All-solid-state battery and method for manufacturing all-solid-state battery

Abstract

The present disclosure is an all-solid battery and a manufacturing method of an all-solid battery. As a problem, the main object of the present disclosure is to provide an all-solid battery in which occurrence of short circuit is suppressed. In the present disclosure, the problem is solved by providing the following all-solid battery. The all-solid battery is an all-solid battery having a negative electrode, a positive electrode, and a solid electrolyte layer, the negative electrode having at least a negative electrode current collector, the solid electrolyte layer being disposed between the negative electrode and the positive electrode, a protective layer containing Mg being disposed between the negative electrode current collector and the solid electrolyte layer, the protective layer having a composite layer, the composite layer including Mg-containing particles containing Mg and a solid electrolyte.

Description

Technical Field

[0001] This disclosure relates to all-solid-state batteries and methods for manufacturing all-solid-state batteries. Background Technology

[0002] All-solid-state batteries are batteries with a solid electrolyte layer between the positive and negative electrodes. Compared with liquid batteries with electrolytes containing flammable organic solvents, they have the advantage of being easier to simplify safety devices.

[0003] For example, Patent Document 1 discloses an all-solid-state battery in which the reaction of the negative electrode utilizes the precipitation-dissolution reaction of metallic lithium, and a metallic Mg layer is formed on the negative electrode current collector. Furthermore, Patent Document 2 discloses an all-solid-state battery in which a protective layer comprising a composite metal oxide represented by Li-MO is provided between the negative electrode layer and the solid electrolyte layer.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-184513

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-184407 Summary of the Invention

[0008] From the viewpoint of improving the performance of all-solid-state batteries, it is necessary to suppress the occurrence of short circuits (e.g., micro-short circuits that cause performance degradation). This disclosure was made in view of the above facts, and its main objective is to provide an all-solid-state battery that suppresses the occurrence of short circuits.

[0009] To address the aforementioned issues, this disclosure provides an all-solid-state battery having a negative electrode, a positive electrode, and a solid electrolyte layer. The negative electrode has at least a negative current collector, and the solid electrolyte layer is disposed between the negative electrode and the positive electrode. A protective layer containing Mg is disposed between the negative current collector and the solid electrolyte layer. The protective layer includes a composite layer containing Mg-containing particles and a solid electrolyte.

[0010] According to this disclosure, by distributing a protective layer containing a composite material layer containing Mg particles and a solid electrolyte layer between the negative electrode current collector and the solid electrolyte layer, an all-solid-state battery that suppresses the occurrence of short circuits is achieved.

[0011] In the above disclosure, in the above composite layer, the ratio of the Mg-containing particles to the total of the Mg-containing particles and the solid electrolyte can be 10% by weight or more and 90% by weight or less.

[0012] In the above disclosure, the solid electrolyte contained in the solid electrolyte layer and the solid electrolyte contained in the composite material layer can be sulfide solid electrolytes, respectively.

[0013] In the above disclosure, the protective layer may have a Mg layer at a position closer to the negative electrode current collector than the composite layer, and the Mg layer is a metal thin film containing Mg.

[0014] In the above disclosure, the negative electrode may have a layer of negative electrode active material containing precipitated Li between the negative electrode current collector and the solid electrolyte layer.

[0015] In the above disclosure, the negative electrode may not have a layer of negative electrode active material containing precipitated Li between the negative electrode current collector and the solid electrolyte layer.

[0016] In the above disclosure, the fill rate of the composite layer can be 70% or more.

[0017] Furthermore, this disclosure provides a method for manufacturing an all-solid-state battery, the all-solid-state battery having a negative electrode, a positive electrode, and a solid electrolyte layer, wherein the negative electrode has at least a negative electrode current collector, and the solid electrolyte layer is disposed between the negative electrode and the positive electrode.

[0018] A protective layer containing Mg is disposed between the aforementioned negative electrode current collector and the aforementioned solid electrolyte layer.

[0019] The protective layer includes a composite layer comprising Mg-containing particles containing the aforementioned Mg and sulfide glass.

[0020] The manufacturing method includes a particle layer formation process, a precursor layer formation process, and a composite material layer formation process.

[0021] In the particle layer formation process, a particle layer containing Mg particles is formed on the negative electrode current collector.

[0022] In the precursor layer formation process, the aforementioned particle layer is impregnated with a sulfide glass solution to form the precursor layer. The sulfide glass solution is formed by dissolving the sulfide glass in a solvent.

[0023] In the composite layer forming process, the precursor layer is dried to obtain the composite layer.

[0024] According to this disclosure, a composite layer is formed by impregnating a particle layer containing Mg particles with a sulfide glass solution and then drying it, thereby obtaining an all-solid-state battery that suppresses short circuits and has good cycle characteristics.

[0025] In the above disclosure, the sulfide glass may have a composition of Li 7-a PS6-a X a The composition represented by (X is at least one of Cl, Br and I, and a is a number greater than 0 and less than 2).

[0026] In the above disclosure, the content of the sulfide glass in the sulfide glass solution can be 10% by weight or more and 30% by weight or less.

[0027] In the above disclosure, the drying process in the above composite layer formation step can be carried out at a temperature of 60°C or higher and 80°C or lower.

[0028] In this disclosure, an all-solid-state battery is achieved that suppresses the occurrence of short circuits. Attached Figure Description

[0029] Figure 1 This is a schematic cross-sectional view illustrating the all-solid-state battery of this disclosure.

[0030] Figure 2 This is a schematic cross-sectional view illustrating the all-solid-state battery of this disclosure.

[0031] Figure 3 This is a schematic cross-sectional view illustrating the all-solid-state battery of this disclosure.

[0032] Figure 4 This is a flowchart illustrating a method for manufacturing an all-solid-state battery according to the present disclosure.

[0033] Figure 5 This is a schematic cross-sectional view illustrating a portion of the all-solid-state battery produced in the embodiments and comparative examples.

