Electrode body and power storage element

Abstract

To provide an electrode body that can constitute a power storage element in which the decrease in capacity during high-rate discharge is suppressed, and a power storage element in which the decrease in capacity during high-rate discharge is suppressed.SOLUTION: An electrode body according to an embodiment of the present invention includes an active material layer containing an active material, a solid electrolyte, and an additive, and the additive contains a polymer having a number average molecular weight of 400 or more and 3000 or less, in which hydrocarbon groups and ester bonds are alternately repeated along the main chain.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrode assembly and an energy storage element. [Background technology]

[0002] An electrode assembly has been reported that includes an active material layer containing a polymer as an additive in addition to an active material and a solid electrolyte.

[0003] Patent Document 1 states: [Synthesis Example 1: Synthesis of polymer PS1 (for polymers D-01, D-06, D-07, and D-08) leading to polymer segments] "(Paragraph

[0164] )" and "(Paragraph

[0169] )" also state, "Polymers PS7, PS8, and PS9, which lead to the segment represented by formula (1), were synthesized in the same manner as in Synthesis Example 1, except that in the synthesis of Synthesis Example 1, the amount of ε-caprolactone used was changed to the amount corresponding to each polymer shown in the above chemical formula, and the amount of catalyst used was changed accordingly." The statement, [Synthesis Example 10: Synthesis of Polymer D-01] Polymer D-01 was synthesized as follows. A 500 mL three-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with diphenylmethane diisocyanate (17.5 g), polyethylene glycol 200 (number average molecular weight 200, 13.2 g), polymer PS1 (7.7 g) synthesized in Synthesis Example 1, and tetrahydrofuran (dehydrated, 149.5 g), and the mixture was heated to 60°C under a nitrogen stream. Next, Neostan U-600 (manufactured by Nitto Kasei, 0.08 mg) as a bismuth catalyst and tetrahydrofuran (dehydrated, 4.0 g) were added, and the mixture was stirred at 60°C for 5 hours. Methanol (1.2 g) was then added, and the mixture was stirred at 60°C for 30 minutes. The reaction mixture was then cooled to obtain polymer D-01 solution. Next, a dispersion of polymer D-01 was prepared as follows. A 300-mL three-neck flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube was charged with the polymer D-01 solution (15.0 g) and tetrahydrofuran (dehydrated, 15.0 g), and stirred under a nitrogen stream at room temperature. To the solution, butyl butyrate (90 g) was gradually added, and the solvent was distilled off under reduced pressure. butyl butyrate was added to obtain a 5% solids concentration, thereby preparing a dispersion of polymer D-01. [Synthesis Examples 11 to 21: Synthesis of Polymers D-02 to D-12 and Preparation of Dispersions] Polymers D-02 to D-12 were synthesized in the same manner as in Synthesis Example 1, except that the compounds from which the respective constituent components shown in Table 1 were derived were used in the amounts shown in Table 1." (Paragraphs

[0170] to

[0171] ) The statement, "In Example 1, a sheet for an all-solid-state secondary battery and an all-solid-state secondary battery having the layer structure shown in Figure 1 were fabricated using a solid electrolyte composition prepared using the polymer D-01 dispersion, and their performance was evaluated. The results are shown in Table 2." (Paragraph

[0179] ) and "In the preparation of solid electrolyte composition D-01, the production of all-solid-state secondary battery positive electrode sheet D-01, the production of all-solid-state secondary battery negative electrode sheet D-01, and the manufacture of all-solid-state secondary battery D-01, the positive electrode sheet for all-solid-state secondary battery and the negative electrode sheet for all-solid-state secondary battery were produced in the same manner as in Example 1, except that the polymer D-01 dispersion was replaced with a composition prepared using the polymer dispersion shown in Table 2, and all-solid-state secondary batteries Nos. D-02 to D-12 and cD-01 were produced, respectively." (Paragraph

[0183] ) It is stated that: Table 1 of Cited Document 1 describes, as No. D-10, a polymer having a mass average molecular weight of 50,000, synthesized by reacting 20 mass % of PS7 (number average molecular weight 2,000), 47 mass % of diphenylmethane diisocyanate, 3 mass % of 2,2-bis(hydroxymethyl)butyric acid, and 30 mass % of polyethylene glycol 200.

[0004] Patent Document 2 states: A 2-L three-neck flask equipped with a reflux condenser and a gas inlet cock was charged with 7.2 g of a 40% by mass heptane solution of macromonomer M-1 (monomer 1a solution), 12.4 g of methyl acrylate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (monomer 2a), 6.7 g of acrylic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (monomer 3a), 207 g of heptane (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), and 1.4 g of 2,2'-azobis(isobutyronitrile) (initiator 1a). Nitrogen gas was introduced at a flow rate of 200 mL / min for 10 minutes, and the temperature was then raised to 100°C. In a separate vessel, 93.1 g of a 40% by mass heptane solution of macromonomer M-1 (monomer 1b solution) and 93.1 g of methyl acrylate (monomer 1b solution) were added. A mixture of 222.8 g of [monomer 2b], 120.0 g of acrylic acid [monomer 3b], 300.0 g of heptane, and 2.1 g of 2,2'-azobis(isobutyronitrile) [initiator 1b] was added dropwise over a period of 4 hours. After the addition was complete, 0.5 g of 2,2'-azobis(isobutyronitrile) [initiator 1c] was added. The mixture was then stirred at 100°C for 2 hours, cooled to room temperature, and filtered to obtain a dispersion of particulate polymer (1). (Paragraph

[0254] ) The statement, "A self-condensate (GPC polystyrene standard number average molecular weight: 2,000) of 12-hydroxystearic acid (manufactured by Fujifilm Wako Pure Chemical Industries) was reacted with glycidyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) to produce a macromonomer, which was then polymerized with methyl methacrylate and glycidyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) in a molar ratio of 1:0.99:0.01, and this polymer was reacted with acrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.) to obtain macromonomer M-1. The SP value of this macromonomer M-1 was 9.3, and the number average molecular weight was 11,000." (Paragraph

[0255] ) and A 45 mL zirconia container (manufactured by Fritsch) was charged with 160 zirconia beads having a diameter of 5 mm, and 4.0 g of a sulfide-based inorganic solid electrolyte having an average particle diameter of 1.5 μm, a dispersion of particulate polymer (1) in an amount such that the particulate polymer (1) was 0.24 g, and 12.3 g of heptane were added. The container was then set in a Fritsch planetary ball mill P-7, and wet dispersion was carried out at room temperature and a rotation speed of 150 rpm for 60 minutes to obtain a solid electrolyte composition. ... To the solid electrolyte composition, 18.8 g of lithium cobalt oxide (average particle size 3 μm) and 0.47 g of acetylene black were added, and the container was set in a Fritsch planetary ball mill P-7. Wet dispersion was carried out at room temperature and a rotation speed of 150 rpm for 10 minutes to obtain a slurry of a positive electrode composition. In addition, 5 g of carbon black with an average particle size of 2.1 μm and 3 g of butadiene rubber (binder, product number 182907, manufactured by Aldrich) were added to 100 g of xylene and dispersed at room temperature (25°C) for 1 hour using a planetary mixer to obtain a composition for forming a carbon coating layer. ... A carbon coating layer-forming composition was applied to a 20 μm-thick aluminum foil using an applicator (product name: SA-201 Baker-type applicator, manufactured by Tester Sangyo Co., Ltd.), and then heated and dried at 100°C for four hours to form a carbon coating layer. A slurry of the positive electrode composition was applied to the carbon coating layer using an applicator, and then heated and dried at 100°C for one hour to obtain a positive electrode sheet under condition 3." (Paragraph

