battery

Abstract

As a problem, the main object of the present disclosure is to provide a battery with good safety against heat generation. In the present disclosure, the problem is solved by providing a battery having a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector in this order in the thickness direction, the battery having a coating layer containing an oxide active material on a surface of the negative electrode current collector on the negative electrode active material layer side, the solid electrolyte layer having a first solid electrolyte layer containing a halide solid electrolyte and a second solid electrolyte layer containing a sulfide solid electrolyte disposed between the first solid electrolyte layer and the negative electrode active material layer.

Description

Technical Field

[0001] This disclosure relates to batteries. Background Technology

[0002] Batteries with a solid electrolyte layer between the positive and negative electrode active material layers have the advantage of simplifying safety devices compared to batteries with electrolytes containing flammable organic solvents.

[0003] Si-based active materials are known as negative electrode active materials with good capacity characteristics. Patent Document 1 discloses a negative electrode for a sulfide all-solid-state battery, which contains at least one material selected from Si and Si alloys as the negative electrode active material.

[0004] Furthermore, although not concerning battery technology with a solid electrolyte layer, Patent Document 2 discloses a negative electrode for a non-aqueous electrolyte secondary battery, which has a current collector, a first layer containing lithium titanate, and a second layer containing carbon material, wherein the ratio of the thickness T1 of the first layer to the thickness T2 of the second layer, T1 / T2, is 0.15 or more and 0.55 or less. Additionally, Patent Document 3 discloses a battery in which a sulfide solid electrolyte and a halide solid electrolyte are included as the solid electrolyte.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-142431

[0008] Patent Document 2: Japanese Patent Application Publication No. 2014-199714

[0009] Patent Document 3: International Publication No. 2019-135323 Summary of the Invention

[0010] To reduce heat generation, for example, during a short circuit, it is effective to apply the coating described later between the negative electrode current collector and the negative electrode active material layer. On the other hand, for example, since a large current is generated in a short circuit caused by a large conductive foreign object, it is desirable to further improve safety against heat generation.

[0011] This disclosure was made in view of the above-mentioned circumstances, and its main purpose is to provide a battery with good safety against heat generation.

[0012] To address the aforementioned issues, this disclosure provides a battery comprising, sequentially along its thickness, a positive current collector, a positive active material layer, a solid electrolyte layer, a negative active material layer, and a negative current collector. The surface of the negative current collector on the side of the negative active material layer has a coating containing an oxide active material. The solid electrolyte layer comprises a first solid electrolyte layer and a second solid electrolyte layer disposed between the first solid electrolyte layer and the negative active material layer. The first solid electrolyte layer contains a halide solid electrolyte, and the second solid electrolyte layer contains a sulfide solid electrolyte.

[0013] According to this disclosure, by configuring a coating between the negative electrode current collector and the negative electrode active material layer, and by having the first solid electrolyte layer contain a halide solid electrolyte, a battery with good safety against heat generation is achieved.

[0014] In the above disclosure, the oxide active material may include at least one of lithium titanate and niobium titanium oxide.

[0015] In the above disclosure, the above-mentioned halide solid electrolyte may also be represented by the following compositional formula (1).

[0016] Li α M β X γ …Formula (1)

[0017] α, β and γ are values ​​greater than 0, M contains at least one metallic element and half-metallic element selected from Li, and X contains at least one selected from F, Cl, Br and I.

[0018] In the above disclosure, the halide solid electrolyte can be Li 6-3A M A X6 (A satisfies 0 < A < 2, M is at least one of Y and In, and X is at least one of Cl and Br) represents.

[0019] In the above disclosure, the halide solid electrolyte can be a chloride solid electrolyte.

[0020] In the above disclosure, the sulfide solid electrolyte may contain Li, P, and S.

[0021] In the above disclosure, the negative electrode active material layer may contain a negative electrode active material with a total volume expansion rate of 14% or more due to charging.

[0022] In the above disclosure, the negative electrode active material can be a Si-based active material.

[0023] In the above disclosure, the ratio of the thickness of the coating to the thickness of the negative electrode active material layer can be more than 3% and less than 20%.

[0024] The battery disclosed herein achieves good safety against heat generation. Attached Figure Description

[0025] Figure 1 This is a schematic cross-sectional view illustrating the battery in this disclosure.

[0026] Figure 2 This is a schematic cross-sectional view illustrating the battery in this disclosure.

[0027] Figure 3 This is a schematic cross-sectional view illustrating the battery in this disclosure.

