Electrode mixture paste and solid-state battery electrode

Abstract

A purpose of the present invention is to provide an electrode mixture paste capable of producing an electrode for a solid-state battery having a discharge capacity that is maintained even after repeated charging and discharging, and a method for manufacturing the electrode mixture paste; and to provide a solid-state battery electrode that maintains discharge capacity even after repeated charging and discharging, and a method for manufacturing the solid-state battery electrode.　Provided are an electrode mixture paste and a solid-state battery electrode made therefrom, the electrode mixture paste being characterized by: containing a CNT-containing powder containing a dispersant and CNTs, an electrode active material, an electrolyte, and a solvent A; and having an interaction parameter χ between the dispersant and the solvent A in the range of 0.6 to 2.2.

Description

Electrode mixture paste and solid-state battery electrode

[0001] The present invention relates to an electrode mixture paste and a method for producing the same, and an electrode for a solid state battery and a method for producing the same.

[0002] Lithium-ion batteries, which have been widely used in mobile devices, have traditionally used liquid electrolytes (electrolytic solutions) or gel polymers. However, due to problems with liquid electrolytes, such as evaporation, decomposition, leakage, and fire, development is underway to develop new solid-state batteries, which use solid or semi-solid electrolytes.

[0003] Solid-state batteries require electrodes that are resistant to a decrease in discharge capacity even after repeated charge and discharge. Examples of such electrodes include an electrode for use in a solid-state battery that includes a current collector layer and an active material layer that contains an active material and a solid electrolyte and is partially in contact with the current collector layer, and the active material layer has a region in the thickness direction toward the side in contact with the current collector layer where the active material exhibits a concentration gradient in which the active material decreases, and the solid electrolyte exhibits a concentration gradient in the thickness direction (Patent Documents 1 and 2). However, providing a concentration gradient of the active material in the thickness direction of an electrode requires dedicated equipment, which poses challenges in terms of cost and productivity.

[0004] JP 2021-39848 A JP 2021-39849 A

[0005] An object of the present invention is to provide an electrode mixture paste capable of producing an electrode for a solid state battery that maintains its discharge capacity even after repeated charge and discharge, and a method for manufacturing the same. Another object of the present invention is to provide an electrode for a solid state battery that maintains its discharge capacity even after repeated charge and discharge, and a method for manufacturing the same.

[0006] The present inventors have been conducting extensive research to develop an electrode for a solid-state battery with excellent performance, and have focused on the interaction parameter χ between a dispersant attached to the surface of a carbon nanotube (CNT)-containing powder and a solvent contained in an electrode mixture paste. They have found that the discharge capacity retention rate of an electrode produced using an electrode mixture paste in which this interaction parameter χ is adjusted to fall within a specific range is significantly improved, and have completed the present invention.

[0007] An embodiment of the present invention relates to an electrode mixture paste comprising a CNT-containing powder containing a dispersant and CNTs, an electrode active material, an electrolyte, and a solvent A, wherein the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 or more and 2.2 or less.

[0008] Another embodiment of the present invention relates to a method for producing an electrode mixture paste, comprising: a step of obtaining a CNT-containing powder containing CNTs and a dispersant; and a step of mixing the CNT-containing powder, an electrode active material, an electrolyte, and a solvent A to produce an electrode mixture paste, wherein the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 or more and 2.2 or less.

[0009] In another embodiment, the present invention relates to an electrode for a solid state battery produced from the electrode mixture paste.

[0010] In addition, another embodiment of the present invention relates to a method for producing an electrode for a solid state battery, comprising: a step of applying the electrode mixture paste to a surface of a current collector; and a step of removing solvent A from the applied electrode mixture paste to form an electrode mixture layer.

[0011] The discharge capacity retention rate of the electrode produced using the electrode mixture paste of the present invention is significantly high, and therefore, by incorporating this electrode into a solid-state battery, it becomes possible to maintain the battery performance of the solid-state battery even after repeated charging and discharging.

[0012] Hereinafter, an embodiment of the present invention will be described.

