Slurry for power storage device positive electrode, positive electrode for power storage device, and power storage device

Abstract

The present invention provides a slurry for a power storage device positive electrode, with which it is possible to produce, without using lithium or a transition metal element that are a bottleneck to mass production and to increases in size, a positive electrode for a power storage device, the positive electrode having little odor and high strength, and being capable of reducing battery resistance.　A slurry for a power storage device positive electrode according to the present invention contains a positive electrode active material (A), a polymer (B), and a liquid medium (C). The positive electrode active material (A) contains at least one sulfur-containing compound that is selected from the group consisting of a sulfur-containing compound represented by general formula (1) and a sulfur-containing compound represented by general formula (2). The polymer (B) is at least one that is selected from the group consisting of a conjugated diene polymer, an acrylic polymer, an acrylonitrile polymer, a polyurethane, a polyimide, and a polyamide-imide.　(1): MxSyOz (In formula (1), M is Na or K, x is more than 0 but not more than 3, y is 1 to 8 inclusive, and z is 1 to 8 inclusive.)　(2): MxHSyOz (In formula (2), M is Na or K, x is more than 0 but not more than 3, y is more than 0 but not more than 8, and z is 1 to 8 inclusive.)

Description

Slurry for positive electrode of electric storage device, positive electrode for electric storage device, and electric storage device

[0001] The present invention relates to a slurry for a positive electrode of an electricity storage device, a positive electrode for an electricity storage device formed by applying the slurry to a current collector and drying the slurry, and an electricity storage device including the positive electrode for an electricity storage device.

[0002] In recent years, there has been a demand for high-voltage, high-energy-density power storage devices as power sources for electronic devices. Lithium-ion batteries and lithium-ion capacitors are expected to be such power storage devices.

[0003] On the other hand, lithium, the main constituent element of the positive electrode active material in lithium-ion secondary batteries, is facing bottlenecks to mass production and large-scale production due to factors such as the rising price of lithium due to the expanding demand for lithium-ion secondary batteries and limited lithium reserves.

[0004] For this reason, research is being conducted on sodium batteries that use sodium, which is an abundant and low-cost resource, instead of lithium, and secondary batteries that do not require lithium or transition metal elements (see, for example, Patent Documents 1 to 4).

[0005] JP 2013-203565 A JP 2014-229452 A JP 2012-206925 A Japanese Patent No. 7246789 A

[0006] However, the positive electrode active materials for sodium secondary batteries disclosed in Patent Documents 1 to 3 require transition metal elements such as cobalt and nickel, which are scarce resources. In addition, the positive electrode active material disclosed in Patent Document 4 does not use lithium or transition metal elements, but further improvement in battery performance has been desired.

[0007] Some aspects of the present invention provide a slurry for a positive electrode of an electricity storage device that can produce a positive electrode for an electricity storage device that has little odor, high strength, and reduces battery resistance, without using lithium or transition metal elements, which are bottlenecks in mass production and upsizing.

[0008] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized as any of the following aspects.

[0009] One embodiment of the slurry for a positive electrode of an electricity storage device according to the present invention comprises a positive electrode active material (A), a polymer (B), and a liquid medium (C), wherein the positive electrode active material (A) contains at least one sulfur-containing compound selected from the group consisting of sulfur-containing compounds represented by the following general formula (1) and sulfur-containing compounds represented by the following general formula (2), and the polymer (B) is at least one selected from the group consisting of conjugated diene-based polymers, acrylic polymers, acrylonitrile-based polymers, polyurethanes, polyimides, and polyamideimides. ｘ S ｙ O ｚ (1) (In formula (1), M is Na or K, x is greater than 0 and equal to or less than 3, y is equal to or greater than 1 and equal to or less than 8, and z is equal to or greater than 1 and equal to or less than 8.) M ｘ H.S. ｙ O ｚ (2) (In formula (2), M is Na or K, x is greater than 0 and less than or equal to 3, y is greater than 0 and less than or equal to 8, and z is greater than or equal to 1 and less than or equal to 8.)

[0010] In one embodiment of the slurry for a positive electrode of an electric storage device, the sulfur-containing compound is Na ２ SO ３ , NaHSO ３ , Na ２ SO ４ , NaHSO ４ , Na ２ SO ５ , Na ２ SO ８ , Na ２ S ２ O ３ , Na ２ S ２ O ４ , Na ２ S ２ O ５ , Na ２ S ２ O ６ , Na ２ S ２ O ７ and Na２ S ２ O ８ It may be at least one selected from the group consisting of:

[0011] In one embodiment of the slurry for a positive electrode of an electric storage device, the sulfur-containing compound is ２ SO ３ , K.H.S.O. ３ , K. ２ SO ４ , K.H.S.O. ４ , K. ２ SO ５ , K. ２ SO ８ , K. ２ S ２ O ３ , K. ２ S ２ O ４ , K. ２ S ２ O ５ , K. ２ S ２ O ６ , K. ２ S ２ O ７ and K. ２ S ２ O ８ It may be at least one selected from the group consisting of:

[0012] In any embodiment of the slurry for a positive electrode of an electricity storage device, the positive electrode active material (A) may be a composite of the sulfur-containing compound represented by the general formula (1) or the sulfur-containing compound represented by the general formula (2) and a carbide.

[0013] In any of the embodiments of the slurry for a positive electrode of an electricity storage device, the charcoal may be derived from a tire.

[0014] In any embodiment of the slurry for a positive electrode of an electricity storage device, the liquid medium (C) may be at least one selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, esters, ethers, glycol ethers, lactams, lactones, amides, and aliphatic sulfoxides.

[0015] In any of the embodiments of the slurry for a positive electrode of an electricity storage device, the slurry may further contain a conductive additive (D) which is at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, acetylene black, ketjen black, and furnace black.

[0016] In any of the above embodiments of the slurry for a positive electrode of an electricity storage device, a thickener (E) may be further contained.

[0017] One aspect of the positive electrode for an electricity storage device according to the present invention includes a current collector and an active material layer formed by applying the slurry for an electricity storage device positive electrode according to any one of the above aspects to a surface of the current collector and drying the applied slurry.

[0018] An aspect of the electricity storage device according to the present invention includes the electricity storage device positive electrode of the above aspect.

[0019] In one embodiment of the electricity storage device, the device may have an electrolyte solution containing a sodium salt or a potassium salt.

[0020] The slurry for a positive electrode of an electric storage device according to the present invention can produce a positive electrode for an electric storage device that has low odor, high strength, and reduced battery resistance. Furthermore, the positive electrode active material contained in the slurry for a positive electrode of an electric storage device according to the present invention does not contain lithium or transition metal elements such as cobalt and nickel, which are scarce in resources, and is therefore expected to reduce costs and ultimately contribute to the mass production and upsizing of electric storage devices.