[0265] ) It is stated that:

[0005] Patent Document 3 states: (Synthesis Example 1: Synthesis of Block Copolymer 1 for Additives) A flask equipped with a distiller and a mixer stirrer was charged with 73 g of polyethylene glycol 600 (PEG 600). The mixture was heated to 85-90°C under a nitrogen atmosphere while stirring. 450 g of 12-hydroxystearic acid was added to the flask, followed by 1.4 g of tetrabutyl orthotitanate (TBT) as a catalyst. While monitoring the acid value, the flask was heated to a temperature of 222°C. Heating was stopped when the acid value reached 10 mgOH / g or less, and block copolymer 1 was synthesized. The number-average molecular weight of the resulting block copolymer 1 was measured by gel permeation chromatography (GPC). The number-average molecular weight was 3,400. The GPC measurement conditions were as described above (the same applies hereinafter). ... (Synthesis Example 2: Synthesis of Block Copolymer 2 for Additives) Block copolymer 2 was synthesized in the same manner as in Example 1, except that 219 g of polyethylene glycol 1500 (PEG1500) was used instead of polyethylene glycol 600. The number average molecular weight of the obtained block copolymer 2 was 4,900. ... (Synthesis Example 3: Synthesis of Block Copolymer 3 for Additives) Block copolymer 3 was synthesized in the same manner as in Example 1, except that 91 g of polyethylene glycol 1500 (PEG1500) and 202 g of polyethylene glycol 4000 (PEG4000) were used instead of polyethylene glycol 600. The number-average molecular weight of the resulting block copolymer 3 was 6,400. (Paragraphs

[0106] to

[0108] ) and "Next, each block copolymer synthesized as described above or each reference compound described above was used as an additive to manufacture an energy storage device (a half-cell of an all-solid-state lithium-ion secondary battery). The manufactured energy storage device is also referred to as an all-solid-state secondary battery." (Paragraph

[0110] ) It is stated that: [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2020 / 196041 [Patent Document 2] WO2020 / 067003 [Patent Document 3] Japanese Patent Application Publication No. 2023-86417 Summary of the Invention [Problem to be solved by the invention]

[0007] In an energy storage device having an electrode body containing a solid electrolyte in the active material layer, a decrease in capacity during high-rate discharge has been a problem.

[0008] An object of the present invention is to provide an electrode body that can be used to form an energy storage element in which the decrease in capacity during high-rate discharge is suppressed, and an energy storage element in which the decrease in capacity during high-rate discharge is suppressed. [Means for solving the problem]

[0009] An electrode assembly according to one aspect of the present invention includes an active material layer containing an active material, a solid electrolyte, and an additive, wherein the additive contains a polymer having a number average molecular weight of 400 or more and 3000 or less, in which hydrocarbon groups and ester bonds are alternately repeated along the main chain.

[0010] An energy storage device according to another aspect of the present invention includes the electrode assembly according to the above aspect of the present invention. [Effects of the Invention]

[0011] The electrode assembly according to one aspect of the present invention can constitute an energy storage element in which the decrease in capacity during high-rate discharge is suppressed.

[0012] An energy storage device according to another aspect of the present invention can suppress a decrease in capacity during high-rate discharge. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of an electrode assembly. [Figure 2] FIG. 2 is a schematic diagram showing an embodiment of an electricity storage device configured by assembling a plurality of electricity storage elements. DETAILED DESCRIPTION OF THE INVENTION

[0014] First, an overview of the electrode assembly and the energy storage element disclosed in this specification will be described.

[0015] [1] An electrode assembly according to one embodiment of the present invention comprises an active material layer containing an active material, a solid electrolyte, and an additive, wherein the additive contains a polymer having a number average molecular weight of 400 or more and 3000 or less, in which hydrocarbon groups and ester bonds are alternately repeated along the main chain.

[0016] According to the electrode assembly described in [1] above, it is possible to configure an energy storage element in which the decrease in capacity during high-rate discharge is suppressed.

[0017] [2] In the electrode assembly described in the above [1], the polymer may be a nonionic polymer.

[0018] According to the electrode assembly described in [2] above, it is possible to configure an energy storage element in which the decrease in capacity during high-rate discharge is further suppressed.

[0019] [3] In the electrode assembly described in [1] or [2] above, the polymer may be a polymer represented by the following general formula (1): In general formula (1), R1 is a saturated hydrocarbon group having 1 to 4 carbon atoms, R2' and R2'' are each independently a saturated hydrocarbon group having 4 to 20 carbon atoms, A and B are each independently an alkyl group, hydrogen, or other monovalent characteristic group, m, n1, and n2 are each independently a positive integer, and the ratio of m to the sum of m, n1, and n2 is 0 or 0.50 or less.

[0020] [ka]

[0021] According to the electrode assembly described in [3] above, it is possible to configure an energy storage element in which the decrease in capacity during high-rate discharge is further suppressed.

[0022] [4] An energy storage device according to another embodiment of the present invention includes the electrode assembly according to any one of the above [1] to [3].

[0023] According to the energy storage element described in [4] above, it is possible to suppress a decrease in capacity during high-rate discharge.

[0024] The configuration of an electrode assembly, the configuration of an energy storage element, the configuration of an energy storage device, a method for manufacturing an electrode assembly, and a method for manufacturing an energy storage element according to one embodiment of the present invention will be described in detail below. Note that the names of the components used in each embodiment may differ from the names of the components used in the background art.

[0025] <Configuration of electrode body and configuration of energy storage element> An energy storage device according to one embodiment of the present invention includes an electrode assembly having a positive electrode, a negative electrode, and a solid electrolyte layer, and a container for accommodating the electrode assembly. The electrode assembly is typically a laminated type in which multiple positive electrodes and multiple negative electrodes are stacked with a solid electrolyte layer interposed therebetween. The electrode assembly may also be a so-called "bipolar type" in which a positive electrode active material layer is formed on one surface of a substrate and a negative electrode active material layer is formed on the other surface.

[0026] Fig. 1 shows an example of the structure of an electrode assembly constituting an energy storage element. The electrode assembly 10 is configured by arranging a positive electrode 1 and a negative electrode 2 with a solid electrolyte layer 3 interposed therebetween. The positive electrode 1 has a positive electrode substrate 4 and a positive electrode active material layer 5. The negative electrode 2 has a negative electrode substrate 7 and a negative electrode active material layer 6. In the electrode assembly 10 shown in Fig. 1, the negative electrode active material layer 6, the solid electrolyte layer 3, the positive electrode active material layer 5, and the positive electrode substrate 4 are layered in this order on the negative electrode substrate 7.