[0013] <Electrode Mixture Paste> An electrode mixture paste according to an embodiment of the present invention (hereinafter also referred to as the electrode mixture paste of the present invention) contains a CNT-containing powder containing a dispersant and CNTs, an electrode active material, an electrolyte, and a solvent A, and is characterized in that the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 or more and 2.2 or less.

[0014] In the present invention, the CNT-containing powder refers to a powder obtained by preparing a mixture of a dispersant, CNTs, and solvent B, and then drying solvent B.

[0015] The dispersant is not particularly limited as long as its SP value is publicly known or its SP value can be measured by the method described below, but examples of polymer dispersants that can be easily adsorbed to the particle surfaces of CNTs include poly(meth)acrylic acid derivatives, polyvinyl acetal derivatives, polyvinyl alcohol derivatives, polyvinylpyrrolidone derivatives, polyacrylonitrile derivatives, nitrile rubbers, polyimide derivatives, cellulose derivatives, chitosan, and gelatin. In the present invention, a simple method is to select a dispersant that matches the solvent A used so that the interaction parameter χ falls within a predetermined range.

[0016] Examples of the CNT include single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The SWCNTs and MWCNTs may be any that can be used in solid-state battery electrodes, and there are no particular limitations on the diameter, length, and aspect ratio of the SWCNTs or MWCNTs. In the present invention, the SWCNTs and MWCNTs may be used alone or in combination.

[0017] The solvent B may be any solvent that dissolves or is compatible with the dispersant, and is not particularly limited. Examples of the solvent B include alcohol-based solvents, amine-based solvents, ether-based solvents, glycol ester-based solvents, and ketone-based solvents. Examples of the alcohol-based solvents include methanol, ethanol, normal propyl alcohol, isopropyl alcohol (IPA), butyl alcohol, octyl alcohol, cyclohexanol, allyl alcohol, benzyl alcohol, cresol, furfuryl alcohol, propylene glycol monomethyl ether (PM), ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol tertiary butyl ether (ETB), ethylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, ethylene glycol monopropyl ether, ethylene glycol phenyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether. Examples of the amine-based solvents include N,N-dimethylaminopropylamine and diethylenetriamine. Examples of the ether-based solvents include methyl phenyl ether (anisole), tetrahydrofuran, dioxane, and ethylene glycol dimethyl ether. Examples of the glycol ester solvent include propylene glycol monomethyl ether acetate (PMA), ethylene glycol monoethyl ether acetate, 3-methoxybutyl acetate, and ethylene glycol diacetate. Examples of the ketone solvent include acetone, methyl ethyl ketone (MEK), cyclopentanone, and cyclohexanone. Solvent B can be used alone or in combination of two or more types.

[0018] The amount of solvent B to be mixed with the CNTs and the dispersant is not particularly limited as long as a paste-like kneaded product can be obtained.

[0019] The CNT-containing powder can be produced by kneading the CNTs, the dispersant, and solvent B to produce a paste-like kneaded mixture, and then drying the kneaded mixture to remove solvent B.

[0020] Examples of mixers used for the kneading include planetary mixers, kneaders, extrusion mixers, thin film rotary high-speed mixers, etc. The planetary mixer is a machine that mixes materials by centrifugal force generated by rotation and revolution (planetary motion), and by shear stress, and is also called a rotation-revolution mixer. The planetary mixer may be a commercially available manufacturing device, and is not particularly limited.

[0021] The conditions for preparing the kneaded mixture are not particularly limited. As for the temperature, it is preferable to knead the mixture at a temperature lower than the boiling point of the solvent B.

[0022] The means for drying the kneaded product obtained as described above is not particularly limited, and may be an apparatus capable of adjusting the temperature to a temperature equal to or higher than the volatilization temperature of the solvent B, an apparatus capable of removing the solvent B by reducing pressure, a freeze-drying apparatus, etc. For example, from the viewpoint of efficient drying, it is preferable to volatilize the solvent B while kneading the kneaded product by increasing the treatment temperature in the planetary mixer.