[0034] Figure 6 This is a graph showing the results of the cyclic tests in Example 4 and Comparative Examples 3 and 4.

[0035] Explanation of reference numerals in the attached figures

[0036] 1…Negative electrode active material layer

[0037] 2… Negative current collector

[0038] 3… Positive electrode active material layer

[0039] 4…Positive current collector

[0040] 5… Solid electrolyte layer

[0041] 6…protective layer

[0042] 6a…Laminated layer

[0043] 6b…Mg layer

[0044] 10… All-solid-state batteries Detailed Implementation

[0045] The following provides a detailed description of the all-solid-state battery and its manufacturing method. In this specification, when describing the arrangement of other components relative to a component, the use of "above" or "below" includes, unless otherwise specified, both the case where other components are arranged directly above or below a component in contact with it, and the case where other components are arranged above or below a component, separated by another component.

[0046] A. All-solid-state battery

[0047] Figure 1 This is a schematic cross-sectional view illustrating the all-solid-state battery of this disclosure. Figure 1 The all-solid-state battery 10 shown has a negative electrode AN, a positive electrode CA, and a solid electrolyte layer 5. The negative electrode AN has a negative current collector 2, the positive electrode CA has a positive active material layer 3 and a positive current collector 4, and the solid electrolyte layer 5 is disposed between the negative electrode AN and the positive electrode CA. Furthermore, in Figure 1 In this configuration, a protective layer 6 containing Mg is disposed between the negative electrode current collector 2 and the solid electrolyte layer 5. The protective layer 6 includes a composite layer 6a, which comprises Mg-containing particles and a solid electrolyte. Furthermore, as... Figure 1 As shown, the protective layer 6 can also be understood as a component of the negative electrode AN.

[0048] For example, if Figure 1 When the all-solid-state battery shown is charged, a layer of negative electrode active material containing deposited Li is formed between the negative electrode current collector 2 and the solid electrolyte layer 5. Specifically, as... Figure 2 As shown, a negative electrode active material layer 1 containing deposited Li is formed between the negative electrode current collector 2 and the solid electrolyte layer 5. Thus, the all-solid-state battery of this disclosure can be a battery utilizing the precipitation-dissolution reaction of metallic lithium. Figure 2 In this design, a negative electrode active material layer 1 is formed between the composite layer 6a and the solid electrolyte layer 5. However, depending on the charging conditions and state of charge, it is also conceivable that the negative electrode active material layer 1 may be formed between the composite layer 6a and the negative electrode current collector 2. Furthermore, if the composite layer 6a has internal voids, it is also conceivable that Li may precipitate in these voids. Additionally, it is conceivable that the Mg contained in the protective layer 6 may alloy with Li.

[0049] According to this disclosure, by distributing a protective layer containing a composite material layer containing Mg particles and a solid electrolyte layer between the negative electrode current collector and the solid electrolyte layer, an all-solid-state battery that suppresses the occurrence of short circuits is achieved.

[0050] As mentioned in reference 1, there is a known technique for depositing a Mg layer on the negative electrode current collector in all-solid-state batteries where the reaction utilizes the precipitation-dissolution reaction of metallic lithium as the negative electrode. Depositing a Mg layer can improve the charge-discharge efficiency of the all-solid-state battery. On the other hand, under high current loads, there is a risk of uneven precipitation and dissolution of metallic lithium, potentially leading to short circuits. Furthermore, uneven precipitation of Li could result in the stripping of the Li layer (the negative electrode active material layer). This could lead to increased battery resistance and decreased capacity retention in the all-solid-state battery.

[0051] In contrast, in this disclosure, since the protective layer comprises a composite layer containing Mg particles and a solid electrolyte, it becomes an all-solid-state battery that suppresses the occurrence of short circuits. This is believed to be because: through the contact between the solid electrolyte contained in the solid electrolyte layer and the solid electrolyte contained in the composite layer, power concentration is suppressed, thereby suppressing localized Li deposition and the occurrence of short circuits. Furthermore, it is believed that the deposited Li alloys with the Mg particles, and the Li diffuses within the alloy. Thus, it is believed that the deposited Li layer and the composite layer are tightly bonded through an anchoring effect, suppressing the peeling of the deposited Li layer. Moreover, by suppressing the peeling of the deposited Li layer, the redissolution of the deposited Li layer is facilitated during discharge, suppressing the increase in battery resistance. Therefore, since the protective layer comprises a composite layer containing Mg particles and a solid electrolyte, the input-output characteristics of Li at the negative electrode layer side interface of the solid electrolyte layer are improved, resulting in an all-solid-state battery that suppresses the occurrence of short circuits.

[0052] 1. Protective layer

[0053] The protective layer in this disclosure is a layer containing Mg disposed between the negative electrode current collector and the solid electrolyte layer. The protective layer includes at least a composite layer comprising Mg-containing particles and a solid electrolyte.

[0054] (1) Composite layer

[0055] The composite layer contains Mg-containing particles and a solid electrolyte. The Mg-containing particles and the solid electrolyte are mixed together in the composite layer.

[0056] (i) Containing Mg particles

[0057] Mg-containing particles contain Mg. Mg-containing particles can be particles of elemental Mg (Mg particles) or particles containing Mg and elements other than Mg. Examples of elements other than Mg include Li, and metals other than Li (including half-metals). Other examples of elements other than Mg include nonmetals such as O.

[0058] Li nuclei readily and stably form on Mg-containing particles; therefore, using Mg-containing particles enables more stable Li precipitation. Furthermore, Mg can form a large single-phase region with Li, thus achieving more efficient Li dissolution and precipitation.

[0059] Mg-containing particles can be alloy particles containing Mg and metals other than Mg (Mg alloy particles). Mg alloy particles are preferably alloys containing Mg as the main component. Examples of metals M other than Mg in Mg alloy particles include Li, Au, Al, and Ni. Mg alloy particles can contain one type of metal M or two or more types of metal M. Furthermore, Mg-containing particles can contain Li or not. In the former case, the alloy particles can contain a β-phase alloy of Li and Mg.

