Electricity storage device and method for manufacturing same

Abstract

Provided are: an electricity storage device (10) capable of suppressing increases in the mass and volume of the electricity storage device and of reducing the growth of dendrites; and a method for manufacturing the electricity storage device (10). This electricity storage device is provided with a positive electrode (11), a negative electrode (15), and a separator (14) that separates the positive electrode from the negative electrode, and the negative electrode contains, in the order toward the positive electrode: an active material layer (17) that contains an active material that reduces carrier ions; an electrolyte layer (18) that is in contact with the active material layer and contains an electrolyte solution and a conductive solid electrolyte having carrier ions; and a conductive layer (19) that has electron conductivity, is in contact with the electrolyte layer, and captures an element deposited at the interface between the active material layer and the electrolyte layer.

Description

Energy storage devices and their manufacturing methods Technical Field

[0001] This invention relates to energy storage devices that utilize ions as charge carriers and methods for manufacturing the same. Background Technology

[0002] In energy storage devices that utilize ions as charge carriers, metal sometimes deposits at the negative electrode during charging. Due to variations in ion concentration and electric field distribution during deposition, needle-like dendritic crystals (dendritic crystals) easily form at the negative electrode. Dendritic crystal growth reduces charging efficiency and can cause malfunctions. Non-Patent Document 1 discloses the following prior art: a device for pressurizing individual cells is incorporated into the energy storage device, and charging and discharging are performed simultaneously with pressurizing the individual cells, thereby densifying the deposits and reducing dendrite growth.

[0003] Existing technical documents

[0004] Non-patent literature

[0005] Non-Patent Document 1: Shoichi Matsuda, "The Influence of Constraint Pressure in the Precipitation and Dissolution Reaction of Lithium Metal Electrodes," Summary of the 62nd Battery Symposium, Battery Technology Committee of the Electrochemical Society, November 30, 2021 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the prior art, the increase in mass and volume of the energy storage device corresponds to the increase in the pressure of the single cell, thus resulting in a significant decrease in the actual energy density compared to the theoretical energy density determined by the active materials contained in the energy storage device.

[0008] This invention was made to solve this problem, and its purpose is to provide an energy storage device and a method thereof that can suppress the increase in mass and volume of the energy storage device and reduce dendrite growth.

[0009] Methods for solving problems

[0010] A first method for achieving this objective is an energy storage device comprising a positive electrode, a negative electrode, and a membrane separating the positive and negative electrodes, and utilizing ion conduction, wherein the negative electrode comprises, in order toward the positive electrode: an active material layer containing an active material that undergoes a redox reaction; an electrolyte layer containing a solid electrolyte and an electrolyte solution with carrier ion conductivity, and in contact with the active material layer; and a conductive layer having electronic conductivity and in contact with the electrolyte layer, and capturing elements deposited at the interface between the active material layer and the electrolyte layer.

[0011] The second method is as follows: In the first method, the conductive layer comprises a metal layer that forms an alloy with the elements generated by the reaction of the carrier ions.

[0012] The third method is as follows: In the first method, the conductive layer contains a trap that has electronic conductivity and adsorbs molecules, and the molecules contain elements generated by the reaction of the carrier ions.

[0013] The fourth method is as follows: In the third method, the molecules adsorbed on the trapping body contain a first phase and a second phase in order of proximity to the trapping body. In the fully charged state, the proportion of elements in the second phase that are likely to become ions during discharge is greater than the proportion of elements in the first phase that are likely to become ions during discharge.

[0014] The fifth method is as follows: In any one of the methods 1 to 4, the carrier ion is lithium ion, and the solid electrolyte is an oxide containing Li, La and Zr with a garnet-type crystal structure.

[0015] The sixth method is a manufacturing method for an energy storage device comprising a positive electrode, a negative electrode, and a separator isolating the positive and negative electrodes, and utilizing ion conduction. The negative electrode comprises: an active material layer containing an active material that undergoes a redox reaction; an electrolyte layer containing a solid electrolyte and an electrolyte solution with carrier ion conductivity, and in contact with the active material layer; and a conductive layer with electronic conductivity, in contact with the electrolyte layer, and capturing carrier ions. The manufacturing method includes: a step of sequentially stacking the positive electrode, the separator, and the negative electrode; and a step of allowing current to flow from the negative electrode to the positive electrode, causing elements contained in the electrolyte layer to precipitate at the interface between the active material layer and the electrolyte layer.

