All-solid-state batteries

Abstract

Provided is an all-solid-state battery capable of improving cycle characteristics. The all-solid-state battery comprises a first current collector layer, a first collector tab protruding from an edge of the first current collector layer, a first active material layer stacked on the first current collector layer, a second current collector layer, a second collector tab protruding from an edge of the second current collector layer, a second active material layer stacked on the second current collector layer, and a solid electrolyte layer disposed between the first and second active material layers and containing a polymer electrolyte, the solid electrolyte layer being disposed so as to also cover end surfaces of the first current collector layer and the first active material layer, and the first collector tab protruding through the solid electrolyte layer.

Description

Technical Field

[0001] The present disclosure relates to all-solid-state batteries. Background Art

[0002] Patent Document 1 discloses an all-solid-state battery having a resin layer covering the side surfaces of an all-solid-state battery stack, and shows the use of a sulfide solid electrolyte.

[0003] Patent Document 2 discloses a bipolar lithium ion battery having a bipolar electrode current collector in which a first current collector, an adhesive resin layer having through-holes, and a second current collector are sequentially stacked, and the first current collector and the second current collector are bonded via the adhesive resin layer.

[0004] Patent Document 3 discloses a structure in which a solid electrolyte layer and an insulating portion on the side surface of a stacked body include a solid electrolyte material composed of a sulfide solid electrolyte material or an oxide solid electrolyte material.

[0005] Patent Document 4 discloses a structure in which a solid electrolyte layer and a side surface of a stacked body are formed as the same member.

[0006] Prior art literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-192610

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-073374

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2014-235990

[0010] Patent Document 4: Japanese Patent Application Publication No. 2018-142534 Summary of the Invention

[0011] In all-solid-state batteries, cycling characteristics (such as capacity retention) degrade due to volume changes in the negative electrode active material during charge and discharge. This is because the mechanical properties of the sulfide solid electrolyte cannot withstand the expansion and contraction of the negative electrode active material during charge and discharge, causing delamination and cracking at the interface between the negative electrode layer and the solid electrolyte layer, at the interface between the negative electrode active material and the solid electrolyte layer, and within the solid electrolyte layer.

[0012] Therefore, in view of the above-mentioned problems, an object of the present disclosure is to provide an all-solid-state battery capable of improving cycle characteristics.

[0013] In all-solid-state batteries, ions and electrons are conducted at the interface between solids, so the bonding state at this interface significantly affects battery performance. On the other hand, when the active material expands and contracts (volume changes) during charge and discharge, the interface cannot maintain a good bonding state, resulting in increased resistance.

[0014] For example, Si-based active materials are well known as high-capacity negative electrode active materials, but their volume changes associated with charge and discharge are large. In order to suppress the battery performance degradation caused by the expansion and contraction of the negative electrode active material, the inventors considered using a soft polymer electrolyte as the solid electrolyte of the negative electrode layer. However, the ion conductivity of the polymer electrolyte is mostly lower than that of the inorganic solid electrolyte. Therefore, from the viewpoint of improving battery performance, it is envisaged to use an inorganic solid electrolyte in the positive electrode layer. Moreover, by using a polymer electrolyte and an inorganic solid electrolyte in combination, it is possible to obtain good battery performance while suppressing the deterioration of the bonding state of the solid and solid interfaces in the negative electrode layer.

[0015] However, the inventors have come to the following understanding: In an all-solid-state battery in which one of the positive and negative electrode layers contains an inorganic solid electrolyte and the other contains a polymer electrolyte, the inorganic solid electrolyte is generally harder than the polymer electrolyte. Therefore, the layer containing the inorganic solid electrolyte (e.g., the positive electrode layer) becomes a hard layer, and the layer containing the polymer electrolyte (e.g., the negative electrode layer) becomes a soft layer. As a result, when pressing to join the layers, the layer containing the polymer electrolyte is prone to deformation (e.g., elongation, warping). If such deformation causes the positive and negative electrode layers to come into contact, an internal short circuit occurs, and cycle characteristics are degraded.

[0016] Based on the above insights, the present application discloses an all-solid-state battery as one of the means for solving the above-mentioned problems, comprising: a first current collector layer, a first collector ear protruding from the edge of the first current collector layer, a first active material layer stacked on the first current collector layer, a second current collector layer, a second collector ear protruding from the edge of the second current collector layer, a second active material layer stacked on the second current collector layer, and a solid electrolyte layer arranged between the first active material layer and the second active material layer and containing a polymer electrolyte, the solid electrolyte layer being arranged to also cover the end surfaces of the first current collector layer and the first active material layer, and the first collector ear protruding through the solid electrolyte layer.

[0017] In the above-mentioned all-solid-state battery, the second collector layer, the second active material layer, the solid electrolyte layer, the first active material layer, the first collector layer, the first active material layer, the solid electrolyte layer, the second active material layer and the second collector layer can be stacked in sequence to form a power generation element.

[0018] In the above-described all-solid-state battery, at least a portion of the end surfaces of the second current collector layer and the second active material layer, other than the side where the second collector tab is disposed, may also be covered by the solid electrolyte layer. In this case, a plurality of power-generating elements may be stacked, connected by the solid electrolyte layer covering the end surfaces of the second current collector layer and the second active material layer.

[0019] According to the all-solid-state battery disclosed herein, short circuit is unlikely to occur even if a polymer electrolyte is used in the negative electrode active material layer, so the polymer electrolyte can be used in the negative electrode active material layer. This can inhibit peeling and cracking within the negative electrode layer and at the interface between the negative electrode layer and the solid electrolyte layer during charging and discharging, thereby obtaining good cycle characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a perspective view of the external appearance of the power generating element 10 .

[0021] Figure 2 It is a plan view of the power generating element 10 .

[0022] Figure 3 It is a front view of the power generating element 10 .

[0023] Figure 4 It is a left side view of the power generating element 10 .

