JP2017228344A - Conductive composition, backing-attached current collector for power storage device, electrode for power storage device, and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device which achieves superior output and other characteristics without marring the energy density of a power storage device, and which can suppress excessive heat generation and combustion by increasing the internal resistance when the temperature rises; and an electrode, a current collector, a conductive composition for constituting the power storage.SOLUTION: A conductive composition for forming an underlying layer of an electrode for a power storage device comprises: a conductive carbon material (A); a water-soluble resin (B); water-dispersible resin fine particles (C); and an aqueous liquid medium (D). The water-dispersible resin fine particles include olefin-based resin fine particles. To a total of 100 mass% of solid contents of the conductive composition, the content of conductive carbon material (A) is 30-70 mass%, the content of the water-soluble resin (B) is 1-40 mass%, and the content of the water-dispersible resin fine particles (C) is 20-60 mass%. The conductive carbon material (A) is 30 m/g or less in total specific surface area.SELECTED DRAWING: None

Description

  The present invention relates to an electrode for a conductive composition, and 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, etc.) obtained by using the composition, and The present invention relates to 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 the batteries to be mounted are also required to be small, light, and have a large capacity. 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 entire battery is low.

  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 additive that does 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 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 are problems such that the internal resistance during normal operation of the battery is high and the output characteristics of the battery are low.

  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 is not sufficient when the temperature in 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, but the resistance rises when the temperature inside the battery rises. Is not enough.

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

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

The present invention is a conductive composition comprising 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. Sometimes the resistance of the current collector increases and the current is cut off, thereby avoiding ignition of the electricity storage device.
When the present inventors appropriately control the solid content ratio of the conductive composition and the total specific surface area of the conductive carbon material (A), surprisingly, the internal resistance during normal operation is reduced, and the electric storage device. As a result, the inventors have found that a dramatic increase in resistance occurs when the internal temperature rises, leading to the present invention.

That is, the present invention provides an electrode for an electricity storage device comprising 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 include at least olefin resin fine particles, and the conductive carbon material (A) is contained in a total of 100% by mass of the solid content of the conductive composition. The rate is 30 to 70% by mass, the content of the water-soluble resin (B) is 1 to 40% by mass, the content of the water-dispersed resin fine particles (C) is 20 to 60% by mass, The conductive carbon material (A) has a total specific surface area of 30 m ² / g or less, and relates to a conductive composition for forming a base layer of an electrode for an electricity storage device.

  Further, the present invention provides the above conductive for forming an underlayer, wherein 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. It relates to a sex composition.

Further, in the present invention, 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 maximum peak of 2800 to 3000 cm ⁻¹ in the infrared absorption spectrum of the polyolefin resin fine particles. The ratio (Y) / (X) between the height (maximum absorbance) (X) and the maximum peak height (maximum absorbance) (Y) of 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 comprising a current collector and an underlayer formed from the conductive composition for forming an underlayer for the 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, a base layer formed from the conductive composition for forming the base layer of the electrode for an electricity storage device, and an electrode forming composition containing an electrode active material and a binder. The present invention relates to an electrode for an electricity storage device having a composite 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 electricity storage device, wherein the electricity storage device is any one of a nonaqueous electrolyte secondary battery, an electric double layer capacitor, and a lithium ion capacitor.

  By this invention, it is excellent in the output characteristic of the electrical storage device at the time of a normal operation, etc., and when the internal temperature of an electrical storage device rises, an electrical storage device (for example, a lithium ion secondary battery etc.) which can suppress excessive heat generation and ignition Non-aqueous electrolyte secondary batteries, electric double layer capacitors, lithium ion capacitors, etc.) can be provided.

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

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

  In the total 100% by mass of the solid content of the conductive composition, the content of the water-soluble resin (B) is 1 to 40 masses from the viewpoint of electrode adhesion and conductivity, and increase in internal resistance of the battery during heat generation. %, Preferably 5 to 30% by mass. When the content of the water-soluble resin (B) is 1 to 40% by mass, even when the polyolefin resin fine particles are melted by heating, the effect of the water-soluble resin (B) preventing re-contact between carbons is confirmed. This is preferable because it significantly improves the safety.

