Electricity storage device and manufacturing method thereof

Abstract

Provided are a power storage device (10) and a method for manufacturing same, with which dendrite growth can be reduced while suppressing an increase in the mass and volume of the power storage device. The power storage device comprises: a positive electrode (11); a negative electrode (15); and a separator (14) that separates the positive electrode and the negative electrode. The negative electrode comprises, in order toward the positive electrode: an active material layer (17) that includes an active material which reduces carrier ions; an electrolyte layer (18) that includes a solid electrolyte having carrier ion conductivity and an electrolytic solution, and that is in contact with the active material layer; and a conductive layer (19) that has electron conductivity, is in contact with the electrolyte layer, and takes in an element which has precipitated at an interface between the active material layer and the electrolyte layer.

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device that uses ions as carriers and a method for manufacturing the same. [Background technology]

[0002] In energy storage devices that use ions as carriers, metals can precipitate on the negative electrode during charging. Needle-shaped dendrites are likely to form on the negative electrode due to fluctuations in ion concentration and electric field distribution during precipitation, and the growth of dendrites can lead to reduced charging efficiency and malfunctions. Non-Patent Document 1 discloses a prior art technique in which a device that applies pressure to a single battery (cell) is provided in an energy storage device, and charging and discharging are performed while pressurizing the cell, thereby densifying the precipitates and reducing the growth of dendrites. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Shoichi Matsuda, "Effect of Confining Pressure on the Precipitation-Dissolution Reaction of Metallic Lithium Electrodes," Abstracts of the 62nd Battery Symposium, Battery Technology Committee of the Electrochemical Society of Japan, November 30, 2021 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, the mass and volume of the energy storage device increase by the amount of the device that pressurizes the cell, which causes a problem in that the actual energy density is significantly lower than the theoretical energy density determined by the active material contained in the energy storage device.

[0005] The present invention has been made to solve this problem, and has an object to provide an electricity storage device that can reduce dendrite growth while suppressing an increase in the mass and volume of the electricity storage device, and a method for manufacturing the same. [Means for solving the problem]

[0006] A first aspect for achieving this object is an electricity storage device that utilizes ionic conduction and includes a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode. The negative electrode includes, in order toward the positive electrode, an active material layer containing an active material that undergoes an oxidation-reduction reaction, an electrolyte layer that contains a solid electrolyte and an electrolytic solution and has carrier ion conductivity and is in contact with the active material layer, and a conductive layer that has electronic conductivity and is in contact with the electrolyte layer and takes in elements that have precipitated at the interface between the active material layer and the electrolyte layer.

[0007] In a second embodiment, in the first embodiment, the conductive layer includes a metal layer that forms an alloy with an element produced by the reaction of the carrier ions.

[0008] In the third aspect, in the first aspect, the conductive layer includes a capture body that has electronic conductivity and adsorbs molecules, and the molecules include elements generated by the reaction of carrier ions.

[0009] In the fourth aspect, in the third aspect, the molecules adsorbed to the capture body include a first phase and a second phase in order of proximity to the capture body, and the ratio of elements that are likely to become ions during discharge to elements contained in the second phase in the fully charged state is greater than the ratio of elements that are likely to become ions during discharge to elements contained in the first phase in the fully charged state.

[0010] In a fifth aspect, in any one of the first to fourth aspects, the carrier ions are lithium ions, and the solid electrolyte is an oxide containing Li, La, and Zr and having a garnet-type crystal structure.

[0011] A sixth aspect is a method for manufacturing an electricity storage device that utilizes ionic conduction and that includes a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode, wherein the negative electrode includes an active material layer containing an active material that undergoes an oxidation-reduction reaction, an electrolyte layer that contains a solid electrolyte and an electrolytic solution and has carrier ion conductivity and is in contact with the active material layer, and a conductive layer that has electronic conductivity and is in contact with the electrolyte layer and takes in carrier ions, and the method includes the steps of stacking the positive electrode, separator, and negative electrode in this order, and passing a current from the negative electrode to the positive electrode to precipitate elements contained in the electrolyte layer at the interface between the active material layer and the electrolyte layer. [Effects of the Invention]