[0024] Figure 5 It is a VV cross-sectional view of the power generating element 10 .

[0025] Figure 6 It is a VI-VI cross-sectional view of the power generating element 10 .

[0026] Figure 7 This is a diagram illustrating an example in which a negative electrode laminate is covered with a solid electrolyte layer.

[0027] Figure 8 This is a diagram illustrating an example in which a negative electrode laminate is covered with a solid electrolyte layer.

[0028] Figure 9 This is a diagram illustrating an example in which a negative electrode laminate is covered with a solid electrolyte layer.

[0029] Figure 10 1 is a diagram illustrating the structure of the all-solid-state battery 1 .

[0030] Figure 11 It is a cross-sectional view of the power generating element 20 .

[0031] Figure 12 It is a cross-sectional view of the power generating element 20 .

[0032] Figure 13 It is a diagram showing a stacked state of the power generating elements 20 .

[0033] Description of Reference Numerals

[0034] 1 All-solid-state battery

[0035] 10 Power generation element

[0036] 11. Negative electrode collector layer

[0037] 11a Negative collector tab

[0038] 12 Negative electrode active material layer

[0039] 13 Solid electrolyte layer

[0040] 14. Positive electrode active material layer

[0041] 15. Positive electrode current collector layer

[0042] 15a Positive collector lug DETAILED DESCRIPTION

[0043] 1. Power generation element

[0044] The all-solid-state battery disclosed herein comprises one or more power-generating elements, stacked as a single cell, housed in an outer casing (case) (not shown), and has a desired capacity.

[0045] Figures 1 to 6 A diagram illustrating a power generating element 10 according to one embodiment is shown. Figure 1 is a perspective view of the power generating element 10. Figure 2 is a top view of the power generating element 10 (from Figure 1 (as viewed in the direction indicated by arrow II in the figure), Figure 3 This is a front view of the power generating element 10 (from Figure 1 (as viewed in the direction indicated by arrow III), Figure 4 This is a left side view of the power generating element 10 (from Figure 1 (as viewed in the direction indicated by arrow IV in the figure), Figure 5 yes Figure 3 VV-direction cross-sectional view, and Figure 6 yes Figure 4 VI-VI cross-sectional view.

[0046] exist Figures 1 to 6 In the figures shown below, shapes (e.g., thickness, width, etc.) are sometimes exaggerated for ease of viewing, and portions of duplicated symbols are sometimes omitted. In addition, directions of a three-dimensional orthogonal coordinate system (x, y, z) are sometimes shown together for ease of understanding.

[0047] 1.1. Components of a power generation element

[0048] like Figures 1 to 6As shown, the power generation element 10 includes a negative electrode current collector layer 11, a negative electrode active material layer 12, a solid electrolyte layer 13, a positive electrode active material layer 14, and a positive electrode current collector layer 15. In this embodiment, the negative electrode current collector layer 11, the negative electrode active material layer 12, the positive electrode active material layer 14, and the positive electrode current collector layer 15 are all sheet-like members having quadrilateral front and back surfaces in the xy plane, and a thin thickness between the front and back surfaces.

[0049] 1.1a. Negative Electrode Current Collector Layer (First Current Collector Layer)

[0050] In this embodiment, the negative electrode current collector layer 11 is one of the components constituting the negative electrode stack as the first current collector layer, and is composed of metal foil or metal mesh. Metal foil is particularly preferred, and examples of its metal include Cu, Ni, Fe, Ti, Co, Zn, stainless steel, and the like. The negative electrode current collector layer 11 may have a coating layer on its surface for adjusting the contact resistance. Examples of materials constituting the coating layer include carbon. The thickness (z-direction size) of the negative electrode current collector layer 11 is not particularly limited, and is preferably greater than 0.1 μm and less than 1 mm, and more preferably greater than 1 μm and less than 100 μm.

[0051] A negative electrode collector tab 11a, serving as a first collector tab, is disposed on the negative electrode current collector layer 11. Negative electrode collector tab 11a facilitates electrical connection between the negative electrode current collector layers 11. The material of negative electrode collector tab 11a may be the same as or different from that of negative electrode current collector layer 11. Furthermore, the thickness of negative electrode collector tab 11a may be the same as or different from that of negative electrode current collector layer 11.

[0052] In this embodiment, the negative electrode collector tab 11a is arranged so as to protrude in the x direction from one side (the x-direction end) that is part of the edge of the negative electrode collector layer 11, and its thickness (z-direction dimension) is the same as that of the negative electrode collector layer 11. In addition, the width (y-direction dimension) of the negative electrode collector tab 11a is smaller than that of the negative electrode collector layer 11.

[0053] 1.1b. Negative Electrode Active Material Layer (First Active Material Layer)

[0054] In this embodiment, the negative electrode active material layer 12 is one of the members constituting the negative electrode stack as the first active material layer, and may contain at least a negative electrode active material and a polymer electrolyte as a solid electrolyte, and may optionally contain a conductive material and a binder.

[0055] The thickness (size in the z direction) of the negative electrode active material layer is, for example, not less than 0.1 μm and not more than 1000 μm.

[0056] [Negative electrode active material]

[0057] As the negative electrode active material, for example, metal active materials such as Si, Sn, and Li; carbon active materials such as graphite; oxide active materials such as lithium titanate. In addition, the negative electrode active material may also be a Si-based active material containing at least Si. Si-based active materials undergo large volume changes accompanying charge and discharge, and are therefore prone to degradation of battery performance due to expansion and contraction. In this regard, by containing a soft polymer electrolyte, degradation of the battery's cycle characteristics due to expansion and contraction can be suppressed. As the Si-based active material, for example, Si simple substance, Si alloy, and Si oxide may be mentioned. Si alloy preferably contains Si element as the main component. In the Si alloy, the proportion of Si is, for example, 50 atomic % or more, 70 atomic % or more, or 90 atomic % or more.

