JP2016072234A - Positive electrode slurry, power storage device positive electrode, method for manufacturing power storage device positive electrode, power storage device, and method for manufacturing power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode slurry, a power storage device positive electrode, a method for manufacturing a power storage device positive electrode, a power storage device, and a method for manufacturing a power storage device which enable the exhibition of superior charge and discharge characteristics.SOLUTION: A positive electrode slurry comprises: (A) a polymer; (B) an olivine type lithium-containing phosphate compound; and (C) a liquid medium. The polymer (A) includes a diene based polymer having a repeating unit Mc originating from an unsaturated carboxylic acid, a repeating unit Md originating from a conjugated diene compound, and a repeating unit Me originating from aromatic vinyl. Supposing that the content of the olivine type lithium-containing phosphate compound (B) is 100 pts.mass, the content of the polymer (A) is within a range of 0.5-1.5 pts.mass.SELECTED DRAWING: None

Description

  The present invention relates to a positive electrode slurry, a power storage device positive electrode, a method for manufacturing a power storage device positive electrode, a power storage device, and a method for manufacturing a power storage device.

  As a positive electrode active material with high safety, a lithium-containing phosphate compound having an olivine structure (olivine-type lithium-containing phosphate compound) has attracted attention. The olivine-type lithium-containing phosphate compound has high thermal stability because phosphorus and oxygen are covalently bonded, and does not release oxygen even at high temperatures.

  The olivine-type lithium-containing phosphate compound has a low output voltage because the occlusion / release voltage of Li ions is around 3.4 V. In order to compensate for the drawbacks, attempts have been made to improve the properties of peripheral materials such as electrode binders and electrolytes (see Patent Documents 1 to 3).

JP 2007-294323 A WO2010 / 113940 JP 2012-216322 A

  However, with the techniques disclosed in Patent Documents 1 to 3, it has been difficult to sufficiently improve the charge / discharge characteristics of an electricity storage device including a positive electrode using an olivine-type lithium-containing phosphate compound as a positive electrode active material. The present invention has been made in view of the above points, and an object thereof is to provide a slurry for a positive electrode, a power storage device positive electrode, a method for manufacturing a power storage device positive electrode, a power storage device, and a method for manufacturing a power storage device that can solve the above-described problems. And

  The slurry for positive electrode of the present invention contains (A) a polymer, (B) an olivine-type lithium-containing phosphate compound, and (C) a liquid medium, and the (A) polymer is an unsaturated carboxylic acid. A diene polymer having a repeating unit Mc derived from the above, a repeating unit Md derived from the conjugated diene compound, and a repeating unit Me derived from the aromatic vinyl, and (B) the olivine-type lithium-containing phosphoric acid The content of the polymer (A) is in the range of 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the compound.

When the electricity storage device positive electrode and the electricity storage device including the electricity storage device positive electrode are produced using the positive electrode slurry of the present invention, excellent charge / discharge characteristics can be exhibited.
The manufacturing method of the electrical storage device positive electrode of the present invention is characterized in that a layer is formed by applying and drying the above-described positive electrode slurry on the surface of a current collector. If an electrical storage device is manufactured using the electrical storage device positive electrode manufactured by this invention, the outstanding charging / discharging characteristic can be expressed.

  The electricity storage device positive electrode of the present invention comprises a current collector and a layer formed on the surface of the current collector, and the layer comprises (A) a polymer and (B) an olivine-type lithium-containing phosphoric acid. The polymer (A) has a repeating unit Mc derived from an unsaturated carboxylic acid, a repeating unit Md derived from a conjugated diene compound, and a repeating unit Me derived from an aromatic vinyl. It contains a diene polymer, and the content of the (A) polymer is in the range of 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the (B) olivine type lithium-containing phosphate compound. It is characterized by that. If an electrical storage device is manufactured using this electrical storage device positive electrode, the outstanding charge / discharge characteristic can be expressed.

The electricity storage device of the present invention includes the above-described electricity storage device positive electrode. The electricity storage device of the present invention can exhibit excellent charge / discharge characteristics.
The manufacturing method of the electrical storage device of this invention manufactures an electrical storage device positive electrode with the manufacturing method mentioned above. The electricity storage device manufactured according to the present invention can exhibit excellent charge / discharge characteristics.

  An embodiment of the present invention will be described. It should be understood that the present invention is not limited only to the embodiments described below, and includes various modifications that are implemented within a scope that does not change the gist of the present invention.

  In this specification, “(meth) acrylic acid” is a concept encompassing both “acrylic acid” and “methacrylic acid”. Further, “˜ (meth) acrylate” is a concept encompassing both “˜acrylate” and “˜methacrylate”.

  Moreover, it is clear from experience that the performance of the positive electrode active materials (binding properties) and the bonding capability (adhesive properties) between the positive electrode active material layer and the current collector are almost proportional. It has become. Therefore, in the present specification, hereinafter, these may be collectively expressed using the term “binding property”.

1. Positive electrode slurry The positive electrode slurry according to the present embodiment means a composition used for forming a layer containing a positive electrode active material (positive electrode active material layer) on the surface of a current collector. A positive electrode active material layer can be formed on the surface of a current collector by, for example, applying and drying the positive electrode slurry on the surface of the current collector.

  The positive electrode slurry according to the present embodiment includes (A) a polymer (hereinafter also referred to as “component (A)”) and (B) an olivine-type lithium-containing phosphate compound (hereinafter referred to as “component (B)”). And (C) a liquid medium (hereinafter also referred to as “component (C)”). Hereinafter, the positive electrode slurry according to the present embodiment will be described in detail.

1.1. Component (A) The component (A) is a diene polymer having a repeating unit Mc derived from an unsaturated carboxylic acid, a repeating unit Md derived from a conjugated diene compound, and a repeating unit Me derived from an aromatic vinyl. contains.

  In the positive electrode slurry, the component (A) may be, for example, polymer particles or a water-soluble polymer (for example, a water-soluble binder). When the component (A) is polymer particles, the component (A) is, for example, dispersed in a latex form in the liquid medium (C). By dispersing in the latex state, the stability of the positive electrode slurry is improved, and the applicability of the positive electrode slurry to the current collector is improved.

  When the component (A) is a polymer particle, the average particle size of the component (A) is preferably in the range of 90 to 170 nm, and more preferably in the range of 100 to 165 nm. When the average particle diameter of (A) component exists in the said range, (A) component can fully adsorb | suck to the surface of (B) component. As a result, the migration of the component (A) can be suppressed, and the optimal distribution of the component (A) with less uneven distribution in the positive electrode structure can be realized. As a result, sufficient adhesion between the positive electrode active material layer and the current collector can be expressed, and deterioration of electrical characteristics in the electricity storage device can be suppressed.

  The average particle size of component (A) is the particle size distribution measured using a particle size distribution measuring apparatus based on the light scattering method, and the number of particles is accumulated in order from the smallest particle size in the particle size distribution. This is the value of the particle diameter (number average particle diameter, D50) when the cumulative frequency of the number of particles is 50% of the total number of particles.

  Examples of such a particle size distribution measuring apparatus include Coulter LS230, LS100, LS13320 (above, manufactured by Beckman Coulter. Inc), FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.), and the like. In the measurement method, an aqueous dispersion (latex) of component (A) is used as a sample.