[0027] (positive electrode) The positive electrode 1 has a positive electrode substrate 4 and a positive electrode active material layer 5 disposed on the positive electrode substrate 4 directly or via an intermediate layer.

[0028] The positive electrode substrate 4 has electrical conductivity. Whether or not the positive electrode substrate 4 has electrical conductivity is determined by whether or not the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 7 The threshold value is Ω·cm. The material for the positive electrode substrate 4 is a metal such as aluminum, titanium, tantalum, or stainless steel, or an alloy thereof. Among these, aluminum or an aluminum alloy is preferred from the viewpoints of potential resistance, high conductivity, and cost. Examples of the positive electrode substrate 4 include foil, vapor deposition film, mesh, and porous material, with foil being preferred from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferred for the positive electrode substrate 4. Examples of aluminum or aluminum alloys include A1085, A3003, and A1N30 specified in JIS-H-4000 (2014) or JIS-H-4160 (2006).

[0029] The average thickness of the positive electrode substrate 4 is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, even more preferably 8 μm to 30 μm, and particularly preferably 10 μm to 25 μm. By setting the average thickness of the positive electrode substrate 4 within the above range, the strength of the positive electrode substrate 4 can be increased while increasing the energy density per volume of the energy storage element.

[0030] The intermediate layer (not shown) is a layer disposed between the positive electrode substrate 4 and the positive electrode active material layer 5. The intermediate layer contains a conductive agent such as carbon particles, thereby reducing the contact resistance between the positive electrode substrate 4 and the positive electrode active material layer 5. The configuration of the intermediate layer is not particularly limited, and may contain, for example, a binder and a conductive agent.

[0031] The positive electrode active material layer 5 contains a positive electrode active material and a solid electrolyte. At least one of the positive electrode active material layer 5 and the negative electrode active material layer 6 described below contains an additive. The positive electrode active material layer 5 contains optional components such as a conductive agent, a binder, a thickener, and a filler, as necessary.

[0032] The positive electrode active material can be appropriately selected from known positive electrode active materials. When the energy storage device is a lithium ion secondary battery, a material capable of absorbing and releasing lithium ions is usually used as the positive electrode active material. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2 type crystal structure, lithium transition metal composite oxides having a spinel type crystal structure, polyanion compounds, chalcogen compounds, sulfur, etc. Examples of lithium transition metal composite oxides having an α-NaFeO2 type crystal structure include Li[Li x Ni (1-x) ]O2(0≦x<0.5), Li[Li x Ni γ Co (1-x-γ) ]O2(0≦x<0.5, 0<γ<1), Li[Li x Co (1-x) ]O2(0≦x<0.5), Li[Li x Ni γ Mn (1-x-γ) ]O2(0≦x<0.5, 0<γ<1), Li[Li x Ni γ Mnβ Co (1-x-γ-β) ]O2(0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1), Li[Li x Ni γ Co β Al (1-x-γ-β) ]O2 (0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1). Lithium transition metal composite oxides with spinel crystal structure include Li x Mn2O4, Li x Ni γ Mn (2-γ) Examples of polyanion compounds include LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, iron sulfide, cobalt sulfide, copper sulfide, nickel sulfide, and copper Chevrel salts. Sulfur, bismuth oxide, bismuth plumbate, copper oxide, and vanadium oxide can also be used as the positive electrode active material. Atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements. The surfaces of these materials may be coated with other materials. In the positive electrode active material layer 5, one of these materials may be used alone, or two or more may be mixed and used.

[0033] When a material capable of absorbing and releasing lithium ions is used as the positive electrode active material, it may be coated with a coating layer containing a material such as a lithium ion conductive oxide. Examples of lithium ion conductive oxides include LiNbO3, Li2WO4, and Li4Ti5O. 12 , Li3PO4, etc. Among these, it is preferable to select LiNbO3. The coating layer may cover the entire surface of the positive electrode active material, or may cover only a portion of the surface.

[0034] The positive electrode active material may be in the form of particles (powder) or a film. When the positive electrode active material is in the form of particles, the average particle size is preferably, for example, 0.1 μm to 20 μm. Setting the average particle size of the positive electrode active material to be equal to or greater than the lower limit facilitates the production and handling of the positive electrode active material. Setting the average particle size of the positive electrode active material to be equal to or less than the upper limit improves the electronic conductivity of the positive electrode active material layer 5. When a composite of the positive electrode active material and another material is used, the average particle size of the composite is taken as the average particle size of the positive electrode active material. The term "average particle size" refers to the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50% based on the particle size distribution measured by laser diffraction / scattering in a diluted solution of particles diluted with a solvent in accordance with JIS-Z-8825 (2013).

[0035] To obtain powders with a predetermined particle size, grinders, classifiers, etc. are used. Grinding methods include, for example, methods using a mortar, ball mill, sand mill, vibration ball mill, planetary ball mill, jet mill, counter jet mill, swirling airflow jet mill, or sieves. Wet grinding in the presence of water or an organic solvent such as hexane can also be used during grinding. As classification methods, sieves, air classifiers, etc. are used as needed for both dry and wet methods.

[0036] The content of the positive electrode active material in the positive electrode active material layer 5 is preferably 10% by mass to 95% by mass, more preferably 20% by mass to 90% by mass, and even more preferably 30% by mass to 80% by mass. By setting the content of the positive electrode active material within the above range, it is possible to achieve both a high energy density and a low resistance of the positive electrode active material layer 5.

[0037] A solid electrolyte is an ion-conductive material that conducts ions such as lithium, sodium, potassium, magnesium, and calcium, and is a compound that remains solid even in a nitrogen atmosphere at 1 atmosphere pressure and 25° C. Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, and nitride solid electrolytes.

[0038] The solid electrolyte is preferably a sulfide solid electrolyte. The solid electrolyte contained in the positive electrode active material layer 5 may be the same as or different from the solid electrolytes contained in the negative electrode active material layer 6 and the solid electrolyte layer 3, which will be described later. Preferably, both are sulfide solid electrolytes. The sulfide solid electrolyte has the advantage of increasing the conductivity of charge-transporting ions such as lithium ions. Furthermore, since particles of the sulfide solid electrolyte are more easily deformed, the contact area between the solid electrolyte particles and between the solid electrolyte and the active material can be increased. This has the advantage of reducing the interfacial resistance between the solid electrolyte and the active material.

[0039] The sulfide solid electrolyte is a solid electrolyte containing sulfur element as an essential component. When used in a lithium ion secondary battery, examples of the sulfide solid electrolyte include Li2S-P2S5, Li2S-GeS2, LiI-Li2S-P2S5, and Li 10 Ge-P2S 12 , Li6PS5X (X = Cl, Br, I), etc. 10 Ge-P2S 12 is called the LGPS type, and Li6PS5X is called the argyrodite type.