[0021] Preferred embodiments of the present invention will be described in detail below. It should be understood that the present invention is not limited to the embodiments described below, but also includes various modifications that are implemented within the scope of the present invention.

[0022] In this specification, a numerical range described as "X to Y" is interpreted as including the numerical value X as the lower limit and the numerical value Y as the upper limit.

[0023] In this specification, "(meth)acrylic acid" refers to "acrylic acid" or "methacrylic acid".

[0024] 1. Slurry for Positive Electrode of Electrical Storage Device A slurry for a positive electrode of an electrical storage device according to one embodiment of the present invention contains a positive electrode active material (A), a polymer (B), and a liquid medium (C), in which the positive electrode active material (A) contains at least one sulfur-containing compound selected from the group consisting of sulfur-containing compounds represented by the following general formula (1) and sulfur-containing compounds represented by the following general formula (2), and the polymer (B) is at least one selected from the group consisting of conjugated diene-based polymers, acrylic polymers, acrylonitrile-based polymers, polyurethanes, polyimides, and polyamideimides. ｘ S ｙ O ｚ (1) (In formula (1), M is Na or K, x is greater than 0 and equal to or less than 3, y is equal to or greater than 1 and equal to or less than 8, and z is equal to or greater than 1 and equal to or less than 8.) M ｘ H.S. ｙ O ｚ (2) (In formula (2), M is Na or K, x is greater than 0 and less than or equal to 3, y is greater than 0 and less than or equal to 8, and z is greater than or equal to 1 and less than or equal to 8.)

[0025] The slurry for a positive electrode of an electric storage device according to this embodiment can be used as a material for producing a positive electrode (positive electrode active material layer) for an electric storage device that has high strength and reduces the resistance of the battery. Hereinafter, components that can be contained in the slurry for a positive electrode of an electric storage device according to this embodiment and a production method thereof will be described in detail.

[0026] 1.1. Components 1.1.1. Positive Electrode Active Material (A) The slurry for a positive electrode of an electricity storage device according to this embodiment contains a positive electrode active material (A) containing at least one sulfur-containing compound selected from the group consisting of sulfur-containing compounds represented by the following general formula (1) and sulfur-containing compounds represented by the following general formula (2):

[0027] M ｘ S ｙ O ｚ(1) In formula (1), M is sodium (Na) or potassium (K). x represents the proportion of M and is in the range of more than 0 and not more than 3. y represents the proportion of sulfur (S) and is in the range of 1 to 8. z represents the proportion of oxygen (O) and is in the range of 1 to 8. In formula (1), x, y, and z each may not be an integer (i.e., a decimal). In other words, the sulfur-containing compound represented by general formula (1) may also be a non-stoichiometric oxide. In formula (1), when x, y, and z are within the above ranges, the positive electrode active material can provide a positive electrode capable of repeated charge and discharge. The values ​​of x, y, and z can be adjusted by controlling the amount of raw materials used, production conditions, etc.

[0028] M ｘ H.S. ｙ O ｚ (2) In formula (2), M is sodium (Na) or potassium (K). x represents the proportion of M and is in the range of more than 0 to 3. y represents the proportion of sulfur (S) and is in the range of more than 0 to 8. z represents the proportion of oxygen (O) and is in the range of 1 to 8. In formula (2), x, y, and z each may not be an integer (i.e., a decimal). In other words, the sulfur-containing compound represented by general formula (2) may also be a non-stoichiometric oxide. In formula (2), when x, y, and z are within the above ranges, the positive electrode active material can provide a positive electrode capable of repeated charge and discharge. The values ​​of x, y, and z can be adjusted by controlling the amount of raw materials used, production conditions, etc.

[0029] Hereinafter, when there is no need to distinguish between the sulfur-containing compound represented by general formula (1) and the sulfur-containing compound represented by general formula (2), they will be collectively referred to as "specific sulfur-containing compounds."

[0030] Suitable examples of the specific sulfur-containing compound include sulfur-containing compounds in which M is Na in the above general formula (1) or (2). ２ SO ３ , NaHSO ３ , Na ２ SO４ , NaHSO ４ , Na ２ SO ５ , Na ２ SO ８ , Na ２ S ２ O ３ , Na ２ S ２ O ４ , Na ２ S ２ O ５ , Na ２ S ２ O ６ , Na ２ S ２ O ７ and Na ２ S ２ O ８ Among these, sodium thiosulfate (Na ２ S ２ O ３ ) is particularly preferred.

[0031] Other preferred examples of the specific sulfur-containing compound include sulfur-containing compounds represented by the general formula (1) or (2) in which M is K. Such specific sulfur-containing compounds include K ２ SO ３ , K.H.S.O. ３ , K. ２ SO ４ , K.H.S.O. ４ , K. ２ SO ５ , K. ２ SO ８ , K. ２ S ２ O ３ , K. ２ S ２ O ４ , K. ２ S ２ O ５ , K. ２ S ２ O ６ , K. ２ S ２ O ７ and K. ２ S ２ O ８ Among these, potassium thiosulfate (K ２ S２ O ３ ) is particularly preferred.

[0032] The specific sulfur-containing compound is not limited to a crystalline form, but may be amorphous or a mixture of crystalline and amorphous forms. The specific sulfur-containing compound may be either a non-hydrate or a hydrate.

[0033] The positive electrode active material (A) may contain one kind of the specific sulfur-containing compound alone or two or more kinds of the specific sulfur-containing compound.

[0034] The positive electrode active material (A) may contain only the specific sulfur-containing compound, but may also contain other components, such as carbides, as long as the effects of the present invention are not impaired.

[0035] The term "carbide" as used herein refers to a carbonized carbon-containing raw material (organic material), and may contain only carbon (C), but may also contain elements other than carbon as long as the object of the present invention is not impaired. Examples of elements other than carbon include nitrogen (N), sulfur (S), oxygen (O), and metal elements such as iron (Fe), but are not limited thereto as long as the object of the present invention is not impaired.

[0036] The carbonized material can also be made porous, depending on the carbon-containing raw material and the firing conditions. The conditions for producing the carbonized material are determined appropriately in consideration of the type of carbon-containing raw material and the physical properties (crystallinity, porosity, etc.) of the desired carbonized material. Typically, the carbonized raw material is heated under a low oxygen partial pressure (for example, N ２ The carbonization treatment is carried out by heating the mixture in an inert gas atmosphere (such as a gas atmosphere) at a temperature of 500°C or higher and 2000°C or lower, for example.

[0037] The carbon-containing raw material used as the raw material for the carbonized material may be any material as long as it does not impair the object of the present invention, and examples thereof include biomass raw materials (for example, wood, bamboo, rice husks, etc.), various resin materials, and plastics such as rubber materials.