[0023] The degree to which the solvent B is evaporated is not particularly limited as long as the kneaded material is in a powder form. If the kneaded material is not sufficiently dried or has an odor of the solvent when removed from the drying device, additional drying may be performed. The CNT-containing powder has the property of being resistant to aggregation even in such a drying process.

[0024] Furthermore, the CNT-containing powder has a structure in which the dispersant is attached to the surface of the CNTs. By having such a structure, the CNT-containing powder has excellent dispersibility within the electrode material and can adhere widely to the surface of electrode materials such as electrode active materials and electrolytes, thereby exhibiting excellent conductivity. The presence of this structure can be confirmed, for example, by dispersing the CNT-containing powder in a solvent such as N-methyl-2-pyrrolidone (NMP) and examining the weight of the dispersant that is liberated. If the weight of the liberated dispersant is less than 10% of the weight of the dispersant contained in the CNT-containing powder, it can be determined that the CNT-containing powder has the structure.

[0025] The content of each component in the CNT-containing powder is not particularly limited, but it is preferable that the CNT content be 25% by weight or more and the dispersant content be 10 to 70% by weight, for example.

[0026] The electrode active material used in the present invention includes an active material used in either the positive or negative electrode of a solid-state battery. The positive electrode active material is a compound represented by the general formula Li ｘ M ｙ O ｚ (M is a transition metal element, x = 0.02 to 2.2, y = 1 to 2, z = 1.4 to 4). In the above general formula, M is preferably at least one selected from the group consisting of Co, Mn, Ni, V and Fe, and more preferably at least one selected from the group consisting of Co, Ni and Mn. Specific examples of such oxide active materials include LiCoO ２ , LiMnO ２ , LiNiO ２ , LiVO ２ , LiNi １／３ Co １／３ Mn １／３ O ２ Rock salt layered active materials such as LiMn ２ O ４ , Li(Ni ０．５ Mn １．５ ) O ４ In addition, the above-mentioned general formula Li ｘ M ｙ O ｚ As oxide active materials other than LiFePO ４ , LiMnPO ４ Olivine type active materials such as Li ２ FeSiO ４ , Li ２ MnSiO ４ Examples of the negative electrode active material include carbon-based materials (graphite, non-graphitizable carbon, amorphous carbon, fired polymer compounds (e.g., phenolic resins, furan resins, etc., fired and carbonized), cokes (e.g., pitch coke, needle coke, petroleum coke, etc.), carbon fibers, etc.), oxide-based materials (Li ２ TiO ３ , TiNbｘ O, etc.), silicon-based (Si, SiO, etc.), etc. The positive electrode active material and the negative electrode active material may each be used alone or in combination of two or more.

[0027] The electrolyte used in the present invention refers to a material capable of conducting ions, and includes solid electrolytes and electrolytic solutions. The electrolyte may be any that can be used in solid-state batteries such as semi-solid batteries or all-solid batteries. For example, the following can be mentioned as lithium ion conductive solid electrolytes. Oxide-based solid electrolytes: crystalline (Li １．３ Al ０．３ Ti １．７ (P.O. ４ ) ３ , La ０．５１ Li ０．３４ TiO ２．９４ , Li ７ La ３ Zr ２ O １２ etc.), amorphous (Li ２．９ P.O. ３．３ N ０．４６ etc.) ・Sulfide-based solid electrolyte: Crystalline (Li １０ GeP ２ S １２ , Li ３．２５ Ge ０．２５ P ０．７５ S ４ , Li ６ P.S. ５ Cl, etc.), glass ceramics (Li ７ P ３ S １１ etc.), amorphous (75Li ２ S-25P ２ S ５ , 70Li ２ S-30P ２ S ５ etc.) Others (Li ２ B １２ H １２ , Li ３ OCl ０．５ Br ０．５ etc.)