[0040] The oxide solid electrolyte is a solid electrolyte containing oxygen as an essential component, and examples of the oxide solid electrolyte include perovskite-type oxides, NASICON-type oxides, LISICON-type oxides, and garnet-type oxides. Examples of perovskite oxides include Li x La 1-x Examples of such oxides include oxides represented by TiO3 (Li-La-Ti-O perovskite oxides). 0.29 La 0.57 TiO3, Li 0.35 La 0.55 Examples include TiO3. Examples of NASICON-type oxides include Li 1.3 Al 0.3 Ti 1.7(PO4)3, etc. Examples of LISICON-type oxides include Li4SiO4-Li3PO4 and Li3BO3-Li3PO4. Garnet-type oxides include, for example, Li7La3Zr2O 12 Li-La-Zr-O based oxides such as those mentioned above can be cited.

[0041] An example of the nitride solid electrolyte is Li3N.

[0042] The particle size of the solid electrolyte is not particularly limited, but when used in combination with a particulate positive electrode active material, the average particle size is preferably 1 / 10 to 1 / 2 of the average particle size of the positive electrode active material. By setting the average particle size within this range, there is an advantage in that the interfacial resistance between the solid electrolyte and the active material can be further reduced.

[0043] The solid electrolyte may include an inorganic solid electrolyte such as the sulfide solid electrolyte or the oxide solid electrolyte, and may further include a polymer solid electrolyte. Examples of the polymer solid electrolyte include ion-conductive polymers. Examples of such ion-conductive polymers include chemically modified and crosslinked polyether-, polyester-, polyamine-, or polysulfide-based polymers.

[0044] The content of the solid electrolyte in the positive electrode active material layer 5 is preferably 5% by mass to 90% by mass, more preferably 10% by mass to 80% by mass, and even more preferably 15% by mass to 70% by mass. By setting the content of the solid electrolyte within the above range, the electric capacity of the energy storage element can be increased.

[0045] At least one of the positive electrode active material layer 5 and the negative electrode active material layer 6 described below contains, as an additive, a polymer having a number-average molecular weight of 400 to 3,000, in which hydrocarbon groups and ester bonds are alternately repeated along the main chain. The polymer has a structural unit in which each hydrocarbon group is located between two ester bonds, i.e., a structural unit in which two hydrocarbon groups are bonded to one ester bond, in the molecule. In addition to the structural unit, the polymer may also have other structural units in the molecule, such as a structural unit in which each hydrocarbon group is located between two ether bonds, i.e., a structural unit in which two hydrocarbon groups are bonded to one ether bond, to the extent that the effects of the present invention are not impaired. The hydrocarbon group in the polymer may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. The hydrocarbon group in the polymer may be a linear hydrocarbon group, a branched hydrocarbon group, or an aromatic or alicyclic cyclic hydrocarbon group. Hereinafter, the effects and preferred embodiments of the positive electrode active material layer 5 containing the above polymer will be described, but these also apply to the negative electrode active material layer 6.

[0046] In this disclosure, the main chain of a polymer refers to the longest series of covalently bonded atoms. However, in cases where the series of covalently bonded atoms that could form the main chain are present at multiple locations separate from each other in the polymer molecule, or where the series of covalently bonded atoms that could form the main chain are crosslinked to another series via a side chain, and in other cases where the main chain is not necessarily limited to one, the series of covalent bonds generated when the polymer is synthesized from monomers, etc., is considered to be the main chain.

[0047] In the polymer, the number of carbon atoms in each hydrocarbon group located between the ester bonds may be 2 or more, 4 or more, 6 or more, 7 or more, or 8 or more. On the other hand, the number of carbon atoms in each hydrocarbon group in the polymer may be 20 or less, or 18 or less. In the above polymer, each hydrocarbon group located between ester bonds is preferably a saturated chain hydrocarbon group having from 2 to 20 carbon atoms, more preferably a saturated chain hydrocarbon group having from 4 to 20 carbon atoms. In this case, the saturated chain hydrocarbon group may be a saturated linear hydrocarbon group or a saturated branched hydrocarbon group, but is preferably a saturated branched hydrocarbon group.

[0048] The polymer has a number-average molecular weight of 400 or more and 3000 or less. When the number-average molecular weight of the polymer is within the above range, the positive electrode active material layer 5 containing the polymer has high uniformity. In addition, it is possible to form an energy storage device in which the decrease in capacity during high-rate discharge is suppressed. The number-average molecular weight of the polymer is preferably 500 or more and 2500 or less, and more preferably 600 or more and 2000 or less.

[0049] The number average molecular weight is measured by gel permeation chromatography (GPC) under the following measurement conditions. Detector: Refractive index (RI) Column temperature: 40℃ Flow rate: 0.8mL / min. Column: 30 x 300 mm PLgel 100A, 1000A, and 10,000A connected in series Calibration curve: Standard polystyrene (150-450,000 Da) Eluent: tetrahydrofuran (THF) (containing 1% by mass of triethylamine (TEA))

[0050] The polymer is preferably a nonionic polymer. The nonionic nature of the polymer contributes to the uniformity of the positive electrode active material layer 5 containing the polymer. This is presumably due to the following reasons. The polymer-containing positive electrode active material layer 5 is often formed by preparing a positive electrode active material layer-forming paste in which a positive electrode active material, a solid electrolyte, an additive, and the like are dispersed in a dispersion medium, and then applying the paste. In this case, an organic solvent is used as the dispersion medium because the solid electrolyte may be deteriorated by water. Nonionic polymers are easily soluble in organic solvents and therefore easily distributed uniformly in the positive electrode active material layer-forming paste containing an organic solvent. Therefore, when the polymer is a nonionic polymer, the components are uniformly distributed in the positive electrode active material layer-forming paste, resulting in a highly uniform positive electrode active material layer 5.

[0051] The polymer may be a mixture of a polymer structure other than a polymer structure in which hydrocarbon groups and ester bonds are alternately repeated along the main chain, an interpenetrating polymer network (IPN) structure, or a copolymer. The copolymer may be a random copolymer, but is preferably a block copolymer. When the copolymer is a block copolymer, the properties derived from a polymer structure in which hydrocarbon groups and ester bonds are alternately repeated along the main chain, a feature of the present invention, are fully exhibited without dilution, compared to when the copolymer is a random copolymer. The polymer structure other than a polymer structure in which hydrocarbon groups and ester bonds are alternately repeated along the main chain may be a polyether structure. In this case, the polymer may be a polymer represented by the following general formula (1): In general formula (1), R1 is a saturated hydrocarbon group having 1 to 4 carbon atoms, R2' and R2'' are each independently a saturated hydrocarbon group having 4 to 20 carbon atoms, A and B are each independently an alkyl group, hydrogen, or other monovalent characteristic group, m, n1, and n2 are each independently a positive integer, and the ratio of m to the sum of m, n1, and n2 is 0 or 0.50 or less.

[0052] [ka]

[0053] In the general formula (1), R1 is preferably a saturated hydrocarbon group having 2 or 3 carbon atoms. R2' and R2" are each independently preferably a saturated branched-chain hydrocarbon group having 4 to 20 carbon atoms, more preferably a saturated branched-chain hydrocarbon group having 5 to 20 carbon atoms, even more preferably a saturated branched-chain hydrocarbon group having 6 to 20 carbon atoms, still more preferably a saturated branched-chain hydrocarbon group having 7 to 20 carbon atoms, and particularly preferably a saturated branched-chain hydrocarbon group having 8 to 20 carbon atoms. A and B are preferably each independently an alkyl group or hydrogen. The ratio of m to the sum of m, n1, and n2 is preferably 0 or 0.45 or less, more preferably 0 or 0.40 or less, even more preferably 0 or 0.35 or less, and even more preferably 0 or 0.30 or less. This significantly improves the uniformity of the positive electrode active material layer 5 and significantly suppresses the decrease in capacity during high-rate discharge of the energy storage device.