[0028] Figure 4 The results are from puncture tests conducted on the batteries produced in Example 1 and Comparative Examples 1-3.

[0029] Explanation of reference numerals in the attached figures

[0030] 1: Positive current collector

[0031] 2: Positive electrode active material layer

[0032] 3: Solid electrolyte layer

[0033] 4: Negative electrode active material layer

[0034] 5: Negative current collector

[0035] 6: Coating

[0036] 10: Battery Detailed Implementation

[0037] The battery in this disclosure will now be described in detail using the accompanying drawings. The figures shown below are schematic and the size and shape of the parts have been appropriately exaggerated for ease of understanding. Furthermore, section lines representing the cross-sections of the components have been appropriately omitted in the figures.

[0038] Figure 1 This is a schematic cross-sectional view illustrating the battery in this disclosure. Figure 1 The battery 10 shown has a thickness direction D. TThe device sequentially comprises a positive current collector 1, a positive active material layer 2, a solid electrolyte layer 3, a negative active material layer 4, and a negative current collector 5. A coating 6 containing an oxide active material is provided on the surface of the negative current collector 5 on the side of the negative active material layer 4. Furthermore, the solid electrolyte layer 3 comprises a first solid electrolyte layer 3x and a second solid electrolyte layer 3y disposed between the first solid electrolyte layer 3x and the negative active material layer 4. The first solid electrolyte layer 3x contains a halide solid electrolyte, and the second solid electrolyte layer 3y contains a sulfide solid electrolyte. In this disclosure, the positive current collector 1 and the positive active material layer 2 are sometimes referred to as "positive electrode," and the negative active material layer 4, the coating 6, and the negative current collector 5 are sometimes referred to as "negative electrode."

[0039] According to this disclosure, a battery with good safety against heat generation is achieved by distributing a coating between the negative electrode current collector and the negative electrode active material layer, and by containing a halide solid electrolyte in the first solid electrolyte layer. As described above, it is effective to provide a coating containing an oxide active material between the negative electrode current collector and the negative electrode active material layer in order to reduce heat generation, for example, during a short circuit. The oxide active material exhibits electronic conductivity when Li is inserted and insulation when the inserted Li is removed. Therefore, by utilizing the electronic conductivity of the oxide active material to form an electronic conduction path, the increase in internal resistance can be suppressed. On the other hand, when a short circuit occurs, for example, Li is removed from the oxide active material, and by utilizing its insulation (shutdown function) to cut off the electronic conduction path, heat generation can be reduced.

[0040] For example, since large currents are generated in short circuits caused by large conductive foreign objects, it is desirable to further improve safety against heat generation. In this disclosure, by using a halide solid electrolyte with good thermal stability as the solid electrolyte used in the solid electrolyte layer, further improvement in safety against heat generation can be achieved. On the other hand, since the halide solid electrolyte has relatively low reduction resistance, it is used in the first solid electrolyte layer on the positive electrode active material layer side where reduction resistance is not required. Moreover, a sulfide solid electrolyte with relatively high reduction resistance is used in the second solid electrolyte layer on the negative electrode active material layer side where reduction resistance is required. As a result, a battery with high safety against heat generation and good cycle characteristics can be obtained.

[0041] 1. Negative electrode

[0042] The negative electrode in this disclosure has a negative electrode active material layer and a negative electrode current collector. In addition, a coating containing an oxide active material is provided on the surface of the negative electrode current collector on the side of the negative electrode active material layer.

[0043] (1) Coating

[0044] The coating is a layer disposed on the surface of the negative electrode active material layer of the negative electrode current collector. Furthermore, the coating contains an oxide active material. The oxide active material typically exhibits electronic conductivity in the Li-intercalated state and insulation in the Li-deintercalated state. When the electronic conductivity (25°C) of the oxide active material in the Li-intercalated state is denoted as C1, and the electronic conductivity (25°C) of the oxide active material in the Li-deintercalated state is denoted as C2, the ratio of C1 to C2 is, for example, 10. 4 The above can be 10 5 The above. When the C1 / C2 ratio is sufficiently large, good shut-off function can be obtained. The electronic conductivity (25°C) of the oxide active material in the Li-intercalated state is, for example, 8.0 × 10⁻⁶. -1 S / cm or higher. On the other hand, the electronic conductivity (25°C) of the oxide active material in the Li-deintercalated state is, for example, 2.1 × 10⁻⁶. -6 Below S / cm.