  These particle size distribution measuring devices are not intended to evaluate only the primary particles of the polymer particles, but can also evaluate the secondary particles formed by aggregation of the primary particles. Therefore, the particle size distribution measured by these particle size distribution measuring devices can be used as an indicator of the dispersion state of the component (A) contained in the positive electrode slurry.

(A) Content of a component exists in the range of 0.5-1.5 mass parts with respect to 100 mass parts of content of (B) component, and exists in the range of 1-1.5 mass parts. Further preferred.
When the positive electrode slurry is applied to the surface of the current collector and dried to form the positive electrode active material layer, the positive electrode active material layer contains the component (A) and the component (B). Here, since the (A) component has lower electron conductivity than the (B) component, the (A) component is generally an electrical element that inhibits the flow of electrons from the (B) component to the current collector. It tends to be a resistance component. When the content of the component (A) with respect to 100 parts by mass of the component (B) is in the above range, it is difficult to impair the adhesion between the current collector and the positive electrode active material layer, and the electrical resistance can be suppressed. . As a result, it is possible to produce a positive electrode that achieves both good electrical characteristics and adhesion.

1.1.1. Configuration of Diene Polymer (A) The component contains a diene polymer. The diene polymer has a repeating unit Mc derived from an unsaturated carboxylic acid, a repeating unit Md derived from a conjugated diene compound, and a repeating unit Me derived from an aromatic vinyl.

1.1.1.1. Repeating unit Mc derived from unsaturated carboxylic acid
When the diene polymer has the repeating unit Mc derived from the unsaturated carboxylic acid, the stability of the positive electrode slurry is improved.

  Specific examples of the unsaturated carboxylic acid include one or more selected from mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. In particular, at least one selected from acrylic acid, methacrylic acid, and itaconic acid is preferable.

  The content ratio of the repeating unit Mc derived from the unsaturated carboxylic acid is preferably 30 parts by mass or less, and 0.3 to 25 parts by mass when all the repeating units of the diene polymer are 100 parts by mass. It is more preferable. When the content ratio of the repeating unit Mc is within the above range, since the dispersion stability of the component (A) is excellent at the time of preparing the positive electrode slurry, aggregates are hardly generated. Further, an increase in slurry viscosity over time can be suppressed.

1.1.1.2. Repeating unit Md derived from conjugated diene compound
When the diene polymer has the repeating unit Md derived from the conjugated diene compound, the binding force of the diene polymer is increased. Therefore, the binding property between the positive electrode active material layer and the current collector is improved. Moreover, rubber elasticity is provided to a diene polymer because a diene polymer has the repeating unit Md derived from a conjugated diene compound. Therefore, the positive electrode active material layer can follow changes such as volume shrinkage and expansion of the current collector. As a result, the charge / discharge characteristics of the electricity storage device can be maintained for a long time.

  The conjugated diene compound is selected from, for example, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and the like. 1 type or more is mentioned. As the conjugated diene compound, 1,3-butadiene is particularly preferable.

  The content ratio of the repeating unit Md derived from the conjugated diene compound is preferably 30 to 60 parts by mass, and more preferably 40 to 55 parts by mass when the total repeating units are 100 parts by mass. When the content ratio of the repeating unit Md is in the above range, the binding property between the positive electrode active material layer and the current collector is further improved.

1.1.1.3. Repeating unit Me derived from aromatic vinyl
When the diene polymer has a repeating unit Me derived from aromatic vinyl, when the positive electrode slurry contains a conductivity-imparting agent, the affinity between the component (A) and the conductivity-imparting agent may be improved. it can.

  Specific examples of the aromatic vinyl include one or more selected from styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like. As the aromatic vinyl, styrene is particularly preferable among the above specific examples.

  The content ratio of the repeating unit Me derived from the aromatic vinyl is preferably 10 to 55 parts by mass, and more preferably 15 to 50 parts by mass when the total repeating unit is 100 parts by mass. When the content ratio of the repeating unit Me is in the above range, the component (A) has an appropriate binding property to the component (B). Further, the flexibility of the obtained positive electrode active material layer and the binding property of the positive electrode active material layer to the current collector are good.

1.1.1.4. Other repeating units The diene polymer may have other repeating units. Examples of the repeating unit other than the above include the repeating unit Mb derived from an unsaturated carboxylic acid ester.

  When the diene polymer has a repeating unit Mb derived from an unsaturated carboxylic acid ester, the affinity between the diene polymer and the electrolytic solution becomes better, and the diene polymer becomes an electrical resistance component in the electricity storage device. An increase in internal resistance due to can be suppressed. In addition, it is possible to more effectively suppress a decrease in the binding property between the positive electrode active material layer and the current collector caused by excessive absorption of the electrolytic solution by the diene polymer.

  The unsaturated carboxylic acid ester is preferably a (meth) acrylic acid ester. Specific examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and (meth) acrylic acid n. -Butyl, i-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid 2 -Ethylhexyl, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, (Meth) acrylic acid ethylene glycol, di (meth) acrylic acid ethylene glycol, di (meth) acrylic Select from propylene glycol acid, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, allyl (meth) acrylate, ethylene di (meth) acrylate, etc. 1 type or more to be mentioned.

  Among these, at least one selected from methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxymethyl (meth) acrylate and hydroxyethyl (meth) acrylate It is preferable that it is one or more selected from methyl (meth) acrylate, hydroxymethyl (meth) acrylate and hydroxyethyl (meth) acrylate.

  The content ratio of the repeating unit Mb derived from the unsaturated carboxylic acid ester in the diene polymer is preferably 0 to 40 parts by mass, and 10 to 30 parts by mass when all repeating units are 100 parts by mass. It is more preferable.

Examples of the other repeating unit include a repeating unit derived from an α, β-unsaturated nitrile compound.
Specific examples of the α, β-unsaturated nitrile compound include one or more selected from acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide, and the like. Of these, at least one selected from acrylonitrile and methacrylonitrile is preferable, and acrylonitrile is more preferable.

  In addition, the diene polymer may further have a repeating unit derived from the compound shown below. Examples of the compound include alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylol acrylamide; vinyl carboxylic acid esters such as vinyl acetate and vinyl propionate; acid anhydrides of ethylenically unsaturated dicarboxylic acids Monoalkyl ester; monoamide; one or more selected from aminoalkylamides of ethylenically unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethylmethacrylamide, methylaminopropylmethacrylamide and the like.

1.1.2. Synthesis of Diene Polymer The method for synthesizing the diene polymer is not particularly limited. For example, the diene polymer can be easily synthesized by a known emulsion polymerization process or a process appropriately combining them. For example, a diene polymer can be easily synthesized by using the method described in Japanese Patent No. 4957932.

1.1.3. Physical properties of diene polymer 1.1.3.1. Counter ion In order to improve the stability of the positive electrode slurry, ammonia, alkali metal (lithium, sodium, potassium, rubidium, cesium, etc.) hydroxide, inorganic ammonium compound (ammonium chloride, etc.), organic amine compound (ethanolamine) in advance It is preferable to adjust the pH of the diene polymer by adding an aqueous solution such as diethylamine).