[0038] The positive electrode active material (A) is preferably composed of a composite of a specific sulfur-containing compound and a carbide (hereinafter also simply referred to as a "composite"). Here, the composite does not simply mean a mixture of the specific sulfur-containing compound and the carbide, but a composite in which the specific sulfur-containing compound and the carbide are physically and / or chemically combined. The physical composite is a composite in which the specific sulfur-containing compound is physically held on the carbide, for example, a composite in which the specific sulfur-containing compound is supported on the carbide, a composite in which the specific sulfur-containing compound is adsorbed on the carbide, a composite in which the specific sulfur-containing compound is precipitated on the carbide, etc. The chemical composite is a composite in which the specific sulfur-containing compound and the carbide are chemically bonded, for example, it can be produced by mixing the specific sulfur-containing compound or its precursor compound with the carbide and heat-treating it under an inert gas atmosphere.

[0039] In the composite of the specific sulfur-containing compound and the carbide, the specific sulfur-containing compound composited with the carbide may be in a solid, liquid, or mixed state of a solid and a liquid.

[0040] The use of a composite of a specific sulfur-containing compound and a carbide as the positive electrode active material (A) improves battery performance. Although the reason for this is not entirely clear at this stage, it is presumed that one of the reasons is that the formation of a composite of a specific sulfur-containing compound and a carbide allows for smoother electron transfer between the carbide and the sulfur-containing compound compared to a mixture of the specific sulfur-containing compound and a carbide.

[0041] A suitable example of the carbon-containing raw material that serves as the raw material for the carbide in the composite is a tire. Tires are primarily made of rubber (e.g., natural rubber (NR), styrene-butadiene rubber (SBR), isoprene rubber (IR)), and contain various compounding agents and structural materials. Thus, a suitable example of the positive electrode active material (A) is a composite using a tire-derived carbide.

[0042] The content of the specific sulfur-containing compound in the positive electrode active material (A) is, for example, 5 to 100 mass % when the total mass of the positive electrode active material (A) is taken as 100 mass %.

[0043] The content of the positive electrode active material (A) in the slurry for a positive electrode of an electric storage device according to this embodiment is preferably 10 to 60 mass %, more preferably 20 to 55 mass %, and particularly preferably 25 to 50 mass %, when the total mass of the slurry for a positive electrode of an electric storage device is taken as 100 mass %. When the content of the positive electrode active material (A) is within this range, the resistance of the battery is easily reduced, and the battery performance is further improved.

[0044] 1.1.2. Polymer (B) The slurry for a positive electrode of an electricity storage device according to this embodiment contains a polymer (B). The polymer (B) is at least one selected from the group consisting of a conjugated diene polymer, an acrylic polymer, an acrylonitrile polymer, a polyurethane, a polyimide, and a polyamideimide. These polymers (B) may be used alone or in combination of two or more. These polymers (B) may be commercially available polymers or may be manufactured.

[0045] The content of the polymer (B) in the slurry for the positive electrode of the electricity storage device according to this embodiment is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, even more preferably 3 to 12 parts by mass, and particularly preferably 5 to 10 parts by mass, relative to 100 parts by mass of the positive electrode active material (A). When the content of the polymer (B) is within the above range, the dispersibility of the positive electrode active material (A) in the slurry is good, and the coating properties of the slurry are also excellent.

[0046] 1.1.3. Liquid Medium (C) The slurry for an electricity storage device positive electrode according to this embodiment contains a liquid medium (C). The liquid medium (C) is not particularly limited, but may be an aliphatic hydrocarbon such as hexane, heptane, octane, decane, or dodecane; an alicyclic hydrocarbon such as cyclohexane, cycloheptane, cyclooctane, or cyclodecane; an aromatic hydrocarbon such as toluene, xylene, mesitylene, naphthalene, or tetralin; a ketone such as methylhexyl ketone, dipropyl ketone, or diisobutyl ketone; an ester such as butyl acetate, butyl butyrate, or methyl butanoate; an ether such as dibutyl ether, tetrahydrofuran, or anisole; (mono-, di-, tri-, or poly)ethylene glycol monomethyl ether; Examples of the liquid medium (C) that can be used include glycol ethers such as (tri- or poly)ethylene glycol dimethyl ether and ethylene glycol phenyl ether; lactams such as β-lactam, γ-lactam, δ-lactam, N-methyl-2-pyrrolidone and 2-pyrrolidone; lactones such as α-acetolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone and ε-caprolactone; amides such as N-methylacetamide, dimethylacetamide, N-methylformamide and dimethylformamide; and aliphatic sulfoxides such as dimethyl sulfoxide and di-n-butyl sulfoxide. These liquid media (C) can be used alone or in combination of two or more.

[0047] The content of the liquid medium (C) in the slurry for a positive electrode of an electric storage device according to this embodiment is preferably 100 to 10,000 parts by mass, more preferably 500 to 2,000 parts by mass, per 100 parts by mass of the polymer component. When the content of the liquid medium (C) is equal to or greater than the lower limit, the mixing of the polymer component and the positive electrode active material is improved when preparing the slurry for a positive electrode of an electric storage device. On the other hand, when the content of the liquid medium (C) is equal to or less than the upper limit, the coating properties of the slurry for a positive electrode of an electric storage device are improved when producing a positive electrode active material layer, and concentration gradients of the polymer component and the positive electrode active material are less likely to occur during the drying process after coating. Here, the polymer component includes the polymer (B) and the thickener (E) described below.

[0048] 1.1.4 Other Additives The slurry for a positive electrode of an electricity storage device according to this embodiment may contain additives other than the components described above, as necessary. Examples of such additives include a conductive additive (D), a thickener (E), a pH adjuster, and a corrosion inhibitor.

[0049] <Conductive Aid (D)> A conductive aid (D) may be further added to the slurry for the positive electrode of an electricity storage device according to this embodiment for the purpose of imparting conductivity.

[0050] Specific examples of the conductive additive (D) include carbon such as carbon nanotubes, carbon nanofibers, acetylene black, ketjen black, furnace black, graphite, fullerene, carbon nanohorns, activated carbon, graphite, and carbon fibers. Among these, at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, acetylene black, ketjen black, and furnace black can be preferably used.

[0051] Examples of carbon nanotubes include single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multi-walled carbon nanotubes (MWCNT). Carbon nanotubes may be composed of only carbon, or may have a structure partially substituted with other elements or chemically modified, or may be a composite with a metal (e.g., gold, silver, copper, aluminum, nickel, cobalt, titanium, platinum, etc.).

[0052] The content of the conductive additive (D) is preferably 0.01 to 10 parts by mass, more preferably 0.02 to 8 parts by mass, and particularly preferably 0.03 to 6 parts by mass, relative to 100 parts by mass of the total solid content of the slurry for the positive electrode of an electricity storage device.

