All-solid-state batteries

Abstract

The main purpose of the present disclosure is to provide an all-solid-state battery that suppresses the occurrence of internal short circuits. In the present disclosure, the above-mentioned problems are solved by providing an all-solid-state battery, which comprises a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in order along the thickness direction, wherein at least one of the positive electrode layer and the solid electrolyte layer contains an inorganic solid electrolyte, and the negative electrode layer contains a polymer electrolyte. When the all-solid-state battery is viewed from above along the thickness direction, the area of ​​the negative electrode layer is smaller than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer.

Description

Technical Field

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

[0002] All-solid-state batteries are batteries that have a solid electrolyte layer between a positive electrode layer and a negative electrode layer. Compared to liquid batteries that have an electrolyte solution containing a flammable organic solvent, they have the advantage of being able to simplify safety devices.

[0003] For example, Patent Document 1 discloses a method for manufacturing an all-solid-state battery, wherein the all-solid-state battery has a negative electrode layer, a solid electrolyte layer, and a positive electrode layer in sequence, and the area of ​​the positive electrode layer in the surface direction is smaller than the area of ​​the negative electrode layer in the surface direction. Figure 2 Disclosed is an all-solid-state battery having a solid electrolyte layer, wherein the solid electrolyte layer contains an inorganic solid electrolyte and a polymer electrolyte.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-107414

[0006] Patent Document 2: U.S. Patent Application Publication No. 2016 / 0149261 Summary of the Invention

[0007] In all-solid-state batteries, ions and electrons are conducted at the solid / solid interface, so the bonding state at this interface significantly impacts battery performance. Furthermore, when the active material expands and contracts (volume changes) during charge and discharge, it can sometimes become difficult to maintain a good bonding state at the interface, increasing resistance.

[0008] For example, Si-based active materials are known as high-capacity negative electrode active materials, but their volume changes associated with charge and discharge are large. In order to suppress the reduction in battery performance caused by the expansion and contraction of the negative electrode active material, it is envisaged to use a soft polymer electrolyte as the solid electrolyte of the negative electrode layer. On the other hand, the ion conductivity of polymer electrolytes is mostly lower than that of inorganic solid electrolytes. Therefore, from the viewpoint of improving battery performance, it is envisaged to use an inorganic solid electrolyte for at least one of the positive electrode layer and the solid electrolyte layer. 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 / solid interface in the negative electrode layer.

[0009] Here, as an all-solid-state battery in which at least one of the positive electrode layer and the solid electrolyte layer contains an inorganic solid electrolyte, and the negative electrode layer contains a polymer electrolyte, there are the following unique issues. That is, because the inorganic solid electrolyte is generally harder than the polymer electrolyte, at least one of the positive electrode layer and the solid electrolyte layer becomes a hard layer, and the negative electrode layer becomes a soft layer. As a result, when the layers are pressed together, the negative electrode layer is prone to deformation (e.g., elongation, warping). When the negative electrode layer deforms and contacts the positive electrode layer, an internal short circuit occurs.

[0010] The present disclosure has been made in view of the above-mentioned circumstances, and a main object of the present disclosure is to provide an all-solid-state battery in which the occurrence of internal short circuits is suppressed.

[0011] In the present disclosure, an all-solid-state battery is provided, which has a positive electrode layer, a solid electrolyte layer and a negative electrode layer in sequence along the thickness direction, at least one of the above-mentioned positive electrode layer and the above-mentioned solid electrolyte layer contains an inorganic solid electrolyte, and the above-mentioned negative electrode layer contains a polymer electrolyte. When the above-mentioned all-solid-state battery is viewed from above along the above-mentioned thickness direction, the area of ​​the above-mentioned negative electrode layer is smaller than the area of ​​the above-mentioned solid electrolyte layer and the area of ​​the above-mentioned positive electrode layer.

[0012] According to the present disclosure, the area of ​​the negative electrode layer is smaller than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer, so even if at least one of the positive electrode layer and the solid electrolyte layer contains an inorganic solid electrolyte and the negative electrode layer contains a polymer electrolyte, the occurrence of internal short circuit can be suppressed.