[0016] Invention Effects

[0017] According to the manufacturing method of the energy storage device of the present invention, when current flows from the negative electrode to the positive electrode, elements contained in the electrolyte layer are deposited at the interface between the electrolyte layer and the active material layer. When dendrites grow in the electrolyte layer towards the positive electrode, elements are also deposited at the interface of the electrolyte layer, which becomes electronically conductive due to the dendrites. The electronic conductivity of the electrolyte layer is lower than that of the active material layer, therefore the reaction at the interface of the electrolyte layer is rate-limited 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 when there is no electrolyte layer. Therefore, compared with the reaction at the interface of the negative electrode when there is no electrolyte layer, the reaction at the interface of the electrolyte layer occurs approximately uniformly throughout the entire interface of the electrolyte layer. Furthermore, the conductive layer, which is electronically conductive, is in contact with the electrolyte layer, so elements are also deposited in the conductive layer. The deposited elements are captured by the conductive layer.

[0018] The energy storage device of the present invention has a conductive layer and an electrolyte layer. Therefore, the element precipitation reaction during charging occurs approximately uniformly throughout the entire interface of the conductive layer compared to the reaction at the interface of the negative electrode when the energy storage device lacks a conductive layer and an electrolyte layer. Elements also precipitate within the conductive layer, but these precipitated elements are captured by the conductive layer, thereby increasing the elemental fill rate in the conductive layer and reducing dendrite growth. Since it is not necessary to simultaneously pressurize and charge / discharge the individual cells to reduce dendrite growth, the increase in the mass and volume of the energy storage device can be suppressed, and dendrite growth can be reduced. Attached Figure Description

[0019] Figure 1 is a cross-sectional view of an energy storage device according to one embodiment.

[0020] Figure 2 is a schematic diagram illustrating the garnet-type crystal structure.

[0021] Figure 3 is a schematic diagram of the conductive layer. Detailed Implementation

[0022] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG1 is a schematic cross-sectional view of an energy storage device 10 according to one embodiment. The energy storage device 10 utilizes ions as charge carriers. Examples of ions that serve as charge carriers include Li. + Na + K + Mg 2+ Cu + Ag + Metal ions, OH - F - H - It can be anion, but there is no restriction on the type of ion.

[0023] Storage device 10 can be exemplified by using Li + Na + K + Mg 2+ F - H - Lithium-ion batteries using plasma as charge carriers; plasma batteries utilizing redox reactions of electrodes, redox reactions of ions in the electrolyte, and electrochemical capacitors with double electric layers; metal-air batteries using oxygen from the air as the positive electrode active material and metals such as Li, Zn, Al, Mg, and Fe as the negative electrode active material. The energy storage device 10 sequentially includes a positive electrode 11, a separator 14, and a negative electrode 15.

[0024] There are no limitations as long as the separator 14 isolates the positive electrode 11 from the negative electrode 15. Examples of separator 14 include: (1) a porous separator with electrically insulating properties, in which carrier ions contained in the electrolyte can move; (2) a separator in which a solid electrolyte with ionic conductivity replaces the porous structure and the electrolyte; (3) a separator in which a gel-like electrolyte with ionic conductivity is provided, or a separator in which a mixture of a solid electrolyte with ionic conductivity and the electrolyte is provided. In the case of separator 14 (1), the energy storage device 10 can be categorized as a liquid metal-ion battery, a metal-air battery, or an electrochemical capacitor. In the case of separator 14 (2), the energy storage device 10 is a so-called all-solid-state battery. In the case of separator 14 (3), the energy storage device 10 is a so-called semi-solid-state battery.

[0025] In the positive electrode 11, the current collector 12 is stacked with the reaction layer 13. The current collector 12 is a conductive component. Examples of materials for the current collector 12 include metals selected from Ni, Ti, Fe and Al, alloys containing two or more of these elements, stainless steel, and carbon materials.