[0053] <Thickener (E)> The slurry for a positive electrode of an electricity storage device according to this embodiment may contain a thickener (E). By containing the thickener (E), it may be possible to further improve the coatability of the slurry and the charge / discharge characteristics of the obtained electricity storage device.

[0054] Examples of the thickener (E) include cellulose-based polymers such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose; poly(meth)acrylic acid; ammonium salts or alkali metal salts of the above-mentioned cellulose compounds or the above-mentioned poly(meth)acrylic acid; modified polyvinyl alcohol, polyethylene oxide; polyvinylpyrrolidone, polycarboxylic acid, oxidized starch, starch phosphate, casein, various modified starches, chitin, and chitosan derivatives. Among these, cellulose-based polymers are preferred.

[0055] Commercially available thickeners (E) include alkali metal salts of carboxymethyl cellulose such as CMC1120, CMC1150, CMC2200, CMC2280, and CMC2450 (all manufactured by Daicel Corporation).

[0056] When the slurry for a positive electrode of an electricity storage device according to this embodiment contains a thickener (E), the content of the thickener (E) is preferably 5% by mass or less, and more preferably 0.1 to 3% by mass, relative to 100% by mass of the total of the polymer components. Here, the polymer components include the polymer (B) and the thickener (E).

[0057] <pH Adjuster> A pH adjuster may be further added to the slurry for the positive electrode of the electricity storage device according to this embodiment, depending on the type of active material, for the purpose of suppressing corrosion of the current collector.

[0058] Examples of pH adjusters include hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, formic acid, ammonium phosphate, ammonium sulfate, ammonium acetate, ammonium formate, ammonium chloride, sodium hydroxide, potassium hydroxide, etc. Among these, sulfuric acid, ammonium sulfate, sodium hydroxide, and potassium hydroxide are preferred.

[0059] <Corrosion Inhibitor> A corrosion inhibitor may be further added to the slurry for the positive electrode of the electricity storage device according to this embodiment, depending on the type of active material, for the purpose of suppressing corrosion of the current collector.

[0060] Examples of the corrosion inhibitor include ammonium metavanadate, sodium metavanadate, potassium metavanadate, ammonium metatungstate, sodium metatungstate, potassium metatungstate, ammonium paratungstate, sodium paratungstate, potassium paratungstate, ammonium molybdate, sodium molybdate, potassium molybdate, etc. Among these, ammonium paratungstate, ammonium metavanadate, sodium metavanadate, potassium metavanadate, and ammonium molybdate are preferred.

[0061] 1.2. Manufacturing Method of Slurry for Electricity Storage Device Positive Electrode The slurry for the electricity storage device positive electrode according to this embodiment may be manufactured by any method as long as it contains the above-described components. From the viewpoint of manufacturing a slurry having better dispersibility and stability more efficiently and inexpensively, it is preferable to manufacture the slurry by adding and dissolving the polymer (B) in the liquid medium (C), then adding the positive electrode active material (A) and any optional additional components used as needed, and mixing them.

[0062] As a mixing and stirring means for producing a slurry for a positive electrode of an electric storage device, it is necessary to select a mixer that can stir the active material particles to an extent that no agglomerates remain in the slurry, and necessary and sufficient dispersion conditions. The degree of dispersion can be measured using a particle gauge, but it is preferable to mix and disperse the active material particles so that no agglomerates larger than 100 μm remain. Examples of mixers that meet these conditions include a ball mill, a bead mill, a sand mill, a defoamer, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and a Hobart mixer.

[0063] It is preferable that at least a part of the preparation of the slurry for the positive electrode of an electric storage device (the operation of mixing each component) is carried out under reduced pressure. This can prevent the formation of bubbles in the obtained positive electrode active material layer. The degree of reduced pressure is 5.0 × 10 absolute pressure. ３ ~5.0 x 10 ５ It is preferable to set it to about Pa.

[0064] 2. Positive Electrode for Electricity Storage Device A positive electrode for an electricity storage device according to one embodiment of the present invention comprises a current collector and an active material layer formed by applying the above-described slurry for a positive electrode for an electricity storage device to the surface of the current collector and drying the slurry. Such a positive electrode for an electricity storage device can be produced by applying the above-described slurry for a positive electrode for an electricity storage device to the surface of a current collector such as a metal foil to form a coating film, and then drying the coating film to form a positive electrode active material layer. The positive electrode for an electricity storage device produced in this manner has a positive electrode active material layer bound to the surface of the current collector, the positive electrode active material layer containing the above-described positive electrode active material (A), polymer (B), and optional components added as needed, and therefore has high strength and can reduce battery resistance.

[0065] The current collector is not particularly limited as long as it is made of a conductive material. Metal current collectors such as iron, copper, aluminum, nickel, and stainless steel are commonly used, but the effect of the slurry for the positive electrode of an electricity storage device described above is most pronounced when aluminum is used. The shape and thickness of the current collector are not particularly limited, but a sheet-like current collector with a thickness of about 0.001 to 0.5 mm is preferred.

[0066] There are no particular limitations on the method for applying the slurry for the positive electrode of an electric storage device to a current collector. Application can be performed by any suitable method, such as a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, an immersion method, or a brush coating method. The amount of the slurry for the positive electrode of an electric storage device is also not particularly limited. However, it is preferably an amount such that the thickness of the positive electrode active material layer formed after removing the liquid medium (C) is 0.005 to 5 mm, more preferably 0.01 to 2 mm. By ensuring that the thickness of the positive electrode active material layer is within the above range, the electrolyte can be effectively impregnated into the positive electrode active material layer. As a result, metal ions can be easily exchanged between the positive electrode active material in the positive electrode active material layer and the electrolyte during charge and discharge, which is preferable because it can further reduce electrode resistance. Furthermore, when the thickness of the positive electrode active material layer is within the above range, even when the electrode is processed by folding, rolling, or the like, the positive electrode active material layer does not peel off from the current collector, has good adhesion, and is therefore preferred in that a highly flexible positive electrode for an electricity storage device can be easily obtained.

[0067] The method for drying and removing the liquid medium (C) from the coating film after application is not particularly limited, and can be, for example, drying with warm air, hot air, or low-humidity air; vacuum drying; or drying by irradiation with (far) infrared rays, electron beams, etc. The drying speed can be appropriately set so that the liquid medium can be removed as quickly as possible within a speed range that does not cause cracks in the positive electrode active material layer due to stress concentration or peeling of the positive electrode active material layer from the current collector.