[0012] According to the method for manufacturing an electricity storage device of the present invention, when a current is passed from the negative electrode to the positive electrode, elements contained in the electrolyte layer precipitate at the interface between the electrolyte layer and the active material layer. When dendrites grow in the electrolyte layer toward the positive electrode, elements also precipitate at the interface of the electrolyte layer, which has become electronically conductive due to the dendrites. Because the electronic conductivity of the electrolyte layer is lower than that of the active material layer, the reaction at the interface of the electrolyte layer is rate-determined by electronic conduction, and the difference between the carrier ion concentration at the interface of the electrolyte layer and the carrier ion concentration in the separator is smaller than the difference between the carrier ion concentration at the interface of the negative electrode and the carrier ion concentration in the separator in the absence of an electrolyte layer. Therefore, the reaction at the interface of the electrolyte layer occurs more uniformly across the entire interface of the electrolyte layer than the reaction at the interface of the negative electrode in the absence of an electrolyte layer. Furthermore, because a conductive layer with electronic conductivity is in contact with the electrolyte layer, elements also precipitate in the conductive layer. The precipitated elements are incorporated into the conductive layer.

[0013] Because the energy storage device of the present invention has a conductive layer and an electrolyte layer, the reaction of elements precipitating during charging occurs almost uniformly across the entire interface of the conductive layer, compared to the reaction at the interface of the negative electrode when the energy storage device does not have a conductive layer or electrolyte layer. Although elements are also precipitated inside the conductive layer, the incorporation of the precipitated elements into the conductive layer improves the element packing rate in the conductive layer, thereby reducing dendrite growth. Because there is no need to pressurize the cell while charging and discharging in order to reduce dendrite growth, dendrite growth can be reduced while suppressing increases in the mass and volume of the energy storage device. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of an electricity storage device according to an embodiment. [Figure 2] FIG. 1 is a diagram schematically illustrating a garnet-type crystal structure. [Figure 3] FIG. 2 is a schematic diagram of a conductive layer. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of an electricity storage device 10 according to one embodiment. The electricity storage device 10 uses ions as carriers. The ions that serve as carriers are Li + , Na + , K. + , Mg 2+ , Cu + , Ag + Metal ions such as OH - , F - , H - However, there is no limitation on the type of ion.

[0016] The electricity storage device 10 is + , Na + , K. + , Mg 2+ , F - , H -Examples of such batteries include ion batteries such as lithium ion batteries that use ions such as lithium ions as carriers, electrochemical capacitors that use redox reactions of electrodes or ions in an electrolyte, or electric double layers, and metal-air batteries that use oxygen in the air as the positive electrode active material and a metal such as Li, Zn, Al, Mg, or Fe as the negative electrode active material. The power storage device 10 includes, in order, a positive electrode 11, a separator 14, and a negative electrode 15.

[0017] There are no limitations on the separator 14 as long as it separates the positive electrode 11 and the negative electrode 15. Examples of the separator 14 include (1) a separator in which an electrically insulating porous body is disposed, through which carrier ions contained in the electrolyte solution move; (2) a separator in which an ion-conductive solid electrolyte is disposed instead of a porous body and an electrolyte solution; and (3) a separator in which an ion-conductive gel electrolyte is disposed, or a separator in which a mixture of an ion-conductive solid electrolyte and an electrolyte solution is disposed. In the case of the separator 14 of (1), examples of the electricity storage device 10 include so-called liquid metal ion batteries, metal-air batteries, and electrochemical capacitors. In the case of the separator 14 of (2), the electricity storage device 10 is a so-called all-solid-state battery. In the case of the separator 14 of (3), the electricity storage device 10 is a so-called semi-solid battery.

[0018] The positive electrode 11 is formed by stacking a current collector 12 and a reaction layer 13. The current collector 12 is a conductive member. Examples of materials for the current collector 12 include a metal selected from Ni, Ti, Fe, and Al, an alloy containing two or more of these elements, stainless steel, and a carbon material.

[0019] When the electricity storage device 10 is an ion battery or an electrochemical capacitor, the reaction layer 13 contains a positive electrode active material. The positive electrode active material is appropriately selected depending on the type of carrier ion.

[0020] When the electricity storage device 10 is a metal-air battery, the reaction layer 13 includes a gas diffusion layer through which air diffuses and a catalyst layer in which an oxygen reduction reaction occurs, in order to use oxygen in the atmosphere as the positive electrode active material. The catalyst layer includes a decomposition catalyst such as manganese oxide or a porphyrin-based compound that enhances the decomposition ability of hydrogen peroxide ions.