[0013] In the above disclosure, the above polymer electrolyte may be a dry polymer electrolyte.

[0014] In the above disclosure, the polymer electrolyte may contain a polyether polymer as a polymer component.

[0015] In the above disclosure, the polyether polymer may have a polyethylene oxide structure in a repeating unit.

[0016] In the above disclosure, both the positive electrode layer and the solid electrolyte layer may contain an inorganic solid electrolyte.

[0017] In the above disclosure, the inorganic solid electrolyte may be a sulfide solid electrolyte.

[0018] The all-solid-state battery of the present disclosure has the effect of being able to suppress the occurrence of internal short circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic cross-sectional view illustrating an all-solid-state battery in the present disclosure.

[0020] Figure 2(a) is a schematic plan view illustrating the relationship between the negative electrode layer and the solid electrolyte layer in the present disclosure, Figure 2 (b) is a schematic plan view illustrating the relationship between the negative electrode layer and the positive electrode layer in the present disclosure.

[0021] Figure 3 This is a schematic cross-sectional view illustrating an all-solid-state battery in the present disclosure.

[0022] Description of Reference Numerals

[0023] 1…positive electrode layer

[0024] 2…Negative electrode layer

[0025] 3…Solid electrolyte layer

[0026] 4…Positive electrode collector

[0027] 5…Negative electrode current collector

[0028] 10…All-solid-state batteries DETAILED DESCRIPTION

[0029] The following figures describe the all-solid-state battery disclosed herein in detail. Each of the following figures is a schematic diagram, and the size and shape of each part are exaggerated for ease of understanding. Furthermore, hatching to indicate component cross-sections is omitted in each figure.

[0030] Figure 1 This is a schematic cross-sectional view illustrating an all-solid-state battery in the present disclosure. Figure 1 The all-solid-state battery 10 shown in FIG. T The all-solid-state battery 10 includes, in this order, a positive electrode layer 1, a solid electrolyte layer 3, and a negative electrode layer 2. Specifically, the all-solid-state battery 10 includes a positive electrode layer 1, a negative electrode layer 2, and the solid electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2. Furthermore, the all-solid-state battery 10 includes a positive electrode current collector 4 that collects electrons from the positive electrode layer 1, and a negative electrode current collector 5 that collects electrons from the negative electrode layer 2. Furthermore, at least one of the positive electrode layer 1 and the solid electrolyte layer 3 contains an inorganic solid electrolyte. Furthermore, the negative electrode layer 2 contains a polymer electrolyte.

[0031] Figure 2 (a) is a schematic top view illustrating the relationship between the negative electrode layer and the solid electrolyte layer in the present disclosure. Figure 1 The upper side of the accompanying drawings faces the lower side of the accompanying drawings Figure 1 A schematic top view of the negative electrode layer 2 and the solid electrolyte layer 3 in FIG. Figure 2 (b) is a schematic top view illustrating the relationship between the negative electrode layer and the positive electrode layer in the present disclosure. Figure 1 The upper side of the accompanying drawings faces the lower side of the accompanying drawings Figure 1 A schematic top view of the negative electrode layer 2 and the positive electrode layer 1 in FIG. Figure 2 As shown in (a) and (b), when the all-solid-state battery is viewed in plan along the thickness direction, the area of ​​the negative electrode layer 2 is smaller than the area of ​​the solid electrolyte layer 3 and the area of ​​the positive electrode layer 1.