[0058] The shape of the negative electrode active material may be, for example, a granular shape. The average particle size (D50) of the negative electrode active material may be, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D50) of the negative electrode active material may be, for example, 50 μm or less, or 20 μm or less. The average particle size (D50) may be calculated, for example, by measurement using a laser diffraction particle size analyzer or a scanning electron microscope (SEM).

[0059] The proportion of the negative electrode active material in the negative electrode active material layer is, for example, 20 wt % or more, 40 wt % or more, or 60 wt % or more. Meanwhile, the proportion of the negative electrode active material in the negative electrode active material layer is, for example, 80 wt % or less.

[0060] [Polymer Electrolyte]

[0061] A polymer electrolyte contains at least a polymer component. Examples of polymer components include polyether polymers, polyester polymers, polyamine polymers, and polysulfide polymers. Polyether polymers are preferred because they have high ion conductivity and excellent mechanical properties such as Young's modulus and breaking strength.

[0062] The polyether polymer has a polyether structure in the repeating unit. In addition, the polyether polymer preferably has a polyether structure in the main chain of the repeating unit. As the polyether structure, for example, polyethylene oxide (PEO) structure and polypropylene oxide (PPO) structure can be enumerated. The polyether polymer preferably has a PEO structure as the main repeating unit. In the polyether polymer, the ratio of the PEO structure in all repeating units is, for example, more than 50 mol %, can be more than 70 mol %, or can be more than 90 mol %. In addition, the polyether polymer can also be a homopolymer or a copolymer of, for example, an epoxy compound (for example, ethylene oxide, propylene oxide).

[0063] The polymer component may have the following ion-conducting units. Examples of the ion-conducting units include polyethylene oxide, polypropylene oxide, polymethacrylate, polyacrylate, polydimethylsiloxane, polyacrylic acid, polymethacrylic acid, polyvinyl acetate, polyimide, polyamine, polyamide, polyalkyl carbonate, polynitrile, polyphosphazene, polyolefin, and polydiene.

[0064] The weight average molecular weight (Mw) of the polymer component is not particularly limited, and is, for example, 1,000,000 or more and 10,000,000 or less. Mw is determined by gel permeation chromatography (GPC). In addition, the glass transition temperature (Tg) of the polymer component is, for example, 60°C or less, 40°C or less, or 25°C or less. In addition, the polymer electrolyte may contain only one polymer component, or may contain two or more. In addition, the polymer electrolyte may be a cross-linked polymer electrolyte in which the polymer components are cross-linked, or may be an uncross-linked polymer electrolyte in which the polymer components are not cross-linked.

[0065] The polymer electrolyte may be a dry polymer electrolyte or a gel electrolyte. A dry polymer electrolyte refers to an electrolyte containing a solvent component of 5% by weight or less. The solvent component content may be 3% by weight or less, or 1% by weight or less. Furthermore, when a sulfide solid electrolyte with high reactivity with polar solvents is used in the positive electrode active material layer, a dry polymer electrolyte is preferably used.

[0066] The dry polymer electrolyte may contain a supporting salt. Examples of the supporting salt include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. The ratio of the supporting salt to the dry polymer electrolyte is not particularly limited. For example, when the dry polymer electrolyte has an EO unit (C2H5O unit), the EO unit may be, for example, 5 or more molar parts, 10 or more molar parts, or 15 or more molar parts relative to 1 molar part of the supporting salt. On the other hand, the EO unit may be, for example, 40 or less molar parts, or 30 or less molar parts relative to 1 molar part of the supporting salt.

[0067] Gel electrolytes usually contain an electrolyte component in addition to the polymer component. The electrolyte component contains a supporting salt and a solvent. The supporting salt is the same as described above. As a solvent, for example, carbonates can be mentioned. As carbonates, for example, cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC); chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) can be mentioned. In addition, as a solvent, for example, acetates such as methyl acetate and ethyl acetate, and ethers such as 2-methyltetrahydrofuran can be mentioned. In addition, as a solvent, for example, γ-butyrolactone, cyclopentane sulfone, N-methylpyrrolidone (NMP) and 1,3-dimethyl-2-imidazolidinone (DMI) can be mentioned. In addition, the solvent can also be water.

[0068] The ratio of the polymer electrolyte to the total solid electrolyte is, for example, 50% by volume or more, 70% by volume or more, or 90% by volume or more. The solid electrolyte may contain only the polymer electrolyte.

[0069] The proportion of the polymer electrolyte in the negative electrode active material layer is, for example, 20% by volume or more, 30% by volume or more, or 40% by volume or more. On the other hand, the proportion of the polymer electrolyte in the negative electrode active material layer is, for example, 70% by volume or less, or 60% by volume or less.

[0070] [Conductive materials]

[0071] The addition of a conductive material improves the electron conductivity of the negative electrode active material layer. Examples of the conductive material include granular carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs).

[0072] [Adhesive]

[0073] The addition of the binder allows the constituent materials of the negative electrode active material layer to be firmly bound together. Examples of the binder include fluoride-based binders, polyimide-based binders, and rubber-based binders.

[0074] 1.1c. Solid electrolyte layer

[0075] The solid electrolyte layer 13 is a layer containing a solid electrolyte, and in the present disclosure, contains a polymer electrolyte as the solid electrolyte.

[0076] The polymer electrolyte contained in the solid electrolyte layer 13 is a cross-linked polymer electrolyte in which the polymer components are cross-linked. The polymer electrolyte contained in the solid electrolyte layer 13 is the same as the polymer electrolyte described above for the negative electrode active material layer 12 except that the polymer components are cross-linked.

[0077] Examples of polymerization initiators used to crosslink the polymer components include peroxides such as benzoyl peroxide, di-tert-butyl peroxide, tert-butylbenzoyl peroxide, tert-butyl peroxyoctanoate, and cumene hydroxyperoxide; and azo compounds such as azobisisobutyronitrile. The polymer electrolyte in the solid electrolyte layer and the polymer electrolyte in the negative electrode active material layer may have the same or different compositions. Furthermore, when using a sulfide solid electrolyte that is highly reactive with polar solvents in the positive electrode active material layer, a dry polymer electrolyte is preferred.