  In the total 100% by mass of the solid content of the conductive composition, the content of the water-dispersed resin fine particles (C) 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. Preferably, it is 30-50 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 (water-dispersed resin fine particles (C)) is sufficiently expressed, and 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) in the total solid content of 100% by mass of the conductive composition is determined by the internal resistance, conductivity, and battery during heat generation. From the viewpoint of an increase in internal resistance, it is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. You may add arbitrary components to the said composition as needed.

  The optional component is not particularly limited. For example, the material that adsorbs or consumes the acid generated by the reaction of the electrolytic solution, the material that generates gas when the temperature exceeds a predetermined temperature, the inorganic PTC material, and the polyolefin resin fine particles expand in volume. A material for holding the conductive path after the process may be added.

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 acid generated by the reaction of the electrolyte include metal carbonates such as magnesium carbonate and calcium carbonate, sodium carboxylate, potassium carboxylate, sodium sulfonate, potassium sulfonate, sodium benzoate, potassium benzoate, etc. Metal silicates such as sodium silicate, potassium silicate, aluminum silicate, magnesium silicate, and silicon dioxide, and alkali hydroxides such as magnesium hydroxide.

  Examples of materials that generate gas when the temperature exceeds a predetermined temperature include carbonates such as lithium carbonate, zinc carbonate, lead carbonate, and strontium carbonate, and expanded graphite.

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

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

  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.

<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 fiber (carbon nanotube, carbon nano). Fiber, carbon fiber), fullerene and the like can be used alone or in combination of two or more. In particular, graphite is preferably used from the viewpoint of increasing the internal resistance of the battery during heat generation. By incorporating graphite into the conductive carbon material (A), the olefin-based resin fine particles expand in volume, and at the same time, the graphite expands in volume, and the contact between the conductive carbon materials breaks from point contact or contact. For this reason, 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. Examples of the present invention include natural graphite such as earthy graphite, massive graphite, and scaly graphite, and artificial graphite. In addition, exfoliated graphite, exfoliated graphite with improved moldability and conductivity by flaking, spheroidized graphite with reduced orientation by spheroidizing and pulverizing, and molten pig iron, the temperature drops due to hot metal pretreatment, etc. Also included is quiche graphite, which is a carbon crystallized in a planar manner. In addition, expanded graphite refers to, for example, immersing natural graphite or the like in a strong oxidizing solution of a mixture of concentrated sulfuric acid and nitric acid, or a mixture of concentrated sulfuric acid and hydrogen peroxide to form a graphite intercalation compound. It is a powder obtained by washing with water and then rapidly heating to expand the C-axis direction of the graphite crystal, or a powder obtained by pulverizing it once rolled into a sheet. 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.

  Commercially available graphite includes Showa Denko's SCMG-AH, SCMG-AR, SCMG-AR-H, SCMG-AF, SCMG-AFC, UF-G10, UF-G30, TIM-6's KS-6, SFG -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 Industries 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 Industries, 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, manufactured by Chuetsu Graphite Industries 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 -BH, SNO-20, SNO-10, SNO-5, SNE-20, SNE-10, SNE-5, etc. manufactured by SEC Carbon Co., are not limited to these, but two or more types You may combine.

  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.

  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.

Furthermore, the total specific surface area of the conductive carbon material (A) in the present invention is 30 m ² / g or less from the viewpoint of the electrical conductivity of the electricity storage device during normal use and the increase in resistance when the temperature rises. Preferably not more than 1.0 m ² / g or more and 30 m ² / g, more preferably not more than 5.0 m ² / g or more and 30 m ² / g. Moreover, it is thought that the effect which water-soluble resin (B) prevents the recontact of carbons can be heightened because the total specific surface area of electroconductive carbon material (A) is 30 m < ² > / g or less.
The total specific surface area in the conductive carbon material (A) of the present invention is mixed with the BET specific surface area of each conductive carbon material from the BET specific surface area measured by JIS K6217-2 using a gas adsorption amount measuring device. The weighted average value of the ratio is calculated.