[0026] When the energy 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 can be appropriately selected according to the type of carrier ion.

[0027] Regarding the reaction layer 13, in the case where the energy storage device 10 is a metal-air battery, atmospheric oxygen is used as the positive electrode active material. Therefore, it includes a gas diffusion layer for air diffusion and a catalyst layer for oxygen reduction reaction. The catalyst layer includes decomposition catalysts such as manganese oxides and porphyrin compounds that enhance the decomposition ability of hydrogen peroxide ions.

[0028] The negative electrode 15 comprises an active material layer 17, an electrolyte layer 18, and a conductive layer 19 in order of orientation toward the positive electrode 11. A conductive current collector 16 may be disposed on the active material layer 17. Examples of materials for the current collector 16 include metals selected from Ni, Ti, Fe, Cu, and Si, alloys containing two or more of these elements, stainless steel, and carbon materials.

[0029] The active material layer 17 contains the active material (negative electrode active material). There are no restrictions on the material as long as it can intercalate / deintercalate with the support ions. The active material can be appropriately selected based on the type of support ions.

[0030] In the case where the energy storage device 10 is an ion battery or electrochemical capacitor that uses metal ions as carrier ions, examples of active materials include porous carbon, natural graphite, artificial graphite, easily graphitized carbon (hard carbon), difficult-to-graphitize carbon (soft carbon), carbon fiber, and other carbon-based materials, as well as Li4Ti5O. 12The active material can be 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. SiOx can be exemplified by oxides of Si or materials having a structure in which microcrystalline or amorphous Si is dispersed in an amorphous SiO2 matrix. In the case where the energy storage device 10 is a metal-air battery, the active material can be exemplified by metals such as Li, Zn, Al, Mg, and Fe. One or more of these materials can be selected as the active material.

[0031] The active material layer 17 can be exemplified as an aggregate of particles composed of these materials, a plate composed of these materials, or a porous body loaded with these materials. Preferably, it is lithium metal or an alloy-based active material with a higher density than carbon-based active materials. When the active material layer 17 is an aggregate of particles, a conductive additive can be included in the active material layer 17 to reduce its resistance. Examples of conductive additives include carbon black, acetylene black, Ketjen black, carbon fiber, Ni, Pt, and Ag.

[0032] Electrolyte layer 18 comprises a solid electrolyte and an electrolyte solution with lithium-ion conductivity. The solid electrolyte includes one or more selected from sulfide-based, oxide-based, hydride-based, halide-based, and organic-based systems. Examples of sulfide-based solid electrolytes include crystalline thio-LISICON type (lithium thiophosphate superion conductor type), Li... 10 GeP2S 12 Type, sulfide-germanium ore type, Li7P3S 11 Type, represented by Li2S-P2S5, glass or glass-ceramic system.

[0033] Oxide-based solid electrolytes can be exemplified by oxides with a NASICON-type (sodium superionic conductor) structure, oxides with a perovskite structure, and oxides with a garnet-type structure. Oxides with a NASICON-type structure can be listed as oxides containing at least Li, M (where 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 with a perovskite structure can be listed as oxides containing at least Li, Ti, and La, such as La. 2 / 3-X Li 3X TiO3.

[0034] Examples of hydride-based solid electrolytes include solid solutions of LiBH4 with lithium halides (LiI, LiBr, LiCl) and lithium amines (LiNH2). Examples of halide-based solid electrolytes include Li3YCl6. Examples of organic-based solid electrolytes include polyethylene oxide, polypropylene oxide, and polyacrylonitrile.

[0035] The solid electrolyte is preferably a composite oxide containing Li, La, and Zr with a garnet-type crystal structure. This is because it has 10 -3 It exhibits ionic conductivity on the order of S / cm and resistance to reduction by metallic lithium. The garnet-type crystal structure is based on the general formula C3A2B3O. 12 express.