[0032] According to the present disclosure, the area of ​​the negative electrode layer is smaller than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer, so even if at least one of the positive electrode layer and the solid electrolyte layer contains an inorganic solid electrolyte and the negative electrode layer contains a polymer electrolyte, the occurrence of internal short circuits can be suppressed. As mentioned above, in all-solid-state batteries in which at least one of the positive electrode layer and the solid electrolyte layer contains an inorganic solid electrolyte and the negative electrode layer contains a polymer electrolyte, there is a unique problem of internal short circuits being prone to occur. In particular, as shown in Patent Document 1, in all-solid-state batteries in which the area of ​​the negative electrode layer is larger than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer, the occurrence of internal short circuits becomes significant. In contrast, in the present disclosure, the area of ​​the negative electrode layer is smaller than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer, so the occurrence of internal short circuits is effectively suppressed. In addition, because the negative electrode layer contains a soft polymer electrolyte, the reduction in battery performance caused by the expansion and contraction of the negative electrode active material is suppressed. In addition, because at least one of the positive electrode layer and the solid electrolyte layer contains an inorganic solid electrolyte with high ion conductivity, an all-solid-state battery with good battery performance can be obtained.

[0033] 1. Negative electrode layer

[0034] The negative electrode layer in the present disclosure generally contains a negative electrode active material and a polymer electrolyte. In addition, when the all-solid-state battery is viewed from above along the thickness direction, the area of ​​the negative electrode layer is smaller than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer.

[0035] exist Figure 2 In (a), the solid electrolyte layer 3 is arranged to cover the entire periphery of the negative electrode layer 2, and the area of ​​the negative electrode layer 2 is smaller than that of the solid electrolyte layer 3. Figure 2 In (b), the positive electrode layer 1 is arranged to cover the entire periphery of the negative electrode layer 2 , and the area of ​​the negative electrode layer 2 is smaller than that of the positive electrode layer 1 .

[0036] Here, the area of ​​the positive electrode layer is set to S1, the area of ​​the negative electrode layer is set to S2, and the area of ​​the solid electrolyte layer is set to S3. The ratio of S3 to S2 (S3 / S2) is, for example, greater than 1.01, may be greater than 1.03, or may be greater than 1.05. If S3 / S2 is small, the occurrence of internal short circuit may not be fully suppressed. On the other hand, the upper limit of the ratio of S3 to S2 (S3 / S2) is not particularly limited. If S3 / S2 is large, the volume energy density may decrease. In addition, the ratio of S1 to S2 (S1 / S2) is, for example, greater than 1.01, may be greater than 1.03, or may be greater than 1.05. On the other hand, the upper limit of the ratio of S1 to S2 (S1 / S2) is not particularly limited.

[0037] In addition, if Figure 3 As shown, the solid electrolyte layer 3 may have multiple layers (3a, 3b, 3c). In the embodiment described later, the first layer 3a is transferred to the positive electrode layer 1, and the third layer 3c is transferred to the negative electrode layer 2. Then, the second layer 3b is arranged between the first layer 3a and the third layer 3c and pressed to form the solid electrolyte layer 3. In this case, the solid electrolyte layer 3 has a portion with the same area as the negative electrode layer 2 ( Figure 3 The portion corresponding to the third layer 3c) and the portion having the same area as the positive electrode layer 1 ( Figure 3 In this way, when the solid electrolyte layer 3 has portions with different areas when viewed from above, the area S3 of the solid electrolyte layer is the area of ​​the largest portion.

[0038] Furthermore, an interface may exist between the first layer 3a and the second layer 3b, but this interface may disappear during pressing. In other words, there may not be an interface between the first layer 3a and the second layer 3b. Similarly, an interface may exist between the second layer 3b and the third layer 3c, but this interface may disappear during pressing. In other words, there may not be an interface between the second layer 3b and the third layer 3c.

[0039] (1) Polymer electrolyte

[0040] 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.

[0041] 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 be a homopolymer or a copolymer of, for example, an epoxy compound (for example, ethylene oxide, propylene oxide).

[0042] The polymer component may have the following ion-conducting units. Examples of the ion-conducting unit include polyethylene oxide, polypropylene oxide, polymethacrylate, polyacrylate, polydimethylsiloxane, polyacrylic acid, polymethacrylic acid, polyvinyl acetate, polyimide, polyamine, polyamide, polyalkyl carbonate, polynitrile, polyphosphazene, polyolefin, and polydiene.

[0043] 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.