<Water-soluble resin (B)>
In the present specification, the water-soluble resin (B) means that 1 g of the water-soluble resin (B) is put in 99 g of water at 25 ° C. and stirred and left at 25 ° C. for 24 hours, and then separated in water without separation / precipitation. Can be dissolved.

  The water-soluble resin (B) 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, High molecular compounds containing polysaccharide resins such as phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicon resin, polyvinyl alcohol resin, fluororesin, carboxymethyl cellulose, and the like. 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. By including a predetermined amount of the water-soluble resin (B) in the conductive composition, even when the polyester resin fine particles or the polyurethane resin fine particles are dissolved, the water-soluble resin (B) prevents re-contact between carbons. 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), there is little change over time, and the coating properties when forming the underlayer are excellent.

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

  Moreover, in this invention, it is preferable to use carboxymethylcellulose for water-soluble resin (B), and said mass mean molecular weight is 10,000-70, from a viewpoint of an increase in resistance when the internal temperature of an electrical storage device rises. More preferably, the degree of etherification is 0.3 to 1.0. Etherification is determined by boiling the incinerated sample with sulfuric acid, adding it to the phenolphthalein indicator, and back titrating excess acid with potassium hydroxide.

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

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

<Water-dispersed resin fine particles (C)>
The water-dispersed resin fine particles (C) of the present invention are generally called aqueous emulsions, and the resin fine particles are dispersed in the form of fine particles without being dissolved in water. Since it is water-dispersed resin fine particles, the electrical resistance 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 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. Moreover, two or more types of olefin resin fine particles may be included, and water-dispersed resin fine particles other than the olefin resin fine particles may be included as necessary. 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. Can be mentioned.

The water-dispersed resin fine particles are resins that can break contact between conductive carbon materials dispersed in the conductive layer by volume expansion of the olefin-based resin fine particles within a range of 80 to 180 ° C. It is preferable. Thereby, since the resistance of the electrode itself is increased, it is considered that the current flowing through the short-circuited portion is reduced, the Joule heat generation is suppressed, and the battery safety is maintained.
Examples of the olefin component in the polyolefin resin fine particles include ethylene, propylene, isobutylene, isobutene, 1-butene, 2-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1- Examples include hexene, 1-octene and norbornene. These olefin components may be one type or two or more types. In addition, modification or copolymerization with carboxylic acid or carboxylic acid ester may be performed from the effect of maintaining 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, olefin resin fine particles modified with carboxylic acid or carboxylic acid ester are preferable. Since having a carbonyl group can provide melting resistance of resin fine particles, the volume expansion of polyolefin resin fine particles can be maintained when the internal temperature of the electricity storage device rises due to an internal short circuit, etc., and the cutting effect between carbon materials is maintained. It is thought that it 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 piperate.

The content of the 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 spectrometer (FT-IR: Spectrum One / 100 manufactured by PerkinElmer). Ratio (Y) / (maximum peak height (maximum absorbance) (X) derived from an olefin of ˜3000 cm ⁻¹ to maximum peak height (maximum absorbance) (Y) derived from a carbonyl group of 1690 to 1740 cm ⁻¹ X) is preferably from 0.05 to 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 content of the carbonyl group in the polyolefin resin fine particle is based on a straight line connecting two points, a point indicating the absorbance at 2700 m ⁻¹ and a point indicating the absorbance at 3000 cm ⁻¹ , using a spectrum in which the absorbance is plotted against the wave number. The height (maximum absorbance) (X) from the maximum peak to the baseline BX among 2 or 4 derived from olefins seen at 2800 to 3000 cm ⁻¹ when the line BX is taken, and the absorbance at 1650 m ⁻¹ The height from the maximum peak derived from the carbonyl group at 1690 to 1740 cm ⁻¹ to the baseline BY when the straight line connecting the two points of the point indicating the absorbance and the point indicating the absorbance at 1850 cm ⁻¹ is defined as the baseline BY (maximum) It can be determined from the ratio (Y) / (X) to (absorbance) (Y). In general, two peaks are observed for polyethylene-based resins and four peaks for polypropylene-based resins, and in both cases, the maximum peak is observed in the vicinity of 2915 cm ⁻¹ .