[0068] Furthermore, it is preferable to further press the coating film after removing the liquid medium (C) to increase the density of the positive electrode active material layer. Examples of pressing methods include die pressing and roll pressing. The pressing conditions should be appropriately set depending on the type of pressing equipment used and the desired density of the positive electrode active material layer. These conditions can be easily set by a person skilled in the art through a few preliminary experiments. For example, in the case of roll pressing, the linear pressure of the roll press machine can be set to 0.1 to 10 t / cm, preferably 0.5 to 5 t / cm, and the roll temperature can be set to 20 to 100°C, and the feed rate of the coating film after removing the liquid medium (C) (roll rotation speed) can be set to 1 to 80 m / min, preferably 5 to 50 m / min.

[0069] 3. Electricity Storage Device An electricity storage device according to one embodiment of the present invention includes the above-described electricity storage device positive electrode. The electricity storage device according to this embodiment contains, in addition to the above-described electricity storage device positive electrode, an electricity storage device negative electrode, and an electrolyte solution, and can be manufactured according to a conventional method using components such as a separator. Specific manufacturing methods include, for example, stacking the negative electrode and positive electrode with a separator interposed between them, rolling or folding the stack according to the battery shape, and then encasing the stack in a battery container, injecting the electrolyte solution into the battery container, and sealing the container. The battery can have any suitable shape, such as a coin shape, a cylindrical shape, a rectangular shape, or a laminate shape.

[0070] The electricity storage device according to this embodiment includes the above-described electricity storage device positive electrode, electricity storage device negative electrode, and electrolyte, and the electricity storage device positive electrode is formed using the above-described electricity storage device positive electrode slurry. In the electricity storage device positive electrode and electricity storage device according to this embodiment, known secondary battery components can be used for components other than those described above.

[0071] The negative electrode for the power storage device used in the power storage device according to this embodiment has a current collector and a negative electrode active material layer formed on the surface of the current collector. The negative electrode active material layer is typically formed of a negative electrode mixture containing a negative electrode active material and a binder.

[0072] Examples of the negative electrode active material include carbon materials capable of absorbing and desorbing sodium ions and potassium ions, such as natural graphite, artificial graphite, cokes, hard carbon, carbon black, pyrolytic carbons, carbon fiber, and baked organic polymer compounds. The carbon material may be in any shape, such as flakes like natural graphite, spherical like mesocarbon microbeads, fibrous like graphitized carbon fiber, or aggregates of fine powder. Here, the carbon material may also function as a conductive material.

[0073] As described above, the negative electrode active material in the negative electrode for an electricity storage device is not limited to a particular material, but is preferably hard carbon.

[0074] Hard carbon is a carbon material whose stacking order hardly changes even when heat-treated at high temperatures of 2000°C or higher, and is also called non-graphitizable carbon. Examples of hard carbon include carbon fibers obtained by carbonizing infusible yarn, an intermediate product in the carbon fiber manufacturing process, at about 1000°C to 1400°C, and carbon materials obtained by air-oxidizing an organic compound at about 150°C to 300°C and then carbonizing it at about 1000°C to 1400°C. There are no particular limitations on the method for manufacturing hard carbon, and hard carbon manufactured by a conventionally known method can be used.

[0075] The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but is preferably 80 to 95 mass %.

[0076] The binder may be the same as the polymer (B) usable for the positive electrode for the electricity storage device described above, and therefore a description thereof will be omitted. The current collector is made of a conductive material such as nickel, copper, or stainless steel (SUS). The current collector is made of a foil, mesh, expanded grid (expanded metal), punched metal, or the like, similar to the current collector for the positive electrode for the electricity storage device.

[0077] The method for forming the negative electrode active material layer on the current collector can be the same as the method for forming the positive electrode active material layer on the current collector.

[0078] <Electrolyte> The electrolyte used in the electricity storage device according to this embodiment may be liquid or gel-like, and may be selected from known electrolytes used in electricity storage devices that effectively exhibit the functions of a battery depending on the type of active material. The electrolyte is not particularly limited and may be in either liquid or solid form. Typically, a solution in which a sodium salt or potassium salt of an electrolyte salt is dissolved in an electrolyte solution (non-aqueous solvent) is used. The electrolyte contained in the electrolyte used in the electricity storage device according to this embodiment is not particularly limited, but the electrolyte disclosed in the examples is a suitable example.

[0079] The electrolyte salt may be any electrolyte salt commonly used in sodium secondary batteries or potassium secondary batteries. One type of electrolyte salt may be used, or two or more types may be used in combination.

[0080] As the electrolyte, electrolytes used in sodium secondary batteries or potassium secondary batteries can be used, and examples thereof include carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; ethers such as 1,2-dimethoxyethane and 1,3-dimethoxypropane; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; phosphates such as tris(2,2,2-trifluoroethyl)phosphate; and the above organic solvents further having a fluorine substituent introduced therein.

[0081] 4. Examples The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. "Parts" and "%" in the examples and comparative examples are by mass unless otherwise specified.

[0082] 4.1. Synthesis of Positive Electrode Active Material <Positive Electrode Active Material (A-1)> Positive electrode active material (A-1) was obtained according to Experimental Example 1 of JP 2023-98729 A. That is, 5.5 g (24.2% of the total raw materials) of waste tire-derived charcoal "Renesis A1 (product number)" (manufactured by Renesis Corporation) as a charcoal, 8.44 g of sodium percarbonate (37.2% of the total raw materials), 2.75 g of coal tar (12.1% of the total raw materials), and 6 g of sulfur (26.4% of the total raw materials) were kneaded in a stainless steel container and placed in a heating furnace, and nitrogen gas was introduced into the container to create an inert atmosphere. After 10 minutes, heating was started. The temperature was raised to 300 ° C in 50 minutes, and heating continued even after reaching 300 ° C., and stopped at 350 ° C. After that, the temperature dropped to 200 ° C., and the mixture was removed from the heating furnace and allowed to cool naturally. The synthesized product was taken out after the temperature inside the container became 50° C. or less. The weight of the synthesized product was 15.2 g. The synthesized product was pulverized in a mixer to obtain a positive electrode active material (A-1) consisting of powder with an average particle size of 20 μm.

[0083] <Positive Electrode Active Material (A-2)> Positive electrode active material (A-2) was obtained according to Experimental Example 4 of JP 2023-98729 A. That is, 10 g (20.5% of the total raw materials) of waste tire-derived charcoal "Renesis A1 (product number)" (manufactured by Renesis Corporation) as the charcoal, 25 g of potassium bicarbonate (51.2% of the total raw materials), 3.8 g of coal tar (7.8% of the total raw materials), 10 g of sulfur (20.5% of the total raw materials) total raw materials of 48.8 g were kneaded in a stainless steel container and placed in a heating furnace, and nitrogen gas was introduced into the container to create an inert atmosphere, and heating began 10 minutes later. The temperature was increased to 300 ° C in 50 minutes, and heating continued even after reaching 300 ° C and stopped at 350 ° C. Thereafter, the temperature dropped to 200 ° C, and the product was removed from the heating furnace and allowed to cool naturally. The synthesized product was removed after the temperature inside the container reached 50 ° C or below. The weight of the synthesized product was 32.5 g, which was a yield of 67%. The synthesized product was pulverized in a mixer to obtain a positive electrode active material (A-2) made of powder having an average particle size of 20 μm.