[0060] Mg-containing particles can also be oxide particles containing both Mg and O (Mg oxide particles). Examples of Mg oxide particles include oxides of elemental Mg and composite metal oxides represented by Mg-M′-O (where M′ is at least one of Li, Au, Al, and Ni). Mg oxide particles preferably contain at least Li as M′. M′ may or may not contain a metal other than Li. In the former case, M′ may be one or more metals other than Li. On the other hand, Mg-containing particles may not contain O.

[0061] Mg-containing particles can be primary particles or secondary particles formed by the aggregation of primary particles. Additionally, the average particle size (D) of Mg-containing particles... 50 The preferred size is small. This is because a smaller average particle size increases the dispersion of Mg particles in the composite layer, increases the reaction sites with Li, and is more effective in suppressing short circuits. The average particle size of Mg particles (D) 50 For example, it can be 500 nm or larger, or even 800 nm or larger. On the other hand, the average particle size (D) of Mg-containing particles... 50 For example, it can be less than 20 μm, less than 10 μm, or less than 5 μm. Furthermore, the average particle size can be a value calculated using particle size distribution by laser diffraction or a value determined based on image analysis using electron microscopes such as SEM.

[0062] In addition, the average particle size (D) of Mg-containing particles 50 This can be compared with the average particle size (D) of the solid electrolyte described later. 50 The average particle size of Mg-containing particles can be the same, larger, or smaller. Here, when the average particle size of the Mg-containing particles is denoted as X and the average particle size of the solid electrolyte is denoted as Y, the so-called average particle size of Mg-containing particles (D) is... 50) and the average particle size of solid electrolytes (D 50 "Same" means that the difference between the two (the absolute value of X and Y) is less than 5 μm. The so-called average particle size (D) of Mg-containing particles... 50 ) compared to the average particle size (D) of solid electrolytes 50 "Large" refers to X / Y ratios greater than 5 μm. In this case, X / Y can be 1.2 or higher, 2 or higher, or 5 or higher. On the other hand, X / Y can be 100 or lower, or 50 or lower. The so-called average particle size (D) of Mg-containing particles... 50 ) compared to the average particle size (D) of solid electrolytes 50 "Small" means that Y / X is greater than 5 μm. In this case, Y / X can be greater than 1.2, greater than 2, or greater than 5. On the other hand, Y / X can be less than 100 or less than 50.

[0063] The proportion of Mg particles in the composite layer is, for example, 10% by weight or more, and may be 30% by weight or more. On the other hand, the above-mentioned proportion of Mg particles is, for example, 90% by weight or less, and may be 70% by weight or less.

[0064] (ii) Solid electrolytes

[0065] The composite layer contains a solid electrolyte. Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, halide solid electrolytes, and coordinated hydrides. Among these, sulfide solid electrolytes are particularly preferred. Sulfide solid electrolytes typically contain sulfur (S) as the main anionic element. Oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes typically contain oxygen (O), nitrogen (N), and halogen (X) as the main anionic elements, respectively.

[0066] Sulfide solid electrolytes preferably contain, for example, Li, X (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In), and S. Additionally, sulfide solid electrolytes may also contain at least one of O and a halogen element. Furthermore, sulfide solid electrolytes preferably contain S as the main component of the anionic element.

[0067] The sulfide solid electrolyte can be a glassy sulfide solid electrolyte (sulfide glass), a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. Sulfide glass is amorphous. Preferably, the sulfide glass has a glass transition temperature (Tg). Furthermore, when the sulfide solid electrolyte has a crystalline phase, examples of such crystalline phases include the Thio-LISICON type, the LGPS type, and the argentite-germanium type.

[0068] Examples of sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-P₂S₅-LiI, Li₂S-P₂S₅-GeS₂, Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-P₂S₅-LiBr, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, and Li₂S-P₂S₅-Z. m S n (Where m and n are positive numbers. Z is any one of Ge, Zn, and Ga.) Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (Where x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.)

[0069] The composition of sulfide solid electrolytes is not particularly limited, but examples include xLi2S·(100-x)P2S5 (70≤x≤80) and yLiI·zLiBr·(100-yz)(xLi2S·(1-x)P2S5) (0.7≤x≤0.8, 0≤y≤30, 0≤z≤30).

[0070] Sulfide solid electrolytes can have the following general formula: Li 4-x Ge 1-x P x The composition represented by S4 (0 < x < 1). In the above general formula, at least a portion of Ge can be substituted by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, at least a portion of P can be substituted by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, a portion of Li can be substituted by at least one of Na, K, Mg, Ca, and Zn. In the above general formula, a portion of S can be substituted by at least one of a halogen (F, Cl, Br, and I).

[0071] Sulfide solid electrolytes, for example, can have Li 7-a PS 6-a X aThe composition is represented by (X is at least one of Cl, Br, and I, and a is a number greater than 0 and less than 2). a can be 0 or greater than 0. In the latter case, a can be greater than 0.1, greater than 0.5, or greater than 1. In addition, a can be less than 1.8 or less than 1.5.

[0072] Solid electrolytes can be glassy or have a crystalline phase. They are typically in particle form. The average particle size (D) of solid electrolytes... 50 For example, it is 0.01 μm or larger. On the other hand, the average particle size (D) of solid electrolytes... 50 For example, the thickness can be below 10 μm, or below 5 μm. The ionic conductivity of a solid electrolyte at 25 °C is, for example, 1 × 10⁻⁶. -4 For values ​​above S / cm, it can be 1×10 -3 S / cm or higher.