[0044] 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. It is particularly preferred that the negative electrode layer contain a dry polymer electrolyte, and that at least one of the positive electrode layer and the solid electrolyte layer contain a sulfide solid electrolyte. This is because it can suppress degradation of the sulfide solid electrolyte caused by the solvent.

[0045] 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.

[0046] 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.

[0047] The negative electrode layer contains at least a polymer electrolyte as a solid electrolyte. The negative electrode layer preferably contains a polymer electrolyte as the main component of the solid electrolyte. In the negative electrode layer, the proportion 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 negative electrode layer may contain only a polymer electrolyte as the solid electrolyte.

[0048] The proportion of the polymer electrolyte in the negative electrode 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 layer is, for example, 70% by volume or less, or 60% by volume or less.

[0049] (2) Negative electrode active material

[0050] The negative electrode layer in the present disclosure contains a negative electrode active material. Examples of the negative electrode active material include metal active materials such as Si, Sn, and Li; carbon active materials such as graphite; and oxide active materials such as lithium titanate. In addition, the negative electrode active material may be a Si-based active material containing at least Si. Si-based active materials undergo large volume changes associated with charge and discharge, and are therefore prone to degradation of battery performance due to expansion and contraction. In response to this, in the present disclosure, degradation of battery performance due to expansion and contraction can be suppressed by using a soft polymer electrolyte for the negative electrode layer. Examples of the Si-based active material include Si element, Si alloy, and Si oxide. The Si alloy preferably contains element Si as a 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.

[0051] In addition, the total volume expansion rate caused by charging of the negative electrode active material can be 13% or more. Here, the total volume expansion rate caused by charging of graphite is 13% (Simon Schweidler et al., "Volume Changes of Graphite Anodes Revisited: A Combined Operando X-ray Diffraction and In Situ Pressure Analysis Study", J. Phys. Chem. C 2018, 122, 16, 8829-8835). That is, the total volume expansion rate of the negative electrode active material in the present disclosure caused by charging can be equal to or higher than that of graphite. The total volume expansion rate of the negative electrode active material caused by charging can be 100% or more, or 200% or more. The total volume expansion rate caused by charging can be obtained by space group independent evaluation as described by Simon Schweidler et al.

[0052] The shape of the negative electrode active material may be, for example, a granular shape. The average particle size (D 50 ) is, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D 50 ) is, for example, 50 μm or less, or 20 μm or less. 50 ) can be calculated, for example, by measurement using a laser diffraction particle size distribution analyzer or a scanning electron microscope (SEM).

[0053] The proportion of the negative electrode active material in the negative electrode layer is, for example, 20% by weight or more, 40% by weight or more, or 60% by weight or more. Alternatively, the proportion of the negative electrode active material is, for example, 80% by weight or less.

[0054] (3) Negative electrode layer

[0055] The negative electrode layer may contain a conductive material. By adding a conductive material, the electronic conductivity of the negative electrode layer is improved. Examples of carbon materials 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). In addition, the negative electrode layer may also contain a binder. By adding a binder, the constituent materials of the negative electrode layer are firmly bonded. Examples of binders include fluoride-based binders, polyimide-based binders, and rubber-based binders. In addition, the thickness of the negative electrode layer is, for example, not less than 0.1 μm and not more than 1000 μm.

[0056] 2. Positive electrode layer

[0057] The positive electrode layer in the present disclosure contains at least a positive electrode active material. The positive electrode layer preferably contains a solid electrolyte. Examples of solid electrolytes include inorganic solid electrolytes and polymer electrolytes. Regarding the polymer electrolyte, the same information as described in "1. Negative Electrode Layer" above is provided.

[0058] Examples of inorganic solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. Furthermore, the inorganic solid electrolyte may be glass (amorphous), glass ceramic, or crystal. Glass is obtained, for example, by amorphizing a raw material. Glass ceramics are obtained, for example, by heat-treating glass. Crystals are obtained, for example, by heating a raw material.

[0059] For example, the sulfide solid electrolyte preferably contains 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 at least one of O (oxygen) and 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 ratio among all anionic elements.