[0078] Here, the solid electrolyte layer 13 is preferably self-supporting. "Self-supporting" means that it can maintain its shape even without a support. For example, if the solid electrolyte material is wet-coated onto a substrate and the substrate is peeled off after drying, the solid electrolyte layer can be said to be "self-supporting" if it maintains its shape.

[0079] The solid electrolyte layer 13 preferably contains a polymer electrolyte as the main component of the solid electrolyte. In the solid electrolyte layer, the proportion of the polymer electrolyte relative to the total solid electrolyte is, for example, 50% by volume or more, 70% by volume or more, or 90% by volume or more. The solid electrolyte layer may contain only the polymer electrolyte as the solid electrolyte.

[0080] The thickness (z-direction dimension) of the solid electrolyte layer 13 is, for example, not less than 0.1 μm and not more than 1000 μm.

[0081] 1.1d. Positive Electrode Active Material Layer (Second Active Material Layer)

[0082] In this embodiment, the positive electrode active material layer 14 is a member of the positive electrode stack as the second active material layer. In this embodiment, it contains at least a positive electrode active material and a solid electrolyte, and may optionally contain a conductive material and a binder. The conductive material and binder are the same as those described for the negative electrode active material layer 12, so their description is omitted here.

[0083] The thickness (size in the z direction) of the positive electrode active material layer is, for example, not less than 0.1 μm and not more than 1000 μm.

[0084] [Positive electrode active material]

[0085] Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include LiCoO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layered active materials, LiMn2O4, Li4Ti5O 12Spinel-type active materials such as LiFePO4, olivine-type active materials such as Li2S, and sulfur-based active materials such as transition metal sulfides.

[0086] A protective layer containing a Li-ion-conducting oxide can be formed on the surface of the oxide active material. This can suppress the reaction between the oxide active material and the solid electrolyte. An example of a Li-ion-conducting oxide is LiNbO3. The thickness of the protective layer is, for example, 1 nm to 30 nm.

[0087] The shape of the positive electrode active material may be, for example, a granular shape. The average particle size (D50) of the positive electrode active material is not particularly limited, and may be, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D50) of the positive electrode active material may be, for example, 50 μm or less, or 20 μm or less.

[0088] [Solid Electrolyte]

[0089] As the solid electrolyte of the positive electrode active material layer, an inorganic solid electrolyte can be used. Examples of the inorganic solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. In addition, the inorganic solid electrolyte can be glass (amorphous), glass ceramics, or crystals. Glass is obtained, for example, by amorphizing the raw material. Glass ceramics are obtained, for example, by heat-treating glass. Crystals are obtained, for example, by heating the raw material.

[0090] The sulfide solid electrolyte preferably contains, for example, Li, A (A is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain O (oxygen) and at least one of a halogen. Examples of halogens include F, Cl, Br, and I. The sulfide solid electrolyte may contain only one halogen or two or more halogens. Furthermore, when the sulfide solid electrolyte contains anionic elements other than S (e.g., O and halogens), S preferably has the highest molar proportion among all the anionic elements.

[0091] The sulfide solid electrolyte preferably has an anion structure of the original composition (PS4 3- Structure, SiS4 4- Structure, GeS4 4- Structure, AlS3 3- Structure, BS3 3- The anionic structure is the main component of the sulfide solid electrolyte. This is because of its high chemical stability. The proportion of the anionic structure in the original composition relative to the total anionic structure in the sulfide solid electrolyte is, for example, 50 mol% or more, 60 mol% or more, or 70 mol% or more.

[0092] The sulfide solid electrolyte may include a crystal phase having ion conductivity. Examples of the crystal phase include a Thio-LISICON crystal phase, an LGPS crystal phase, and an Argentite crystal phase.

[0093] In addition, the oxide solid electrolyte preferably contains, for example, Li, Z (Z is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S) and O. Specific examples of the oxide solid electrolyte include Li7La3Zr2O 12 Garnet-type solid electrolytes such as (Li,La)TiO3; perovskite-type solid electrolytes such as (Li,La)TiO3; sodium superion conductor-type solid electrolytes such as Li(Al,Ti)(PO4)3; Li-PO4-based solid electrolytes such as Li3PO4; and Li-BO3-based solid electrolytes such as Li3BO3. Furthermore, when the oxide solid electrolyte contains anionic elements other than O (e.g., S and halogens), it is preferred that O has the highest molar proportion among all anionic elements.

[0094] A halide solid electrolyte is an electrolyte containing a halogen (X). Examples of halogens include F, Cl, Br, and I. Examples of halide solid electrolytes include Li3YX6 (X is at least one of F, Cl, Br, and I). In addition, when the halide solid electrolyte contains anion elements other than halogens (such as S and O), it is preferred that the molar ratio of halogen is the highest among all anion elements. Examples of the shape of the inorganic solid electrolyte include granular. The average particle size (D50) of the inorganic solid electrolyte is not particularly limited, and may be, for example, greater than 10 nm, or greater than 100 nm. On the other hand, the average particle size (D50) of the inorganic solid electrolyte may be, for example, less than 50 μm, or less than 20 μm.

[0095] The positive electrode active material layer 14 preferably contains an inorganic solid electrolyte as the main component of the solid electrolyte. In the positive electrode active material layer 14, the ratio of the inorganic solid electrolyte to the total solid electrolyte is, for example, 50% by volume or more, 70% by volume or more, or 90% by volume or more. The positive electrode active material layer 14 may also contain only an inorganic solid electrolyte as the solid electrolyte.