[0073] The proportion of solid electrolyte in the composite layer is, for example, 10% by weight or more, and can be 30% by weight or more. On the other hand, the proportion of solid electrolyte in the composite layer is, for example, 90% by weight or less, and can be 70% by weight or less. Furthermore, in the composite layer, the proportion of Mg particles relative to the total amount of Mg particles and solid electrolyte is, for example, 10% by weight or more, and can be 30% by weight or more. On the other hand, the aforementioned proportion of Mg particles is, for example, 90% by weight or less, and can be 70% by weight or less.

[0074] (iii) Composite layer

[0075] The fill rate of the composite layer is not particularly limited, but a high fill rate is preferred. This is because a high fill rate of the composite layer results in better cycle characteristics of the all-solid-state battery. The fill rate of the composite layer can be, for example, 70% or more, 80% or more, 90% or more, 95% or more, or 98% or more. Alternatively, the fill rate of the composite layer can be 100%. Furthermore, the fill rate of the composite layer can be calculated using the following method: The total volume obtained by dividing the weight of each material contained in the composite layer (including Mg particles, solid electrolyte, etc.) by the true density of each material is taken as the "volume of the composite layer calculated from the true density," and the volume calculated from the actual dimensions of the composite layer is taken as the "actual volume of the composite layer." The fill rate (%) can then be obtained using the following formula.

[0076] Fill power (%) = (Volume of the composite layer calculated from true density) / (Actual volume of the composite layer) × 100

[0077] The composite layer may also contain an adhesive as needed. This helps to suppress cracking in the composite layer itself. Examples of adhesives include fluorinated adhesives and rubber-based adhesives. Examples of fluorinated adhesives include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Examples of rubber-based adhesives include butadiene rubber (BR), acrylate-butadiene rubber (ABR), and styrene-butadiene rubber (SBR). The thickness of the composite layer is, for example, 0.1 μm or more and 1000 μm or less.

[0078] The protective layer in this disclosure may consist of only one composite layer or two or more composite layers. Furthermore, as a method for forming the composite layer, for example, a method of coating a slurry containing at least Mg particles and a solid electrolyte onto a substrate can be listed. Another method is to form a particle layer containing Mg particles, then impregnate the particle layer with an electrolyte solution formed by dissolving a solid electrolyte in a solvent, and then dry it.

[0079] (2) Mg layer

[0080] like Figure 3 As shown, the protective layer 6 may also have a Mg layer 6b containing Mg but not a solid electrolyte at a position closer to the negative electrode current collector 2 than the composite layer 6a. By distributing a Mg layer between the negative electrode current collector and the composite layer, Li diffusion can be further promoted. In addition, since the solid electrolyte contained in the composite layer does not directly contact the negative electrode current collector, the deposition starting point of Li can be limited to the Mg layer. As a result, Li can be deposited more uniformly.

[0081] The Mg layer is the layer in which Mg has the highest proportion of all constituent elements. The proportion of Mg in the Mg layer can be, for example, 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. Examples of Mg layers include Mg-containing metal thin films (e.g., vapor-deposited films) and layers containing Mg particles. Mg-containing metal thin films are preferably Mg-dominant. Regarding Mg particles, the above applies. The Mg layer can also be a layer containing only Mg particles.

[0082] The thickness of the Mg layer is, for example, 10 nm or more and 10 μm or less. When the Mg layer is a Mg-containing metal thin film, its thickness is preferably 5000 nm or less, but can be 3000 nm or less, 1000 nm or less, or 700 nm or less. Alternatively, the thickness of the Mg layer can be 50 nm or more, or 100 nm or more.

[0083] The protective layer in this disclosure may have only one Mg layer or two or more Mg layers. On the other hand, the protective layer in this disclosure may not have a Mg layer. As a method for forming the Mg layer, examples include PVD methods such as vapor deposition and sputtering, or plating methods such as electrolytic plating and electroless plating, to form a film on the negative electrode current collector; and methods of pressing Mg-containing particles.

[0084] In addition, such as Figure 3 As shown, the Mg layer 6b and the composite layer 6a can be in direct contact. Similarly, the composite layer 6a and the solid electrolyte layer 5 can also be in direct contact. Likewise, the Mg layer 6b and the negative electrode current collector 2 can also be in direct contact. Additionally, as... Figure 1 As shown, the composite layer 6a and the negative current collector 2 can also be in direct contact.

[0085] 2. Negative electrode

[0086] The negative electrode in this disclosure has at least a negative current collector. For example... Figure 1 As shown, the negative electrode AN can be positioned between the negative electrode current collector 2 and the solid electrolyte layer 5 without having a layer of negative electrode active material containing deposited Li. Additionally, as... Figure 2 As shown, the negative electrode AN can also have a negative electrode active material layer 1 containing precipitated Li between the negative electrode current collector 2 and the solid electrolyte layer 5.

[0087] When the negative electrode has a negative electrode active material layer, the negative electrode active material layer preferably contains at least one of elemental Li and Li alloy as the negative electrode active material. Furthermore, in this disclosure, elemental Li and Li alloy are sometimes collectively referred to as Li-based active materials. When the negative electrode active material layer contains Li-based active materials, the Mg-containing particles in the protective layer may or may not contain Li.

[0088] For example, in an all-solid-state battery manufactured using Li foil or Li alloy foil as the negative electrode active material and Mg particles as the Mg-containing active material, it is presumed that the Mg particles alloy with Li during the first discharge. On the other hand, in an all-solid-state battery manufactured without a negative electrode active material layer, using Mg particles as the Mg-containing active material and using Li-containing positive electrode active material, it is presumed that the Mg particles alloy with Li during the first charge.

[0089] In the negative electrode active material layer, as a Li-based active material, it may contain only one of elemental Li and Li alloy, or it may contain both elemental Li and Li alloy.

[0090] Li alloys are preferably alloys containing Li as the main component. Examples of Li alloys include Li-Au, Li-Mg, Li-Sn, Li-Al, Li-B, Li-C, Li-Ca, Li-Ga, Li-Ge, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Cd, Li-In, Li-Sb, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, and Li-At. A Li alloy may consist of only one type or two or more types.

