles contained in the water-dispersed resin fine particles (C) are polyolefin resin fine particles having a carbonyl group, and the infrared absorption spectrum of the polyolefin resin fine particles has a maximum peak height of 2800 to 3000 cm ^-1 (maximum absorbance). The ratio (Y) / (X) of (X) and the maximum peak height (maximum absorbance) (Y) of 1690 to 1740 cm ⁻¹ is 0.05 to 1.0. 1. The underlayer-forming conductive composition as described in 1 or 2. A current collector with an underlayer for an electricity storage device, comprising a current collector and an underlayer formed from the conductive composition for forming an underlayer of an electrode for an electricity storage device according to claim 1. An electrode forming composition comprising a current collector, an underlayer formed from the conductive composition for forming an underlayer of an electrode for an electricity storage device according to any one of claims 1 to 3, an electrode active material and a binder. An electrode for a power storage device having a composite material layer formed from. An electricity storage device comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein at least one of the positive electrode and the negative electrode is the electrode for an electricity storage device according to claim 5. The power storage device according to claim 6, wherein the power storage device is a non-aqueous electrolyte secondary battery, an electric double layer capacitor or a lithium ion capacitor.