[0096] The proportion of the inorganic solid electrolyte in the positive electrode active material layer 14 is, for example, 10% by volume or more, or 20% by volume or more. Meanwhile, the proportion of the inorganic solid electrolyte in the positive electrode active material layer 14 is, for example, 60% by volume or less, or 50% by volume or less.

[0097] 1.1e. Positive Electrode Current Collector Layer (Second Current Collector Layer)

[0098] In this embodiment, the positive electrode collector layer 15 is one of the components constituting the positive electrode laminate as the second collector layer, and can be composed of metal foil or metal mesh. Metal foil is particularly preferred, and examples of metals include Ni, Cr, Au, Pt, Al, Fe, Ti, Zn, stainless steel, and the like. The positive electrode collector layer 15 may have a coating layer on its surface for adjusting resistance, for example, a carbon coating layer, and the like. The thickness of the positive electrode collector layer 15 is not particularly limited. For example, it is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less.

[0099] A positive electrode collector tab 15a is provided on the positive electrode current collector layer 15 as a second collector tab. This tab facilitates electrical connection between the positive electrode current collector layers 15. The material of the positive electrode collector tab 15a can be the same as or different from that of the positive electrode current collector layer 15. Furthermore, the thickness of the positive electrode collector tab 15a can be the same as or different from that of the positive electrode current collector layer 15.

[0100] In this embodiment, the positive electrode collector tab 15a is arranged to protrude in the x direction from one side (x-direction end) that is part of the edge of the positive electrode collector layer 15, and its thickness is the same as that of the positive electrode collector layer 15. In addition, the width (y-direction dimension) of the positive electrode collector tab 15a is smaller than that of the positive electrode collector layer 15.

[0101] 1.2. Structure of power generation element

[0102] In this embodiment, the power generating element 10 is formed by arranging the above-mentioned constituent members as follows.

[0103] The first active material layer is disposed on the front and back of the first current collector layer. That is, in this embodiment, the negative electrode active material layer 12 is disposed on the front and back of the negative electrode current collector layer 11. Figure 5 、 Figure 6 It can be seen that the end face 12 t of the negative electrode active material layer 12 is located inside (does not protrude) the end face 11 t of the negative electrode current collector layer 11 .

[0104] The solid electrolyte layer is disposed on the side of the first active material layer opposite to the side in contact with the first current collector layer. In this embodiment, the solid electrolyte layer 13 is disposed on the side of the negative electrode active material layer 12 opposite to the side in contact with the negative electrode current collector layer 11.

[0105] Furthermore, in this method, Figure 5 、 Figure 6As can be seen, the end face 11t of the negative electrode current collector layer 11, serving as the first current collector layer, and the end face 12t of the negative electrode active material layer 12, serving as the first active material layer, are entirely covered by the solid electrolyte layer 13. Furthermore, the negative electrode collector tab 11a, serving as the first collector tab, protrudes outward, penetrating the solid electrolyte layer 13. Thus, even if the negative electrode active material layer 12 is deformed, for example, when pressed using a soft polymer electrolyte, the solid electrolyte layer 13 covers the negative electrode active material layer 12, thereby preventing it from contacting the positive electrode active material layer 14 and / or the positive electrode current collector layer 15 and causing a short circuit.

[0106] A positive electrode active material layer 14, serving as a second active material layer, is disposed on the opposite side of the surface of the solid electrolyte layer 13 that contacts the surface of the negative electrode active material layer 12, serving as the first current collector layer. Furthermore, a positive electrode current collector layer 15, serving as a second current collector layer, is disposed on the opposite side of the surface of the positive electrode active material layer 14, serving as the second active material layer, that contacts the solid electrolyte layer 13.

[0107] In this embodiment, the negative electrode collector tab 11a and the positive electrode collector tab 15a are arranged so as to protrude in the same direction. Figure 2 、 Figure 4 It is clear that the negative electrode collector tab 11a and the positive electrode collector tab 15a are arranged at different positions in the width direction (y direction). Figure 2 are positioned in a non-overlapping manner when viewed from a top-down perspective.

[0108] In this embodiment, the "first" is the negative electrode and the "second" is the positive electrode. That is, the configuration of the various components is described with the first current collector layer serving as the negative electrode current collector layer, the first collector tab serving as the negative electrode collector tab, the first active material layer serving as the negative electrode active material layer, the second current collector layer serving as the positive electrode current collector layer, the second collector tab serving as the positive electrode collector tab, and the second active material layer serving as the positive electrode active material layer. However, this is not limiting; the various components can also be configured conversely, with the "first" serving as the positive electrode and the "second" serving as the negative electrode. The same applies to the following description.

[0109] 1.3. Method for manufacturing power generation element

[0110] The method for manufacturing the power generating element 10 is not particularly limited, and the power generating element 10 can be manufactured, for example, as follows.

[0111] The material for the positive electrode active material layer 14 is applied to the surface of the positive electrode current collector layer 15 by a wet method, dried, and compacted by pressing to obtain a positive electrode laminate (a laminate of the positive electrode current collector layer 15 and the positive electrode active material layer 14 ).

[0112] On the other hand, the material for the negative electrode active material layer 12 is applied to the front and back surfaces of the negative electrode collector layer 11 by a wet method and dried, and then densified by pressing to obtain a negative electrode laminate (a laminate of the negative electrode collector layer 11 and the negative electrode active material layer 12).

[0113] The solid electrolyte layer is arranged so as to cover the negative electrode laminate, and the positive electrode laminate is arranged on both sides of the outer side of the solid electrolyte layer, and the positive electrode laminate is pressed and formed into an integrated structure, thereby obtaining the power generation element 10. The pressing pressure at this time is not particularly limited, for example, it is preferably 0.5 tons / cm 2 above.

[0114] Here, the method of arranging the solid electrolyte layer so as to cover the negative electrode laminate is not particularly limited, and can be performed, for example, as follows. Figures 7 to 9 A diagram is shown for explanation. Figures 7 to 9 A top view is shown in the upper portion, and a diagram showing a stacked state in the thickness direction (a cross section along the center in the y direction) is shown in the lower portion.