[0021] The negative electrode 15 includes, in order toward the positive electrode 11, an active material layer 17, an electrolyte layer 18, and a conductive layer 19. A conductive current collector 16 can be disposed on the active material layer 17. Examples of materials for the current collector 16 include a metal selected from Ni, Ti, Fe, Cu, and Si, an alloy containing two or more of these elements, stainless steel, and a carbon material.

[0022] The active material layer 17 contains an active material (negative electrode active material). There are no limitations on the material of the active material as long as it can absorb and release carrier ions. The active material is appropriately selected depending on the type of carrier ions.

[0023] When the electricity storage device 10 is an ion battery or an electrochemical capacitor that uses metal ions as carrier ions, the active material may be a carbon-based material such as porous carbon, natural graphite, artificial graphite, graphitizable carbon (hard carbon), non-graphitizable carbon (soft carbon), or carbon fiber, or Li4Ti5O 12 Examples of the active material include Si, Si-Li alloys, compounds containing Si and O as constituent elements (hereinafter referred to as "SiOx" where 0.5≦X≦1.5), metallic lithium, lithium alloys such as Li-Al alloys, Li-Sn alloys, Li-Si alloys, Li-Mg alloys, and Li-Si alloys, In-Sb alloys, and Si-Li alloys. Examples of SiOx include oxides of Si and those having a structure in which microcrystalline or amorphous Si is dispersed in an amorphous SiO2 matrix. When the power storage device 10 is a metal-air battery, examples of the active material include metals such as Li, Zn, Al, Mg, and Fe. One or more of these materials are selected as the active material.

[0024] Examples of the active material layer 17 include an aggregate of particles made of these materials, a plate made of these materials, and a porous body supported by these materials. Among these, metallic lithium and alloy-based active materials, which have a higher capacity density than carbon-based active materials, are preferred. When the active material layer 17 is an aggregate of particles, the active material layer 17 may contain a conductive additive to reduce the resistance of the active material layer 17. Examples of conductive additives include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag.

[0025] The electrolyte layer 18 contains a solid electrolyte having lithium ion conductivity and an electrolytic solution. The solid electrolyte contains at least one selected from sulfide-based, oxide-based, hydride-based, halide-based, and organic-based solid electrolytes. The sulfide-based solid electrolyte is a crystalline thiolithium type, Li 10 GeP2S 12 type, argyrodite type, Li7P3S 11 Examples include glass and glass ceramic systems such as Li2S-P2S5.

[0026] Examples of oxide-based solid electrolytes include oxides having a NASICON structure, oxides having a perovskite structure, and oxides having a garnet structure. Oxides having a NASICON structure include oxides containing at least Li, M (M is one or more elements selected from Ti, Zr, and Ge) and P, such as Li(Al,Ti)2(PO4)3 and Li(Al,Ge)2(PO4)3. Oxides having a perovskite structure include oxides containing at least Li, Ti, and La, such as La 2 / 3-X Li 3X Examples include TiO3.

[0027] Examples of hydride solid electrolytes include solid solutions of LiBH4 with lithium halide compounds (LiI, LiBr, LiCl) and lithium amide (LiNH2). Examples of halide solid electrolytes include Li3YCl6. Examples of organic solid electrolytes include polyethylene oxide, polypropylene oxide, and polyacrylonitrile.

[0028] The solid electrolyte is preferably a composite oxide containing Li, La, and Zr and having a garnet-type crystal structure. -3 This is because it has an ionic conductivity of the order of 500 S / cm and is resistant to reduction by metallic lithium. The garnet-type crystal structure has the general formula C3A2B3O 12 It is expressed as:

[0029] FIG. 2 is a diagram schematically illustrating a garnet-type crystal structure. In the garnet-type crystal structure, Sc at the C site is dodecahedrally coordinated with an oxygen atom Oa, Sa at the A site is octahedrally coordinated with an oxygen atom Oa, and Sb at the B site is tetrahedrally coordinated with an oxygen atom Oa. In the solid electrolyte 19, Li can exist in a vacancy V, which would otherwise be octahedrally coordinated with an oxygen atom Oa in a typical garnet-type crystal structure. The vacancy V is, for example, a location sandwiched between the B site Sb1 and the B site Sb2. The Li present in the vacancy V is octahedrally coordinated with an oxygen atom Oa that constitutes an octahedron including the tetrahedral face Fb1 forming the B site Sb1 and the tetrahedral face Fb2 forming the B site Sb2. For example, in the case of Li7La3Zr2O having a garnet-type crystal structure, 12 In the formula, La can occupy the C-site Sc, Zr can occupy the A-site Sa, and Li can occupy the B-site Sb and the vacant V.