[0091] Examples of the shapes of Li-based active materials include foil and granules. Additionally, Li-based active materials can also be deposited metallic lithium.

[0092] The thickness of the negative electrode active material layer is not particularly limited, but it can be, for example, greater than 1 nm and less than 1000 μm, or greater than 1 nm and less than 500 μm.

[0093] Examples of materials for the negative electrode current collector include SUS (stainless steel), Cu, Ni, In, Al, and C. Examples of shapes for the negative electrode current collector include foil, mesh, and porous structures. Furthermore, the surface of the negative electrode current collector may or may not be roughened. A smooth surface is preferred from the viewpoint of wettability. Conversely, a rough surface is preferred from the viewpoint of increasing the contact area with the negative electrode current collector. Increased contact area results in stronger interfacial bonding and better suppression of component delamination. The surface roughness (Ra) of the negative electrode current collector is, for example, 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. On the other hand, the surface roughness (Ra) of the negative electrode current collector is, for example, 5 μm or less, or 3 μm or less. The surface roughness (Ra) can be determined using a method based on JIS B0601.

[0094] 4. Positive electrode

[0095] The positive electrode in this disclosure preferably comprises a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer in this disclosure is a layer containing at least a positive electrode active material. In addition, the positive electrode active material layer may also contain at least one of a solid electrolyte, a conductive material, and a binder, as needed.

[0096] The positive electrode active material is not particularly limited if it has a higher reaction potential than the negative electrode active material; any positive electrode active material suitable for all-solid-state batteries can be used. The positive electrode active material may or may not contain lithium.

[0097] Lithium oxides are an example of positive electrode active materials containing lithium. Examples of lithium oxides include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layered active substances, Li4Ti5O 12 LiMn2O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4 and LiMn 1.5 Zn 0.5 Spinel-type active materials such as O4, and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. Other examples of positive electrode active materials containing lithium include LiCoN, Li2SiO3, Li4SiO4, lithium sulfide (Li2S), and lithium polysulfide (Li2S). x (2≤x≤8).

[0098] On the other hand, examples of positive electrode active materials that do not contain lithium include transition metal oxides such as V2O5 and MoO3; S-based active materials such as S and TiS2; Si-based active materials such as Si and SiO; and lithium storage intermetallic compounds such as Mg2Sn, Mg2Ge, Mg2Sb, and Cu3Sb.

[0099] Alternatively, a coating containing an ion-conducting oxide can be formed on the surface of the positive electrode active material. This coating can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of ion-conducting oxides include LiNbO3 and Li4Ti5O3. 12 Li3PO4.

[0100] The proportion of positive electrode active material in the positive electrode active material layer is, for example, 20% by weight or more, 30% by weight or more, or 40% by weight or more. On the other hand, the proportion of positive electrode active material in the positive electrode active material layer is, for example, 80% by weight or less, 70% by weight or less, or 60% by weight or less.

[0101] Examples of conductive materials include carbon materials. Specific examples of carbon materials include acetylene black, Ketjen black, VGCF, and graphite. The solid electrolyte and binder are the same as described in "1. Protective Layer". Furthermore, the thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

[0102] A positive current collector is, for example, disposed on the side opposite to the solid electrolyte layer, with the positive active material layer as a reference. Examples of materials for the positive current collector include Al, Ni, and C. Examples of shapes for the positive current collector include foil, mesh, and porous structures.

[0103] 5. Solid electrolyte layer

[0104] The solid electrolyte layer in this disclosure is a layer containing at least a solid electrolyte. Additionally, the solid electrolyte layer may also contain an adhesive if necessary. The description of the solid electrolyte and adhesive is the same as that in "1. Protective Layer".

[0105] The solid electrolyte in the solid electrolyte layer and the solid electrolyte in the composite layer are preferably the same type of solid electrolyte. This is because it improves the adhesion between the solid electrolyte layer and the composite layer. Specifically, if the solid electrolyte in the solid electrolyte layer is a sulfide solid electrolyte, it is preferable that the solid electrolyte in the composite layer is also a sulfide solid electrolyte. The same applies when other inorganic solid electrolytes, such as oxide solid electrolytes or nitride solid electrolytes, are used instead of sulfide solid electrolytes. Furthermore, the thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0106] 6. All-solid-state batteries

[0107] The all-solid-state battery of this disclosure may also include a restraining jig that applies restraining pressure to the positive electrode, the solid electrolyte layer, and the negative electrode along the thickness direction. Known jigs can be used as the restraining jig. The restraining pressure is, for example, 0.1 MPa or more, and can be 1 MPa or more. On the other hand, the restraining pressure is, for example, 50 MPa or less, 20 MPa or less, 15 MPa or less, and 10 MPa or less.

[0108] The type of all-solid-state battery disclosed herein is not particularly limited, but a typical example is a lithium-ion secondary battery. The all-solid-state battery in this disclosure can be a single cell or a stacked battery. The stacked battery can be a unipolar stacked battery (parallel-connected stacked battery) or a bipolar stacked battery (series-connected stacked battery). Examples of battery shapes include coin-shaped, laminated, cylindrical, and square.

[0109] Examples of applications for the all-solid-state batteries disclosed herein include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. Furthermore, the all-solid-state batteries disclosed herein can also be used as power sources for mobile bodies other than vehicles (e.g., railway trains, ships, and aircraft), and as power sources for electrical products such as information processing devices.

[0110] B. Manufacturing method of all-solid-state batteries

[0111] Figure 4 This is a flowchart illustrating a method for manufacturing an all-solid-state battery according to this disclosure. Figure 4 In the manufacturing method shown, firstly, a particle layer containing Mg particles is formed on the negative electrode current collector (particle layer formation process). Next, the particle layer is impregnated with a sulfide glass solution formed by dissolving sulfide glass in a solvent to form a precursor layer (precursor layer formation process). Next, the precursor layer is dried to obtain a composite layer (composite layer formation process).