[0060] 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, BS4 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.

[0061] The sulfide solid electrolyte may include a crystalline phase having ion conductivity. Examples of the crystalline phase include a Thio-LISICON type crystalline phase, an LGPS type crystalline phase, and an Argentite type crystalline phase.

[0062] 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(Al,Ti)(PO4)3; sodium superion conductor-type solid electrolytes, such as Li3PO4; Li-PO4-based solid electrolytes, such as Li3BO3. Furthermore, when the oxide solid electrolyte contains anionic elements other than O (such as S and halogens), it is preferred that O has the highest molar ratio among all anionic elements.

[0063] 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). When a halide solid electrolyte contains an anion element other than a halogen (e.g., S and O), the halogen preferably has the highest molar ratio among all the anion elements.

[0064] The shape of the inorganic solid electrolyte may be, for example, a granular shape. The average particle size (D 50 ) 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 (D 50 ) is, for example, less than 50 μm, or less than 20 μm.

[0065] The positive electrode layer preferably contains an inorganic solid electrolyte as the main component of the solid electrolyte. In the positive electrode layer, 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 layer may contain only an inorganic solid electrolyte as the solid electrolyte.

[0066] The proportion of the inorganic solid electrolyte in the positive electrode layer 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 layer is, for example, 60% by volume or less, or 50% by volume or less.

[0067] In addition, the positive electrode layer contains a positive electrode active material. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active materials include LiCoO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layered active materials, LiMn2O4, Li4Ti5O 12 Spinel-type active materials such as LiFePO4 and olivine-type active materials such as LiFePO4.

[0068] 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. Examples of Li-ion-conducting oxides include LiNbO₃. The thickness of the protective layer is, for example, from 1 nm to 30 nm. Alternatively, Li₂S can be used as the positive electrode active material.

[0069] The shape of the positive electrode active material may be, for example, a granular shape. The average particle size (D 50 ) 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 (D 50 ) is, for example, less than 50 μm, or less than 20 μm.

[0070] The positive electrode layer may further contain at least one of a conductive material and a binder. The conductive material and binder are the same as those described in "1. Negative Electrode Layer" above, so their description is omitted here. The thickness of the positive electrode layer is, for example, not less than 0.1 μm and not more than 1000 μm.

[0071] 3. Solid electrolyte layer

[0072] The solid electrolyte layer in the present disclosure is arranged between the positive electrode layer and the negative electrode layer, and contains at least a solid electrolyte. As the solid electrolyte, for example, an inorganic solid electrolyte and a polymer electrolyte can be cited. Regarding the inorganic solid electrolyte and the polymer electrolyte, the contents are the same as those described in the above "1. Negative electrode layer" and the above "2. Positive electrode layer". The solid electrolyte layer preferably contains an inorganic solid electrolyte as the main component of the solid electrolyte. In the solid electrolyte layer, the proportion of the inorganic solid electrolyte to the total solid electrolyte is, for example, 50% by volume or more, can be 70% by volume or more, or can be 90% by volume or more. The solid electrolyte layer may contain only an inorganic solid electrolyte as the solid electrolyte.

[0073] In addition, in the present disclosure, at least one of the positive electrode layer and the solid electrolyte layer contains an inorganic solid electrolyte. For example, when both the positive electrode layer and the solid electrolyte layer contain an inorganic solid electrolyte, both the positive electrode layer and the solid electrolyte layer become hard layers. On the other hand, the negative electrode layer containing a polymer electrolyte becomes a soft layer. As a result, when the layers are pressed together, deformation is particularly likely to occur in the negative electrode layer. Even in this case, the occurrence of internal short circuits can be effectively suppressed by making the area of ​​the negative electrode layer smaller than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer. The composition of the inorganic solid electrolyte in the positive electrode layer and the inorganic solid electrolyte in the solid electrolyte layer may be the same or different.

[0074] The solid electrolyte layer may contain a binder. The binder is the same as described in "1. Negative Electrode Layer" above, so its description is omitted here. The thickness of the solid electrolyte layer is, for example, 0.1 μm to 1000 μm.