[0030] The garnet-type crystal structure can be identified by X-ray diffraction. The garnet-type crystal structure is identified in X-ray diffraction file No. 422259 (Li7La3Zr2O) of the CSD (Cambridge Structural Database). 12 ) has an XRD pattern similar to that of No. 422259. Compared to No. 422259, the solid electrolyte may have different constituent elements and Li concentrations, resulting in different diffraction angles and intensity ratios. A typical crystal structure of this type is a cubic system (space group Ia-3d (- indicates an overline indicating a reversal operation), JCPDS: 84-1753).

[0031] Solid electrolytes with a garnet-type crystal structure are typically Li7La3Zr2O 12 The solid electrolyte is Li7La3Zr2O 12 Some of the constituent elements may be substituted with other elements, or a small amount of other elements may be added without substituting the constituent elements. Examples of other elements include at least one element selected from the group consisting of Mg, Al, Si, Ca, Ti, V, Ga, Sr, Y, Nb, Sn, Sb, Ba, Hf, Ta, W, Bi, Rb, and lanthanides (excluding La).

[0032] The solid electrolyte is, for example, Li6La3Zr 1.5 W 0.5 O 12 、Li 6.15 La3Zr 1.75 Ta 0.25 Al 0.2 O 12 、Li 6.15 La3Zr 1.75 Ta 0.25 Ga 0.2 O 12 、Li 6.25 La3Zr2Ga 0.25 O 12 、Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li 6.5 La3Zr 1.75 Te 0.25 O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 、Li 6.9 La3Zr 1.675 Ta 0.289 Bi 0.036 O 12 、Li 6.46 Ga 0.23 La3Zr 1.85 Y 0.15 O 12 、Li 6.8 La 2.95 Ca 0.05 Zr 1.75 Nb 0.25 O 12 、Li 7.05 La 3.00 Zr 1.95 Gd 0.05 O 12 、Li 6.20 Ba 0.30 La 2.95 Rb 0.05 Zr2O 12 and the like can be mentioned.

[0033] The solid electrolyte preferably contains at least one of Mg and element A (A is at least one element selected from the group consisting of Ca, Sr, and Ba), with the molar ratio of each element satisfying all of the following (1) to (3), or contains both Mg and element A, with the molar ratio of each element satisfying all of the following (4) to (6). Element A is preferably Sr, as it increases the ionic conductivity of the solid electrolyte. Li7La3Zr2O 12 This is because when some of the constituent elements are substituted with Mg and Sr, the ionic conductivity of the solid electrolyte increases, and metallic lithium precipitates more densely.

[0034] (1) 1.33≦Li / (La+A)≦3 (2) 0≦Mg / (La+A)≦0.5 (3) 0≦A / (La+A)≦0.67 (4) 2.0≦Li / (La+A)≦2.5 (5) 0.01≦Mg / (La+A)≦0.14 (6) 0.04≦A / (La+A)≦0.17

[0035] Returning to FIG. 1 , the explanation will be made. The electrolyte solution contained in the electrolyte layer 18 is a medium through which carrier ions move, and is a solution in which a metal salt is dissolved in a solvent. There are no particular limitations on the solvent as long as it dissolves the metal salt. Aqueous solvents and non-aqueous solvents can be used without limitation. Examples of non-aqueous solvents include carbonate esters, aliphatic carboxylic acid esters, phosphate esters, γ-lactones, ethers, nitriles, sulfolane, dimethyl sulfoxide, fluorous solvents, and ionic liquids. Mixtures of these may also be used.

[0036] Examples of carbonate esters include cyclic carbonate esters such as propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate, and chain carbonate esters such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate.

[0037] Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, and ethyl propionate. Examples of phosphate esters include trimethyl phosphate. Examples of γ-lactones include γ-butyrolactone. Examples of ethers include chain ethers such as 1,2-dialkoxyethane, and cyclic ethers such as 1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of nitriles include acetonitrile and propionitrile. Fluorous solvents are compounds in which the hydrogen atoms of hydrocarbons are replaced with fluorine atoms, and derivatives thereof.