[0036] Figure 2 is a schematic diagram illustrating a garnet-type crystal structure. In this structure, the C site Sc forms a dodecahedral coordination with the oxygen atom Oa, the A site Sa forms an octahedral coordination with Oa, and the B site Sb forms a tetrahedral coordination with Oa. In a typical garnet-type crystal structure, solid electrolyte 19 may contain Li at sites that form octahedral coordination with Oa and become vacancies V. Vacancy V is, for example, a site sandwiched between B sites Sb1 and Sb2. The Li present in vacancy V forms octahedral coordination with the oxygen atom Oa that constitutes the octahedron containing the tetrahedron face Fb1 forming B site Sb1 and the tetrahedron face Fb2 forming B site Sb2. For example, Li7La3Zr2O has a garnet-type crystal structure. 12 In this context, La can occupy site C (Sc), Zr can occupy site A (Sa), and Li can occupy site B (Sb) and the void (V).

[0037] Garnet-type crystal structures can be identified using X-ray diffraction. The garnet-type crystal structure corresponds to X-ray diffraction file No. 422259 (Li7La3Zr2O) in the CSD (Cambridge Structural Database). 12 Similar XRD patterns. Solid electrolytes sometimes differ from No. 422259 in the types of constituent elements, Li concentration, etc., resulting in different diffraction angles and intensity ratios. This representative crystal structure is cubic (space group Ia-3d (- indicates an overline signifying a rotational inversion operation), JCPDS: 84-1753).

[0038] Solid electrolytes with garnet-type crystal structures can typically be exemplified by Li7La3Zr2O. 12 In solid electrolytes, Li7La3Zr2O 12A portion of the constituent elements may be replaced by other elements, or other elements may be added in trace amounts without replacing the constituent elements. Other elements may be exemplified by 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 the lanthanides (excluding La).

[0039] Solid electrolytes, for example, include 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 Zr2O12 .

[0040] Solid electrolytes are particularly preferred to be solid electrolytes containing at least one of Mg and element A (A being at least one element selected from the group consisting of Ca, Sr, and Ba) and whose molar ratios satisfy all of the following (1) to (3); or solid electrolytes containing both Mg and element A and whose molar ratios satisfy all of the following (4) to (6). To improve the ionic conductivity of the solid electrolyte, element A is preferably Sr. This is because if Li7La3Zr2O 12 When some of the constituent elements are replaced by Mg and Sr, the ionic conductivity of the solid electrolyte increases, and metallic lithium is deposited more densely.

[0041] (1) 1.33≤Li / (La+A)≤3

[0042] (2) 0 ≤ Mg / (La+A) ≤ 0.5

[0043] (3) 0 ≤ A / (La+A) ≤ 0.67

[0044] (4) 2.0 ≤ Li / (La+A) ≤ 2.5

[0045] (5) 0.01 ≤ Mg / (La+A) ≤ 0.14

[0046] (6) 0.04 ≤ A / (La+A) ≤ 0.17

[0047] Let's return to Figure 1 for further explanation. The electrolyte layer 18 contains an electrolyte solution that serves as the medium for the movement of carrier ions; it is a solution in which a metal salt is dissolved. There are no particular restrictions 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 carbonates, aliphatic carboxylic esters, phosphate esters, γ-lactones, ethers, nitrile compounds, sulfolane, dimethyl sulfoxide, fluorinated solvents, and ionic liquids. Mixtures of these may also be used.

[0048] Examples of carbonates include cyclic carbonates such as propylene carbonate, ethylene carbonate, butyl carbonate, vinylene carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate; and chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0049] Aliphatic carboxylic acid esters include methyl formate, methyl acetate, and ethyl propionate. Phosphate esters include trimethyl phosphate. Gamma-lactones include γ-butyrolactone. Ethers include chain ethers such as 1,2-dialkoxyethane, and cyclic ethers such as 1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran. Nitriles include acetonitrile and propionitrile. Fluorinated solvents are compounds and their derivatives in which hydrogen atoms of hydrocarbons are replaced with fluorine atoms.

[0050] Ionic liquids are compounds composed of cations and anions, and are liquids at room temperature and pressure. Using an ionic liquid as the solvent in an electrolyte can improve its flame retardancy. Ionic liquids have a relatively wide potential window, making them preferred. Ammonium and imidazole are preferably selected as ionic liquids. pyrrolidine and piperidine One or more of the groups are classified as cations.