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

  As a dispersion medium for the water-dispersed resin fine particles (C), it is preferable to use water. However, for stabilization of the resin fine particles, the following aqueous liquid medium (D) 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 average particle size 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 produce stably, while if the particle size is too large, it will be difficult to keep the conductivity of the conductive layer uniform, increasing the internal resistance during normal operation, and output Performance etc. deteriorates.

  In addition, the average particle diameter in this specification represents the volume average particle diameter (D50), and refers to the value 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.

<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 the coating property to the current collector. 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.

<Other additives>
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.

<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 “Clairemix” 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 power storage device, electrode for power 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 is an electrode-forming composition (composite material) comprising an underlayer formed from the conductive composition of the present invention on a current collector, an electrode active material, and a binder. 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 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 a conductive composition and the mixture ink mentioned later on a collector, A well-known method can be used. Specific examples 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 the like. Examples of methods that can be used include standing drying, blow dryers, hot air dryers, infrared heaters, and far infrared heaters, but are not limited to these, and rolling treatment with a lithographic press or calender roll after application. May be performed.

  The thickness of the underlayer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and still more preferably 0.5 to 3 μm. If 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 formed uniformly, and when the battery generates heat, the current blocking effect due to the increased resistance of the underlayer portion is sufficient It becomes. On the other hand, it is preferable that the thickness of the underlayer is 10 μm or less because the capacity of the electricity storage device is unlikely to decrease.

From the viewpoint of the electrical conductivity of the electricity storage device during normal use and the increase in resistance when the temperature rises, the density of the underlayer 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. If 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. In particular, it is possible to use graphite for the carbon material. preferable.

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

<Composite ink>
As described above, a general ink mixture for a power storage device essentially includes 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.

  Although the solvent (dispersion medium) of compound ink is not specifically limited, It can be used properly according to the binder to be used. For example, when a resin-type binder is used, a solvent capable of dissolving the resin is used. When an emulsion-type binder is used, it is preferable to use a solvent that can maintain dispersion of the emulsion. Examples of the solvent include amides such as dimethylformamide, dimethylacetamide, and methylformamide, amines such as N-methyl-2-pyrrolidone (NMP), dimethylamine, ketones such as methyl ethyl ketone, acetone, and cyclohexanone, alcohols, Examples include glycols, cellosolves, amino alcohols, sulfoxides, carboxylic acid esters, phosphate esters, ethers, nitriles, and water. Moreover, you may use it in combination of 2 or more types of the said solvent 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 a binder, CMC is dissolved and 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.

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, MnO, V ₂ O ₅ , V ₆ O ₁₃ ,
Transition metal oxide powders such as TiO _2, lithium nickelate with layered structure, lithium cobaltate, lithium manganate, composite oxide powder of lithium and transition metal such as spinel structure lithium manganate, phosphate compound with olivine structure Examples thereof include lithium iron phosphate materials, 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.

The negative electrode active material for the lithium ion secondary battery 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, Li _x Fe ₂ O ₃ , Li _x Fe ₃ O ₄ , Li _x WO ₂ , lithium titanate, lithium vanadate, 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 Examples thereof include carbonaceous powders such as graphite, carbon black, mesophase carbon black, resin-fired carbon materials, air-growth carbon fibers, and carbon fibers. These negative electrode active materials can be used alone or in combination.

Although it does not specifically limit as an electrode active material for electric double layer capacitors, Activated carbon, polyacene, carbon whisker, graphite, etc. are mentioned, These powder or fiber etc. are mentioned. The preferred electrode active material for the electric double layer capacitor is activated carbon, specifically activated carbon activated with phenolic, coconut shell, rayon, acrylic, coal / petroleum pitch coke, mesocarbon microbeads (MCMB), etc. Can be mentioned. Those having a large specific surface area capable of forming an interface having a larger area even with the same weight are preferred. Specifically, the specific surface area is 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, or two or more kinds of carbons having different volume average particle diameter (D50) or particle size distribution may be used in combination.