[0084] 4.2. Production of Negative Electrode Active Material The negative electrode active material used was a waste tire-derived charcoal "Renesis A1" (manufactured by Renesis Corporation), produced as follows. First, waste tires were heated to 400°C for two hours in an inert atmosphere container, and the components within the waste tires were gasified and cooled to convert them into oil (approximately 55% total gasification and oil conversion). The remaining residue was then recovered. The recovered waste tire pyrolysis residue was then further heat-treated and pulverized to an average particle size of 20 μm. Magnetic material was then completely removed using a 16,000 gauss electromagnetic separator, yielding "Renesis A1," a waste tire pyrolysis residue-derived charcoal.

[0085] 4.3. Synthesis of Polymer (B) <Synthesis of Conjugated Diene Polymer> An aqueous polymer dispersion was obtained by single-stage polymerization as shown below. A reactor was charged with 200 parts by mass of water, a monomer mixture consisting of 50 parts by mass of 1,3-butadiene, 35 parts by mass of styrene, 5 parts by mass of methacrylic acid, and 10 parts by mass of acrylonitrile, 0.5 parts by mass of tert-dodecyl mercaptan as a chain transfer agent, 1 part by mass of sodium dodecylbenzenesulfonate as an emulsifier, 0.02 parts by mass of cumene hydroperoxide, 0.01 parts by mass of ethylenediaminetetraacetic acid tetrasodium salt, 0.006 parts by mass of iron(II) sulfate heptahydrate, and 0.03 parts by mass of sodium formaldehyde sulfoxylate as polymerization initiators, and the mixture was polymerized at 15°C for 10 hours with stirring to obtain an aqueous polymer dispersion.

[0086] Next, the polymer aqueous dispersion was added dropwise to 3,000 parts by mass of a 0.5% aqueous calcium chloride solution. The resulting aggregates were washed with water. The resulting aggregates were added to N-methyl-2-pyrrolidone and stirred overnight to prepare a conjugated diene polymer solution in which the polymer was dissolved in N-methyl-2-pyrrolidone. The polymer content was adjusted to 8% by mass when the entire conjugated diene polymer solution was taken as 100% by mass.

[0087] <Synthesis of Acrylic Polymer> An aqueous polymer dispersion was obtained by single-stage polymerization as shown below. A reactor was charged with 500 parts by mass of water, a monomer mixture consisting of 1 part by mass of styrene, 5 parts by mass of acrylic acid, 64 parts by mass of 2-ethylhexyl acrylate, 25 parts by mass of acrylonitrile, and 5 parts by mass of isopropylidenemalononitrile, 1 part by mass of sodium dodecylbenzenesulfonate as an emulsifier, and 0.3 part by mass of potassium persulfate as a polymerization initiator, and the mixture was polymerized at a polymerization temperature of 75°C for 8 hours to obtain an aqueous polymer dispersion.

[0088] Next, the polymer aqueous dispersion was added dropwise to 3,000 parts by mass of a 0.5% aqueous calcium chloride solution. The resulting aggregates were washed with water. The resulting aggregates were added to N-methyl-2-pyrrolidone and stirred overnight to prepare an acrylic polymer solution in which the polymer was dissolved in N-methyl-2-pyrrolidone. The polymer content was adjusted to 8% by mass when the total acrylic polymer solution was taken as 100% by mass.

[0089] Synthesis of hydrogenated NBR (nitrile rubber) 240 parts by mass of water, 2.5 parts by mass of sodium alkylbenzenesulfonate, 20 parts by mass of acrylonitrile, 30 parts by mass of butyl acrylate, and 4.5 parts by mass of methacrylic acid were placed in an autoclave equipped with a stirrer in this order, and after the atmosphere inside the bottle was replaced with nitrogen, 45.5 parts by mass of butadiene was added under pressure, and 0.25 parts by mass of ammonium persulfate was added, followed by polymerization reaction at a reaction temperature of 40°C, to obtain a polymer comprising polymerization units having nitrile groups and conjugated diene monomer units. The iodine value was 280.

[0090] 400 mL (48 g total solids) of the polymer, adjusted to a total solids concentration of 12 wt%, was placed in a 1 L autoclave equipped with a stirrer, and nitrogen gas was passed through for 10 minutes to remove dissolved oxygen in the polymer. Then, 75 mg of palladium acetate was dissolved in 180 mL of water containing 4 times the molar amount of nitric acid relative to Pd as a hydrogenation catalyst and added. After the system was purged with hydrogen gas twice, the contents of the autoclave were heated to 50°C under pressure of 3 MPa with hydrogen gas, and hydrogenation reaction was carried out for 6 hours. At this time, the iodine value of the polymer was 35.

[0091] Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate was dissolved in 60 mL of water containing 4 times the molar amount of nitric acid relative to Pd as a hydrogenation catalyst and added. After the system was purged with hydrogen gas twice, the contents of the autoclave were heated to 50°C under a pressure of 3 MPa with hydrogen gas, and hydrogenation reaction was carried out for 6 hours.

[0092] Thereafter, the contents were returned to room temperature, the system was emptied into a nitrogen atmosphere, and the mixture was concentrated using an evaporator to a solids concentration of 40%, to obtain a polymer aqueous dispersion. The iodine value of the obtained polymer was 10. 320 parts by mass of N-methylpyrrolidone was added to 100 parts by mass of this polymer aqueous dispersion, and water was evaporated under reduced pressure to prepare a hydrogenated NBR solution in which the polymer was dissolved in N-methylpyrrolidone.

[0093] <Synthesis of Polyurethane> A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 455.5 parts by mass of a polyester polyol obtained from terephthalic acid, adipic acid, and 3-methyl-1,5-pentanediol ("Kuraray Polyol P-2011" manufactured by Kuraray Co., Ltd., Mn=2011), 16.5 parts by mass of dimethylolbutanoic acid, 105.2 parts by mass of isophorone diisocyanate, and 140 parts by mass of toluene, and the mixture was reacted at 90°C for 3 hours under a nitrogen atmosphere, and 360 parts by mass of toluene was added to obtain a urethane prepolymer solution having isocyanate groups. Next, 969.5 parts by mass of the obtained urethane prepolymer solution having isocyanate groups was added to a mixture of 19.9 parts by mass of isophorone diamine, 0.63 parts by mass of di-n-butylamine, 294.5 parts by mass of 2-propanol, and 335.5 parts by mass of toluene, and the mixture was reacted at 50°C for 3 hours and then at 70°C for 2 hours. The mixture was diluted with 126 parts by mass of toluene and 54 parts by mass of 2-propanol to obtain a polyurethane solution having Mw = 61,000, an acid value = 10 mgKOH / g, and a total equivalent of 0.98 of the amino groups in the polyamino compound and the reaction terminator relative to the free isocyanate groups at both ends of the urethane prepolymer.