[0054] The polymer is synthesized, for example, by a self-condensation reaction of a monohydroxy fatty acid or an esterification reaction of a polyoxyalkylene glycol with a monohydroxy fatty acid.

[0055] The polymer represented by the above general formula (1) is preferably a polymer represented by the following general formula (2): In the following general formula (2), the values ​​of A and B, m, n1, and n2, and the ratio of m to the sum of m, n1, and n2 are the same as those in the above general formula (1).

[0056] [ka]

[0057] The positive electrode active material layer 5 preferably contains 0.01 parts by mass or more, and more preferably 0.05 parts by mass or more, of the polymer relative to 100 parts by mass of the positive electrode active material. When the content of the polymer is equal to or greater than the lower limit, the positive electrode active material layer 5 becomes more uniform. Furthermore, a storage device can be configured in which the decrease in capacity during high-rate discharge is further suppressed. On the other hand, the positive electrode active material layer 5 preferably contains 10 parts by mass or less, and more preferably 5 parts by mass or less, of the polymer relative to 100 parts by mass of the positive electrode active material. When the content of the polymer is equal to or less than the upper limit, the positive electrode active material layer 5 can achieve both high energy density and low resistance.

[0058] The positive electrode active material layer 5 may contain a conductive agent, if necessary. The conductive agent is not particularly limited as long as it is a material having conductivity. Examples of such conductive agents include carbonaceous materials, metals, conductive ceramics, etc. Examples of carbonaceous materials include graphite, non-graphitic carbon, graphene-based carbon, etc. Examples of non-graphitic carbon include carbon nanofiber, pitch-based carbon fiber, carbon black, etc. Examples of carbon black include furnace black, acetylene black, ketjen black, etc. Examples of graphene-based carbon include graphene, carbon nanotubes (CNT), fullerene, etc. The conductive agent may be in the form of powder, fiber, etc. As the conductive agent, one of these materials may be used alone, or two or more types may be mixed and used. Furthermore, these materials may be used in combination. For example, a composite material of carbon black and CNT may be used.

[0059] The content of the conductive agent in the positive electrode active material layer 5 is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the conductive agent within the above range, the energy density of the energy storage element can be increased. Note that when a conductive material such as a carbonaceous material is used as the positive electrode active material, the conductive agent may not be used.

[0060] The positive electrode active material layer 5 may contain a binder as needed. Examples of binders include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0061] The content of the binder in the positive electrode active material layer 5 is preferably 0.01% by mass to 10% by mass, and more preferably 0.1% by mass to 7.0% by mass. By setting the binder content within the above range, the positive electrode active material and the solid electrolyte can be stably maintained.

[0062] The positive electrode active material layer 5 may contain a thickener, if necessary. Examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose (CMC), methyl cellulose, and ethyl cellulose. When the thickener has a functional group that reacts with lithium or the like, the functional group may be deactivated in advance by methylation or the like.

[0063] The positive electrode active material layer 5 may contain a filler, if necessary. The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene; inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; carbonates such as calcium carbonate; sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate; nitrides such as aluminum nitride and silicon nitride; mineral-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica; and artificial products thereof.

[0064] The positive electrode active material layer 5 may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, and W as components other than the positive electrode active material, solid electrolyte, additive, conductive agent, binder, thickener, and filler.

[0065] (Negative electrode) The negative electrode 2 has a negative electrode substrate 7 and a negative electrode active material layer 6 disposed on the negative electrode substrate 7 directly or via an intermediate layer. The configuration of the intermediate layer is not particularly limited and can be selected from the configurations exemplified for the positive electrode above, for example.

[0066] The negative electrode substrate 7 is electrically conductive. Metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, alloys of these metals, and carbonaceous materials are used as the material for the negative electrode substrate 7. Among these, copper and copper alloys are preferred. Examples of negative electrode substrates include foils, vapor-deposited films, meshes, and porous materials, with foils being preferred from the viewpoint of cost. Therefore, copper foil or copper alloy foil is preferred as the negative electrode substrate 7. Examples of copper foil include rolled copper foil and electrolytic copper foil.

[0067] The average thickness of the negative electrode substrate 7 is preferably 2 μm to 35 μm, more preferably 3 μm to 30 μm, even more preferably 4 μm to 25 μm, and particularly preferably 5 μm to 20 μm. By setting the average thickness of the negative electrode substrate 7 within the above range, the strength of the negative electrode substrate 7 can be increased while increasing the energy density per volume of the energy storage element.

[0068] If the negative electrode active material layer 6 is conductive, the negative electrode substrate 7 does not need to be used.

[0069] The negative electrode active material layer 6 contains a negative electrode active material and a solid electrolyte. At least one of the negative electrode active material layer 6 and the above-described positive electrode active material layer 5 contains the above-described polymer as an additive. The negative electrode active material layer 6 contains optional components such as a conductive agent, a binder, a thickener, and a filler as needed. The optional components such as the solid electrolyte, the additive, the conductive agent, the binder, the thickener, and the filler can be selected from the materials exemplified for the positive electrode above.

[0070] The negative electrode active material layer 6 may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W as components other than the negative electrode active material, solid electrolyte, additive, conductive agent, binder, thickener, and filler.

[0071] The negative electrode active material can be appropriately selected from known negative electrode active materials. When the energy storage device is a lithium ion secondary battery, a material capable of absorbing and releasing lithium ions is usually used as the negative electrode active material. Examples of the negative electrode active material include metallic Li; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide; and Li4Ti5O 12 , LiTiO 2、 Examples of the material include titanium-containing oxides such as TiNbO; polyphosphate compounds; silicon carbide; and carbon materials such as graphite and non-graphitic carbon (easily graphitizable carbon or non-graphitizable carbon). Among these materials, graphite and non-graphitic carbon are preferred. In the negative electrode active material layer 6, one of these materials may be used alone, or two or more may be used in combination.

[0072] "Graphite" refers to graphite that has an average lattice spacing (d 002 ) is 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferred from the viewpoint of being able to obtain a material with stable physical properties.

[0073] "Non-graphitic carbon" refers to the carbon that has an average lattice spacing (d 002 ) is 0.34 nm or more and 0.42 nm or less. Non-graphitic carbon includes non-graphitizable carbon and graphitizable carbon. Examples of non-graphitic carbon include resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, and alcohol-derived materials.

[0074] Here, the "discharged state" refers to a state in which the negative electrode active material, a carbonaceous material, is discharged so that lithium ions capable of being absorbed and desorbed during charging and discharging are sufficiently released. For example, in a single-electrode battery using a negative electrode containing a carbonaceous material as a negative electrode active material as a working electrode and metallic Li as a counter electrode, this refers to a state in which the open circuit voltage is 0.7 V or higher.