[0115] First, if Figure 7 As shown, a material 13 ′ serving as a solid electrolyte layer is stacked on a release sheet (eg, a polyethylene terephthalate sheet, a PET sheet) 17 .

[0116] Then, if Figure 8 As shown, a negative electrode stack 18 is further stacked on the material 13'. Here, one end 18a of the negative electrode stack 18 in the x-direction is positioned so as not to protrude from the end of the material 13' (only the negative electrode collector tab 11a protrudes), and the other end 18b of the negative electrode stack 18 in the x-direction is positioned approximately at the center line C of the material 13' in the x-direction. Furthermore, the x-direction length of the negative electrode active material layer and the negative electrode current collector layer (excluding the negative electrode collector tab) of the negative electrode stack 18 is shorter than the x-direction length of the solid electrolyte layer. Furthermore, the x-direction length, including the negative electrode collector tab, is longer than the x-direction length of the solid electrolyte layer. Furthermore, in the width direction (y-direction), the width of the negative electrode stack 18 is made smaller than the width of the material 13', forming exposed portions 13'c of the material 13' at both ends of the material 13' in the width direction (y-direction).

[0117] from Figure 8 From the configuration point of view, Figure 8 As shown by the arrow D, the release sheet 17 and the material 13' on the side where the negative electrode laminate 18 is not laminated are folded inward at the center line C, so that the material 13' is laminated on the negative electrode laminate 18. Then, if the release sheet 17 at the folded portion is peeled off, the result is as shown in FIG. Figure 9 That is, in Figure 9 In the arrangement mode, the material 13 ′ is wound around the front and back surfaces of the negative electrode stack 18 to form a bag-shaped material 13 ′.

[0118] Furthermore, since the bent upper and lower materials 13' are easily attached, they are joined by contact, but physical joining by pressing or chemical joining by welding, ultraviolet irradiation, or thermal cross-linking reaction can also be performed.

[0119] While this example illustrates a method in which the material serving as the solid electrolyte layer is bent to cover the negative electrode stack, the present invention is not limited thereto. Alternatively, two sheets of solid electrolyte layer material may be prepared, the negative electrode stack disposed therebetween, and the solid electrolyte layer may be disposed so as to cover the negative electrode stack. Alternatively, a release sheet such as a PET film may be disposed in place of the negative electrode stack 18 to form a bag-shaped solid electrolyte layer. The release sheet may then be removed to dispose the negative electrode stack.

[0120] 2. All-solid-state batteries

[0121] The all-solid-state battery in the present disclosure is formed by stacking the above-mentioned power generation elements 10 . Figure 10 A diagram is shown for illustration purposes. Figure 10 As can be seen, the all-solid-state battery is stacked by overlapping the positive electrode current collector layer 15 and the positive electrode collector tab 15a of the power generation element 10. Furthermore, the multiple negative electrode collector tabs 11a are electrically connected, and the multiple positive electrode current collector sheets 15a are electrically connected, thereby forming the positive and negative electrodes of the all-solid-state battery. Furthermore, in the all-solid-state battery, the stacked power generation elements 10 are housed in an exterior body. Examples of the exterior body include a laminated exterior body and a can-type exterior body.

[0122] Typically, the all-solid-state battery in the present disclosure is an all-solid-state lithium-ion secondary battery. The use of the all-solid-state battery is not particularly limited, and for example, a power source for vehicles such as hybrid electric vehicles (HEV), electric vehicles (BEV), gasoline vehicles, and diesel vehicles can be cited. It is particularly preferred to use it as a driving power source for hybrid electric vehicles or electric vehicles. In addition, the all-solid-state battery in the present disclosure can be used as a power source for mobile bodies (such as railways, ships, and aircraft) other than vehicles, and can also be used as a power source for electrical appliances such as information processing devices.

[0123] 3. Other methods

[0124] 3.1. Other methods example 1

[0125] Figures 11 to 13 A diagram illustrating a power generating element 20 used in an all-solid-state battery according to another embodiment 1 is shown. Figure 11 is with Figure 5 The same perspective image, Figure 12 is with Figure 6 Same perspective image.

[0126] The power generation element 20 is an example in which a solid electrolyte layer 23 is applied instead of the solid electrolyte layer 13 of the power generation element 10. Other components can be considered similarly to the power generation element 10, and thus are given the same reference numerals and their description is omitted.

[0127] The solid electrolyte layer 23 is outside the structure of the solid electrolyte layer 13 of the power generation element 10, and covers at least a portion of the end faces (11t, 12t) of the first collector layer (negative collector layer 11) and the first active material layer (negative active material layer 12) except for the portion where the first collector tab (negative collector tab 11a) is arranged. Figure 11 W1) and / or length ( Figure 12 L1), which is greater than the width of the second current collector layer (positive electrode current collector layer 14) and the second active material layer (positive electrode active material layer 15) ( Figure 11 W2) and / or length ( Figure 12 Furthermore, in this larger portion, the end face of the second active material layer (end face 14t of the positive electrode active material layer 14) and the second current collector layer (end face 15t of the positive electrode current collector layer 15) are also covered by the solid electrolyte layer 23. This further prevents short circuits.

[0128] In addition, if Figure 13 As shown, a structure can be formed in which two or more power generation elements 20 are joined together in a portion other than the portion where the first current collector tab (negative electrode current collector tab 11a) and the second current collector tab (positive electrode current collector tab 15a) are arranged, using a solid electrolyte layer that covers the end surfaces of the first current collector layer, the first active material layer, the second current collector layer, and the second active material layer. This integration can suppress misalignment and the like.

[0129] In the above method, the first current collector layer, the first active material layer, the second current collector layer, and the second active material layer are all quadrilaterals. Therefore, the first collector ear is arranged on one side of the first current collector layer, and the second collector ear is arranged on one side of the second current collector layer. The end face of the second current collector layer and the second active material layer are covered by the solid electrolyte layer on at least two of the remaining three sides.