[0051] The anionic composition of ionic liquids is not particularly limited. An example of anionic composition is BF4. - N(SO2F)2 - Inorganic anions; B(C6H5)4 - CH3SO3 - CF3SO3 - N(SO2CF3)2 - N(SO2C4F9)2 - Organic anions, such as N(SO₂F)₂, are sometimes used. - Abbreviated as [FSI] - : Bis(fluorosulfonyl)imide anion, N(SO2CF3)2 - Abbreviated as [TFSI] - : Bis(trifluoromethanesulfonyl)imide anion.

[0052] 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), and 1-ethyl-3-methylimidazolium. Bis(fluorosulfonyl)imide (EMI-FSI), 1-ethyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imine (EMI-TFSI), N-butyl-N-methylpiperidine Bis(fluorosulfonyl)imide, N-methyl-N-propylpiperidine Bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpyrrolidine Bis(fluorosulfonyl)imide (P13FSI), N-methyl-N-propylpyrrolidine Bis(trifluoromethanesulfonyl)imide (P13TFSI). Mixtures of these can also be used.

[0053] Ionic liquids can be solvated ionic liquids. Examples of solvated ionic liquids include materials in which metal salts are dissolved in sulfolane, sulfolane derivatives, or ethylene glycol dimethyl ether solvents such as tetraethylene glycol dimethyl ether.

[0054] Anions of metal salts can be exemplified by OH-.- Halogen 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, phenyl, or naphthyl group with 1-4 carbon atoms). Metal salts can also be mixtures of these.

[0055] The concentration of the metal salt in the electrolyte is 0.2 mol / dm³. 3 The above, preferably 0.5 mol / dm 3 The above explains why, as the salt concentration increases, the number of solvent molecules coordinated to the carrier ions increases, while the number of uncoordinated solvent molecules decreases, thus reducing the interfacial resistance of the solid electrolyte. The preferred salt concentration of the electrolyte is 4.0 mol / dm³. 3 The following is true. This is because the salt concentration of the electrolyte exceeds 4.0 mol / dm³. 3 At that time, the increase in electrolyte viscosity leads to a significant tendency for a decrease in ionic conductivity.

[0056] In the electrolyte layer 18, the volume of the solid electrolyte accounts for 52% or more and less than 100% of the total volume of the solid electrolyte and the electrolyte, preferably 61% or more and less than 100%. By combining the solid electrolyte and the electrolyte, the interfacial resistance of the solid electrolyte can be reduced, thus enabling the ion transport number of the electrolyte layer 18 to be greater than that of a typical electrolyte. As a result, the operational stability of the energy storage device 10 is increased.

[0057] Regarding the content (volume %) of the solid electrolyte, analysis was performed using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) at a randomly selected field of view of 5000x magnification from a cross-section of electrolyte layer 18. The elemental distribution was determined, or image analysis of the contrast of the backscattered electron image was performed to determine the area of ​​the solid electrolyte and the area of ​​the electrolyte solution. The proportion of the solid electrolyte area to the total area of ​​the solid electrolyte and the electrolyte solution was considered as the volume ratio, thus yielding the solid electrolyte content (volume %).

[0058] The cross-section of the electrolyte layer 18 used in the analysis is a polished surface, a surface obtained by irradiation 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 the electrolyte layer 18 in a tetrafunctional epoxy resin and then polishing it after curing.

[0059] The electrolyte layer 18 may include an adhesive for bonding the solid electrolyte. Examples of adhesives include fluorinated resins, polyolefins, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, styrene-butadiene rubber, and other rubber-like polymers. 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.

[0060] Polymers containing vinylidene fluoride (PVDF) are not particularly limited as long as they contain the -CH2CF2- group. Examples of PVDF polymers include homopolymers of PVDF and copolymers of PVDF with comonomers. Comonomers can include halogenated monomers (excluding PVDF) and non-halogenated comonomers. Halogenated monomers include chlorinated monomers such as vinyl chloride; fluorinated monomers such as trifluoroethylene, tetrafluoroethylene, trifluorochloroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ethers. Non-halogenated comonomers include olefins such as ethylene and propylene; acrylic monomers such as acrylic acid, methacrylic acid, their esters or salts; and vinyl monomers such as acrylonitrile, vinyl acetate, and styrene. One or more of the comonomers polymerize with PVDF to form copolymers.