[0075] 4. Other structures

[0076] The all-solid-state battery disclosed herein generally comprises a positive electrode current collector that collects electrons from the positive electrode layer and a negative electrode current collector that collects electrons from the negative electrode layer. Examples of materials for the positive electrode current collector include SUS, aluminum, nickel, and carbon. Examples of shapes for the positive electrode current collector include foil. On the other hand, examples of materials for the negative electrode current collector include SUS, copper, nickel, and carbon. Examples of shapes for the negative electrode current collector include foil.

[0077] The all-solid-state battery disclosed herein may also have a constraining fixture that applies constraining pressure to the positive electrode layer, solid electrolyte layer, and negative electrode layer along the thickness direction. By applying the constraining pressure, a good ion conduction path and electron conduction path are formed. The constraining pressure is, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. On the other hand, the constraining pressure is, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0078] 5. All-solid-state batteries

[0079] The all-solid-state battery disclosed herein has a power generation unit, and the power generation unit has a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. The all-solid-state battery may have only one power generation unit, or may have two or more power generation units. In the case where the all-solid-state battery has multiple power generation units, they may be connected in parallel or in series. In addition, the all-solid-state battery has an outer casing that accommodates the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. Examples of the outer casing include a laminated outer casing and a canned outer casing.

[0080] The all-solid-state battery in the present disclosure is typically an all-solid-state lithium-ion secondary battery. The purpose 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 products such as information processing devices.

[0081] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely illustrative, and any solutions that have substantially the same technical concept as that described in the claims of the present disclosure and that exhibit the same functions and effects are all encompassed within the technical scope of the present disclosure.

[0082] Example

[0083] [Comparative Example 1]

[0084] (Preparation of Polymer Electrolyte Solution)

[0085] Polyethylene oxide (PEO; Mw: approximately 4,000,000) and lithium bis(trifluoromethylsulfonyl)imide (Li-TFSI) were weighed to a molar ratio of EO unit:Li = 20:1 and dissolved in acetonitrile to obtain a polymer electrolyte solution.

[0086] (Preparation of Sulfide Solid Electrolyte)

[0087] Li2S, P2S5 and LiI are prepared as starting materials. Next, Li2S and P2S5 are weighed to a molar ratio of 75Li2S·25P2S5 (Li3PS4, original composition). Next, LiI is weighed so that the proportion of LiI becomes 15 mol%. The weighed starting materials are mixed in an agate mortar for 5 minutes, and the mixture is placed in a container of a planetary ball mill, dehydrated heptane is added, and then ZrO2 balls (φ=5mm) are added, and the container is completely sealed. The container is mounted on a planetary ball mill (P7 made by Feichi) and mechanical milling is performed at a base speed of 500 rpm for 40 hours. Then, it is dried at 100°C to remove the heptane and obtain sulfide glass. The obtained sulfide glass is placed in a glass tube and heat-treated at 190°C for 10 hours to obtain a sulfide solid electrolyte as a glass ceramic.

[0088] (Fabrication of Positive Electrode Structure)

[0089] Prepare and mix the following ingredients.

[0090] Lithium nickel cobalt aluminum oxide (positive electrode active material)

[0091] ·Sulphide solid electrolyte (solid electrolyte) produced

[0092] Vapor-grown carbon fiber (conductive material)

[0093] A butyl butyrate solution containing a polyvinylidene fluoride-based binder at a ratio of 5% by weight (binder solution)

[0094] Butyl butyrate (dispersion medium)

[0095] Furthermore, the volume ratio of the positive electrode active material to the sulfide solid electrolyte was 75:25.

[0096] The resulting mixture was stirred for 30 seconds using an ultrasonic dispersing device. It was then vibrated for 30 minutes to obtain a positive electrode slurry. The resulting positive electrode slurry was applied to an Al foil (positive electrode current collector) using a doctor blade method using an applicator. After natural drying, it was dried on a hot plate at 100°C for 30 minutes. Thus, a positive electrode structure having a positive electrode current collector and a positive electrode layer was obtained.