  In particular, it is preferable to neutralize the repeating unit Mc derived from the unsaturated carboxylic acid, which is a constituent unit of the diene polymer, using at least one cation selected from ammonium ions and sodium ions to form a salt. When the diene polymer is neutralized in advance and the pH of the positive electrode slurry is adjusted to a range of 5 to 13, preferably 6 to 12, the binding property between the current collector and the positive electrode active material layer can be improved. .

1.1.3.2. Tetrahydrofuran (THF) Insoluble Content The THF insoluble content of the diene polymer is preferably 80% or more, and more preferably 90% or more. The THF-insoluble content is estimated to be approximately proportional to the amount of insoluble content in the electrolytic solution used in the electricity storage device. For this reason, if THF insoluble content is the said range, even when an electrical storage device is produced and charging / discharging is repeated over a long period of time, the elution of the diene polymer to electrolyte solution can be suppressed.

1.1.3.3. Transition temperature The transition temperature of the diene polymer can be measured by differential scanning calorimetry (DSC) in accordance with JIS K7121. The diene polymer preferably has only one endothermic peak in the temperature range of −50 to 5 ° C.

1.2. Component (B) As the component (B) contained in the positive electrode slurry according to the present embodiment, for example, a lithium atom-containing oxide (olivine type) represented by the following general formula (1) and having an olivine type crystal structure: 1 or more types selected from lithium-containing phosphate compounds).

Li _1-x M ¹ _x (XO ₄ ) (1)
(In the formula (1), ^{M 1} is, Mg least, Ti, V, Nb, Ta , Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, are selected from the group consisting of Ge and Sn (It is one kind of metal ion, X is at least one selected from the group consisting of Si, S, P and V, and x is a number satisfying the relationship of 0 <x <1.)
The value of x in the general formula (1) is selected according to the valences of M ¹ and X so that the valence of the whole general formula (1) becomes zero.

Olivine-type lithium-containing phosphate compound represented by the general formula (1), the electrode potential varies depending on the kind of the metal element M ^1. Therefore, by selecting the type of metal element M ^1, it can be set electrode voltage appropriate.

Typical examples of the olivine-type lithium-containing phosphate compound include LiFePO ₄ , LiCoPO ₄ , Li _0.90 Ti _0.05 Nb _0.05 Fe _0.30 Co _0.30 Mn _0.30 PO _{4, and the} like. It is done. Among these, LiFePO ₄ (lithium iron phosphate) is particularly preferable because it is easy to obtain an iron compound as a raw material and is inexpensive.

  In addition, a compound obtained by substituting Fe ions in a compound as a representative example with Co ions, Ni ions, or Mn ions also has the same crystal structure as that of the compound before substitution, and thus has the same effect as a positive electrode active material. Have.

  In the positive electrode slurry, the component (B) may be provided with various substances such as a conductive substance on the particle surface. An example of a typical conductive material is carbon. Such (B) component can be manufactured by well-known methods, such as Unexamined-Japanese-Patent No. 2009-09670.

The average particle size of the component (B) is preferably in the range of 1 to 30 μm, more preferably in the range of 1 to 25 μm, and particularly preferably in the range of 1 to 20 μm.
In the step of applying and drying the positive electrode slurry on the surface of the current collector to form a coating film (positive electrode active material layer), the component (A) and / or (B) is It may move along the thickness direction of the coating film (hereinafter also referred to as “migration”). Specifically, the component (A) and / or the component (B) tend to move to the interface (gas-solid interface) opposite to the current collector in the coating film.

  As a result, since the distribution of the component (A) and / or the component (B) is not uniform in the thickness direction of the coating film, the electrode characteristics are deteriorated or the binding property between the current collector and the positive electrode active material layer is reduced. Problems such as damage may occur.

  For example, the component (A) acting as a binder bleeds (transfers) to the gas-solid interface side of the positive electrode active material layer, and the amount of the component (A) at the interface between the current collector and the positive electrode active material layer is relatively In the case where the amount is too small, the penetration of the electrolyte into the positive electrode active material layer is hindered, so that the electrical characteristics of the positive electrode tend to deteriorate. Further, in this case, the binding property between the current collector and the positive electrode active material layer is lowered, and the positive electrode active material layer tends to be easily separated from the current collector. Furthermore, in this case, the smoothness of the surface of the positive electrode active material layer tends to be impaired due to bleeding of the component (A).

  However, when the average particle size of the component (A) is in the above-described range (range of 90 to 170 nm) and the average particle size of the component (B) is in the above-mentioned range, the occurrence of the above problem is suppressed. Thus, it is possible to produce a positive electrode that achieves both better electrical characteristics and binding properties.

Moreover, when the average particle diameter of (A) component and (B) component exists in the said range, adsorption | suction of (A) component to (B) component becomes still stronger, and the powder fall property mentioned later improves further. .
Here, the average particle size of the component (B) is a particle size distribution measuring device using a particle size distribution measuring apparatus based on the laser diffraction method, and the number of particles is accumulated in order from the smallest particle size in the particle size distribution. Thus, the value is the value of the particle diameter (number average particle diameter, D50) when the cumulative frequency of the number of particles is 50% of the total number of particles.

  Examples of the particle size distribution measuring apparatus based on such a laser diffraction method include HORIBA LA-300 series, HORIBA LA-920 series (above, manufactured by Horiba, Ltd.) and the like. The sample used in the measurement method is obtained by centrifuging the positive electrode slurry to settle the component (B), and then removing the supernatant.

  In addition, the said particle size distribution measuring apparatus does not consider only the primary particle of (B) component as evaluation object, but also makes evaluation object the secondary particle formed by the aggregation of primary particles. Therefore, the average particle diameter obtained by this particle size distribution measuring apparatus can be used as an indicator of the dispersion state of the component (B) contained in the positive electrode slurry.

1.3. (C) Component The positive electrode slurry according to the present embodiment contains (C) a liquid medium. (C) The liquid medium is preferably an aqueous medium containing water. The aqueous medium may be composed of water, or may contain water and a non-aqueous medium other than water. Examples of the non-aqueous medium include one or more selected from amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, and the like.

  (C) When the liquid medium contains water and a non-aqueous medium other than water, 90% by mass or more is preferably water, and 98% by mass or more is 100% by mass of the total amount of the (C) liquid medium. More preferably, it is water.

  Further, the content ratio of the non-aqueous medium contained in the aqueous medium is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and substantially contained with respect to 100 parts by mass of the aqueous medium. It is particularly preferred not to do so.

  Here, “substantially does not contain” means that (C) a non-aqueous medium is not intentionally added to the liquid medium, and is inevitably mixed when the positive electrode slurry is produced. An aqueous medium or a non-aqueous medium produced after the production of the positive electrode slurry may be included.

The positive electrode slurry according to the present embodiment (C) uses an aqueous medium as the liquid medium, so that it does not adversely affect the environment and the safety of the handling operator is increased.
1.4. Other Components The positive electrode slurry according to the present embodiment can contain components other than the components described above as necessary. Examples of such components include a conductivity-imparting agent, a non-aqueous medium, a thickener, and a preservative.

1.4.1. Conductivity-imparting agent Specific examples of the conductivity-imparting agent include carbon. Carbon is suitable when the positive electrode slurry is used in a lithium ion secondary battery (an example of an electricity storage device). Examples of carbon include graphite, activated carbon, acetylene black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black or furnace black is preferable. The use ratio of the conductivity-imparting agent is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, and particularly preferably 2 to 10 parts by mass with respect to 100 parts by mass of the component (B).