[0130] 3.2. Other methods example 2

[0131] Thus far, power generation elements 10 and 20 have been described as examples in which the end surfaces of the negative electrode current collector layer 11 and the negative electrode active material layer 12 are covered with a solid electrolyte layer, and the negative electrode current collector tab 11a and the positive electrode current collector tab 15a are arranged in the same direction. However, this is not limiting, and the same applies to power generation element 10 in which the negative electrode current collector tab 11a and the positive electrode current collector tab 15a are arranged in different directions.

[0132] In addition, regarding the power generation element 20, a structure in which the solid electrolyte layers covering the end faces of the first collector layer, the first active material layer, the second collector layer, and the second active material layer are connected to each other can be formed in a portion other than the portion where the first collector tab and the second collector tab are arranged.

[0133] 4. Effects, etc.

[0134] According to the power generation element and the all-solid-state battery using the power generation element disclosed in the present invention, in order to suppress the reduction in battery performance caused by the expansion and contraction of the negative electrode active material, a soft polymer electrolyte is used as the solid electrolyte of the negative electrode layer, thereby suppressing the reduction in battery performance caused by the expansion and contraction of the negative electrode active material during charging and discharging.

[0135] In addition, according to the power generation element of the present disclosure and the all-solid-state battery using the power generation element, the end face of the first collector layer (negative electrode collector layer) other than the first collector ear (negative electrode collector ear) and the end face of the first active material layer (negative electrode active material layer) are covered by the solid electrolyte layer. Thus, even if there is deformation when the negative electrode active material layer is pressed using a soft polymer electrolyte, since the negative electrode active material layer is covered by the solid electrolyte layer, it is possible to suppress the situation of short circuiting due to contact with the positive electrode active material layer and the positive electrode collector layer. Moreover, since no short circuit occurs, it is possible to suppress peeling and cracking in the negative electrode layer and at the interface between the negative electrode layer and the solid electrolyte layer during charge and discharge, and good cycle characteristics can be obtained.

[0136] 5. Examples

[0137] 5.1. Fabrication of the All-Solid State Battery of Example 1

[0138] 5.1a. Fabrication of negative electrode stack

[0139] The negative electrode active material (Si particles, average particle size 2.5 μm), the conductive material (VGCF-H: Showa Denko K.K., VGCF is a registered trademark) and the binder (PVdF-HFP) are weighed so that the weight ratio of the negative electrode active material: the conductive material: the binder = 94:4:2 is obtained and mixed with the dispersion medium (diisobutyl ketone). The obtained mixture is dispersed with an ultrasonic homogenizer (UH-50, SMT Co., Ltd.) to obtain a negative electrode slurry. The obtained negative electrode slurry is applied to the negative electrode collector layer (Ni foil, thickness 15 μm) by a doctor blade coating method using an applicator and dried at 100°C for 30 minutes. Then, by similarly applying on the surface on the opposite side of the negative electrode collector layer, an intermediate body having a negative electrode active material layer and a negative electrode active material layer stacked on both sides of the negative electrode collector layer is obtained.

[0140] Separately, PEO (polyethylene oxide, Mw approximately 4,000,000) and LiTFSI (LiN(SO2CF3)2) were weighed to a molar ratio of EO:Li = 20:1, mixed with acetonitrile, and stirred until a uniform solution was obtained. The resulting PEO-LiTFSI solution was applied to the intermediate by a doctor blade coating method using an applicator and dried at 100°C for 60 minutes. Then, the surface on the opposite side of the negative electrode collector layer was similarly coated. Furthermore, after drying, the gap between the doctor blades was adjusted so that the weight ratio of the negative electrode active material to the polymer electrolyte was 68:32. Then, the mixture was densified by pressing to obtain a negative electrode laminate having negative electrode active material layers disposed on both sides of the negative electrode collector layer.

[0141] 5.1b. Fabrication of the positive electrode material layer

[0142] The positive electrode active material (LiNi 0.8 Co 0.15 Al 0.05 O2, average particle size 10μm), sulfide solid electrolyte (10LiI·15LiBr·75(0.75Li2S·0.25P2S5) (mol %), average particle size 0.5μm), conductive material (VGCF-H: Showa Denko K.K.), and binder (SBR) were mixed together with a dispersion medium (diisobutyl ketone) so that the weight ratio of positive electrode active material: sulfide solid electrolyte: conductive material: binder = 85:13:1:1. The mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by SMT Co., Ltd.) to obtain a positive electrode slurry. The obtained positive electrode slurry was applied to an Al foil (thickness 15μm) by a doctor blade coating method using an applicator, dried at 100°C for 30 minutes, and densified by pressing to obtain a positive electrode mixture in which a positive electrode active material layer was laminated on the Al foil.

[0143] 5.1c. Fabrication of Solid Electrolyte Layer

[0144] PEO (polyethylene oxide, Mw approximately 4,000,000) and LiTFSI (LiN(SO2CF3)2) were weighed to a molar ratio of EO:Li = 20:1 and mixed in acetonitrile. The initiator BPO (Benzoyl peroxide) was added to this solution to a 10% by weight ratio of the PEO-LiTFSI solution, and then stirred until a homogeneous solution was achieved. The resulting polymer electrolyte solution was applied to a 7.4 cm wide PET film using a doctor blade coating method using an applicator. After drying at 100°C for 60 minutes, the film was cut into 14.2 cm lengths to produce a self-supporting cross-linked solid electrolyte layer.