[0061] The binder and electrolyte in electrolyte layer 18 can exist separately, or they can be mixed to form a gel. The solvent for dissolving the binder can be included in electrolyte layer 18. Preferably, the binder has a wider potential window than the electrolyte.

[0062] For purposes such as improving the electrochemical stability of the electrolyte layer 18, the electrolyte layer 18 may contain a polymer. Examples of polymer materials include polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polyamide, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyacrylonitrile, polycarbonate, and polysiloxane. The polymer may be in various shapes such as granules, fibers, and flakes.

[0063] The conductive layer 19 is a layer in contact with the electrolyte layer 18 and has electronic conductivity. The conductive layer 19 is used to capture 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 comprises, for example, a metal layer that forms an alloy with elements generated by the reaction of carrier ions.

[0064] Regarding the material of the metal layer, it is appropriately chosen to be non-corrosive to the electrolyte, depending on the type of carrier ions. Examples of metal layers include an aggregate containing particles of the metal forming the alloy, a plate or mesh made of a material containing the metal forming the alloy, a porous body loaded with the metal forming the alloy, and a porous body made of the metal forming the alloy. Examples of alloys include infinitely solid-solution alloys, eutectic alloys, hypoeutectic alloys, hypereutectic alloys, and peritectic alloys.

[0065] Figure 3 is a schematic diagram of the conductive layer 19. The conductive layer 19 may contain, for example, an electronically conductive trap 20 containing adsorbed molecules. The molecules contain elements generated by the reaction of carrier ions. The molecules may sometimes contain more than one of the elements constituting the electrolyte layer 19. The trap 20 may be any trap with molecular adsorption sites. The adsorption mechanism of the trap 20 may be either chemisorption or physisorption.

[0066] The trapping body 20 can be a trapping body that is not corroded by the electrolyte. Examples of trapping body 20 include porous organic polymers with electronic conductivity, porous gels such as conductive tin oxide, porous ceramics such as conductive aluminum nitride, and carbon-based porous bodies. Porous organic polymers are obtained through electrolytic polymerization or chemical redox polymerization of polyaniline, polypyrrole, polythiophene, etc. Examples of carbon-based porous bodies include carbon nanomaterials (graphite, graphene, carbon nanotubes).

[0067] Figure 3 shows a schematic diagram of a conductive layer 19 containing a graphene trap 20. Adsorption sites 21, 22, 23, and 24 of the trap 20 are respectively located on the side surface, inside the graphene, in the valley of the graphene, and between the graphene layers. Molecules generated by the reductive decomposition of compounds constituting the electrolyte layer 18 (e.g., electrolyte, binder) are adsorbed onto adsorption sites 21, 22, 23, and 24. The molecules contain one or more elements constituting the electrolyte layer 18. The molecules contain a first phase 25 and a second phase 26, with the first phase 25 closer to the trap 20 than the second phase 26. This indicates that the first phase 25 adsorbs onto the trap 20 before the second phase 26.

[0068] During charging of the energy storage device 10, the metal is mainly deposited in the second phase 26. The metal deposited in the second phase 26 readily becomes metal ions during discharge. That is, in the fully charged state, the proportion of elements in the second phase 26 that readily become ions during discharge is greater than the proportion of elements in the first phase 25 that readily become ions during discharge.

[0069] An example of the manufacturing method of the energy storage device 10 is illustrated using a lithium-ion battery. The positive electrode active material (in this embodiment, LiNi) is... 0.5 Mn 0.3 Co 0.2 O2), conductive additives, and a solution containing a binder are mixed to prepare a slurry for the active material layer 13. After the slurry coated on the current collector 12 is dried, it is cut into predetermined sizes to form a positive electrode 11 on which the active material layer 13 is stacked on the current collector 12.