[0075] "Non-graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.36 nm or more and 0.42 nm or less.

[0076] "Graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.34 nm or more and less than 0.36 nm.

[0077] Metallic Li may exist as pure metallic Li consisting essentially of lithium element alone, or as a Li alloy containing other metal elements. Examples of Li alloys include Li-Ag alloys, Li-Zn alloys, Li-Ca alloys, Li-Al alloys, Li-Mg alloys, and Li-In alloys. Li alloys may contain multiple metal elements other than lithium element.

[0078] The negative electrode active material is usually in the form of particles (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide, or a polyphosphate compound, the average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to be equal to or greater than the above lower limit, the negative electrode active material can be easily produced or handled. By setting the average particle size of the negative electrode active material to be equal to or less than the above upper limit, the electronic conductivity of the active material layer is improved. To obtain powder with a predetermined particle size, a pulverizer, a classifier, or the like is used. The pulverization method and classification method can be selected from, for example, the methods exemplified for the positive electrode. When the negative electrode active material is a metal such as metallic Li, the negative electrode active material may be in the form of a foil.

[0079] When a particulate negative electrode active material is used in the negative electrode active material layer 6, the content of the negative electrode active material is preferably 10% by mass to 95% by mass, more preferably 20% by mass to 90% by mass, and even more preferably 30% by mass to 80% by mass. By setting the content of the negative electrode active material within the above range, both high energy density and manufacturability of the negative electrode active material layer 6 can be achieved.

[0080] When the negative electrode active material is metallic Li, the negative electrode active material layer 6 may be a layer consisting essentially of metallic Li. The content of metallic Li in the negative electrode active material layer 6 may be 80 mass % or more, 90 mass % or more, 99 mass % or more, or 100 mass %. When the content of metallic Li in the negative electrode active material layer 6 is equal to or more than the above lower limit, the energy density of the electricity storage element can be further increased.

[0081] (solid electrolyte layer) The solid electrolyte layer 3 contains a solid electrolyte. The type of solid electrolyte is not particularly limited and can be selected from, for example, those exemplified for the positive electrode. The particle size of the solid electrolyte contained in the solid electrolyte layer 3 can be appropriately selected depending on the thickness of the solid electrolyte layer 3, but it is preferable that the average particle size be 1 μm or more and 10 μm or less. The solid electrolyte layer 3 may also contain a binder exemplified for the positive electrode.

[0082] The thickness of the solid electrolyte layer 3 may be 5 μm or more and 200 μm or less, or may be 10 μm or more and 100 μm or less.

[0083] <Method of manufacturing electrode body and method of manufacturing energy storage element> A method for manufacturing an energy storage element according to an embodiment of the present invention can be appropriately selected from known methods. The manufacturing method includes, for example, forming a positive electrode active material layer on a positive electrode substrate, forming a negative electrode active material layer on a negative electrode substrate, forming a solid electrolyte layer, and stacking the positive electrode substrate with the positive electrode active material layer and the negative electrode substrate with the negative electrode active material layer formed thereon, with the solid electrolyte layer interposed between them, to form an electrode assembly. Forming the positive electrode active material layer on the positive electrode substrate and forming the negative electrode active material layer on the negative electrode substrate includes, for example, kneading the active material and solid electrolyte components of each active material layer with optional additives, conductive agent, binder, thickener, and filler, and an organic solvent (dispersion medium) to prepare a paste for forming each active material layer, and applying the paste to each substrate and drying it.

[0084] The active material layer-forming pastes each contain the polymer as an additive, which suppresses cracking in the active material layers obtained by applying and drying the paste. This is presumably because the polymer has a molecular chain length with a number-average molecular weight of 400 to 3,000, which is suitable for dispersing the components of the active material layer-forming paste. This excellent dispersion effect is presumably responsible for improving the uniformity of the active material layer in the electrode body and suppressing the decrease in capacity during high-rate discharge in the energy storage device.

[0085] <Configuration of the power storage device> An energy storage element according to one embodiment of the present invention can be mounted as an energy storage unit (battery module) comprising a collection of a plurality of energy storage elements in an automobile power source such as an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV), a power source for electronic devices such as a personal computer or a communication terminal, or a power source for power storage, etc. In this case, the technology of the present invention may be applied to at least one energy storage element included in the energy storage unit. 2 shows an example of a power storage device 300 in which power storage units 200, each of which is an assembly of two or more electrically connected power storage elements 100, are further assembled. The power storage device 300 may include a bus bar (not shown) that electrically connects the two or more power storage elements 100, a bus bar (not shown) that electrically connects the two or more power storage units 200, etc. The power storage unit 200 or the power storage device 300 may include a status monitoring device (not shown) that monitors the status of one or more power storage elements 100.

[0086] <Other embodiments> The energy storage device of the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment or well-known technology. Furthermore, part of the configuration of one embodiment can be deleted. Also, well-known technology can be added to the configuration of one embodiment.

[0087] In the above embodiment, the case where the energy storage element is used as a chargeable and dischargeable all-solid-state secondary battery (for example, an all-solid-state lithium-ion secondary battery) has been described, but the energy storage element may be of any type, shape, size, capacity, etc. For example, the energy storage element of the present invention may be a secondary battery containing an electrolytic solution, or may be a capacitor such as an electric double layer capacitor or a lithium-ion capacitor. [Example]

[0088] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0089] First, each polymer for use as an additive was synthesized according to the following procedure: All of these polymers have the molecular structure of the above general formula (2).

[0090] (Synthesis Example 1: Synthesis of Polymer 1 for Additives) A flask equipped with a distiller and a mixer stirrer was charged with 450 g of 12-hydroxystearic acid. The mixture was heated to 85 to 90°C under a nitrogen atmosphere while stirring. 1.4 g of tetrabutyl orthotitanate (TBT) was added as a catalyst. While checking the acid value, the mixture was heated to a temperature of 222°C. Heating was stopped when the acid value reached 10 mgOH / g or less, and Polymer 1 according to Synthesis Example 1 was synthesized. The number-average molecular weight of the obtained Polymer 1 was measured by gel permeation chromatography (GPC). The number-average molecular weight was approximately 600 to 900. The GPC measurement conditions were the same as those described above, including those for the polymers according to the other Synthesis Examples described below.

[0091] (Synthesis Example 2: Synthesis of Additive Polymer 2) 73 g of polyethylene glycol 600 (PEG600) was charged into a flask equipped with a distiller and a mixer stirrer. The mixture was heated to 85 to 90°C while stirring under a nitrogen atmosphere. 450 g of 12-hydroxystearic acid was added to the flask, and 1.4 g of tetrabutyl orthotitanate (TBT) was added as a catalyst. The subsequent operations were the same as in Synthesis Example 1, and Polymer 2 of Synthesis Example 2 was synthesized. The number average molecular weight of the obtained Polymer 2 was 3,400.

[0092] (Synthesis Example 3: Synthesis of Additive Polymer 3) Polymer 3 of Synthesis Example 3 was synthesized in the same manner as in Synthesis Example 2, except that 219 g of polyethylene glycol 1500 (PEG1500) was used instead of polyethylene glycol 600. The number average molecular weight of the obtained polymer 3 was 4,900.