[0145] 5.1d. Fabrication of All-Solid-State Batteries

[0146] The negative electrode stack cut into 7.0cm×7.0cm and the solid electrolyte layer were laminated so that the negative electrode stack and the solid electrolyte layer were in direct contact, and the end surface on the opposite side of the negative electrode collector ear was aligned with the center of the solid electrolyte layer. The solid electrolyte layer was bent in the long side direction, thereby laminating the negative electrode stack and the solid electrolyte layer. Next, the positive electrode mixture cut into 7.0cm×7.0cm was laminated so that the positive electrode mixture and the solid electrolyte layer were in direct contact, and the positive electrode mixture and the solid electrolyte layer were laminated at 0.5t / cm 2 Then, the terminals were welded together and laminated into a unit (placed inside the outer packaging material) to produce an all-solid-state battery.

[0147] 5.2. Fabrication of the All-Solid State Battery of Example 2

[0148] The following steps up to the preparation of the all-solid-state battery are the same as those in Example 1.

[0149] 5.2a. Fabrication of all-solid-state batteries

[0150] Two power generation elements obtained in Example 1 were stacked, the solid electrolyte layers without edges facing the collector ears were joined to fix the electrodes, and the terminals were welded before being laminated into units (placed in the exterior material) to produce a fully solid-state battery.

[0151] 5.3. Fabrication of the All-Solid State Battery of Comparative Example 1

[0152] The following steps up to the preparation of the all-solid-state battery are the same as those in Example 1.

[0153] 5.3a. Fabrication of All-Solid-State Batteries

[0154] The negative electrode stack cut into 7.2 cm × 7.2 cm and the solid electrolyte layer cut into 7.2 cm × 7.2 cm were laminated so that the negative electrode mixture layer and the solid electrolyte layer were in direct contact and the collector side end faces were aligned. The PET film was peeled off and the solid electrolyte was laminated. Next, the positive electrode mixture was cut into 7.0 cm × 7.0 cm and laminated so that the positive electrode mixture and the solid electrolyte layer were in direct contact. The positive electrode mixture was laminated at 0.5 t / cm 2 Then, the terminals were welded together and laminated into units (placed inside the exterior packaging) to create an all-solid-state battery.

[0155] 5.4. Fabrication of All-Solid-State Battery of Comparative Example 2

[0156] The following procedures up to the preparation of the all-solid-state battery were the same as those in Comparative Example 1.

[0157] 5.4a. Fabrication of All-Solid-State Batteries

[0158] Two power generating elements obtained in Comparative Example 1 were stacked, and after welding the terminals, they were laminated into a unit (placed in an exterior material) to produce an all-solid-state battery.

[0159] 5.5. Evaluation and results

[0160] The short-circuit rate was evaluated by measuring the voltage of 10 of the obtained all-solid-state batteries of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 using a tester. A short circuit was determined when the measured voltage was 0 V, and no short circuit was determined when the measured voltage was greater than 0 V.

[0161] As a result, there were no short circuits in all 10 samples of Example 1 and in all 10 samples of Example 2. On the other hand, among the comparative examples, only 6 samples of Comparative Example 1 and only 2 samples of Comparative Example 2 had no short circuits, and the others had short circuits.

Claims

1. An all-solid-state battery comprising: negative electrode collector layer, a negative electrode collector tab protruding from the edge of the negative electrode collector layer, a negative electrode active material layer stacked on the negative electrode current collector layer, Positive electrode collector layer, a positive electrode collector tab protruding from the edge of the positive electrode collector layer, a positive electrode active material layer stacked on the positive electrode current collector layer, and a solid electrolyte layer disposed between the negative electrode active material layer and the positive electrode active material layer and containing a polymer electrolyte, The solid electrolyte layer is configured to also cover the end surfaces of the negative electrode current collector layer and the negative electrode active material layer. The negative electrode collector ear penetrates the solid electrolyte layer and protrudes, The negative electrode active material layer contains a negative electrode active material and a polymer electrolyte as a solid electrolyte, wherein the proportion of the polymer electrolyte in the negative electrode active material layer is 20 volume % or more and 70 volume % or less. The positive electrode active material layer contains a positive electrode active material and an inorganic solid electrolyte, the proportion of the inorganic solid electrolyte in the positive electrode active material layer is 10 volume % or more and 60 volume % or less, and the inorganic solid electrolyte is a sulfide solid electrolyte, The solid electrolyte layer is capable of self-supporting, The negative electrode collector tab and the positive electrode collector tab are arranged to protrude in the same direction and not overlap when viewed from above. The positive electrode collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode collector layer, the negative electrode active material layer, the solid electrolyte layer, the positive electrode active material layer, and the positive electrode collector layer are sequentially stacked to form a power generation element. The end faces of the positive electrode current collector layer and the positive electrode active material layer are also covered by the solid electrolyte layer on three sides other than the side where the positive electrode collector tab is arranged. In the all-solid-state battery, a plurality of the power generation elements are stacked and connected by the solid electrolyte layer covering the end surfaces of the positive electrode current collector layer and the positive electrode active material layer. The polymer electrolyte is a dry polymer electrolyte having a solvent content of 1% by weight or less, and contains a polyether polymer and a supporting salt. The polyether polymer has a polyethylene oxide structure in the main chain of the repeating unit, and the proportion of the polyethylene oxide structure in all the repeating units is 90 mol% or more. The polyether polymer has an ion conductive unit, the weight average molecular weight of the polyether polymer is 1,000,000 to 10,000,000, and the glass transition temperature of the polyether polymer is 25° C. or less. In the dry polymer electrolyte, the amount of C2H5O units is 15 mol parts or more and 30 mol parts or less relative to 1 mol part of the supporting salt, The sulfide solid electrolyte has a ratio of 70 mol% or more of the anion structure selected from PS4 relative to the total anion structure in the sulfide solid electrolyte. 3- Structure, SiS4 4- Structure, GeS4 4- Structure, AlS3 3- Structure and BS3 3- At least one anionic structure in the structure, The sulfide solid electrolyte includes at least one ion-conductive crystal phase selected from a Thio-LISICON crystal phase, an LGPS crystal phase, and an Argentite crystal phase.

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