[0070] A slurry for electrolyte layer 18 is prepared by mixing a solution containing a binder dissolved in an electrolyte (LiFSI in this embodiment) formed by dissolving a metal salt in a solvent (P13FSI in this embodiment), a solid electrolyte, and a polymer (silicone resin in this embodiment). The slurry, coated onto the active material layer 17 (lithium metal foil in this embodiment) adhered to the current collector 16, is dried to form electrolyte layer 18. A conductive layer 19 (graphene sheet in this embodiment) is then laminated onto electrolyte layer 18 and cut to a predetermined size to form a negative electrode 15 comprising the current collector 16, active material layer 17, electrolyte layer 18, and conductive layer 19 in sequence.

[0071] Terminals (not shown) are connected to current collectors 12 and 16 respectively, and the positive electrode 11 and the separator 13 are immersed in electrolyte. The negative electrode 15, the separator 14 and the positive electrode 11 are stacked in that order, and the device is sealed by vacuum lamination with the terminals extended outward to form the energy storage device 10.

[0072] Next, current flows from the negative electrode 15 to the positive electrode 11 of the energy storage device 10 to reduce the compounds contained in the electrolyte layer 18. For example, elements are captured by the conductive layer 19 through the charging and discharging of the energy storage device 10. The charging and discharging of the energy storage device 10 is preferably constant current-constant voltage charging and discharging (CC·CV charging-CC·CV discharging). This is because by performing constant voltage charging and discharging, the unreacted portion of the active material remaining during constant current charging and discharging can be reduced.

[0073] An example of a 5-cycle charge-discharge process is shown. In an atmosphere at 25°C, charging is performed with a constant current of 0.2C each time until the terminal voltage reaches the upper charging limit (e.g., 4.3V), followed by constant voltage charging until the current value becomes 0.01C. In the first and second cycles, discharging is performed with a constant current of 0.2C until the terminal voltage reaches 3.0V, followed by constant voltage discharging until the current value becomes 0.01C. In the third cycle, discharging is performed with a constant current of 0.5C until the terminal voltage reaches 3.0V, followed by constant voltage discharging until the current value becomes 0.01C. In the fourth cycle, discharging is performed with a constant current of 2C until the terminal voltage reaches 3.0V, followed by constant voltage discharging until the current value becomes 0.01C. In the fifth cycle, discharging is performed with a constant current of 0.2C until the terminal voltage reaches 3.0V, followed by constant voltage discharging until the current value becomes 0.01C.

[0074] When current flows from the current collector 16 of the negative electrode 15 of the energy storage device 10 to the current collector 12 of the positive electrode 11, metallic lithium is deposited at the interface between the electrolyte layer 18 and the active material layer 17. As lithium dendrites grow in the electrolyte layer 18 toward the positive electrode 11, the electrolyte layer 18, which becomes electronically conductive, is electrically connected to the conductive layer 19, which also has electronic conductivity. Metallic lithium is also deposited at the interface between the conductive layer 19 and the separator 14.

[0075] The electrolyte layer 18, which contains a solid electrolyte and an electrolyte solution with lithium-ion conductivity, has lower electronic conductivity than the active material layer 17. Therefore, the reaction at the interface between the conductive layer 19 and the membrane 14 is rate-limited by electronic conduction. As a result, the difference between the lithium-ion concentration at the interface between the conductive layer 19 and the membrane 14 and the lithium-ion concentration in the membrane 14 is smaller than the difference between the lithium-ion concentration at the interface between the active material layer 17 and the membrane 14 and the lithium-ion concentration in the membrane 14 when neither the electrolyte layer 18 nor the conductive layer 19 is present.

[0076] Therefore, compared to the reaction at the interface between the active material layer 17 and the membrane 14 when there is no electrolyte layer 18 and conductive layer 19, the reaction at the interface between the conductive layer 19 and the membrane 14 occurs substantially uniformly across the entire interface. As a result, through the reduction of the compounds contained in the electrolyte layer 18, a phase with a different structure from that of the electrolyte layer 18 is formed at the interface between the conductive layer 19 and the membrane 14, and this phase is captured by the conductive layer 19.

[0077] The energy storage device 10 has a conductive layer 19 and an electrolyte layer 18 between the separator 14 and the active material layer 17. Therefore, the reaction of lithium metal deposition in the conductive layer 19 during charging occurs approximately uniformly across 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 there is no conductive layer 19 and electrolyte layer 18 in the energy storage device 10. The deposited metal is captured by the conductive layer 19, thus reducing the growth of dendrites as needle-like dendritic crystals.