[0038] Ionic liquids are compounds consisting of cations and anions, and are liquid at room temperature and normal pressure. If the solvent of an electrolyte is an ionic liquid, the flame retardancy of the electrolyte can be improved. Ionic liquids are preferred because they have a relatively wide potential window. Suitable ionic liquids have one or more cation species selected from the group consisting of ammonium, imidazolium, pyrrolidinium, and piperidinium.

[0039] The anion component of the ionic liquid is not particularly limited. The anion component is BF4 - ,N(SO2F)2 - Inorganic anions such as B(C6H5)4 - ,CH3SO3 - ,CF3SO3 - ,N(SO2CF3)2 - ,N(SO2C4F9)2 - Examples of organic anions include N(SO2F)2 - is abbreviated as [FSI] - : It is called bis(fluorosulfonyl)imide anion, N(SO2CF3)2 - abbreviated as [TFSI] - : It is sometimes called bis(trifluoromethanesulfonyl)imide anion.

[0040] Examples of ionic liquids include N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(fluorosulfonyl)imide (DEME-FSI), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI), N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (P13FSI), and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13TFSI). Mixtures of these may also be used.

[0041] The ionic liquid may be a solvated ionic liquid, such as a sulfone-based solvent such as sulfolane or a sulfolane derivative, or a glyme-based solvent such as tetraglyme, in which a metal salt is dissolved.

[0042] The anion of the metal salt is OH - , halide ions (I - ,Cl - ,Br - etc.), SCN - ,BF4 - ,BF3(CF3) - ,BF3(C2F5) - ,PF6 - ,ClO4 - ,SbF6 - ,N(SO2F)2 - ,N(SO2CF3)2 - ,N(SO2C2F5)2 - ,B(C6H5)4 - ,B(O2C2H4)2 - ,C(SO2F)3 - ,C(SO2CF3)3 - ,CF3COO- ,CF3SO2O - ,C6F5SO2O - ,B(O2C2O2)2 - ,RCOO - (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group), etc. The metal salt may be a mixture of these.

[0043] The concentration of metal salt in the electrolyte is 0.2 mol / dm 3 or more, preferably 0.5 mol / dm 3 As the salt concentration increases, the number of solvent molecules coordinated to carrier ions increases and the amount of uncoordinated solvent decreases, which reduces the interfacial resistance of the solid electrolyte. The salt concentration of the electrolyte is 4.0 mol / dm 3 The salt concentration of the electrolyte is preferably 4.0 mol / dm or less. 3 This is because, when the temperature exceeds this value, the ionic conductivity tends to decrease significantly due to an increase in the viscosity of the electrolyte.

[0044] In the electrolyte layer 18, the ratio of the volume of the solid electrolyte to the total volume of the solid electrolyte and the electrolytic solution is 52% or more and less than 100%, and preferably 61% or more and less than 100%. The combination of the solid electrolyte and the electrolytic solution can reduce the interfacial resistance of the solid electrolyte, so the ionic transport number of the electrolyte layer 18 can be made larger than that of a typical electrolytic solution. As a result, the operational stability of the electricity storage device 10 is improved.

[0045] The solid electrolyte content (volume %) is determined by analyzing a randomly selected cross section of the electrolyte layer 18 at a magnification of 5000x using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), identifying the distribution of elements and analyzing the contrast of the backscattered electron image to determine the area of ​​the solid electrolyte and the area of ​​the electrolyte solution. The solid electrolyte content (volume %) is obtained by considering the ratio of the area of ​​the solid electrolyte to the total area of ​​the solid electrolyte and the area of ​​the electrolyte solution as the volume ratio.

[0046] The cross section of the electrolyte layer 18 used for analysis is a polished surface, a surface obtained by irradiating with a focused ion beam (FIB), or a surface obtained by ion milling. The polished surface is, for example, a surface obtained by freezing the electrolyte layer 18 or by embedding and solidifying the electrolyte layer 18 in a tetrafunctional epoxy resin or the like and then polishing it.

[0047] The electrolyte layer 18 may contain a binder that binds the solid electrolyte. Examples of binders include fluorinated resins, polyolefins, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, and rubber-like polymers such as styrene-butadiene rubber. Examples of fluorinated resins include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.