[0112] According to this disclosure, an all-solid-state battery with good cycle characteristics and the ability to suppress short circuits can be obtained by impregnating a particle layer containing Mg particles with a sulfide glass solution and then drying it. Specifically, since the composite layer contains Mg particles and sulfide glass, an all-solid-state battery with suppressed short circuits can be obtained. Furthermore, a precursor layer is formed by impregnating the particle layer with a sulfide glass solution. At this time, the sulfide glass solution penetrates into the internal voids of the particle layer (e.g., the voids between Mg particles), and therefore, after subsequent drying, a composite layer with a high fill factor is obtained. As a result, an all-solid-state battery with good cycle characteristics can be obtained. In addition, when a protective layer (Mg layer) is formed using a so-called vapor deposition method, although the fill factor of the protective layer increases, the formation of the protective layer becomes difficult when the battery size increases (scale up). Furthermore, it is generally difficult to form a composite layer containing Mg particles and sulfide glass in the vapor deposition method.

[0113] 1. Particle layer formation process

[0114] The particle layer formation process is a process of forming a particle layer containing Mg particles on the negative electrode current collector. The information regarding the Mg particles and the negative electrode current collector is the same as described in "A. All-Solid-State Cells".

[0115] In the particle layer formation process, for example, a particle layer is formed by coating a slurry and drying it, wherein the slurry is formed by dispersing Mg-containing particles in a solvent (dispersion medium). Examples of solvents (dispersion media) include organic solvents such as mesitylene. Alternatively, a binder may be added to the slurry. Regarding the binder, the information is the same as described in "A. All-Solid-State Batteries".

[0116] The aforementioned slurry can be directly coated onto the negative electrode current collector. Alternatively, the aforementioned slurry can also be coated onto the aforementioned Mg layer formed on the negative electrode current collector. Examples of slurry coating methods include, for instance, the doctor blade method.

[0117] 2. Precursor layer formation process

[0118] The precursor layer formation process is a process in which the particle layer is impregnated with a sulfide glass solution formed by dissolving sulfide glass in a solvent to form the precursor layer of the composite material layer.

[0119] Regarding sulfide glasses (glass-based sulfide solid electrolytes), the information is the same as described in "A. All-Solid-State Batteries". In particular, the sulfide glass preferably has a composition of Li. 7-a PS 6-a X a The composition represented by (X is at least one of Cl, Br and I, and a is a number greater than 0 and less than 2).

[0120] Sulfide glasses can be obtained, for example, by subjecting a raw material composition to an amorphous process. Examples of raw material compositions include mixtures of lithium halides, Li₂S, and P₂S₅. Examples of amorphous processes include, for instance, mechanical milling.

[0121] A sulfide glass solution can be obtained by mixing the aforementioned sulfide glass with a solvent. Examples of solvents include alcohol-based solvents having 1 or more but less than 10 carbon atoms. Ethanol is particularly preferred. In the sulfide glass solution, the sulfide glass may be completely dissolved in the solvent, or only partially dissolved (the sulfide glass solution may also contain undissolved sulfide glass).

[0122] The content of sulfide glass in the sulfide glass solution is, for example, 10% by weight or more, or 15% by weight or more. On the other hand, the aforementioned content of sulfide glass is, for example, 30% by weight or less, or 25% by weight or less, or 20% by weight or less. If the content is too high, it is difficult for the sulfide glass to properly impregnate the particle layer. On the other hand, if the content is too low, there is a risk of prolonged drying time, as described later.

[0123] The method for impregnating the particle layer with a sulfide glass solution is not particularly limited as long as the sulfide glass solution can come into contact with the particle layer. For example, an impregnation method could be described by dripping the sulfide glass solution into the particle layer.

[0124] 3. Composite layer formation process

[0125] The composite layer formation process involves drying the precursor layer to obtain the composite layer. Regarding the composite layer, the information is the same as described in "A. All-Solid-State Cells". In the composite layer formation process, the solvent contained in the aforementioned sulfide glass solution is evaporated.

[0126] Drying can be done naturally or by heating. In the latter case, the drying temperature is not particularly limited if it allows the liquid components to evaporate; for example, it can be between 60°C and 80°C. At such a temperature, the liquid components can evaporate slowly, suppressing the formation of voids in the composite layer. As a result, the fill rate of the composite layer can be further improved.

[0127] There is no particular limitation on the drying time; for example, it can be more than 5 minutes and less than 1 hour. Furthermore, the drying atmosphere can be atmospheric pressure or a reduced pressure atmosphere. For example, a vacuum atmosphere can be used as a reduced pressure atmosphere.

[0128] Furthermore, the laminate layer forming process can include a single-stage drying process or a two-stage drying process. In the latter case, the drying temperature T1 of the first stage is preferably the drying temperature described above, and the drying temperature T2 of the second stage is preferably higher than T1. T2-T1 is, for example, 50°C or higher. By including a two-stage drying process, the laminate layer forming process can suppress the formation of voids in the laminate layer and more reliably allow the liquid components to evaporate.

[0129] 4. Other processes

[0130] In the method for manufacturing an all-solid-state battery disclosed herein, the above-described steps enable the manufacture of a negative electrode having at least a negative current collector and a protective layer. Furthermore, the method for manufacturing an all-solid-state battery typically includes a solid electrolyte layer formation step, a positive electrode active material layer formation step, and a current collector arrangement step. General methods for manufacturing all-solid-state batteries can be listed as these steps. Additionally, a step may be included in which the aforementioned Li layer (negative electrode active material layer) is formed by pre-charging the manufactured all-solid-state battery. The solid electrolyte layer, positive electrode active material layer, negative electrode active material layer, and current collector are the same as those described in "A. All-Solid-State Battery".

[0131] 5. All-solid-state batteries

[0132] The description of the all-solid-state battery manufactured through the above-described process is the same as that described in "A. All-solid-state battery".