[0093] (Synthesis Example 4: Synthesis of Additive Polymer 4) Polymer 4 of Synthesis Example 4 was synthesized in the same manner as in Synthesis Example 2, except that 91 g of polyethylene glycol 1500 (PEG1500) and 202 g of polyethylene glycol 4000 (PEG4000) were used instead of polyethylene glycol 600. The number average molecular weight of the obtained polymer 4 was 6,400.

[0094] [Example 1] <Preparation of paste for forming negative electrode active material layer> Artificial graphite was prepared as the negative electrode active material. An argyrodite-type sulfide solid electrolyte represented by the composition formula Li6PS5Cl was prepared as the solid electrolyte. An SBR-based binder was prepared as the binder. The additive polymer 1 and the binder were added to butyl butyrate as the dispersion medium and kneaded. The solid electrolyte was then added to the resulting mixture and kneaded. The negative electrode active material and butyl butyrate were then added and kneaded to prepare a paste for forming a negative electrode active material layer. The mass ratio of the additive in the paste to the total solid content was 0.2.

[0095] <Preparation of negative electrode> A negative electrode current collector foil was prepared by forming a carbon coating as an intermediate layer on one side of Cu foil (average thickness 10 μm) as the negative electrode substrate. A multi-applicator (MA100, manufactured by Cotec Co., Ltd.) was used to apply a carbon coating to the side of the negative electrode current collector foil where the intermediate layer was formed, with a solids basis weight of 15 mg cm. -2 More than 25mg cm -2 The paste for forming the negative electrode active material layer was applied as follows. This was dried in a dryer in an argon atmosphere set at a temperature at which the butyl butyrate volatilized, forming a negative electrode active material layer on the negative electrode current collector foil. The resulting negative electrode active material layer was homogeneous and free of cracks. The negative electrode current collector foil and the negative electrode active material layer were punched into a circle with a diameter of 10 mm to form the negative electrode according to Example 1.

[0096] <Fabrication of energy storage elements (all-solid-state secondary batteries)> An argyrodite-type sulfide solid electrolyte powder represented by the composition formula Li6PS5Cl was prepared as the solid electrolyte. 80 mg of the sulfide solid electrolyte was placed in a ceramic powder molding machine with an inner diameter of 10 mm and pressure-molded using a uniaxial press at room temperature for several seconds at a pressure of 100 MPa to form a solid electrolyte layer. After releasing the pressure, the negative electrode according to Example 1 was placed on one side of the solid electrolyte layer and pressure-molded at 160°C and a pressure of 360 MPa for 5 minutes. After releasing the pressure, a lithium-indium counter electrode was placed on the surface opposite the negative electrode bonding surface and bonded using a uniaxial press at room temperature for several seconds at a pressure of 50 MPa. The resultant was removed from the ceramic powder molding machine to obtain an all-solid-state secondary battery as an energy storage element according to Example 1.

[0097] [Comparative Example 1] <Preparation of negative electrode> A negative electrode according to Comparative Example 1 was obtained in the same manner as in Example 1, except that when preparing the paste for forming a negative electrode active material layer, the above-mentioned Polymer 2 was used instead of the above-mentioned Polymer 1. Since local cracks were confirmed in the negative electrode active material layer obtained by forming the negative electrode active material layer on the negative electrode current collector foil, when punching out the negative electrode current collector foil and the negative electrode active material layer, portions without cracks were selected and punched out.

[0098] <Fabrication of energy storage elements (all-solid-state secondary batteries)> An all-solid-state secondary battery as an electricity storage element according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the negative electrode according to Comparative Example 1 was used as the negative electrode.

[0099] Comparative Example 2 <Preparation of negative electrode> A negative electrode according to Comparative Example 2 was obtained in the same manner as in Example 1, except that when preparing the paste for forming a negative electrode active material layer, Polymer 3 was used instead of Polymer 1. Since local cracks were confirmed in the negative electrode active material layer obtained by forming the negative electrode active material layer on the negative electrode current collector foil, when punching out the negative electrode current collector foil and the negative electrode active material layer, portions without cracks were selected and punched out.

[0100] <Fabrication of energy storage elements (all-solid-state secondary batteries)> An all-solid-state secondary battery as an electricity storage element according to Comparative Example 2 was obtained in the same manner as in Example 1, except that the negative electrode according to Comparative Example 2 was used as the negative electrode.

[0101] Comparative Example 3 <Preparation of negative electrode> A negative electrode according to Comparative Example 3 was obtained in the same manner as in Example 1, except that when preparing the paste for forming a negative electrode active material layer, Polymer 4 was used instead of Polymer 1. Since cracks were observed throughout the negative electrode active material layer obtained by forming the negative electrode active material layer on the negative electrode current collector foil, when punching out the negative electrode current collector foil and the negative electrode active material layer, portions without cracks were selected and punched out.

[0102] <Fabrication of energy storage elements (all-solid-state secondary batteries)> An all-solid-state secondary battery as an electricity storage element according to Comparative Example 3 was obtained in the same manner as in Example 1, except that the negative electrode according to Comparative Example 3 was used as the negative electrode.

[0103] <Evaluation> For each of the all-solid-state secondary batteries according to Example 1 and Comparative Examples 1 to 3, a charge-discharge test was carried out at 25° C. in the following manner. Here, the application of current in a direction in which the negative electrode is electrochemically oxidized is referred to as "discharge," and the application of current in a direction in which the negative electrode is electrochemically reduced is referred to as "charge." Constant current / constant voltage charging was performed with a charging current of 0.1 C and a charge cut-off voltage of -0.9 V. The charge was terminated until the charging current reached 0.025 C. A 10-minute rest period was then provided. Subsequently, constant current discharge was performed with a discharge current of 0.1 C and a discharge cut-off voltage of 2.5 V, and the discharge capacity was measured. Next, for the all-solid-state secondary battery that had undergone the above constant current / constant voltage charging and rest period, constant current discharge was performed with a discharge current of 5 C and a discharge cut-off voltage of 2.5 V, and the discharge capacity was measured. From each of the above measurement results, the percentage of the discharge capacity when discharged at a discharge current of 5 C relative to the discharge capacity when discharged at a discharge current of 0.1 C was calculated, and the obtained value was taken as the capacity retention rate during high-rate discharge. The results obtained are shown in Table 1, along with the type of polymer contained as an additive in the negative electrode active material layer of each all-solid-state secondary battery and its number average molecular weight.

[0104] [Table 1]

[0105] [Example 2] <Preparation of paste for forming positive electrode active material layer> The positive electrode active material is LiNbO3 coated, with the composition formula LiNi 0.6 Co 0.2 Mn 0.2 Lithium transition metal composite oxide (NCM622) particles represented by the formula O2 were prepared. An argyrodite-type sulfide solid electrolyte represented by the formula Li6PS5Cl was prepared as a solid electrolyte. Vapor-grown carbon fiber (VGCF (registered trademark)-H, fiber diameter 150 nm, manufactured by Resonac) was prepared as a conductive agent. An SBR-based binder was prepared as a binder. The additive polymer 4 and the binder were added to butyl butyrate as a dispersion medium and kneaded. The conductive agent was then added to the resulting mixture and kneaded. The solid electrolyte was then added to the resulting mixture and kneaded. The positive electrode active material was then added and kneaded. Then, butyl butyrate was added and kneaded. A paste for forming a positive electrode active material was prepared by adding the additive to the paste at a mass ratio of 0.2 relative to the total solid content.