[0045] The oxide active material contains at least a metal element and oxygen. Furthermore, it is preferred that the oxide active material has at least one of a layered structure and a spinel-type structure. Lithium titanate is an example of an oxide active material. Lithium titanate is a compound containing Li, Ti, and O; for example, Li₄Ti₅O₅ is an example. 12 Examples of active oxides include Li4TiO4, Li2TiO3, and Li2Ti3O7. Other examples of niobium-titanium oxides include those containing Ti, Nb, and O; for example, TiNb2O7 and Ti2Nb2O7 are also examples. 10 O 29 The coating may contain only one type of oxide active material, or it may contain two or more types of oxide active materials. Furthermore, it is preferable that the oxide active material has a higher Li insertion / deintercalation potential compared to the negative electrode active material.

[0046] The shape of an oxide active material can be exemplified by, for example, particulate matter. The average particle size (D) of the oxide active material... 50 The size is not specifically limited; for example, it can be 10 nm or larger, or even 100 nm or larger. On the other hand, the average particle size (D) of the oxide active material... 50 For example, it can be below 50 μm, or below 20 μm. Average particle size (D) 50 The value can be calculated using measurements such as laser diffraction particle size analyzers or scanning electron microscopes (SEM). The proportion of oxide active material in the coating is, for example, 50% by weight or more, 70% by weight or more, or 90% by weight or more.

[0047] The coating may or may not contain conductive materials. By adding a small amount of conductive material, the shut-off function can be activated quickly, further reducing heat generation. Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), as well as fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs).

[0048] The proportion of conductive material in the coating is, for example, less than 1% by weight, less than 0.5% by weight, or less than 0.3% by weight. The above-mentioned proportion of conductive material can be 0% by weight or greater than 0% by weight, and in the latter case, it is, for example, more than 0.05% by weight.

[0049] The coating may or may not contain a solid electrolyte. Adding a solid electrolyte allows for the formation of a good ion conduction pathway within the coating, enabling the shut-off function to operate rapidly and further reducing heat generation. Conversely, omitting a solid electrolyte suppresses the increase in internal resistance. Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. For sulfide and halide solid electrolytes, the same materials described in "2. Solid Electrolyte Layer" can be used.

[0050] The proportion of solid electrolyte in the coating is, for example, 5% by volume or more, and can be 10% by volume or more. When the proportion of solid electrolyte is too low, it is difficult to obtain the heat reduction effect brought about by the solid electrolyte. On the other hand, the proportion of solid electrolyte in the coating is, for example, 30% by volume or less. When the proportion of solid electrolyte is too high, the internal resistance tends to increase.

[0051] The coating preferably contains an adhesive. Adding an adhesive improves the adhesion of the coating and enhances its bonding with the negative electrode active material layer and the negative electrode current collector. Examples of adhesives include fluoride-based adhesives, polyimide-based adhesives, and rubber-based adhesives. The adhesive content in the coating is, for example, 1% by weight or more and 10% by weight or less.

[0052] In this disclosure, the thickness of the coating is denoted as T1, and the thickness of the negative electrode active material layer is denoted as T2. The ratio of T1 to T2 (T1 / T2) is, for example, 3% or more, and can be 5% or more. When T1 / T2 is too small, it is difficult to obtain a heat reduction effect. On the other hand, the ratio of T1 to T2 (T1 / T2) is, for example, 20% or less, and can be 13% or less, and can be 10% or less. When T1 / T2 is too large, the internal resistance tends to increase. T1 is, for example, 2 μm or more, and can be 3 μm or more, and can be 4 μm or more. On the other hand, T1 is, for example, 15 μm or less, and can be 10 μm or less. T2 is, for example, 20 μm or more, and can be 40 μm or more. On the other hand, T2 is, for example, 200 μm or less, and can be 150 μm or less.

[0053] In addition, such as Figure 2 As shown, the thickness of coating 6 is denoted as T1, and the surface roughness (Rz) of the surface of coating 6 side of negative electrode current collector 5 is denoted as R. Furthermore, the units of T1 and R are set to μm. Additionally, surface roughness Rz refers to the ten-point average roughness, which can be determined, for example, by a stylus-type surface roughness measuring machine. The ratio of R to T1 (R / T1) is, for example, 30% or more, and can be 40% or more. The larger R / T1 is, the easier it is to obtain a heat reduction effect. On the other hand, the ratio of R to T1 (R / T1) is, for example, less than 100%, and can be 90% or less, and can be 80% or less. When R / T1 is less than 100%, it is possible to suppress a portion of the negative electrode current collector from being exposed from the coating, thus further reducing heat generation.