1.4.2. Non-Aqueous Medium The positive electrode slurry according to the present embodiment can contain, for example, a non-aqueous medium having a standard boiling point of 80 to 350 ° C. from the viewpoint of improving the applicability. Specific examples of such a non-aqueous medium include amide compounds such as N-methylpyrrolidone, dimethylformamide and N, N-dimethylacetamide; hydrocarbons such as toluene, xylene, n-dodecane and tetralin; 2-ethyl-1 -Alcohols such as hexanol, 1-nonanol, lauryl alcohol; ketones such as methyl ethyl ketone, cyclohexanone, phorone, acetophenone, isophorone; esters such as benzyl acetate, isopentyl butyrate, methyl lactate, ethyl lactate, butyl lactate; o-toluidine, m- One or more types selected from amine compounds such as toluidine and p-toluidine; lactones such as γ-butyrolactone and δ-butyrolactone; sulfoxide and sulfone compounds such as dimethyl sulfoxide and sulfolane. Among these, it is preferable to use N-methylpyrrolidone from the viewpoints of the stability of the component (A), workability when applying the positive electrode slurry, and the like.

1.4.3. Thickener The positive electrode slurry according to the present embodiment can contain a thickener from the viewpoint of improving its coatability. Specific examples of the thickener include cellulose compounds such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose; ammonium salts or alkali metal salts of the cellulose compounds; poly (meth) acrylic acid, poly (meth) acrylic acid and the like Carboxylic acid; alkali metal salt of polycarboxylic acid; polyvinyl alcohol (co) polymer such as polyvinyl alcohol, modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer; (meth) acrylic acid, maleic acid, fumaric acid, etc. Examples thereof include water-soluble polymers such as saponified products of copolymers of unsaturated carboxylic acids and vinyl esters. Of these, alkali metal salts of carboxymethyl cellulose, poly (meth) acrylic acid and alkali metal salts thereof are particularly preferable.

  Examples of commercially available thickeners include alkali metal salts of carboxymethyl cellulose such as CMC1120, CMC1150, CMC2200, CMC2280, CMC2450 (manufactured by Daicel Chemical Industries, Ltd.).

  When the positive electrode slurry contains a thickener, the use ratio of the thickener is preferably 20% by mass or less, more preferably 0.1 to 15%, with the total solid content of the positive electrode slurry being 100% by mass. It is mass%, Most preferably, it is 0.5-10 mass%.

1.4.4. Preservative The positive electrode slurry according to the present embodiment can contain a preservative. By containing the preservative, when the positive electrode slurry is stored, it is possible to suppress the generation of foreign substances due to the growth of bacteria, sputum and the like. Moreover, since deterioration of a binder is suppressed at the time of charging / discharging of the electrical storage device manufactured using the slurry for positive electrodes, the fall of the charging / discharging characteristic of an electrical storage device can be suppressed. As an antiseptic, particularly when an isothiazoline-based compound is contained, the above-described effects are more remarkable.

  Specific examples of the preservative include 1,2-benzisothiazolin-3-one, 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 5 -Chloro-2-methyl-4-isothiazolin-3-one, Nn-butyl-1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 4,5- One or more selected from dichloro-2-n-octyl-4-isothiazolin-3-one and the like can be mentioned.

  Among these, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 1,2- One or more selected from benzisothiazolin-3-one and the like are preferable.

1.5. Method for Producing Positive Electrode Slurry The positive electrode slurry according to the present embodiment comprises the component (A), the component (B), the component (C), and other components used as necessary. It can be manufactured by mixing. The order of mixing can be set as appropriate. Mixing of each component can be performed by a well-known stirring method, for example, it can mix using a stirrer, a defoaming machine, a bead mill, a high pressure homogenizer, etc.

It is preferable to perform at least a part of the steps in the production of the positive electrode slurry (mixing operation of each component) under reduced pressure. In this case, it can suppress that a bubble arises in the positive electrode obtained using the slurry for positive electrodes. The degree of decompression is preferably about 5.0 × 10 ^{3 to} 5.0 × 10 ⁵ Pa as an absolute pressure.

  In the mixing and stirring for producing the positive electrode slurry, it is possible to select a mixer that can stir to such an extent that the aggregate of the component (B) does not remain in the positive electrode slurry and sufficient dispersion conditions as necessary. desirable.

  The degree of dispersion can be measured with a grain gauge. It is preferable to mix and stir so that aggregates larger than at least 100 μm do not exist in the positive electrode slurry. Examples of the mixer that meets such conditions include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and a Hobart mixer.

  The solid content concentration in the positive electrode slurry according to the present embodiment (the ratio of the total mass of components other than the solvent in the positive electrode slurry to the total mass of the positive electrode slurry) is 20 to 80% by mass. Preferably, it is 30-75 mass%.

1.6. Characteristics of Positive Electrode Slurry The positive electrode slurry according to the present embodiment preferably has a spinnability of 30 to 80%, and more preferably 33 to 79%. When the spinnability is in the above range, a sufficient leveling property can be easily obtained when the positive electrode slurry is applied onto the current collector to form the positive electrode active material layer. In this case, a positive electrode active material layer having a uniform thickness can be formed. When a positive electrode having a uniform thickness of the positive electrode active material layer is used, in-plane variation in charge / discharge reaction can be suppressed, and stable power storage device characteristics can be easily expressed.

The “threadability” can be measured as follows. First, a Zaan cup (made by Dazai Equipment Co., Ltd., Zaan Biscocity Cup No. 5) having an opening with a diameter of 5.2 mm at the bottom is prepared. With the opening of the Zahn cup closed, 40 g of the positive electrode slurry is poured into the Zahn cup. Thereafter, when the opening is opened, the positive electrode slurry flows out from the opening. Here, when the opening time of the opening is T ₀ , the time at which the positive electrode slurry is spun is T _A , and the time at which the positive electrode slurry is discharged is T _B , the “threadability” is It can obtain | require from following formula (2).

Spinnability (%) = ((T _A −T ₀ ) / (T _B −T ₀ )) × 100 (2)
2. Electric storage device positive electrode The electric storage device positive electrode according to the present embodiment includes a current collector and a layer (positive electrode active material layer) formed on the surface of the current collector. The layer contains (A) a polymer and (B) an olivine-type lithium-containing phosphate compound. The (A) polymer and the (B) olivine-type lithium-containing phosphate compound can be, for example, those described in the section “1. Positive electrode slurry”.

The layer is, for example, a layer formed by applying and drying the positive electrode slurry on the surface of the current collector. The layer may be formed by other methods.
In this electricity storage device positive electrode, the binding property between the current collector and the positive electrode active material layer is excellent. Moreover, if an electricity storage device is manufactured using this electricity storage device positive electrode, the charge / discharge rate characteristic which is one of the electricity storage device characteristics is improved.

  The current collector is not particularly limited as long as it is made of a conductive material. When the power storage device positive electrode is used for a lithium ion secondary battery, for example, a current collector made of metal such as iron, copper, aluminum, nickel, and stainless steel can be used, and in particular, a current collector made of aluminum or copper is used. preferable.