[0097] (Fabrication of Negative Electrode Structure)

[0098] Prepare and mix the following ingredients.

[0099] Silicon particles (negative electrode active material)

[0100] Vapor-grown carbon fiber (conductive material)

[0101] A butyl butyrate solution containing a polyvinylidene fluoride-based binder at a ratio of 5% by weight (binder solution)

[0102] Butyl butyrate (dispersion medium)

[0103] The obtained mixture was stirred for 30 seconds using an ultrasonic dispersing device. Then, it was vibrated for 30 minutes to obtain a negative electrode slurry. The obtained negative electrode slurry was applied to Ni foil (negative electrode collector) by a doctor blade method using an applicator. After natural drying, it was dried on a hot plate at 100°C for 30 minutes. Thus, a precursor layer was formed on the negative electrode collector. Then, a polymer electrolyte solution was applied to the precursor layer by a doctor blade method using an applicator. At this time, the gap between the blades was adjusted so that the volume ratio of the negative electrode active material and the polymer electrolyte became 50:50. After natural drying, it was dried on a hot plate at 100°C for 30 minutes. Thus, a negative electrode structure having a negative electrode collector and a negative electrode layer was obtained.

[0104] (Fabrication of Solid Electrolyte Layer)

[0105] Prepare and mix the following ingredients.

[0106] ·Sulphide solid electrolyte (solid electrolyte) produced

[0107] A heptane solution containing a polyvinylidene fluoride-based binder at a ratio of 5% by weight (binder solution)

[0108] Heptane (dispersion medium)

[0109] The resulting mixture was stirred for 30 seconds using an ultrasonic dispersing device. Then, it was vibrated for 30 minutes to obtain a slurry for a solid electrolyte layer. The resulting slurry for a solid electrolyte layer was applied to an Al foil (transfer substrate) using a doctor blade method using an applicator. After natural drying, it was dried on a hot plate at 100°C for 30 minutes. Thus, a solid electrolyte layer was formed on the Al foil.

[0110] (Fabrication of all-solid-state batteries)

[0111] First, the positive electrode layer and solid electrolyte layer of the positive electrode structure are placed facing each other. The stack is then roll-pressed at 165°C and 100 kN. This transfers the solid electrolyte layer to the positive electrode layer and densifies the positive electrode layer. The Al foil is then peeled from the solid electrolyte layer, yielding a positive electrode structure with a solid electrolyte layer.

[0112] Next, the negative electrode layer and solid electrolyte layer in the negative electrode structure were placed facing each other. The stack was roll-pressed at room temperature and 60 kN. This transferred the solid electrolyte layer to the negative electrode layer and densified the negative electrode layer. The Al foil was then peeled from the solid electrolyte layer, yielding a negative electrode structure with a solid electrolyte layer.

[0113] Next, use φ11.28(1cm 2 ) size to punch out the positive electrode structure with the solid electrolyte layer. 2 ) size to punch out the negative electrode structure with the solid electrolyte layer. Place a φ11.74 (1.08 cm) thick sheet between the punched-out solid electrolyte layer of the positive electrode structure and the punched-out solid electrolyte layer of the negative electrode structure. 2 ) are punched out into a solid electrolyte layer and rolled at 100°C and 20 kN to bond the layers. The bonded power generation unit is then fitted with positive and negative terminals and sealed with a laminate film to create a fully solid-state battery.

[0114] [Example 1]

[0115] First, similarly to Comparative Example 1, a solid electrolyte layer, a positive electrode structure having the solid electrolyte layer, and a negative electrode structure having the solid electrolyte layer were prepared.

[0116] Next, with φ11.74(1.08cm 2) size to punch out the positive electrode structure with the solid electrolyte layer. 2 ) size to punch out the negative electrode structure with the solid electrolyte layer. Place a φ11.74 (1.08 cm) thick sheet between the punched-out solid electrolyte layer of the positive electrode structure and the punched-out solid electrolyte layer of the negative electrode structure. 2 ) are punched out into a solid electrolyte layer and rolled at 100°C and 20 kN to bond the layers. The bonded power generation unit is then fitted with positive and negative terminals and sealed with a laminate film to create a fully solid-state battery.