[0094] <Synthesis of Polyimide> In a four-neck flask equipped with a condenser and a nitrogen gas inlet, 1.0 mol of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 0.95 mol of o-tolidine diisocyanate, and N-methyl-2-pyrrolidone (NMP) were mixed to a solids concentration of 20% by mass, and 0.01 mol of diazabicycloundecene was added as a catalyst, followed by stirring and reaction at 120°C for 4 hours to obtain a polyimide solution.

[0095] <Synthesis of Polyamideimide> In a flask equipped with a condenser, a nitrogen gas inlet tube, and a stirrer, 0.7 mol of trimellitic anhydride, 0.3 mol of 3,3',4,4'-benzophenonetetracarboxylic anhydride, 1 mol of naphthalene diisocyanate, and 0.01 mol of diazabicycloundecene were dissolved in N-methyl-2-pyrrolidone (NMP) to prepare a solution with a monomer concentration of 15% by mass, and the reaction was carried out at 80°C for 3 hours to obtain a polyamideimide solution.

[0096] 4.4 Example 1 <Preparation of Positive Electrode> The positive electrode of Example 1 was prepared as follows: 0.8 g (74% of the total) of the positive electrode active material (A-1) obtained above and 0.2 g (19% of the total) of acetylene black as a conductive material were uniformly mixed (kneaded) with the acrylic polymer solution obtained above to a total weight of 0.076 g (7.01% of the total) in terms of solid content, thereby obtaining a positive electrode slurry of Example 1.

[0097] Next, the obtained positive electrode slurry was applied to an aluminum sheet (thickness: 16 μm) that would serve as a positive electrode current collector, and dried at 50° C. for 3 hours to obtain a positive electrode sheet. A piece of 15 mm diameter was cut out from the obtained positive electrode sheet to provide the positive electrode of Example 1.

[0098] <Preparation of Negative Electrode> 1.5 g (92.71% of the total) of the negative electrode active material prepared above and 0.106 g (solid content equivalent, 6.55% of the total) of SBR (trade name "TRD 105A", manufactured by ENEOS Material Corporation) as a binder were dissolved in an aqueous solution containing 0.007 g of carboxymethyl cellulose (CMC) and 0.005 g of CNT (trade name "TUBALL") as a solvent. TM BATT H ２The mixture was mixed (kneaded) with 1.2 g of "O.O. CMC" (manufactured by Kusumoto Chemicals Co., Ltd.) to obtain a negative electrode slurry.

[0099] The resulting negative electrode slurry was then applied to an aluminum sheet (thickness: 16 μm) that would serve as a negative electrode current collector, and dried at 70° C. for 3 hours to obtain a negative electrode sheet. A negative electrode having a diameter of 11.3 mm was then cut out from the resulting negative electrode sheet.

[0100] <Preparation of Secondary Battery> The obtained positive electrode and negative electrode were combined with an electrolyte solution prepared by dissolving sodium bis(fluorosulfonyl)imide (NaFSI) as a sodium salt in tris(2,2,2-trifluoroethyl)phosphate (TFEP) to a concentration of 2 mol / L, and Celgard 2400 as a separator, to obtain a secondary battery of Example 1 (coin-type battery (cylindrical, outer diameter 20 mm / height 3.2 mm)).

[0101] <Odor Evaluation> The positive electrode slurry obtained above was quickly placed in a collection vial with an outer diameter of 40 mm, a height of 75 mm, an inner opening diameter of 20.1 mm, and a capacity of 50 mL. The vial was then closed and stored in a thermostatic chamber at 60°C for 1 hour to fill the collection vial with odor. Next, the collection vial was left to cool to room temperature, and the odor intensity of each sample was evaluated on a 10-point scale by 10 monitors who evaluate odor intensity. The odor evaluation results of the 10 monitors were averaged to determine the odor intensity of that sample. The evaluation criteria were as follows. The evaluation results are shown in Table 1 below. Note that a higher value indicates a lower odor. (Evaluation Criteria) A: 10-7 B: 6-3 C: 2-0

[0102] <Evaluation of Flexibility> The positive electrode obtained above was punched out into a shape of 4 cm x 6 cm. The punched positive electrode was vacuum dried at 160°C for 6 hours. Thereafter, the positive electrode was placed in a dry room using a 0.514-Type 1 coating bending tester manufactured by Yasuda Seiki Co., Ltd., and visually inspected for cracks in the electrode when bent 180° using a cylindrical mandrel method. The mandrel diameters used were φ4, φ8, φ16, and φ32 mm. The evaluation criteria were as follows. The evaluation results are shown in Table 1 below. (Evaluation Criteria) - 5 points: No cracks occurred in the positive electrode with a mandrel diameter of φ4 mm or less. - 4 points: No cracks occurred in the positive electrode with a mandrel diameter of φ8 mm, but cracks occurred in the positive electrode with a mandrel diameter of φ4 mm. - 3 points: No cracks occurred in the positive electrode with a mandrel diameter of φ16 mm, but cracks occurred in the positive electrode with a mandrel diameter of φ8 mm. 2 points: No cracks occurred in the positive electrode when the mandrel diameter was φ32 mm, but cracks occurred in the positive electrode when the mandrel diameter was φ16 mm. 1 point: Cracks occurred in the positive electrode when the mandrel diameter was φ32 mm.

[0103] <Evaluation of Resistance Increase Rate> The secondary battery prepared above was charged at a constant current (1.0 C) in a thermostatic chamber maintained at 25°C. When the voltage reached 2.5 V, charging was continued at a constant voltage (2.5 V). The charge completion (cutoff) was determined when the current reached 0.01 C. Discharge was then initiated at a constant current (0.05 C). The discharge completion (cutoff) was determined when the voltage reached 2.5 V, and the discharge capacity at the 0th cycle was calculated. Further, charging was initiated at a constant current (1.0 C). When the voltage reached 2.5 V, charging was continued at a constant voltage (2.5 V). The charge completion (cutoff) was determined when the current reached 0.01 C. Discharge was then initiated at a constant current (1.0 C). The discharge completion (cutoff) was determined when the voltage reached 0.5 V, and the discharge capacity at the first cycle was calculated. Charge and discharge were repeated 100 times in this manner. After repeating charge and discharge 100 times, charge and discharge were performed in the same manner as in the 0th cycle, and the discharge capacity in the 101st cycle was evaluated. The resistance increase rate was calculated using the following formula (3) and evaluated according to the following criteria. The results are shown in Table 1 below. Resistance increase rate (%) = (discharge capacity at 101st cycle - discharge capacity at 100th cycle) / (discharge capacity at 0th cycle - discharge capacity at 1st cycle) x 100 (3) (Evaluation criteria) - 5 points: Resistance increase rate is 100% or more and less than 110%. - 4 points: Resistance increase rate is 110% or more and less than 120%. - 3 points: Resistance increase rate is 120% or more and less than 130%. - 2 points: Resistance increase rate is 130% or more and less than 140%. - 1 point: Resistance increase rate is 140% or more.