  When the electricity storage device positive electrode is used for a nickel metal hydride secondary battery, for example, a current collector made of a punching metal, an expanded metal, a wire mesh, a foam metal, a mesh metal fiber sintered body, a metal-plated resin plate, or the like can be used. .

The shape and thickness of the current collector are not particularly limited, but for example, a sheet-like current collector having a thickness of about 0.001 to 0.5 mm is preferable.
When the positive electrode slurry is applied to the surface of the current collector, the application method is not particularly limited. As a coating method, for example, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, a brush coating method, or the like can be used as appropriate.

  The coating amount of the positive electrode slurry is not particularly limited. The thickness of the positive electrode active material layer formed after applying the slurry for positive electrode and removing the liquid medium (which is a concept including both water and a non-aqueous medium optionally used) is 0.005 to 0.005. A coating amount of 5 mm is preferable, and a coating amount of 0.01 to 2 mm is more preferable.

  When the thickness of the positive electrode active material layer is within the above range, the positive electrode active material layer can be effectively infiltrated with the electrolytic solution. As a result, since the exchange of metal ions accompanying charging / discharging between the positive electrode active material and the electrolytic solution in the positive electrode active material layer is easily performed, the internal resistance of the positive electrode can be further reduced.

  In addition, since the thickness of the positive electrode active material layer is within the above range, the adhesion between the positive electrode active material layer and the current collector is good even when the positive electrode is processed by folding or winding. Yes, the positive electrode active material layer is difficult to peel off from the current collector. That is, it is possible to obtain a power storage device positive electrode rich in flexibility.

  A method for drying the coating film formed by applying the positive electrode slurry (a method for removing water and a non-aqueous medium that is optionally used) is not particularly limited. For example, it is possible to use a method such as drying with warm air, hot air or low-humidity air; vacuum drying; drying by irradiation with (far) infrared rays or electron beams.

  The drying speed when drying the coating film formed by applying the positive electrode slurry is, for example, under the condition that the positive electrode active material layer is not cracked due to stress concentration or the positive electrode active material layer is not peeled off from the current collector. Thus, it can be set as appropriate so that the liquid medium can be removed as soon as possible.

  After drying the coating film formed by applying the slurry for the positive electrode, the power storage device positive electrode is pressed to increase the density of the positive electrode active material layer and adjust the density and the porosity in the positive electrode active material layer to the ranges shown below. It is preferable.

The density of the positive electrode active material layer after the press is preferably 1.5~2.5g / cm ^3, more preferably 1.6~2.4g / cm ^3, 1.7~2. more preferably from 2 g / cm ^3, particularly preferably 1.8~2.1g / cm ^3.

  If the density of the positive electrode active material layer is in the above range, the electricity storage device positive electrode has good binding properties between the current collector and the positive electrode active material layer, excellent powdering property, and excellent electrical characteristics. Can be obtained.

  The porosity of the positive electrode active material layer after pressing is preferably 10 to 50%, more preferably 15 to 45%, and particularly preferably 20 to 40%. When the porosity of the positive electrode active material layer is within the above range, the electric storage device has good binding properties between the current collector and the positive electrode active material layer, excellent powder fall-off properties, and excellent electrical characteristics. A positive electrode can be obtained.

  In addition, when the porosity of the positive electrode active material layer is within the above range, the electrolyte solution can be sufficiently infiltrated into the positive electrode active material layer, and the surface of the positive electrode active material and the electrolyte solution are in sufficient contact. As a result, it becomes easy to exchange lithium ions between the positive electrode active material and the electrolytic solution, and good charge / discharge characteristics can be exhibited.

  Examples of the pressing method include methods such as a mold press and a roll press. The pressing conditions can be appropriately set according to the type of press equipment to be used, desired values of the porosity and density of the positive electrode active material layer, and the like. The press conditions can be easily set by a few preliminary experiments by those skilled in the art.

The press conditions when using the roll press method can be as follows, for example.
Linear pressure of roll press: 0.1 to 10 (t / cm), preferably 0.5 to 5 (t / cm).

Roll temperature: 20-100 degreeC.
Feed speed of power storage device positive electrode (roll rotational speed): 1 to 80 m / min, preferably 5 to 50 m / min.

3. Power Storage Device The power storage device according to the present embodiment includes the above power storage device positive electrode, and further includes, for example, an electrolyte solution and includes components such as a separator and a power storage device negative electrode. As an electrical storage device, a secondary battery etc. are mentioned, for example. The electricity storage device can be manufactured according to a conventional method.

  As a specific manufacturing method, for example, a power storage device negative electrode and a power storage device positive electrode are overlapped via a separator, and this is wound into a battery container according to the shape of a battery (an example of a power storage device). And a method of injecting an electrolytic solution into a battery container and sealing it. The shape of the battery can be appropriately set such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, and a flat shape.

  The electrolytic solution is a solution in which an electrolyte is dissolved in an appropriate solvent. The electrolytic solution may be liquid or gel. What is necessary is just to select the electrolyte solution which expresses the function as an electrical storage device effectively from the well-known electrolytic solution used for an electrical storage device according to the kind of positive electrode active material.

The electrolyte can be appropriately selected from electrolytes known in the technical field of power storage devices. When the electricity storage device is a lithium ion secondary battery, a conventionally known lithium salt can be appropriately selected and used as the electrolyte. Specific examples thereof include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ CO _2. , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiCl, LiBr, LiB (C ₂ H ₅ ) ₄ , LiCF ₃ SO ₃ , LiCH ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO _{2) 2} N, lithium and the like lower fatty acid.

  The solvent contained in the electrolytic solution is not particularly limited. Examples of the solvent include carbonate compounds such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; lactone compounds such as γ-butyl lactone; trimethoxymethane, 1,2-dimethoxyethane, One or more selected from ether compounds such as diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran; sulfoxide compounds such as dimethyl sulfoxide, and the like. The concentration of the electrolyte in the electrolytic solution is preferably 0.5 to 3.0 mol / L, more preferably 0.7 to 2.0 mol / L.

  The negative electrode included in the electricity storage device according to the present embodiment includes, for example, a current collector and a negative electrode active material layer formed on the surface thereof. The negative electrode active material layer includes a negative electrode active material. The negative electrode includes, for example, a negative electrode active material, and can be manufactured by coating and drying a negative electrode slurry used for negative electrode manufacture on the surface of a current collector to form a negative electrode active material layer.

  The negative electrode active material is not particularly limited, and an appropriate negative electrode active material can be appropriately selected depending on the type of the target electricity storage device. Examples of the negative electrode active material include carbon materials, silicon materials, oxides containing lithium atoms, lead compounds, tin compounds, arsenic compounds, antimony compounds, and aluminum compounds.

  Examples of the carbon material include those known as negative electrode active materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), and pitch-based carbon fibers.

  As said silicon material, a well-known thing can be mentioned as negative electrode active materials, such as a silicon simple substance, a silicon oxide, a silicon alloy, for example. In addition, when a silicon material is used as the active material, it is preferable to use an active material other than the silicon material in combination, and it is preferable to use a carbon material in combination because the volume change associated with insertion and extraction of lithium is small.