[0117] [evaluate]

[0118] The open circuit voltage (OCV) of the all-solid-state batteries produced in Comparative Example 1 and Example 1 was measured to confirm the presence or absence of short circuits. The results are shown in Table 1.

[0119] Table 1

[0120]

[0121] As shown in Table 1, in Comparative Example 1, the OCV was 0 V, indicating an internal short circuit. On the other hand, in Example 1, the OCV was greater than 0, indicating no internal short circuit. This demonstrates that in an all-solid-state battery containing an inorganic solid electrolyte and a polymer electrolyte, internal short circuits can be suppressed by making the area of ​​the negative electrode layer smaller than both the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer.

Claims

1. An all-solid-state battery having a positive electrode layer, a solid electrolyte layer and a negative electrode layer in sequence along the thickness direction, The positive electrode layer and the solid electrolyte layer both contain an inorganic solid electrolyte, the inorganic solid electrolyte is a sulfide solid electrolyte, and the sulfide solid electrolyte has 70 mol% or more of PS4 relative to the total anion structure. 3- Structure or SiS4 4- Structure or GeS4 4- Structure or AlS3 3- Structure or BS4 3- structure, The negative electrode layer contains a negative electrode active material and a polymer electrolyte, wherein the total volume expansion rate of the negative electrode active material caused by charging is greater than 200%. The polymer electrolyte is a dry polymer electrolyte containing a polyether polymer as a polymer component, wherein the dry polymer electrolyte is an electrolyte having a solvent component content of 1% by weight or less, and contains a supporting salt, wherein the dry polymer electrolyte has 15 mol parts or more and 30 mol parts or less of C2H5O units per 1 mol part of the supporting salt, The polyether polymer has a polyethylene oxide structure in a repeating unit, and in the polyether polymer, the polyethylene oxide structure accounts for 90 mol% or more of all the repeating units. The negative electrode active material is a Si-based active material containing at least Si, the Si-based active material is Si elemental substance, Si oxide, or a Si alloy with a Si ratio of 50 atomic % or more, and the ratio of the negative electrode active material in the negative electrode layer is 60 weight % or more and 80 weight % or less, The positive electrode layer contains only the inorganic solid electrolyte as a solid electrolyte, the proportion of the inorganic solid electrolyte in the positive electrode layer is 20 volume % or more and 50 volume % or less, and the positive electrode layer is a layer harder than the negative electrode layer, The solid electrolyte layer contains only the inorganic solid electrolyte as a solid electrolyte, and the solid electrolyte layer is a layer harder than the negative electrode layer. The negative electrode layer contains only the polymer electrolyte as a solid electrolyte, and the proportion of the polymer electrolyte in the negative electrode layer is 40% by volume or more and 60% by volume or less. When the all-solid-state battery is viewed from above along the thickness direction, the area of ​​the negative electrode layer is smaller than the area of ​​the solid electrolyte layer and the area of ​​the positive electrode layer, and the solid electrolyte layer and the positive electrode layer are configured to cover the entire periphery of the negative electrode layer. When the area of ​​the positive electrode layer is set to S1, the area of ​​the negative electrode layer is set to S2, and the area of ​​the solid electrolyte layer is set to S3, the ratio of S3 to S2 (S3 / S2) is greater than or equal to 1.05, the ratio of S1 to S2 (S1 / S2) is greater than or equal to 1.05, and S1=S3, The all-solid-state battery has a restraining jig that applies a restraining pressure of 5 MPa or more and 100 MPa or less to the positive electrode layer, the solid electrolyte layer, and the negative electrode layer in a thickness direction. The all-solid-state battery is obtained by arranging the negative electrode layer and the solid electrolyte layer to face each other and subjecting the stack of the negative electrode layer and the solid electrolyte layer to a roll pressing process under a condition of 60 kN.

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