[0104] 4.5. Examples 2 to 10 and Comparative Examples 1 and 2 Positive electrodes, negative electrodes, and secondary batteries were fabricated and evaluated in the same manner as in Example 1, except that the materials listed in Table 1 below were used.

[0105] 4.6. Evaluation Results Table 1 below shows the materials used in Examples 1 to 10 and Comparative Examples 1 and 2, as well as the evaluation results.

[0106]

[0107] The materials in Table 1 above represent the following compounds: <Positive electrode active material> Sodium thiosulfate: sodium thiosulfate pentahydrate (Na ２ S ２ O３ ・5H ２ O), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Potassium thiosulfate: potassium thiosulfate anhydrous, manufactured by Kishida Chemical Co., Ltd. <Polymer> Acrylonitrile-based: Polyacrylonitrile (manufactured by Aldrich, Mw 150,000, atactic type) was added to N-methyl-2-pyrrolidone and mixed at room temperature to dissolve the polyacrylonitrile, preparing a polyacrylonitrile solution (10% by mass). PVDF: trade name "KF Polymer", manufactured by Kureha Corporation, polyvinylidene fluoride TRD105: trade name "TRD 105A", manufactured by ENEOS Materials Corporation, styrene butadiene rubber (SBR) <Electrolyte> Sodium: sodium bis(fluorosulfonyl)imide (NaFSI) was dissolved in tris(2,2,2-trifluoroethyl)phosphate (TFEP) to give a concentration of 2 mol / L. Potassium: potassium bis(fluorosulfonyl)imide (KFSI) dissolved in tris(2,2,2-trifluoroethyl)phosphate (TFEP) to give a concentration of 2 mol / L.

[0108] As is clear from Table 1 above, the slurries for positive electrodes of electricity storage devices according to the present invention shown in Examples 1 to 10 had less odor and provided better retractability of the positive electrodes for electricity storage devices compared to Comparative Examples 1 and 2. In addition, it was also found that the increase in internal resistance of the electricity storage device was reduced. The reason for this is presumed to be that the positive electrode active material (A) does not react with the polymer (B), thereby stabilizing the slurry and maintaining the strength of the surface of the resulting positive electrode. As a result, it is presumed that the increase in internal resistance of the electricity storage device was suppressed.

[0109] The present invention is not limited to the above-described embodiments, and various modifications are possible. The present invention includes configurations that are substantially identical to the configurations described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). The present invention also includes configurations in which non-essential parts of the configurations described in the above embodiments are replaced with other configurations. Furthermore, the present invention also includes configurations that achieve the same effects or purposes as the configurations described in the above embodiments. Furthermore, the present invention also includes configurations in which publicly known technology is added to the configurations described in the above embodiments.

Claims

1. A slurry for a positive electrode of an electricity storage device, comprising a positive electrode active material (A), a polymer (B), and a liquid medium (C), wherein the positive electrode active material (A) contains at least one sulfur-containing compound selected from the group consisting of sulfur-containing compounds represented by the following general formula (1) and sulfur-containing compounds represented by the following general formula (2), and the polymer (B) is at least one selected from the group consisting of conjugated diene-based polymers, acrylic polymers, acrylonitrile-based polymers, polyurethanes, polyimides, and polyamideimides. ｘ S ｙ O ｚ (1) (In formula (1), M is Na or K, x is greater than 0 and equal to or less than 3, y is equal to or greater than 1 and equal to or less than 8, and z is equal to or greater than 1 and equal to or less than 8.) M ｘ H.S. ｙ O ｚ (2) (In formula (2), M is Na or K, x is greater than 0 and less than or equal to 3, y is greater than 0 and less than or equal to 8, and z is greater than or equal to 1 and less than or equal to 8.) 2. The sulfur-containing compound is Na ２ SO ３ , NaHSO ３ , Na ２ SO ４ , NaHSO ４ , Na ２ SO ５ , Na ２ SO ８ , Na ２ S ２ O ３ , Na ２ S ２ O ４ , Na ２ S ２ O ５ , Na ２ S ２ O ６ , Na ２ S ２ O ７ and Na ２ S ２ O ８ The slurry for a positive electrode of an electricity storage device according to claim 1 , wherein the slurry is at least one selected from the group consisting of:

3. The sulfur-containing compound is K ２ SO ３ , K.H.S.O. ３ , K. ２ SO ４ , K.H.S.O. ４ , K. ２ SO ５ , K. ２ SO ８ , K. ２ S ２ O ３ , K. ２ S ２ O ４ , K. ２ S ２ O ５ , K. ２ S ２ O ６ , K. ２ S ２ O ７ and K. ２ S ２ O ８ The slurry for a positive electrode of an electricity storage device according to claim 1 , wherein the slurry is at least one selected from the group consisting of:

4. A slurry for a positive electrode of an electricity storage device according to claim 1 or 2, wherein the positive electrode active material (A) comprises a composite of a sulfur-containing compound represented by general formula (1) or a sulfur-containing compound represented by general formula (2) and a carbide.

5. A slurry for a positive electrode of an electricity storage device according to claim 4, wherein the charcoal is derived from tires.

6. A slurry for a positive electrode of an electricity storage device according to claim 1 or 2, wherein the liquid medium (C) is at least one selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, ketones, esters, ethers, glycol ethers, lactams, lactones, amides, and aliphatic sulfoxides.

7. A slurry for a positive electrode of an electricity storage device according to claim 1 or 2, further comprising a conductive additive (D) which is at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, acetylene black, ketjen black and furnace black.

8. A slurry for a positive electrode of an electricity storage device according to claim 1 or 2, further comprising a thickener (E).

9. A positive electrode for an electricity storage device, comprising a current collector and an active material layer formed by applying the slurry for a positive electrode of an electricity storage device according to claim 1 or 2 to the surface of the current collector and drying it.

10. An electricity storage device comprising the electricity storage device positive electrode according to claim 9.

11. The electricity storage device according to claim 10, which has an electrolyte solution containing a sodium salt or a potassium salt.

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