[0028] The solvent A used in the present invention is not particularly limited as long as it has a known SP value and can adjust the interaction parameter χ with the dispersant within a predetermined range, and examples thereof include alcohol-based solvents such as methanol, ethanol, normal propyl alcohol, IPA, butyl alcohol, octyl alcohol, cyclohexanol, allyl alcohol, benzyl alcohol, cresol, and furfuryl alcohol; alcohol ether-based solvents such as PM, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ETB, ethylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, ethylene glycol monopropyl ether, ethylene glycol phenyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether; amine-based solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether-based solvents such as anisole, tetrahydrofuran, dioxane, and ethylene glycol dimethyl ether; glycol ester-based solvents such as PMA, ethylene glycol monoethyl ether acetate, 3-methoxybutyl acetate, and ethylene glycol diacetate; Examples of suitable solvents include ketone-based solvents such as acetone, MEK, cyclopentanone, and cyclohexanone; aromatic hydrocarbon-based solvents such as benzene, toluene, xylene, cymene, and mesitylene; aprotic polar solvents such as NMP, dimethyl sulfoxide, and dimethylformamide; aliphatic hydrocarbon-based solvents such as pentane, normal hexane, octane, cyclopentane, and cyclohexane; aldehyde-based solvents such as furfural; ester-based solvents such as butyl acetate, ethyl acetate, methyl acetate, butyl propionate, ethylene glycol monoethyl ether acetate, 3-methoxybutyl acetate, ethylene glycol diacetate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, and butyl butyrate; polyol-based solvents such as glycerol, ethylene glycol, and diethylene glycol; and water.

[0029] The electrode mixture paste of the present invention having the composition described above is characterized in that a dispersant and a solvent A are used in combination such that the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 to 2.2.

[0030] The interaction parameter χ (chi) is a dimensionless parameter that represents the interaction between a polymer and a solvent in the Flory-Huggins theory, and is calculated by the following formula (1) using the SP values ​​of the dispersant and solvent A.

[0031]

[0032] χ: interaction parameter V Ｓｏｌ : Molar volume of solvent A R: Gas constant T: Absolute temperature δ Ｄｉｓ : SP value δ of dispersant Ｓｏｌ : SP value of solvent A

[0033] The closer the interaction parameter χ is to 0, the higher the affinity between the dispersant and solvent A, meaning that solvent A is a good solvent for the dispersant. Furthermore, the affinity of the interaction parameter χ reverses at a boundary of 0.5, and the greater the interaction parameter χ is from 0.5, the lower the affinity between the dispersant and solvent A, meaning that solvent A is a poor solvent for the dispersant.

[0034] In the electrode mixture paste of the present invention, the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 to 2.2, and therefore the discharge capacity retention rate of the resulting electrode for a solid-state battery is significantly improved. For example, when butyl butyrate (molar volume: 166.7 cm) is used as the solvent A, ３ / mol, SP value: 16.8 (J / cm ３ ) ０．５ ), the SP value is 18.3 (J / cm ３ ) ０．５ More than 22.1 (J / cm ３ ) ０．５By using the following dispersant, the interaction parameter χ can be kept within the range of 0.5 to 2.2. In this way, based on the formula (1) and the physical property values ​​of either the dispersant or the solvent A, the physical property values ​​of the other that will make the interaction parameter χ fall within the desired range can be determined, and a dispersant and solvent A that will make the interaction parameter χ fall within the desired range can be used in combination.

[0035] The upper limit of the interaction parameter χ is preferably 2.2 or less, more preferably 2.1 or less, even more preferably 2.0 or less, and particularly preferably 1.5 or less, from the viewpoint of achieving a high discharge capacity retention rate and excellent battery performance.

[0036] The interaction parameter χ is described in detail in, for example, "How to Determine Solubility Parameters (SP Value and HSP Value) and How to Use Them to Stabilize Dispersion of Fine Particles" (pages 109-111, R&D Support Center, Inc., published in 2020).

[0037] The solubility parameter (SP value) in the present invention refers to a value calculated from the Hansen solubility parameter (HSP value). Ｄｉｓ As a method for experimentally calculating the solubility of the polymer, the Hansen dissolved sphere method can be adopted.