In addition to the negative electrode active material, the negative electrode slurry can contain the binder component, liquid medium, conductivity-imparting agent, thickener, preservative, and the like described in “1. Positive electrode slurry”.
Example 1
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. “Part” and “%” in Examples and Comparative Examples are based on mass unless otherwise specified.

(1) Preparation of aqueous dispersion S1 In a temperature-controllable autoclave equipped with a stirrer, water 200 parts by mass, sodium dodecylbenzenesulfonate 0.9 parts by mass, potassium persulfate 1.0 part by mass, sodium bisulfite 0 0.5 parts by mass, 0.2 parts by mass of α-methylstyrene dimer, 0.2 parts by mass of dodecyl mercaptan, and the first-stage polymerization component shown in the column “S1” in Table 1 are charged all at once, and the temperature is raised to 70 ° C. Then, the polymerization reaction was carried out for 2 hours.

なお、表１及び後述する表２における各成分の略称は、それぞれ以下の意味である。
・ＭＭＡ：メタクリル酸メチル
・ＨＥＭＡ：メタクリル酸２−ヒドロキシエチル
・ＡＡ：アクリル酸
・ＴＡ：イタコン酸
・ＡＮ：アクリロニトリル
・ＢＤ：１，３−ブタジエン
・ＳＴ：スチレン
ここで、ＡＡ、及びＴＡは不飽和カルボン酸に由来する繰り返し単位Ｍｃの一例であり、ＢＤは共役ジエン化合物に由来する繰り返し単位Ｍｄの一例であり、ＳＴは芳香族ビニルに由来する繰り返し単位Ｍｅの一例である。ＭＭＡ、ＨＥＭＡ、及びＡＮはその他の繰り返し単位の一例である。

In addition, the abbreviation of each component in Table 1 and Table 2 mentioned later has the following meaning, respectively.
-MMA: methyl methacrylate-HEMA: 2-hydroxyethyl methacrylate-AA: acrylic acid-TA: itaconic acid-AN: acrylonitrile-BD: 1,3-butadiene-ST: styrene where AA and TA are not It is an example of a repeating unit Mc derived from a saturated carboxylic acid, BD is an example of a repeating unit Md derived from a conjugated diene compound, and ST is an example of a repeating unit Me derived from an aromatic vinyl. MMA, HEMA, and AN are examples of other repeating units.

  After confirming that the polymerization addition rate was 80% or more, the second-stage polymerization component shown in the column “S1” in Table 1 was added over 6 hours while maintaining the reaction temperature at 70 ° C. When 3 hours passed from the start of addition of the second stage polymerization component, 1.0 part by mass of α-methylstyrene dimer and 0.3 part by mass of dodecyl mercaptan were added.

  After the addition of the second-stage polymerization component, the temperature was raised to 80 ° C., and the reaction was further continued for 2 hours. After the completion of the polymerization reaction, the pH of the latex was adjusted to 7.5 by adding 5 parts by mass of sodium tripolyphosphate (in terms of solid content). At this time, acrylic acid and itaconic acid (an example of the repeating unit Mc derived from the unsaturated carboxylic acid) are sodium salts.

  Thereafter, the residual monomer was treated with steam distillation and concentrated under reduced pressure to a solid content of 50% to obtain an aqueous dispersion S1 containing 50% of the polymer (A). (A) The polymer has an aspect of polymer particles. The polymer (A) contained in the aqueous dispersion S1 has the composition shown in the column of S1 in Table 2.

水系分散体Ｓ１に含まれる（Ａ）重合体について、平均粒子径と、ＴＨＦ不溶分と、転移温度（Ｔｇ）とを測定した。平均粒子径の測定においては、水系分散体Ｓ１を測定試料とした。測定結果を表２に示す。

For the polymer (A) contained in the aqueous dispersion S1, the average particle size, THF-insoluble matter, and transition temperature (Tg) were measured. In the measurement of the average particle diameter, the aqueous dispersion S1 was used as a measurement sample. The measurement results are shown in Table 2.

(2) Preparation of positive electrode slurry and preparation of electricity storage device positive electrode A biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.) and a thickener (trade name “CMC1120”, Daicel) Chemical Industry Co., Ltd.) 1 part by mass (solid content conversion), Hosen Co., Ltd. Lithium Iron Phosphate (LiFePO ₄ ) 100 parts by mass, acetylene black 5 parts by mass, and water 68 parts by mass were added at 60 rpm. Stir for hours. The lithium iron phosphate is pulverized in an agate mortar and classified using a sieve to have an average particle diameter (D50 value) of 10 μm. The lithium iron phosphate is an example of a positive electrode active material.

  Next, dispersion S1 and preservative 5-chloro-2-methyl-4-isothiazolin-3-one were added. The input amount of the dispersion S1 was an amount containing 1 part by mass of the polymer (A). The amount of the preservative used was such that the concentration of the preservative in the total amount of the positive electrode slurry was 100 ppm.

Then, it stirred for 1 hour and obtained the paste. Water was added to the obtained paste to adjust the solid content concentration to 50%, and then the mixture was stirred at 200 rpm for 2 minutes using a stirring defoamer (trade name “Awatori Nertaro” manufactured by Shinky Co., Ltd.). The slurry for positive electrode was prepared by stirring and mixing at 800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes. This positive electrode slurry has the composition shown in the column of “Example 1” in Table 3.

次に、厚み３０μｍのアルミニウム箔からなる集電体の表面に、前記のように調製した正極用スラリーを、乾燥後の膜厚が１００μｍとなるように、ドクターブレード法によって均一に塗布し、１２０℃で２０分間乾燥した。その後、形成された膜（正極活物質層）の密度が１．９ｇ／ｃｍ^３になるように、ロールプレス機を用いてプレス加工することにより、蓄電デバイス正極を得た。

Next, the positive electrode slurry prepared as described above is uniformly applied to the surface of a current collector made of an aluminum foil having a thickness of 30 μm by a doctor blade method so that the film thickness after drying becomes 100 μm. Dry at 20 ° C. for 20 minutes. Then, the electrical storage device positive electrode was obtained by pressing using a roll-press machine so that the density of the formed film | membrane (positive electrode active material layer) might be 1.9 g / cm < ³ >.

(3) Preparation of slurry for negative electrode and preparation of electricity storage device negative electrode A biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation) and a thickener (trade name “CMC2200”, Daicel) Chemical Industry Co., Ltd.) 1 part by mass (in terms of solid content), 100 parts by mass of graphite as a negative electrode active material (in terms of solid content), and 68 parts by mass of water were added and stirred at 60 rpm for 1 hour.

  Next, 2 parts by mass (in terms of solid content) of the aqueous dispersion S1 was added and further stirred for 1 hour to obtain a paste. Water was added to the obtained paste to adjust the solid content to 50%, and then the mixture was stirred at 200 rpm for 2 minutes at 1800 rpm at 200 rpm using a stirring defoamer (trade name “Netaro Awatori” manufactured by Shinky Corporation). The slurry for negative electrode was prepared by stirring and mixing for 5 minutes at 1800 rpm for 1 minute at 1800 rpm.