  The positive electrode active material for the lithium ion capacitor is not particularly limited as long as it is a material capable of reversibly doping and 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 the lithium ion capacitor is not particularly limited as long as it is a material capable of reversibly doping and dedoping lithium ions. For example, graphite-based materials such as artificial graphite and natural graphite can be used. 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 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.

  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 producing 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.

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

  Secondary batteries include lithium ion secondary batteries, sodium ion secondary batteries, magnesium ion secondary batteries, alkaline secondary batteries, lead storage batteries, sodium sulfur secondary batteries, lithium air secondary batteries, etc. An electrolyte solution, a separator, and the like that are conventionally known for 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 electrolyte, a separator, and the like that are 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, 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, it is also possible to obtain a polymer electrolyte in which the above electrolytic solution 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.

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

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

Evaluation of materials used in Examples and Comparative Examples was performed as follows.
(Total specific surface area of conductive carbon material)
The specific surface area of the conductive carbon material was measured in accordance with JIS K6217-2 using a gas adsorption amount measuring device (BELSORP-mini manufactured by Nippon Bell Co., Ltd.). The total specific surface area was defined as a weighted average value of the specific surface area and mixing ratio of each conductive carbon material.

(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 with a rheometer (AR Instruments G-TA2 manufactured by TA Instruments) 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 fine particles)
The water-dispersed resin fine particle dispersion is diluted with water to 200 to 1000 times depending on the solid content, and about 5 ml of the diluted solution is injected into a nanotrack cell (Wave-EX150 manufactured by Nikkiso Co., Ltd.) to refract water and resin. After inputting the rate condition, measurement was performed to determine 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 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 matter was measured by a total reflection measurement method (ATR) using a Fourier transform infrared spectrometer (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 when used as a baseline BX, 2800 to 3000 cm from the maximum peak derived from olefins ^-1 until the baseline BX height (maximum absorbance) and (X), the absorbance at a point and 1850 cm ^-1 indicating the absorbance at 1650 m ^-1 The ratio from the maximum peak derived from the carbonyl group at 1690 to 1740 cm ^-1 to the baseline BY (maximum absorbance) (Y) when the straight line connecting the two points with the point indicating Y) / (X) was determined.

(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., graphite, specific surface area 10 m ² / g, average particle diameter 6 μm)
A-3: SNO-5 (manufactured by SEC Carbon, graphite, specific area 15 m ² / g, average particle diameter 5 μm)
A-4: Denka Black HS-100 (manufactured by Denka Co., acetylene black, average particle size 48 nm, specific surface area 45 m ² / g)
(Water-soluble resin) (B))
B-1: CMC Daicel # 1240 (Daicel Chemical Industries, carboxymethyl cellulose, viscosity 0.02 Pa · s)
B-2: Sodium polyacrylate (Wako Pure Chemical Industries, average molecular weight 5000)
B-3: Kuraray Poval PVA235 (Kuraray Co., Ltd., polyvinyl alcohol)
(Water-dispersed resin fine particles (C))
C-1: Saixen AC (30% solid content aqueous dispersion, average particle size 0.04 μm, modified amount (Y) / (X) 0.64, polyethylene resin fine particles having a carbonyl group) (Sumitomo Seika Co., Ltd.) Made)
C-2: Arrow Base SB-1200 (25% solid content aqueous dispersion, average particle size 0.10 μm, modified amount (Y) / (X) 0.58, polyethylene resin fine particles having a carbonyl group) (Unitika) (Made by company)
C-3: Chemipearl W4005 (40% solid content aqueous dispersion, average particle size 0.57 μm, unmodified, polyethylene resin fine particles) (Mitsui Chemicals)

<Current Collector with Underlayer> (Examples 1 to 14, Comparative Examples 2 to 3, Reference Example 1)
Conductive compositions (1) to (14) and (17) to (19) were dried with an aluminum foil having a thickness of 20 μm (hereinafter referred to as “the current collector”) so that the thickness after drying becomes the thickness shown in Table 1. (It may be abbreviated as “aluminum”) Using a bar coater, it was coated and then dried at 80 ° C. to obtain a collector with an underlayer (1) to (14), (17) to (19 ) Respectively.