[0054] The surface roughness (Rz) of the negative electrode current collector is, for example, 2 μm or more, 4 μm or more, or 6 μm or more. On the other hand, the surface roughness (Rz) of the negative electrode current collector is, for example, 9 μm or less.

[0055] (2) Negative electrode active material layer

[0056] The negative electrode active material layer contains at least a negative electrode active material, and may also contain at least one of a solid electrolyte, a conductive material, and a binder.

[0057] The negative electrode active material is not particularly limited, and general negative electrode active materials can be used. Among them, it is preferable that the total volume expansion rate caused by charging is 14% or more. This is because active materials with a large total volume expansion rate caused by charging tend to have high capacity characteristics. In addition, when the capacity characteristics are high, for example, the heat generated during short circuits tends to increase. However, in this disclosure, by providing the above-mentioned coating, it is possible to maintain high capacity characteristics and suppress the increase in heat generation.

[0058] Here, graphite, as a common anode active material, has a total volume expansion rate of 13.2% due to charging (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, an anode active material with a total volume expansion rate of 14% or higher due to charging is an active material with a larger total volume expansion rate due to charging than graphite. The total volume expansion rate due to charging, as described by Simon Schweidler et al., can be determined through space-group-independent evaluation. The total volume expansion rate due to charging of an anode active material can be 100% or higher, and can be 200% or higher.

[0059] As an example of a negative electrode active material, Si-based active materials can be cited. Si-based active materials are active materials containing the element Si. Examples of Si-based active materials include elemental Si, Si alloys, and Si oxides. Si alloys preferably contain the element Si as a main component. Another example of a negative electrode active material is Sn-based active materials. Sn-based active materials are active materials containing the element Sn. Examples of Sn-based active materials include elemental Sn, Sn alloys, and Sn oxides. Sn alloys preferably contain the element Sn as a main component.

[0060] The shape of a negative electrode active material can be, for example, particulate. The average particle size (D) of the negative electrode active material... 50 The size is not specifically limited; for example, it can be 10 nm or larger, or even 100 nm or larger. On the other hand, the average particle size (D) of the negative electrode active material... 50 For example, it can be below 50μm, or below 20μm.

[0061] The proportion of negative electrode active material in the negative electrode active material layer is, for example, 20% by weight or more, 40% by weight or more, or 60% by weight or more. On the other hand, the above-mentioned proportion of negative electrode active material is, for example, 80% by weight or less. In addition, the negative electrode active material layer may also contain at least one of a solid electrolyte, a conductive material, and a binder. Regarding these materials, the same materials as those used in the coating described above can be used.

[0062] (3) Negative current collector

[0063] A negative electrode current collector is a component that collects current in the negative electrode active material layer. Examples of negative electrode current collectors include metal current collectors. Examples of metal current collectors include current collectors containing metals such as Cu and Ni. The metal current collector can be an element of the aforementioned metal or an alloy of the aforementioned metals. Examples of the shape of a negative electrode current collector include foil.

[0064] 2. Solid electrolyte layer

[0065] The solid electrolyte layer in this disclosure is a layer disposed between the positive electrode active material layer and the negative electrode active material layer, and contains at least a solid electrolyte. Furthermore, the solid electrolyte layer has a first solid electrolyte layer containing a halide solid electrolyte and a second solid electrolyte layer containing a sulfide solid electrolyte. The first solid electrolyte layer is located closer to the positive electrode active material layer than the second solid electrolyte layer.

[0066] (1) First solid electrolyte layer

[0067] The first solid electrolyte layer is a layer that contains at least a halide solid electrolyte as a solid electrolyte. In this disclosure, "halide solid electrolyte" refers to a solid electrolyte material containing halogen elements and free of sulfur. Furthermore, in this disclosure, "sulfur-free solid electrolyte material" refers to a solid electrolyte material expressed by a formula that does not contain sulfur elements. Therefore, solid electrolytes with trace amounts of sulfur, for example, sulfur content of 0.1% by weight or less, are included in sulfur-free solid electrolytes. The halide solid electrolyte may also contain oxygen as an anion other than a halogen element.

[0068] The first solid electrolyte layer preferably contains a halide solid electrolyte as the main component of the solid electrolyte. This is because it improves safety in the face of heat generation. The term "main component of solid electrolyte" refers to the solid electrolyte that accounts for the largest proportion of all solid electrolytes contained in the layer. The proportion of halide solid electrolyte in the first solid electrolyte layer relative to the total solid electrolyte is, for example, 50% by volume or more, 70% by volume or more, or 90% by volume or more.