[0106] <Preparation of positive electrode> A positive electrode current collector foil was prepared by forming a carbon coating as an intermediate layer on one side of an Al foil (average thickness 20 μm) that served as the positive electrode substrate. A multi-applicator (MA100, manufactured by Cotec Co., Ltd.) was used to apply a coating of 15 mg cm of solids to the side of the positive electrode current collector foil where the intermediate layer was formed. -2 More than 25mg cm -2 The paste for forming a positive electrode active material layer was applied as follows. This was dried in an oven in an argon atmosphere set at a temperature at which the butyl butyrate volatilized, forming a positive electrode active material layer on the positive electrode current collector foil. The positive electrode current collector foil and the positive electrode active material layer were cut into a square with a side length of 24 mm to obtain a positive electrode.

[0107] <Preparation of negative electrode> The negative electrode according to Example 2 was obtained in the same manner as in Example 1, except that the negative electrode current collector foil and the negative electrode active material layer were cut into a square with a side length of 25 mm.

[0108] <Preparation of solid electrolyte layer> An argyrodite-type sulfide solid electrolyte powder represented by the composition formula Li6PS5Cl was prepared as the solid electrolyte. An SBR-based binder was prepared as the binder. In an argon-atmosphere glove box, the binder and butyl butyrate as a dispersant were added to the solid electrolyte and kneaded using a hybrid mixer to prepare a paste for forming a solid electrolyte layer. The paste for forming a solid electrolyte layer was applied to a polyimide film as a release substrate using a multi-applicator (MA100, manufactured by Cortec Co., Ltd.). This was dried in a drying oven in an argon atmosphere set at a temperature at which the butyl butyrate volatilized, forming a solid electrolyte layer on the release substrate. The release substrate was then peeled off from the resulting solid electrolyte layer, and the solid electrolyte layer was cut into a square with a side length of 25 mm to obtain a solid electrolyte layer.

[0109] <Fabrication of energy storage elements (all-solid-state secondary batteries)> The negative electrode according to Example 2 and the solid electrolyte layer were stacked together and transfer-pressed at room temperature under a pressure of 50 MPa. The positive electrode was placed on the surface of the solid electrolyte layer opposite to the surface on which the negative electrode according to Example 2 was placed, and the resulting mixture was sealed in a flexible container under reduced pressure. After that, the resulting mixture was isostatically pressed at a temperature of 160°C under a pressure of 1000 MPa for 5 minutes, and then removed from the container to obtain an all-solid-state secondary battery according to Example 2 as an energy storage element.

[0110] [Comparative Examples 4 and 5] An all-solid-state secondary battery as an electricity storage element according to Comparative Example 4 was obtained in the same manner as in Example 2, except that the negative electrode current collector foil and negative electrode active material layer produced in Comparative Example 2 were used. Furthermore, an all-solid-state secondary battery as an electricity storage element according to Comparative Example 5 was obtained in the same manner as in Example 2, except that the negative electrode current collector foil and negative electrode active material layer produced in Comparative Example 3 were used.

[0111] <Evaluation> For each of the all-solid-state secondary batteries according to Example 2 and Comparative Examples 4 and 5, a discharge capacity test was carried out in the following manner.

[0112] (Discharge capacity test under room temperature environment) Constant current / constant voltage charging was performed with a charging current of 0.1 C and a charge cut-off voltage of 4.25 V. The charge was terminated until the charging current reached 0.025 C. A 10-minute rest period was then provided. Subsequently, constant current discharging was performed with a discharge current of 0.1 C and a discharge cut-off voltage of 2.85 V, and the discharge capacity was measured. Next, constant current / constant voltage charging was performed under the same conditions as above, and after the rest period, the all-solid-state secondary battery was subjected to constant current discharging with a discharge current of 5 C and a discharge cut-off voltage of 2.85 V, and the discharge capacity was measured. Both the above charging and discharging were performed at a temperature of 25°C.

[0113] (Discharge capacity test in low temperature environment) A constant current / constant voltage charge was performed under the same conditions as the discharge capacity test at room temperature. Next, after a two-hour rest period at 0°C, a constant current discharge was performed with a discharge current of 0.1 C and a discharge cut-off voltage of 2.85 V, and the discharge capacity was measured. Next, after a two-hour rest period at 25°C, a constant current / constant voltage charge was performed under the same conditions as the discharge capacity test at room temperature. Next, after a two-hour rest period at 0°C, a constant current discharge was performed with a discharge current of 5 C and a discharge cut-off voltage of 2.85 V, and the discharge capacity was measured.

[0114] From the results of each of the above discharge capacity tests, the percentage of the discharge capacity when discharged at a discharge current of 5 C relative to the discharge capacity when discharged at a discharge current of 0.1 C was calculated, and the obtained value was taken as the capacity retention rate during high-rate discharge. The results obtained are shown in Table 2, along with the type of polymer contained as an additive in the negative electrode active material layer of each all-solid-state secondary battery and its number average molecular weight.

[0115] [Table 2]

[0116] As shown in Tables 1 and 2, it was confirmed that an energy storage device in which the decrease in capacity during high-rate discharge is suppressed can be obtained by using an electrode assembly containing in its active material layer a polymer in which hydrocarbon groups and ester bonds are alternately repeated along the main chain and which has a number-average molecular weight of 400 to 3000. In particular, the results in Table 2 confirm that the use of the electrode assembly makes it possible to obtain an energy storage device in which the decrease in capacity during high-rate discharge in a low-temperature environment is significantly suppressed. [Explanation of symbols]

[0117] 1 positive electrode 2 negative electrode 3 Solid electrolyte layer 4. Positive electrode substrate 5 Cathode active material layer 6 Negative electrode active material layer 7. Negative electrode substrate 10 Electrode body 100 Energy storage element 200 Energy Storage Unit 300 Electricity storage device

Claims

1. an active material layer including an active material, a solid electrolyte, and an additive; The additive contains a polymer in which hydrocarbon groups and ester bonds are alternately repeated along the main chain and which has a number average molecular weight of 400 or more and 3,000 or less. Electrode body.

2. 2. The electrode assembly according to claim 1, wherein the polymer is a nonionic polymer.

3. 2. The electrode body according to claim 1, wherein the polymer is a polymer represented by the following general formula (1): (wherein, in general formula (1), R1 is a saturated hydrocarbon group having 1 to 4 carbon atoms, R2' and R2'' are each independently a saturated hydrocarbon group having 4 to 20 carbon atoms, A and B are each independently an alkyl group, hydrogen, or other monovalent characteristic group, m, n1, and n2 are each independently a positive integer, and the ratio of m to the sum of m, n1, and n2 is 0 or 0.50 or less). 【Chemical 1】

4. An energy storage element comprising the electrode assembly according to claim 1 .

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