<Current Collector with Underlayer> (Example 15)
The conductive composition (15) was applied on a copper foil having a thickness of 20 μm serving as a current collector using a bar coater so that the thickness after drying was 3 μm, and then heat-dried at 80 ° C., A current collector (15) with an underlayer was obtained.

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

<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 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 composition for electrode formation.

<Composite ink for negative electrode of lithium ion secondary battery>
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 a 1.5% aqueous solution of carboxymethyl cellulose (1 part by mass as a solid content) are put in a planetary mixer and kneaded, and 33 parts by mass of water. Part, 2.08 parts by mass of a 48% by mass styrene butadiene emulsion aqueous dispersion (1 part by mass as solid content) was mixed to obtain a mixture ink for negative electrode secondary battery electrode which is a kind of composition for electrode formation. .

<Positive Electrode for Lithium Ion Secondary Battery with Underlayer> (Examples 1 to 14, Comparative Examples 2 to 3, Reference Example 1)
The above lithium-ion secondary battery positive electrode mixture ink is dried on the surface on which the base layers of the current collectors (1) to (14) and (17) to (19) with the base layer for secondary batteries are formed. It apply | coated using the doctor blade so that the amount of subsequent weights might be 20 mg / cm < ² >, and it heat-dried at 80 degreeC. Furthermore, the rolling process by roll press was performed and the positive electrode (1)-(14) and (17)-(19) from which the density of a compound-material layer became 3.1 g / cm < ³ > were produced, respectively.

<Positive electrode for lithium ion secondary battery without base layer> (Example 15, positive electrode for Comparative Example 1)
A doctor blade was used so that the above-mentioned mixture ink for lithium ion secondary battery positive electrode was dried on a 20 μm-thick aluminum foil serving as a current collector so that the basis weight after drying was 20 mg / cm ^2. And then dried by heating at 80 ° C. Furthermore, the rolling process by roll press was performed and the positive electrodes (15) and (16) from which the density of a compound-material layer became 3.1 g / cm < ³ > were produced, respectively.

<Negative Electrode for Lithium Ion Secondary Battery without Base Layer> (Examples 1 to 14, Comparative Examples 1 to 3, Negative Electrode for Reference Example 1)
The above-mentioned ink mixture for negative electrodes of lithium ion secondary batteries was applied using a doctor blade so that the weight per unit area after drying was 12 mg / cm ² and dried by heating at 80 ° C. Furthermore, the rolling process by a roll press was performed, and the negative electrode (1)-(14) and (16)-(19) from which the density of a compound-material layer became 1.5 g / cm < ³ > were produced, respectively.

<Anode for Lithium Ion Secondary Battery with Underlayer> (Example 15)
The above-mentioned ink mixture for negative electrode of lithium ion secondary battery is placed on the surface on which the underlayer of the current collector with underlayer (15) is formed so that the basis weight after drying is 12 mg / cm ^2. Used, and dried by heating at 80 ° C. Furthermore, the rolling process by a roll press was performed and the negative electrode (15) from which the density of a compound material layer was set to 1.5 g / cm < ³ > was produced.

<Laminated lithium ion secondary battery> (Examples 1 to 15, Comparative Examples 1 to 3, Reference Example 1)
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 therebetween is inserted into an aluminum laminate bag, vacuum dried, and then an electrolyte solution After injecting (nonaqueous 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 laminated lithium ion battery was produced. Laminate type lithium ion batteries are produced in a glove box substituted with argon gas. After the production of laminated type lithium ion batteries, the battery characteristics of initial resistance, resistance increase, rate characteristics and cycle characteristics are as follows. 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 above-mentioned laminate type battery was heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min, and resistance measurement was performed. The resistance measured at 25 ° C. was defined as the initial resistance, and the value calculated by the following (Equation 1) was defined as the resistance increase.
(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”
・ Increased resistance ○○: “Increased resistance is more than 10 times the initial resistance. Especially excellent.”
○: “Increase in resistance is 5 to 10 times the initial resistance. Excellent”
Δ: “An increase in resistance is 3 times or more and less than 5 times the initial low ability. Practical level.”
X: “Increased resistance is less than 3 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. Excellent”
Δ: “The rate characteristic is 70 or more and less than 80%. 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 ratio is 85% or more. 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”