Next, the negative electrode slurry prepared as described above was uniformly applied to the surface of a current collector made of copper foil having a thickness of 20 μm by a doctor blade method so that the film thickness after drying was 80 μm. Drying was carried out at 20 ° C. for 20 minutes. Then, the electrical storage device negative electrode was obtained by pressing using a roll press machine so that the density of the formed film | membrane (negative electrode active material layer) might be 1.9 g / cm < ³ >.

(4) Assembling the lithium ion battery In the glove box substituted with Ar so that the dew point is -80 ° C. or lower, the storage device negative electrode manufactured as described above was punched and molded into a circle having a diameter of 15.95 mm. It was placed on a polar coin cell (trade name “HS Flat Cell” manufactured by Hosen Co., Ltd.).

  Next, a separator made of a polypropylene porous film punched into a circle having a diameter of 24 mm (trade name “Celguard # 2400”, manufactured by Celgard Co., Ltd.) was placed on the negative electrode of the electricity storage device.

Furthermore, after injecting 500 μL of the electrolyte so that air does not enter, the storage device positive electrode manufactured as described above was punched into a circular shape with a diameter of 16.16 mm, placed on the separator, A lithium ion battery cell (an example of an electricity storage device) was assembled by closing and sealing the exterior body of the bipolar coin cell with a screw. The electrolytic solution used here is a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio).

(5) Evaluation (5-1) Evaluation of applicability (smoothness) A test piece having a width of 12 cm and a length of 12 cm was cut out from the power storage device positive electrode prepared in (2). The test piece was divided into 36 squares each having a dimension of 2 cm × 2 cm, and the film thickness of the positive electrode active material layer in each square was measured using a film thickness meter (manufactured by Mitutoyo, DIGIMATIC MICROMETER IP65). The ratio (smoothness) of the standard deviation with respect to the average value of the film thickness was calculated.

  In addition, when the ratio of the standard deviation with respect to an average value exceeds 2%, it means that the slurry for positive electrodes is not apply | coated uniformly. In such a case, in the positive electrode prepared by applying the positive electrode slurry over a large area, the smoothness of the positive electrode active material layer formed on the surface of the current collector is impaired. Therefore, the electrical characteristics are not uniform on the positive electrode surface, and stable electrical characteristics cannot be expressed particularly when mass production is performed.

  On the other hand, when the ratio of the standard deviation with respect to the average value is 2% or less, it means that the positive electrode slurry is uniformly applied. In such a case, in the positive electrode prepared by applying the positive electrode slurry to a large area, the smoothness of the positive electrode active material layer formed on the surface of the current collector is good. Therefore, the electrical characteristics are uniform on the positive electrode surface, and stable electrical characteristics can be expressed particularly when mass production is performed. For these reasons, the evaluation criteria for the applicability of the positive electrode slurry were determined as follows. Table 3 shows the smoothness evaluation results based on the evaluation criteria.

○: Smoothness is 2% or less and good.
X: Smoothness exceeds 2% and is poor.
(5-2) Evaluation of powder fall-off property Five 10 cm x 5 cm samples were cut out from the electrical storage device positive electrode created in the above (2), and they were overlapped. A commercially available high-quality paper was placed on the experimental table, and a 100 mesh stainless steel mesh was placed thereon. Five stacked samples were cut with scissors above the mesh. Cutting was performed along the short side direction of the sample, and was cut nine times at 1 cm intervals. Then, the state of the positive electrode active material powder that passed through the stainless steel mesh and spilled on the fine paper during cutting was observed. The powder fall-off property was evaluated as follows according to the observation result. The evaluation results are shown in Table 3.

○: No powder fall off or very little powder fall off. Good.
X: A large amount of powder falling is observed. Bad.
(5-3) Evaluation of binding property Five samples of 10 cm square were cut out from the electricity storage device positive electrode prepared in the above (2), and compressed and molded by 120 ° C hot pressing for 5 minutes. A notch with a depth reaching the current collector was made on the surface of each sample using a knife. The cuts were made in 6 vertical and horizontal directions at 2 mm intervals. As a result, 25 squares partitioned in a grid pattern by cutting were formed on each sample.

  Of the surface of each sample, an adhesive tape was attached to the cut portion and immediately peeled off, and the number of cells in which the positive electrode active material layer was peeled off from the copper foil was counted. The above-described process is performed once for one sample (one side), and the number of masses from which the positive electrode active material layer is peeled is counted out of a total of 125 masses in five samples. Sex was evaluated. The evaluation results are shown in Table 3.

○: The mass of the positive electrode active material layer dropped off was 0 to 20, and the binding property was good.
X: The mass from which the positive electrode active material layer dropped off was 21 or more, and the binding property was poor.
(5-4) Evaluation of Capacity Maintenance Rate The lithium ion secondary battery assembled in (4) above was charged at a constant current (1C) and continued until the voltage reached 4.2V. After the time when the voltage became 4.2, charging was continued at a constant voltage (4.2 V), and the time when the current value reached 0.01 C was defined as completion of charge (cutoff).

  Thereafter, discharging was started at a constant current (1 C), and the time when the voltage reached 3.0 V was regarded as the completion of discharging (cutoff), and the discharge capacity at the first cycle was calculated. Thus, charge / discharge was repeated 50 times, and the discharge capacity at the 50th cycle was calculated. Table 3 shows a value obtained by dividing the discharge capacity at the 50th cycle thus measured by the discharge capacity at the 1st cycle as a discharge capacity retention rate (%). When the discharge capacity maintenance rate is 80% or more, it can be determined to be good.

(5-5) Evaluation of charge / discharge rate characteristics The lithium ion secondary battery assembled in (4) above was charged at a constant current (0.2 C) and continued until the voltage reached 4.2 V. . After the voltage reaches 4.2V, charging is continued at a constant voltage (4.2V). When the current value reaches 0.01C, the charging is completed (cut off). The charge capacity was measured. Thereafter, discharge was started at a constant current (0.2 C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 0.2 C was measured.

  Next, the same lithium ion secondary battery was charged at a constant current (3C) and continued until the voltage reached 4.2V. After the voltage reaches 4.2V, charging is continued at a constant voltage (4.2V). When the current value reaches 0.01C, charging is completed (cutoff), and the charging capacity at 3C Was measured. Thereafter, discharge was started at a constant current (3C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 3C was measured.

  Then, the ratio (%) of the discharge capacity at 3C to the discharge capacity at 0.2C was calculated, and the discharge rate characteristic (%) was calculated. Further, the ratio (%) of the charge capacity at 3C to the charge capacity at 0.2C was calculated, and the charge rate characteristic (%) was calculated.

The discharge rate characteristics and the charge rate characteristics were evaluated according to the following criteria. The evaluation results are shown in Table 3.
Good: Good discharge rate characteristics and charge rate characteristics of 80% or more.

X: The discharge rate characteristic or the charge rate characteristic is poor at less than 80%.
In the measurement conditions of this example, “1C” indicates a current value at which discharge is completed in 1 hour after constant-current discharge of a cell having a certain electric capacity. For example, “0.1 C” is a current value at which discharge is completed over 10 hours, and “10 C” is a current value at which discharge is completed over 0.1 hours.