[0038] SP value of solvent A (δ Ｓｏｌ ) can be calculated from the HSP value included in HSPiP (software used for analyzing HSP values). The HSP value means the Hansen solubility parameter described in "Hansen Solubility Parameters: A User's Handbook, Second Edition" (page 1-310, CRC Press, published in 2007). The HSP value also expresses the solubility of a substance as a multidimensional vector (dispersion term: δ Ｄ , polarity term: δ Ｐ and hydrogen bond term: δ Ｈ ), and these three parameters also mean the coordinates of a point in a three-dimensional space called Hansen space. The relationship between the SP value (δ) and the HSP value is expressed by the following formula (2). The unit of the SP value in the present invention is (J / cm ３ ) ０．５is.

[0039]

[0040] The interaction parameter χ can be adjusted by selecting the types of the dispersant and the solvent A. When two or more types of dispersant and / or solvent A are used, the interaction parameter χ can be calculated using the SP value of the entire dispersant and the molar volume and SP value of the entire solvent A. Here, the SP value of the entire dispersant means a value obtained by averaging the SP values ​​of each dispersant weighted by molar ratio. The same applies to the SP value of the entire solvent A. The molar volume of the entire solvent A can be calculated by dividing the value obtained by averaging the molecular weights of each solvent A weighted by molar ratio by the density of the entire solvent A. The density of solvent A can be determined using a known measurement method.

[0041] The electrode mixture paste of the present invention may also contain a binder. The binder may be any binder that can be used in solid-state battery electrodes, such as polyvinylidene fluoride (PVDF), polyvinyl alcohol, polyvinyl acetal, acrylic resin, polyvinyl acetate, polyvinyl chloride, polystyrene, polyvinyl ether, polyvinylpyrrolidone (PVP), styrene-butadiene rubber (SBR), carboxymethyl cellulose, etc. These may be modified with various functional groups, and polar functional groups such as acidic groups and basic groups can be suitably used as the functional groups. The binders may be used alone or in combination of two or more.

[0042] The weight average molecular weight of the binder is not particularly limited, but for example, one in the range of 110,000 to 5,000,000 can be suitably used. In the present invention, when the binder contains a solvent, the solvent is the solvent A.

[0043] The contents of the CNT-containing powder, electrode active material, electrolyte, solvent A, binder, etc. in the electrode mixture paste of the present invention may be adjusted appropriately from the viewpoint of the thickness and coatability of the resulting electrode. For example, from the viewpoint of dispersibility, it is preferable to adjust the content of solvent A so that the concentration of nonvolatile components is 30 to 90 wt%. The content of each nonvolatile component may vary depending on the type of solid-state battery to be applied, but may be adjusted based on the composition of the electrode mixture layer to be formed. For example, the ratio of the electrode active material and electrolyte content in the electrode mixture layer (electrode active material:electrolyte) is preferably 10:90 to 90:10 by weight. Furthermore, the CNT content in the electrode mixture layer is preferably 0.01 to 50 wt%, more preferably 0.01 to 10 wt%, based on the total weight of the electrode active material and electrolyte. Furthermore, the total weight of polymer components such as dispersants and binders in the electrode mixture layer is preferably 0.01 to 50 wt %, more preferably 0.01 to 10 wt %, based on the total weight of the electrode active material and electrolyte.

[0044] The electrode mixture paste of the present invention can be produced by producing a CNT-containing powder containing CNTs and a dispersant, and then mixing the CNT-containing powder, an electrode active material, an electrolyte, a solvent A, and, if necessary, a binder.

[0045] The mixing method is not particularly limited, but examples of the mixer include a planetary mixer, a kneader, an extrusion kneader, and a thin film rotary high-speed mixer.

[0046] In terms of the mixing order, the components may be mixed simultaneously, or the CNT-containing powder, electrode active material, electrolyte, and, if necessary, binder may be mixed in this order with solvent A. This order is not particularly limited, and the mixture of the CNT-containing powder and electrode active material may be added gradually. Furthermore, when the binder is a solid, solvent A and the binder may be mixed and dissolved in advance.

[0047] <Solid state battery electrode> The solid state battery electrode of the present invention (hereinafter also referred to as the electrode of the present invention) includes an electrode mixture layer formed using the electrode mixture paste of the present invention, and specifically, is obtained by applying the electrode mixture paste of the present invention to a current collector and drying the resulting product. By the drying, solvent A in the electrode mixture paste of the present invention is removed, and an electrode mixture layer is formed on the current collector, thereby obtaining an electrode. In this way, the solid state battery electrode produced from the electrode mixture paste of the present invention has a high discharge capacity retention rate.