[0133] Furthermore, this disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and technical solutions that have substantially the same structure and achieve the same effect as the technical concept described in the claims of this disclosure are included within the technical scope of this disclosure.

[0134] Example

[0135] [Example 1]

[0136] (Creating the protective layer)

[0137] The adhesive solution (styrene-butadiene solution) and solvent (trimethylbenzene and dibutyl ether) were added to a PP (polypropylene) container and mixed using a shaker for 3 minutes. Subsequently, Mg particles (average particle size D) were added. 50 =800nm) and solid electrolyte particles (sulfide solid electrolyte, 10LiI-15LiBr-75Li3PS4, average particle size D 50 =800nm) was weighed to a weight ratio of Mg particles:solid electrolyte particles = 10:90 and placed into a PP container. The mixture was treated with an oscillator for 3 minutes and then with an ultrasonic dispersion device for 30 seconds, repeated twice to prepare a slurry. Next, using an applicator with a coating gap of 25μm, the slurry was applied to a substrate (Al foil) and allowed to dry naturally. After visually confirming that the surface was dry, it was dried on a heated plate at 100°C for 30 minutes. This produced a transfer component with a protective layer (alloy layer) formed on the substrate.

[0138] (The fabrication of an all-solid-state battery)

[0139] An all-solid-state battery was fabricated using a pressed cell (Φ11.28 mm). Specifically, 101.7 mg of a sulfide solid electrolyte (10LiI-15LiBr-75Li3PS4, average particle size D) was used. 50A solid electrolyte layer was obtained by loading a 0.5 μm aluminum foil into a cylinder and pressing it at 588 MPa for 1 minute. Next, a transfer component was laminated with the solid electrolyte layer in contact with the protective layer and pressed at 98 MPa. Then, the Al foil was peeled off. This yielded a laminate with a solid electrolyte layer and a protective layer. An SUS foil (Φ11.28 mm) was placed on the protective layer of the obtained laminate and pressed at 98 MPa for 1 minute. Next, a Li metal foil (Φ11.28 mm) was placed on the surface of the solid electrolyte layer on the opposite side of the protective layer and pressed at 98 MPa for 1 minute to obtain an electrode body. This electrode body was secured with three bolts at a torque of 2 N·m. This yielded an all-solid-state battery. Furthermore, when the all-solid-state battery obtained in Example 1 was charged, it was assumed that... Figure 5 As shown in (a), a Li layer is precipitated between the protective layer (Mg / SE) and the negative electrode current collector (SUS). Additionally, there is the possibility of alloying Mg particles with Li, and the possibility of Li precipitating in the voids of the protective layer.

[0140] [Example 2 and Example 3]

[0141] The weight ratio of Mg particles to solid electrolyte in the protective layer was changed to the values ​​in Table 1, and otherwise carried out in the same manner as in Example 1, resulting in an all-solid-state battery. Furthermore, in Table 1, the solid electrolyte is denoted as "SE".

[0142] [Comparative Example 1]

[0143] Except for the absence of a protective layer, the process was carried out in the same manner as in Example 1, resulting in an all-solid-state battery. Furthermore, when the all-solid-state battery obtained in Comparative Example 1 was charged, it was considered that... Figure 5 As shown in (b), a Li layer is deposited between the solid electrolyte layer (SE) and the negative electrode current collector (SUS).

[0144] [Comparative Example 2]

[0145] Except that no solid electrolyte was used in the protective layer, the process was carried out in the same manner as in Example 1, and an all-solid-state battery was obtained.

[0146] [evaluate]

[0147] (LSV (Linear Sweep Voltammetry) determination)

[0148] The all-solid-state batteries obtained in Examples 1-3 and Comparative Examples 1 and 2 were placed in a constant temperature bath at 25°C for 1 hour. Subsequently, LSV measurements were performed by scanning from the OCV potential to 1V at a rate of 0.1 mV / s. The current value at the point where the current behavior jumps was considered the short-circuit critical current (short-circuit limit current). The results are shown in Table 1.

[0149] Table 1

[0150]

[0151] As shown in Table 1, it was confirmed that Examples 1-3 had higher short-circuit critical current values ​​compared to Comparative Examples 1 and 2, thus suppressing the occurrence of short circuits. Therefore, it was confirmed that by configuring a protective layer containing a composite material layer containing Mg particles and a solid electrolyte layer between the negative electrode current collector and the solid electrolyte layer, an all-solid-state battery that suppresses the occurrence of short circuits was achieved.

[0152] [Example 4]

[0153] (Fabrication of the composite layer)

[0154] Sulfide glass (Li6PS5Cl1) was synthesized by mechanical ball milling. 100 mg of the synthesized sulfide glass was weighed and added to a glass bottle. Ethanol was added dropwise to the bottle to achieve a solid content of 10% by weight, and the mixture was stirred for 3 minutes. This yielded a yellow, transparent sulfide glass solution.

[0155] A 10% by weight SBR solution was prepared by dissolving SBR (styrene-butadiene rubber) adhesive in mesitylene. Mg particles (D...) were weighed... 50 400 mg of Mg (0.8 μm) solution was added, and 22 mg of the above SBR solution was added to the Mg particles. Next, 1200 mg of mesitylene was added, and the mixture was stirred and dispersed to obtain a slurry. The obtained slurry was coated onto the negative electrode current collector (SUS foil) using a SUS doctor blade with a 25 μm gap. It was then dried at 50 °C for 5 minutes, followed by drying at 120 °C for 1 hour. This resulted in a particle layer with a thickness of 5 μm on the negative electrode current collector.

[0156] Next, a sulfide glass solution was dropped onto the particle layer and coated using a SUS doctor blade with a 100 μm gap. This yielded a precursor layer in which the particle layer was impregnated with the sulfide glass solution. The resulting precursor layer was dried in a glove box at 60°C for 5 minutes, followed by drying in a vacuum (0.01 atm) at 120°C for 10 minutes. This formed a composite layer containing Mg particles and sulfide glass on the negative electrode current collector.