(5-6) Evaluation of spinnability The spinnability of the positive electrode slurry prepared in (2) was evaluated. The evaluation results are shown in Table 3.
(Examples 2 to 10, Comparative Examples 1 to 6)
Basically, aqueous dispersions S2 to S13 were prepared in the same manner as the aqueous dispersion S1 in Example 1. However, in the preparation of the aqueous dispersions S2 to S13, the type and amount of the first-stage polymerizable component and the type and amount of the second-stage polymerizable component are as shown in Table 1, and are included in the component (A). The types of monomers and the amounts charged were as shown in Table 2.

  In addition, in the preparation of the aqueous dispersion described as “K” in the row of “neutralization ions” in Table 2, the same amount of potassium hydroxide was added instead of 5 parts by mass of sodium tripolyphosphate. The latex pH was adjusted to 7.5. In this case, the repeating unit Mc derived from the unsaturated carboxylic acid contained in the component (A) is a potassium salt.

In addition, in the preparation of the aqueous dispersion described as “NH ₄ ” in the row of “neutralization ions” in Table 2, by adding the same amount of ammonia instead of 5 parts by mass of sodium tripolyphosphate, The latex pH was adjusted to 7.5. In this case, the repeating unit Mc derived from the unsaturated carboxylic acid contained in the component (A) is an ammonium salt.

For the (A) polymer contained in the aqueous dispersions S2 to S13, the average particle size, THF-insoluble matter, and transition temperature (Tg) were measured. The results are shown in Table 2.
Further, basically, a positive electrode slurry, a power storage device positive electrode, a negative electrode slurry, and a power storage device negative electrode were prepared in the same manner as in Example 1, and a lithium ion battery was assembled.

  However, in Examples 2 to 10 and Comparative Examples 1 to 6, the type and amount of component (A) in the slurry for positive electrode, the type and amount of component (B), the average particle size of component (B), (C ) The types of components and the types and addition amounts of other components are shown in Table 3. In Examples 2 to 10 and Comparative Examples 1 to 6, the component (A) in the negative electrode slurry was set as shown in Table 3. That is, in each of Examples 2 to 10 and Comparative Examples 1 to 6, the component (A) used for the positive electrode slurry and the negative electrode slurry was the same.

  In Example 9, the method for preparing the positive electrode slurry was as follows. In the aqueous dispersion S13, residual monomers were removed by steam distillation, and the pH was adjusted to 7 with sodium hydroxide. Next, N-methylpyrrolidone (NMP) in an amount three times the weight of the obtained latex was added, and water was evaporated by an evaporator to obtain an NMP dispersion binder composition having a solid content concentration of 8% by mass.

Next, an NMP dispersion binder composition in such an amount that the binder solid content becomes 1 part by mass (solid content conversion) in a biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Corporation). 100 parts by mass of lithium iron phosphate (LiFePO ₄ ) manufactured by Hosen Co., Ltd., 3 parts by mass of acetylene black, and 68 parts by mass of NMP were added and stirred at 60 rpm for 1 hour to obtain a paste.

  The lithium iron phosphate is pulverized in advance with an agate mortar and classified using a sieve to have an average particle diameter (D50 value) of 10 μm. The lithium iron phosphate is an example of a positive electrode active material.

Thereafter, NMP was added to the obtained paste to adjust the solid content concentration to 50% by mass, and then the mixture was stirred at 200 rpm with a stirring defoamer (trade name “Awatori Netaro”, manufactured by Shinky Co., Ltd.). A slurry for positive electrode was prepared by stirring and mixing for 1 minute at 1,800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes.

  In Example 10, the method for preparing the positive electrode slurry was the following method. A polymer was precipitated by gradually adding 400 parts of a 10% aqueous sodium carbonate solution to the aqueous dispersion S13. The precipitated polymer was washed with methanol, and further washed with water until the pH of the washing water became 8.0 or less. The polymer after washing was vacuum dried at 50 ° C. for 1 day to obtain a dry polymer. In a separable flask, 80 parts by mass of the obtained dry polymer and 920 parts by mass of NMP were charged and stirred at 50 ° C. for 2 hours to dissolve the dry polymer to obtain a polymer solution.

Next, in a biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.), a polymer solution having an amount of polymer solid content of 1 part by mass, iron phosphate manufactured by Hosen Co., Ltd. 100 parts by mass of lithium (LiFePO ₄ ), 3 parts by mass of acetylene black, and 68 parts by mass of NMP were added, and stirred at 60 rpm for 1 hour to obtain a paste. The lithium iron phosphate is pulverized in advance with an agate mortar and classified using a sieve to have an average particle diameter (D50 value) of 10 μm. The lithium iron phosphate is an example of a positive electrode active material.

Thereafter, NMP was added to the obtained paste to adjust the solid content concentration to 50%, and then the mixture was stirred at 200 rpm for 2 minutes at 200 rpm using a stirring defoamer (trade name “Aritori Netaro”, manufactured by Shinky Co., Ltd.). A positive electrode slurry was prepared by stirring and mixing at 1,800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes.

Examples 2 to 10 and Comparative Examples 1 to 6 were also evaluated in the same manner as Example 1. The results are shown in Table 3.
(Evaluation results of each example and each comparative example)
As is apparent from the description in Table 3, when the positive electrode slurry in Examples 1 to 10 is used, in the spinnability, positive electrode characteristics (applicability, powder falling off, binding property), and power storage device characteristics. It turned out to be excellent.

  On the other hand, when the positive electrode slurry in Comparative Examples 1 to 6 is used, in at least one of the spinnability, the positive electrode characteristic, and the electricity storage device characteristic, compared to the case where the positive electrode slurry of Examples 1 to 10 is used. , Turned out to be inferior.

Claims (7)

(A) a polymer;
(B) an olivine-type lithium-containing phosphate compound;
(C) a liquid medium;
Containing
The polymer (A) is
A repeating unit Mc derived from an unsaturated carboxylic acid;
A repeating unit Md derived from a conjugated diene compound;
A repeating unit Me derived from an aromatic vinyl;
Containing a diene polymer having
The positive electrode, wherein the content of the polymer (A) is in the range of 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the (B) olivine-type lithium-containing phosphate compound. Slurry.   The positive electrode slurry according to claim 1, wherein the (B) olivine-type lithium-containing phosphate compound is lithium iron phosphate.   The slurry for positive electrodes according to claim 1 or 2, wherein the repeating unit Mc derived from the unsaturated carboxylic acid is a salt of at least one cation selected from sodium ions and potassium ions.   The manufacturing method of the electrical storage device positive electrode characterized by forming the layer by apply | coating and drying the slurry for positive electrodes of any one of Claims 1-3 on the surface of an electrical power collector. A current collector, and a layer formed on a surface of the current collector;
With
The layer contains (A) a polymer and (B) an olivine-type lithium-containing phosphate compound,
The polymer (A) is
A repeating unit Mc derived from an unsaturated carboxylic acid;
A repeating unit Md derived from a conjugated diene compound;
A repeating unit Me derived from an aromatic vinyl;
Containing a diene polymer having
(B) Content of said (A) polymer exists in the range of 0.5-1.5 mass part with respect to 100 mass parts of said (B) olivine type lithium containing phosphate compound, The electrical storage characterized by the above-mentioned Device positive electrode.   An electricity storage device comprising the electricity storage device positive electrode according to claim 5.   An electrical storage device positive electrode is manufactured with the manufacturing method of Claim 4, The manufacturing method of the electrical storage device characterized by the above-mentioned.