[0048] The vinylidene fluoride polymer is not particularly limited as long as it contains -CH2CF2-. Examples of the vinylidene fluoride polymer include a homopolymer of vinylidene fluoride and a copolymer of vinylidene fluoride and a copolymerizable monomer. Examples of the copolymerizable monomer include a halogen-containing monomer (excluding vinylidene fluoride) and a non-halogen copolymerizable monomer. Examples of the halogen-containing monomer include a chlorine-containing monomer such as vinyl chloride; and a fluorine-containing monomer such as trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether. Examples of the non-halogen copolymerizable monomer include an olefin such as ethylene or propylene; an acrylic monomer such as acrylic acid, methacrylic acid, or an ester or salt thereof; and a vinyl monomer such as acrylonitrile, vinyl acetate, or styrene. One or more copolymerizable monomers are polymerized with vinylidene fluoride to form a copolymer.

[0049] The binder and the electrolyte solution may be present separately in the electrolyte layer 18, or may be mixed together in a gel state. A solvent that dissolves the binder may be included in the electrolyte layer 18. The binder preferably has a wider potential window than the potential window of the electrolyte solution.

[0050] The electrolyte layer 18 may contain a polymer for purposes such as improving the electrochemical stability of the electrolyte layer 18. Examples of polymer materials include polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polyamide, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyacrylonitrile, polycarbonate, and silicone. The polymer may be in various shapes such as particles, fibers, and flakes.

[0051] The conductive layer 19 is a layer in contact with the electrolyte layer 18 and has electronic conductivity. The conductive layer 19 is a layer for capturing elements deposited at the interface between the active material layer 18 and the electrolyte layer 18. The thickness of the conductive layer 19 is, for example, in the range of 10 μm to 100 μm. The conductive layer 19 includes, for example, a metal layer that forms an alloy with the elements generated by the reaction of carrier ions.

[0052] The material of the metal layer is selected appropriately depending on the type of carrier ion and is not corroded by the electrolyte. Examples of the metal layer include an aggregate of particles containing the alloy-forming metal, a plate or mesh made of a material containing the alloy-forming metal, a porous body carrying the alloy-forming metal, and a porous body made of the alloy-forming metal. Examples of the alloy include a complete solid solution alloy, a eutectic alloy, a hypoeutectic alloy, a hypereutectic alloy, and a peritectic alloy.

[0053] FIG. 3 is a schematic diagram of the conductive layer 19. The conductive layer 19 includes a capture body 20 that has electronic conductivity and adsorbs molecules, for example. The molecules include elements produced by the reaction of carrier ions. The molecules may include one or more elements that constitute the electrolyte layer 19. Any capture body 20 that has a molecular adsorption site can be used without limitation. The adsorption mechanism of the capture body 20 may be either chemical adsorption or physical adsorption.

[0054] The capture body 20 used is one that is not corroded by the electrolyte. Examples of the capture body 20 include an organic polymer porous body with electron conductivity, a porous gel such as conductive tin oxide, a conductive porous ceramic such as aluminum nitride, and a carbon-based porous body. The organic polymer porous body can be obtained by electrolytic polymerization or chemical redox polymerization of polyaniline, polypyrrole, polythiophene, etc. The carbon-based porous body can be exemplified by nanocarbon materials (graphite, graphene, carbon nanotubes).

[0055] FIG. 3 is a schematic diagram of a conductive layer 19 including a capture body 20 made of graphene. The capture body 20 has adsorption sites 21, 22, 23, and 24 located on the side of the graphene, inside the graphene, in the valleys of the graphene, and between the graphene, respectively. Molecules produced by the reductive decomposition of compounds (e.g., electrolyte solution or binder) constituting the electrolyte layer 18 are adsorbed onto the adsorption sites 21, 22, 23, and 24. The molecules contain one or more elements constituting the electrolyte layer 18. The molecules include a first phase 25 and a second phase 26, and the first phase 25 is closer to the capture body 20 than the second phase 26. This shows that the first phase 25 is adsorbed to the capture body 20 before the second phase 26.

[0056] When the electricity storage device 10 is charged, the metal is mainly deposited in the second phase 26. The metal deposited in the second phase 26 is likely to become metal ions when discharged. That is, the ratio of elements that are likely to become ions when discharged to elements contained in the second phase 26 in a fully charged state is greater than the ratio of elements that are likely to become ions when discharged to elements contained in the first phase 25 in a fully charged state.