[0048] Examples of the current collector include a positive electrode current collector and a negative electrode current collector. Examples of materials for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, cobalt, and carbon. Examples of materials for the negative electrode current collector include SUS, copper, nickel, cobalt, and carbon. The thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably selected appropriately depending on the application of the solid-state battery.

[0049] Examples of the shape of the current collector include foil, plate, mesh, net, lath, punched metal, embossed, and combinations thereof (e.g., mesh-like plate, etc.) Furthermore, the surface of the current collector may be formed with irregularities by etching.

[0050] The method for applying the electrode mixture paste of the present invention to the current collector is not particularly limited. Examples include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spraying. Furthermore, drying after application may be performed by heat treatment, or by air drying, vacuum drying, natural drying, or the like. When drying by heat treatment, the temperature is typically about 50 to 150°C. Pressing may also be performed after drying. Examples of pressing methods include mold pressing and roll pressing. The electrode of the present invention can be produced by the methods listed above. Furthermore, the thickness of the electrode is typically about 5 to 500 μm.

[0051] <Solid-State Battery> Examples of solid-state batteries obtained using the electrode of the present invention include various all-solid-state batteries (sulfide-based, oxide-based, nitride-based, hydride-based, polymer-based, etc.), various semi-solid-state batteries (gel polymer-based, clay-based, liquid-added-based), etc.

[0052] The solid-state battery can be manufactured by a known manufacturing method except for using the electrode of the present invention. Furthermore, the structure of the electrode of the present invention included in the solid-state battery may be an appropriate structure depending on the type of solid-state battery, as described above.

[0053] The materials used in the examples are as follows: <CNT> - "LUCAN BT 1003M" (MWCNT, manufactured by LG Chem) <Dispersant> - "CAB-321-0.1" (cellulose acetate butyrate, manufactured by Eastman) - "CAB-381-2" (cellulose acetate butyrate, manufactured by Eastman) - "CAB-500-5" (cellulose acetate butyrate, manufactured by Eastman) - "CAB-553-0.4" (cellulose acetate butyrate, manufactured by Eastman) The SP value (δ Ｄｉｓ ) was calculated using the Hansen soluble sphere method and the results are shown in Table 1.

[0054]

[0055] <Solvent A> Butyl butyrate, mesitylene, anisole SP value of solvent A (δ Ｓｏｌ The results of calculation of the molar volume of each of the compounds from the HSP values ​​included in HSPiP (software used to analyze HSP values) are shown in Table 2.

[0056]

[0057] <Solvent B> Propylene glycol monomethyl ether acetate (PMA) <Positive electrode active material> 1% LiNbO ３ Contains NCM111 (LiNi １／３ Co １／３ Mn １／３ O ２ ) <Solid electrolyte> ・75Li ２ S-25P ２ S ５ (LPS) <Binder> Styrene butadiene rubber (SBR)

[0058] (Preparation Example 1: Production of CNT-containing powder 1) The weight ratio (CNT:dispersant) of CNT to dispersant "CNT+CAB-321-0.1" was adjusted to 80:20, and this was added to PMA so that the solid content was 18 to 22 wt %. A paste-like kneaded product was produced by kneading (at 25°C) using a planetary mixer. The kneaded product was then dried to obtain CNT-containing powder 1.

[0059] Preparation Example 2: Production of CNT-containing powder 2 CNT-containing powder 2 was obtained in the same manner as in Preparation Example 1, except that "CAB-381-2" was used as the dispersant.

[0060] Preparation Example 3: Production of CNT-containing powder 3 CNT-containing powder 3 was obtained in the same manner as in Preparation Example 1, except that "CAB-500-5" was used as the dispersant.

[0061] Preparation Example 4: Production of CNT-containing powder 4 CNT-containing powder 4 was obtained in the same manner as in Preparation Example 1, except that "CAB-553-0.4" was used as the dispersant.