[0078] Furthermore, during charging, metal is also deposited inside the conductive layer 19, and the deposited metal is captured by the conductive layer 19. The elemental filling rate in the conductive layer 19 is increased, thus reducing the dendrites growing in the conductive layer 19.

[0079] To reduce dendrite growth, instead of incorporating a device for pressurizing individual cells in the energy storage device as in existing technologies, charging and discharging are performed simultaneously with pressurization of the individual cells. This suppresses the increase in mass and volume of the energy storage device 10 and reduces dendrite growth. Because the increase in mass and volume of the energy storage device 10 can be suppressed, the energy density of the energy storage device 10 can be ensured.

[0080] The present invention has been described above based on the embodiments, but the present invention is not limited to any of the above embodiments, and it is easy to deduce that various modifications and variations can be made without departing from the spirit of the present invention.

[0081] In this embodiment, a method for manufacturing the energy storage device 10 using a lithium-ion battery has been described as an example, but the method is not limited thereto. + Other ion batteries, electrochemical capacitors, metal-air batteries, etc., that use ion carriers as ions can also be manufactured in the same manner as described above.

[0082] In the embodiment, the energy storage device 10 is described as having a positive electrode 12 with an active material layer 13 on one side of the current collector 12 and a negative electrode 16 with an active material layer 17 on one side of the current collector 16, but it is not necessarily limited to this. For example, in an energy storage device having electrode layers (so-called bipolar electrodes) with active material layers 13 and 17 respectively on both sides of the current collector 12, the elements in the embodiment can certainly be applied. If the bipolar electrodes and the separator 14 are alternately stacked and housed in a housing (not shown), a so-called bipolar structure energy storage device is obtained.

[0083] Symbol Explanation

[0084] 10. Energy Storage Devices

[0085] 11 Positive electrode

[0086] 14. Diaphragm

[0087] 15 Negative electrode

[0088] 17. Active Material Layer

[0089] 18 Electrolyte layer

[0090] 19. Conductive layer

[0091] 20 capture body

[0092] 25 First Phase

[0093] 26 Second Phase

Claims

1. An energy storage device comprising a positive electrode, a negative electrode, and a separator separating the positive electrode from the negative electrode, and utilizing ion conduction, wherein, The negative electrode comprises, in order of orientation toward the positive electrode: an active material layer containing an active material that undergoes a redox reaction; an electrolyte layer containing a solid electrolyte and an electrolyte solution with carrier ions, and in contact with the active material layer; and a conductive layer having electronic conductivity and in contact with the electrolyte layer, and capturing elements deposited at the interface between the active material layer and the electrolyte layer.

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

3. The energy storage device according to claim 1, wherein, The conductive layer contains a trapping body that is electronically conductive and adsorbs molecules, the molecules containing elements generated by the reaction of the carrier ions.

4. The energy storage device according to claim 3, wherein, The molecules adsorbed on the trapping body contain a first phase and a second phase in order of proximity to the trapping body. In the fully charged state, the proportion of elements in the second phase that are prone to becoming ions during discharge is greater than the proportion of elements in the first phase that are prone to becoming ions during discharge during discharge.

5. The energy storage device according to any one of claims 1 to 4, wherein, The carrier ion is lithium ion, and the solid electrolyte is an oxide containing Li, La and Zr with a garnet-type crystal structure.

6. A method for manufacturing an energy storage device, comprising a positive electrode, a negative electrode, and a separator separating the positive electrode from the negative electrode, and utilizing ion conduction in the energy storage device, wherein... The negative electrode comprises: an active material layer containing an active material that undergoes a redox reaction; an electrolyte layer containing a solid electrolyte and an electrolyte solution with carrier ions conductivity, and in contact with the active material layer; and a conductive layer having electronic conductivity and in contact with the electrolyte layer, and capturing the carrier ions. The manufacturing method includes: a step of sequentially stacking the positive electrode, the separator, and the negative electrode; and a step of allowing current to flow from the negative electrode to the positive electrode, causing elements contained in the electrolyte layer to be deposited at the interface between the active material layer and the electrolyte layer.

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