[0057] An example of a method for manufacturing the electricity storage device 10 will be described using a lithium ion battery as an example. 0.5 Mn 0.3 Co 0.2 O2), a conductive additive, and a solution of a binder are mixed to prepare a slurry for the active material layer 13. The slurry applied to the current collector 12 is dried and then cut to a predetermined size to prepare a positive electrode 11 in which the active material layer 13 is laminated on the current collector 12.

[0058] A slurry for the electrolyte layer 18 is prepared by mixing an electrolyte solution in which a metal salt (LiFSI in this embodiment) is dissolved in a solvent (ionic liquid P13FSI in this embodiment), a solid electrolyte, and a polymer (silicone resin in this embodiment) with a solution in which a binder is dissolved. The slurry is applied to an active material layer 17 (lithium metal foil in this embodiment) attached to a current collector 16, and then dried to prepare the electrolyte layer 18. A conductive layer 19 (a graphene sheet in this embodiment) is laminated on the electrolyte layer 18, and then cut to a predetermined size to prepare the negative electrode 15, which includes, in order, the current collector 16, the active material layer 17, the electrolyte layer 18, and the conductive layer 19.

[0059] Terminals (not shown) are connected to the current collectors 12 and 16, respectively, and the positive electrode 11 and separator 13 are immersed in an electrolyte. The negative electrode 15, separator 14, and positive electrode 11 are stacked in this order, and sealed by vacuum lamination with the terminals extended to the outside, to produce the electricity storage device 10.

[0060] Next, a current is passed from the negative electrode 15 to the positive electrode 11 of the electricity storage device 10, reducing the compound contained in the electrolyte layer 18. For example, elements are incorporated into the conductive layer 19 by charging and discharging the electricity storage device 10. Constant current-constant voltage charging and discharging (CC·CV charging and CC·CV discharging) is suitable for charging and discharging the electricity storage device 10. This is because constant voltage charging and discharging can reduce the amount of active material that remains unreacted during constant current charging and discharging.

[0061] For example, in a five-cycle charge / discharge cycle, in an atmosphere of 25°C, each charge is performed at a constant current of 0.2 C until the terminal voltage reaches the upper charging voltage limit (e.g., 4.3 V), followed by a constant voltage charge of 0.01 C. The first and second cycles involve a constant current discharge of 0.2 C until the terminal voltage reaches 3.0 V, followed by a constant voltage discharge of 0.01 C. The third cycle involves a constant current discharge of 0.5 C until the terminal voltage reaches 3.0 V, followed by a constant voltage discharge of 0.01 C. The fourth cycle involves a constant current discharge of 2 C until the terminal voltage reaches 3.0 V, followed by a constant voltage discharge of 0.01 C. The fifth cycle involves a constant current discharge of 0.2 C until the terminal voltage reaches 3.0 V, followed by a constant voltage discharge of 0.01 C.

[0062] When a current is passed from current collector 16 of negative electrode 15 to current collector 12 of positive electrode 11 of electricity storage device 10, metallic lithium is deposited at the interface between electrolyte layer 18 and active material layer 17. When lithium dendrites grow in electrolyte layer 18 toward positive electrode 11, electrolyte layer 18, which has become electronically conductive due to the dendrites, is electrically connected to conductive layer 19, which also has electronic conductivity, and metallic lithium is also deposited at the interface between conductive layer 19 and separator 14.

[0063] The electronic conductivity of electrolyte layer 18, which contains a lithium-ion conductive solid electrolyte and an electrolytic solution, is lower than that of active material layer 17, and therefore electronic conduction is rate-limiting for the reaction at the interface between conductive layer 19 and separator 14. As a result, the difference between the lithium ion concentration at the interface between conductive layer 19 and separator 14 and the lithium ion concentration in separator 14 is smaller than the difference between the lithium ion concentration at the interface between active material layer 17 and separator 14 and the lithium ion concentration in separator 14 when electrolyte layer 18 and conductive layer 19 are not present.

[0064] Therefore, the reaction at the interface between conductive layer 19 and separator 14 occurs almost uniformly across the entire interface between conductive layer 19 and separator 14, compared to the reaction at the interface between active material layer 17 and separator 14 when electrolyte layer 18 and conductive layer 19 are not present. As a result, a phase with a structure different from that of electrolyte layer 18 is formed at the interface between conductive layer 19 and separator 14 due to reduction of the compound contained in electrolyte layer 18, and this phase is incorporated into conductive layer 19.