[0062] (Example 1-1: Production of electrode mixture paste 1-1) CNT-containing powder 1, positive electrode active material, solid electrolyte, binder, and solvent A (butyl butyrate) were kneaded using a planetary stirrer to produce electrode mixture paste 1-1. The weight composition was CNT: dispersant: positive electrode active material: solid electrolyte: binder: solvent = 0.37:0.09:52.08:22.32:2.14:23.00. The parameter χ of electrode mixture paste 1-1 was calculated using the above formula (1) to be 0.90.

[0063] (Example 1-2: Production of electrode mixture paste 1-2) An electrode mixture paste 1-2 was produced in the same manner as in Example 1-1, except that CNT-containing powder 2 was used. The parameter χ of electrode mixture paste 1-2 was calculated using the above formula (1) and was found to be 0.75.

[0064] (Example 1-3: Production of electrode mixture paste 1-3) An electrode mixture paste 1-3 was produced in the same manner as in Example 1-1, except that CNT-containing powder 3 was used. The parameter χ of electrode mixture paste 1-3 was calculated using the above formula (1) and was found to be 0.75.

[0065] Comparative Example 1-1: Production of Comparative Electrode Mixture Paste 1-1 Comparative electrode mix paste 1-1 was produced in the same manner as in Example 1-1, except for using CNT-containing powder 4. The parameter χ of the comparative electrode mix paste 1-1 was calculated using the above formula (1) to be 2.28.

[0066] (Comparative Example 2-1: Production of Comparative Electrode Mixture Paste 2-1) CNT-containing powder 1, positive electrode active material, solid electrolyte, binder, and solvent A (mesitylene) were kneaded using a planetary stirrer to produce comparative electrode mix paste 2-1. The weight composition was CNT: dispersant: positive electrode active material: solid electrolyte: binder: solvent = 0.36:0.09:50.05:21.45:2.05:26.00. The parameter χ of comparative electrode mix paste 2-1 was calculated using the above formula (1) to be 0.50.

[0067] (Comparative Example 2-2: Production of Comparative Electrode Mixture Paste 2-2) Comparative electrode mixture paste 2-2 was produced in the same manner as in Comparative Example 2-1, except for using CNT-containing powder 2. The parameter χ of comparative electrode mixture paste 2-2 was calculated using the above formula (1) and was found to be 0.43.

[0068] Comparative Example 2-3: Production of Comparative Electrode Mixture Paste 2-3 Comparative electrode mix paste 2-3 was produced in the same manner as in Comparative Example 2-1, except that CNT-containing powder 3 was used. The parameter χ of comparative electrode mix paste 2-3 was calculated using the above formula (1) and was found to be 0.43.

[0069] Example 2-1: Production of electrode mixture paste 2-1 An electrode mixture paste 2-1 was produced in the same manner as in Comparative Example 1, except that CNT-containing powder 4 was used. The parameter χ of electrode mixture paste 2-1 was calculated using the above formula (1) and was found to be 1.32.

[0070] (Comparative Example 3-1: Production of Comparative Electrode Mixture Paste 3-1) CNT-containing powder 1, positive electrode active material, solid electrolyte, binder, and solvent A (anisole) were kneaded using a planetary stirrer to produce comparative electrode mix paste 3-1. The weight composition was CNT: dispersant: positive electrode active material: solid electrolyte: binder: solvent = 0.38:0.09:52.75:22.61:2.17:22.00. The parameter χ of comparative electrode mix paste 3-1 was calculated using the above formula (1) to be 0.34.

[0071] Comparative Example 3-2: Production of Comparative Electrode Mixture Paste 3-2 Comparative electrode mix paste 3-2 was produced in the same manner as in Comparative Example 3-1, except that CNT-containing powder 2 was used. The parameter χ of comparative electrode mix paste 3-2 was calculated using the above formula (1) and was found to be 0.34.