[0157] (The fabrication of an all-solid-state battery)

[0158] NCA-based positive electrode active material, sulfide glass solid electrolyte (Li6PS5Cl1), and conductive material (Showa Denko: VGCF-H) were weighed and mixed at a volume ratio of 78:19:3 to obtain 2g. 1200mg of butyl butyrate and 20mg of PVDF binder were added to the resulting mixture, and the mixture was broken down using an ultrasonic homogenizer. This prepared the positive electrode slurry. The prepared positive electrode slurry was coated onto an Al foil using a SUS blade with a 300μm gap, and then dried at 100°C for 1 hour. This yielded the positive electrode film.

[0159] 100 mg of sulfide glass (Li6PS5Cl1) was weighed and added to a cylindrical cylinder with a diameter of 11.28 mm, and then pressed under 1 ton of pressure to form an electrolyte sheet. An electrolyte sheet was thus produced. The aforementioned positive electrode film was deposited on one side of the sheet, and the aforementioned composite layer was deposited on the surface of the sheet opposite to the positive electrode film. The sheet was then pressed under 6 tons of pressure. The resulting laminate was constrained with a pressure of 1 MPa. This produced an all-solid-state battery.

[0160] [Comparative Example 3]

[0161] Except that the particle layer described above was used instead of the composite layer described above, the same procedure as in Example 4 was followed to produce an all-solid-state battery.

[0162] [Comparative Example 4]

[0163] A Mg vapor-deposited film (1000 nm thick) was formed on the negative electrode current collector (SUS foil) using a vapor deposition method. The same procedure as in Example 4 was followed to fabricate an all-solid-state battery, except that the Mg vapor-deposited film was used in place of the composite layer.

[0164] [evaluate]

[0165] (Determination of fill rate)

[0166] The composite layer obtained in Example 4, the particle layer obtained in Comparative Example 3, and the Mg vapor-deposited film obtained in Comparative Example 4 were weighed and placed into a cylindrical tank with a diameter of 11.28 mm, and constrained at 3 MPa. The thickness was measured using a film thickness gauge. The fill rate was calculated from the measured thickness and the weighed amount. The results are shown in Table 2.

[0167] (Cyclic Test)

[0168] Perform charge and discharge operations under the following conditions and determine the capacity retention rate. The results are presented below. Figure 6 .

[0169] Temperature: 60℃

[0170] Voltage range: 3.56V~4.14V

[0171] Current density: 1.5 mA / cm²2

[0172] Number of cycles: 50

[0173] Table 2

[0174]

[0175] As shown in Table 2, it was confirmed that the fill rate of the composite layer in Example 4 was as high as that of the Mg vapor-deposited film in Comparative Example 4, resulting in a very dense composite layer. Furthermore, the fill rate of the composite layer in Example 4 was significantly higher than that of the particle layer in Comparative Example 3. Additionally, as... Figure 6 As shown, in Comparative Example 3, the capacity decreased starting from the second cycle. However, in Comparative Example 4 and Example 4, the capacity retention was good even after 50 cycles. This is believed to be because the high filling rate of the Mg vapor-deposited film and the composite layer in Comparative Example 4 and Example 4 resulted in good contact between Mg and the solid electrolyte layer, suppressing the interruption of the ion conduction path caused by stress changes associated with the dissolution and precipitation of Li. As a result, it is believed that the precipitated Li in Comparative Example 4 and Example 4 did not isolate and could be charged and discharged well. In addition, when using the vapor deposition method as in Comparative Example 4, the formation of the protective layer becomes difficult when the battery size is increased (scale expansion). In contrast, when using the coating method as in Example 4, it has the advantage of easy formation of the protective layer even when the battery size is increased. Furthermore, it is speculated that the Mg contained in the Mg vapor-deposited film itself expands and contracts due to the insertion and detachment of Li, and if the number of charge and discharge cycles is further increased, there is a possibility that the Mg vapor-deposited film will crack. On the other hand, in the composite layer of Example 4, a soft sulfide glass is disposed around the Mg particles, so it is presumed that crack formation in the composite layer can be suppressed even with further increases in the number of charge-discharge cycles. Furthermore, it is believed that although the composite layer of Example 4 is dense, it also has slight voids. Therefore, it is presumed that it can suppress volume changes caused by the insertion and extraction of Li.

Claims

1. A method for manufacturing an all-solid-state battery, The all-solid-state battery has a negative electrode, a positive electrode, and a solid electrolyte layer. The negative electrode has at least a negative electrode current collector, and the solid electrolyte layer is disposed between the negative electrode and the positive electrode. A protective layer containing Mg is disposed between the negative electrode current collector and the solid electrolyte layer. The protective layer includes a composite layer comprising Mg-containing particles and sulfide glass. The manufacturing method includes a particle layer formation process, a precursor layer formation process, and a composite material layer formation process. In the particle layer formation process, a particle layer containing Mg particles is formed on the negative electrode current collector. In the precursor layer formation process, the particle layer is impregnated with a sulfide glass solution to form the precursor layer. The sulfide glass solution is formed by dissolving the sulfide glass in a solvent. In the composite layer forming process, the precursor layer is dried to obtain the composite layer.

2. The method for manufacturing an all-solid-state battery according to claim 1, The sulfide glass has a composition of Li 7-a PS 6-a X a The composition of the representation, in which, X is at least one of Cl, Br and I, and a is a number greater than 0 and less than 2.

3. The method for manufacturing an all-solid-state battery according to claim 1 or 2, The content of the sulfide glass in the sulfide glass solution is more than 10% by weight and less than 30% by weight.

4. The method for manufacturing an all-solid-state battery according to claim 1 or 2, In the composite layer forming process, drying is performed at a temperature of 60°C or higher and 80°C or lower.

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