[0065] Because the electricity storage device 10 has the conductive layer 19 and the electrolyte layer 18 between the separator 14 and the active material layer 17, the reaction of metallic lithium being deposited on the conductive layer 19 during charging occurs almost uniformly over the entire interface between the separator 14 and the conductive layer 19, compared to the reaction at the interface between the active material layer 17 and the separator 14 when the electricity storage device 10 does not have the conductive layer 19 or the electrolyte layer 18. The deposited metal is taken up into the conductive layer 19, which reduces the growth of dendrites, which are needle-like dendritic crystals.

[0066] Furthermore, during charging, metal is also deposited inside the conductive layer 19, and the deposited metal is taken into the conductive layer 19. Since the element filling rate in the conductive layer 19 is improved, dendrites growing in the conductive layer 19 can be reduced.

[0067] In order to reduce dendrite growth, it is not necessary to provide the electricity storage device with a device for pressurizing the single battery (cell) as in the prior art and to charge and discharge the cell while pressurizing it, so it is possible to reduce dendrite growth while suppressing an increase in the mass and volume of the electricity storage device 10. Because an increase in the mass and volume of the electricity storage device 10 can be suppressed, the energy density of the electricity storage device 10 can be ensured.

[0068] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0069] In the embodiment, the method for manufacturing the electricity storage device 10 has been described using a lithium ion battery as an example, but the present invention is not limited to this.+ Other ion batteries, electrochemical capacitors, metal-air batteries, etc. that use other ions as carrier ions can also be manufactured in the same manner as in the above embodiment.

[0070] In the embodiment, the electricity storage device 10 has been described as including a positive electrode 12 in which an active material layer 13 is provided on one side of a current collector 12, and a negative electrode 16 in which an active material layer 17 is provided on one side of a current collector 16, but the present invention is not necessarily limited to this. For example, it is of course possible to apply each element in the embodiment to an electricity storage device including electrode layers in which an active material layer 13 and an active material layer 17 are provided on both sides of a current collector 12 (so-called bipolar electrodes). If bipolar electrodes and separators 14 are alternately stacked and housed in a case (not shown), an electricity storage device with a so-called bipolar structure can be obtained. [Explanation of symbols]

[0071] 10. Energy storage devices 11 Positive electrode 14 Separator 15 negative electrode 17 Active material layer 18 Electrolyte layer 19 Conductive Layer 20 Capture Body 25 First Phase 26 Second Phase

Claims

1. An electricity storage device utilizing ionic conduction, comprising: a positive electrode; a negative electrode; and a separator separating the positive electrode and the negative electrode, The negative electrode is arranged in the order toward the positive electrode as follows: an active material layer containing an active material that undergoes a redox reaction; an electrolyte layer that contains a solid electrolyte having carrier ion conductivity and an electrolytic solution and is in contact with the active material layer; a conductive layer that has electronic conductivity and is in contact with the electrolyte layer and that takes in elements that have precipitated at the interface between the active material layer and the electrolyte layer.

2. The electricity storage device according to claim 1 , wherein the conductive layer includes a metal layer that forms an alloy with an element generated by the reaction of the carrier ions.

3. the conductive layer has electronic conductivity and includes a capture body that adsorbs molecules; The electricity storage device according to claim 1 , wherein the molecules contain elements produced by the reaction of the carrier ions.

4. the molecules adsorbed to the capture body include a first phase and a second phase in order of proximity to the capture body; 4. The electricity storage device according to claim 3, wherein a ratio of the elements that are likely to become ions during discharge to the elements contained in the second phase when the device is fully charged is greater than a ratio of the elements that are likely to become ions during discharge to the elements contained in the first phase when the device is fully charged.

5. the carrier ions are lithium ions, 5. The electricity storage device according to claim 1, wherein the solid electrolyte is an oxide containing Li, La, and Zr and having a garnet-type crystal structure.

6. A method for manufacturing an electricity storage device that utilizes ionic conduction and includes a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode, The negative electrode includes an active material layer containing an active material that undergoes an oxidation-reduction reaction; an electrolyte layer that contains a solid electrolyte having carrier ion conductivity and an electrolytic solution and is in contact with the active material layer; a conductive layer having electronic conductivity, in contact with the electrolyte layer, and capturing the carrier ions; a step of stacking the positive electrode, the separator, and the negative electrode in this order; and applying a current from the negative electrode to the positive electrode to deposit elements contained in the electrolyte layer at the interface between the active material layer and the electrolyte layer.

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