[0072] Comparative Example 3-3: Production of Comparative Electrode Mixture Paste 3-3 Comparative electrode mix paste 3-3 was produced in the same manner as in Comparative Example 3-1, except that CNT-containing powder 3 was used. The parameter χ of the comparative electrode mix paste 3-3 was calculated using the above formula (1) to be 0.34.

[0073] Example 3-1: Production of electrode mixture paste 3-1 An electrode mixture paste 3-1 was produced in the same manner as in Comparative Example 3-1, except for using CNT-containing powder 4. The parameter χ of electrode mixture paste 3-1 was calculated using the above formula (1) and was found to be 0.64.

[0074] (Example 4: Preparation of Evaluation Battery) Using the electrode mixture paste obtained in the above Examples and Comparative Examples, the electrode mixture paste was applied to the surface of a current collector (aluminum foil) in a glove box under an argon atmosphere, and dried at room temperature to remove the solvent component, forming an electrode mixture layer to prepare an evaluation electrode. ２ The electrode for evaluation and the counter electrode were Li—In foil, and LPS was used as the solid electrolyte layer to prepare a powder cell by uniaxial pressing, thereby preparing a battery for evaluation.

[0075] Next, the obtained evaluation electrode was subjected to an impedance test and a charge / discharge rate test according to the following procedures.

[0076] <Impedance Test> The AC impedance of the evaluation battery was measured immediately after production. －２ ~10 ６ In the Bode plot, ２ ~10 ４ A minimum value (corresponding to the end point of the arc in the Nyquist plot) was observed in the 100 Hz frequency range, and relative comparisons between samples were made using this impedance value. The results are shown in Tables 3 to 5.

[0077] <Charge / Discharge Rate Test> A charge / discharge rate test was performed in constant current mode using the evaluation battery after impedance measurement. The end-of-charge voltage and end-of-discharge voltage were set to 3.7 V and 2.4 V. The charge rate was fixed at 0.05 C, and the discharge rate was varied to 0.05 C, 0.1 C, 0.2 C, 0.5 C, 1.0 C, 2.0 C, 3.0 C, 6.0 C, and 10.0 C. Relative comparisons between samples were performed using the discharge capacity retention rate at a discharge rate of 0.5 C. The results are shown in Tables 3 to 5.

[0078]

[0079]

[0080]

[0081] From the results shown in Tables 3 to 5, the electrode mixture pastes 1-1, 1-2, 1-3, 2-1, and 3-1 have an interaction parameter χ in the range of 0.6 to 2.2, and the evaluation electrodes made from these electrode mixture pastes have a high discharge capacity retention rate and low impedance.

[0082] On the other hand, the interaction parameter χ of comparative electrode mixtures 2-1, 2-1, 2-3, 3-1, 3-2, and 3-3 is less than 0.6, and it is understood that the evaluation electrodes made from these electrode mixture pastes have a significantly low discharge capacity retention rate and a significantly high impedance. Furthermore, the interaction parameter χ of comparative electrode mixture 1-1 is greater than 2.2, and it is understood that the evaluation electrodes made from this electrode mixture paste have a significantly low discharge capacity retention rate and a significantly high impedance.

[0083] From the above results, it can be seen that, in the electrode mixture paste of the present invention, the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 or more and 2.2 or less, so that it is possible to produce an electrode for a solid battery in which the discharge capacity is maintained even after repeated charge and discharge.

Claims

1. An electrode mixture paste comprising: a CNT-containing powder containing a dispersant and CNTs; an electrode active material; an electrolyte; and a solvent A, wherein the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 to 2.

2.

2. A method for producing an electrode mixture paste, comprising: a step of obtaining a CNT-containing powder containing CNTs and a dispersant; and a step of mixing the CNT-containing powder, an electrode active material, an electrolyte, and a solvent A to produce an electrode mixture paste, wherein the interaction parameter χ between the dispersant and the solvent A is in the range of 0.6 to 2.

2.

3. An electrode for a solid-state battery made from the electrode mixture paste according to claim 1.

4. A method for manufacturing an electrode for a solid state battery, comprising the steps of: applying the electrode mixture paste according to claim 1 to the surface of a current collector; and removing solvent A from the applied electrode mixture paste to form an electrode mixture layer.

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