  As shown in Table 2, it was confirmed that the internal resistance of the battery increased when the internal temperature of the battery increased by using the base layer formed from the conductive composition of the present invention. From this, for example, when the battery abnormally heats up 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 avoid ignition of the battery.

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

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

<Positive electrode for electric double layer capacitor, mixed ink for negative electrode>
As active materials, 85 parts of activated carbon (specific surface area 1800 m ² / g), 5 parts of conductive additive (acetylene black: Denka Black HS-100, manufactured by Denka), 8 parts of carboxymethyl cellulose (manufactured by Wako Pure Chemical Industries), binder ( Polytetrafluoroethylene 30-J: Mitsui / DuPont Fluorochemical Co., Ltd., 60% aqueous dispersion) 3.3 parts (2 parts as a solid content) and 220 parts of water were mixed to produce a mixture ink for positive and negative electrodes. did.

<Positive electrode and negative electrode for electric double layer capacitor without base layer (Comparative Example 4 and counter electrode for evaluation)>
The above-mentioned composite ink for electric double layer capacitor was applied on a 20 μm thick aluminum foil serving as a current collector using a doctor blade, dried by heating, and then subjected to a rolling process by a roll press to obtain the thickness of the electrode. A positive electrode and a negative electrode having a thickness of 50 μm were prepared.

<Positive electrode and negative electrode for electric double layer capacitor with underlying layer>
(Example 16)
The above mixture ink for electric double layer capacitor was applied to the surface of the current collector with an underlayer (1) of Example 1 on which the underlayer was formed, using a doctor blade, and then heated and dried at 80 ° C. Then, the rolling process by a roll press was performed and the positive electrode from which thickness becomes 50 micrometers was produced.

(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 an underlayer (1) was changed to the current collector shown in Table 3.

<Electric double layer capacitor>
The positive electrode and negative electrode shown in Table 3 were each 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 was prepared. The electric double layer capacitor was used in a glove box substituted with argon gas, and after the electric double layer capacitor was fabricated, predetermined electric characteristics were evaluated.

(Charge / discharge cycle characteristics)
About the obtained electric double layer capacitor, charging / discharging measurement was performed using the charging / discharging apparatus.
After charging to a charge end voltage of 2.0 V at a charge current of 10 C, constant current discharge was performed until the discharge end voltage of 0 V was reached at a discharge current of 10 C. These charge / discharge cycles are defined as one cycle, and 5 cycles of charge / discharge are repeated, and the discharge capacity at the fifth cycle is defined as the initial discharge capacity. (The initial discharge capacity is assumed to be 100% maintenance rate). In addition, the charge / discharge current rate was 1 C, which is the magnitude of current that can discharge the cell capacity in one hour.
Next, charging was performed at a charging current 10C rate in a 50 ° C. constant temperature bath at a charging end voltage of 2.0 V, and then constant current discharging was performed at a discharging current of 10 C rate until reaching a discharging end voltage of 0 V. This charge / discharge cycle was repeated 500 times to calculate the rate of change of the discharge capacity maintenance rate (the closer to 100%, the better).
○: “Change rate is 85% or more. Excellent”
Δ: “Change rate is 80% or more and less than 85%. Equivalent to the discharge capacity maintenance rate of Comparative Example 1 without a base layer.”
X: “Change rate is less than 80%. Inferior”

(Resistance measurement)
A laminate type battery charged to a charge end voltage of 2.0 V at a charging current rate of 10 C was subjected to resistance measurement at 500 kHz with an impedance analyzer (SP-50 manufactured by biologic).
The above-mentioned laminate type battery was heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min, and resistance measurement was performed. 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”
・ Increased resistance ○○: “Increased resistance is more than 10 times the initial resistance. Especially excellent.”
○: “Increase in resistance is 5 to 10 times the initial resistance. Excellent”
Δ: “An increase in resistance is 3 times or more and less than 5 times the initial low ability. Practical level.”
X: “Increased resistance is less than 3 times the initial resistance. Current blocking effect is low. Inferior”

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

<Composite ink for negative electrode for lithium ion capacitor>
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% by weight aqueous solution of hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd., 3. 5 parts) is mixed in a mixer, and 26.3 parts of water and 3.75 parts of binder (SBR: 40% aqueous dispersion of styrene butadiene latex) (1.5 parts as a solid content) are mixed to prepare a negative electrode A composite ink was prepared.

<Positive electrode for lithium ion capacitor without base layer (Example 41, Comparative Example 7)>
After applying the above-mentioned ink mixture for the positive electrode for lithium ion capacitors onto a 20 μm thick aluminum foil serving as a current collector using a doctor blade, after heating and drying under reduced pressure and performing a rolling process 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 above-mentioned ink mixture for positive electrode for lithium ion capacitor was applied to the surface on which the base layer of the current collector with base layer (1) of Example 1 was formed using a doctor blade, and then dried by heating under reduced pressure. After performing the rolling process by the roll press, a positive electrode having a thickness of 60 μm was produced.

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

<Negative Electrode for Lithium Ion Capacitors (Examples 30 to 40, 42, 43, Comparative Examples 7 to 9, Reference Example 3)>
After applying the above-mentioned ink mixture for the negative electrode for lithium ion capacitors on a copper foil having a thickness of 20 μm to be a current collector, using a doctor blade, drying under reduced pressure and performing a rolling process by a roll press, A negative electrode having a thickness of 45 μm was produced.

<Anode for Lithium Ion Capacitor with Underlayer>
(Example 41)
The above-mentioned ink mixture for negative electrode for lithium ion capacitor was applied on the current collector with an underlayer (1) of Example 1 using a doctor blade, then dried under reduced pressure and dried by a roll press. Thereafter, a negative electrode having a thickness of 45 μm was produced.

<Lithium ion capacitor>
A positive electrode shown in Table 4 and a negative electrode previously half-doped with lithium ions were prepared with a diameter of 16 mm, a separator (porous polypropylene film) inserted between them, and an electrolyte (ethylene carbonate and dimethyl). A lithium ion capacitor comprising a non-aqueous electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1 M in a mixed solvent in which carbonate and diethyl carbonate were mixed at a ratio of 1: 1: 1 (volume ratio) was produced. Lithium ion half dope was performed by sandwiching a separator between the negative electrode and lithium metal in a beaker cell, and doping the negative electrode with lithium ions so that the amount was about half of the negative electrode capacity. Moreover, the lithium ion capacitor was performed in a glove box substituted with argon gas, and a predetermined electrical property evaluation was performed after the lithium ion capacitor was fabricated.

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

(Resistance measurement)
A laminate type battery charged to a charge end voltage of 4.0 V at a charging current of 10 C was subjected to resistance measurement at 500 kHz with an impedance analyzer (SP-50 manufactured by biologic).
The above-mentioned laminate type battery was heated from 25 ° C. to 180 ° C. at a heating rate of 10 ° C./min, and resistance measurement was performed. 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”
・ Increased resistance ○○: “Increased resistance is more than 10 times the initial resistance. Especially excellent.”
○: “Increase in resistance is 5 to 10 times the initial resistance. Excellent”
Δ: “An increase in resistance is 3 times or more and less than 5 times the initial low ability. Practical level.”
X: “Increased resistance is less than 3 times the initial resistance. Current blocking effect is low. Inferior”

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

  From the above results, according to the present invention, the output characteristics of the electricity storage device are excellent, and when the internal temperature of the electricity storage device rises due to overcharge or internal short circuit, the current flowing is suppressed by increasing the internal resistance. In addition, it is possible to provide a conductive composition for forming an electricity storage device such as a non-aqueous electrolyte secondary battery having a function of improving battery safety.

Claims (7)

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