[0069] Alternatively, the first solid electrolyte layer may contain only a halide solid electrolyte. On the other hand, if the first solid electrolyte layer contains a solid electrolyte other than a halide solid electrolyte, inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and nitride solid electrolytes can be used as examples.

[0070] The halide solid electrolyte preferably contains: Li; a metal element or half-metal element other than Li; and a halogen element.

[0071] Halogenated solid electrolytes can be represented by the following composition formula (1).

[0072] Li α M β X γ …Formula (1)

[0073] Here, α, β, and γ are values ​​greater than 0.

[0074] M comprises at least one element selected from metals and half-metals other than Li. M may also be at least one element selected from metals and half-metals other than Li. X comprises at least one element selected from F, Cl, Br, and I. X may also be at least one element selected from F, Cl, Br, and I. Based on the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved. Therefore, the output characteristics of the battery can be further improved.

[0075] In formula (1), α, β, and γ can also satisfy 2.5 ≤ α ≤ 3, 1 ≤ β ≤ 1.1, and γ = 6. Based on the above composition, the ionic conductivity of the halide solid electrolyte can be further improved.

[0076] In this disclosure, the term "half-metallic element" refers to B, Si, Ge, As, Sb, and Te. In this disclosure, the term "metallic element" refers to all elements contained in Group 1 (column 1) to Group 12 (column 12) of the periodic table, excluding hydrogen, and all elements contained in Group 13 (column 13) to Group 16 (column 16) of the periodic table, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. That is, the term "half-metallic element" or "metallic element" refers to the group of elements that can become cations when forming halogen compounds and inorganic compounds.

[0077] In formula (1), M can also contain Y (yttrium). That is, the halide solid electrolyte can also contain Y as a metallic element. Based on the above composition, the ionic conductivity of the halide solid electrolyte can be further improved.

[0078] The halide solid electrolyte containing Y can be, for example, Li a Me b Y c The compound represented by the formula X6. Here, a, b, and c satisfy a + mb + 3c = 6 and c > 0. Me is at least one selected from metallic and half-metallic elements excluding Li and Y. m is the valence of Me. X is at least one selected from F, Cl, Br, and I. Me can also be at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. Based on the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

[0079] Halogenated solid electrolytes can also be represented by the following compositional formula (A1).

[0080] Li 6-3d Y d X6… formula (A1)

[0081] In the formula (A1), X is at least one element selected from F, Cl, Br, and I, or two or more elements selected from F, Cl, Br, and I. In the formula (A1), d satisfies 0 < d < 2. Based on the above composition, the ionic conductivity of halide solid electrolytes can be further improved.

[0082] Halogenated solid electrolytes can also be represented by the following compositional formula (A2).

[0083] Formula (A2) for Li3YX6…

[0084] In the formula (A2), X is at least one element selected from F, Cl, Br, and I, or two or more elements selected from F, Cl, Br, and I. Based on this composition, the ionic conductivity of the halide solid electrolyte can be further improved.

[0085] Halogenated solid electrolytes can also be represented by the following compositional formula (A3).

[0086] Li 3-3δ Y 1+δ Cl6… formula (A3)

[0087] In formula (A3), δ satisfies 0 < δ ≤ 0.15. Based on the above composition, the ionic conductivity of the halide solid electrolyte can be further improved.

[0088] Halogenated solid electrolytes can also be represented by the following compositional formula (A4).

[0089] Li 3-3δ Y 1+δ Formula Br6… (A4)

[0090] In formula (A4), δ satisfies 0 < δ ≤ 0.25. Based on the above composition, the ionic conductivity of the halide solid electrolyte can be further improved.

[0091] Halogenated solid electrolytes can also be represented by the following compositional formula (A5).

[0092] Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y…Formula A5

[0093] In formula (A5), Me comprises at least one selected from Mg, Ca, Sr, Ba, and Zn. Me can also be at least one selected from Mg, Ca, Sr, Ba, and Zn. In formula (A5), δ, a, x, and y satisfy -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6. Based on the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

[0094] Halogenated solid electrolytes can also be represented by the following compositional formula (A6).

[0095] Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y …Formula A6

[0096] In formula (A6), Me comprises at least one selected from Al, Sc, Ga, and Bi. Me can also be at least one selected from Al, Sc, Ga, and Bi. In formula (A6), δ, a, x, and y satisfy -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6. Based on the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

[0097] Halogenated solid electrolytes can also be represented by the following compositional formula (A7).

[0098] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y …Formula (A7)

[0099] In formula (A7), Me comprises at least one selected from Zr, Hf, and Ti. Me can also be at least one selected from Zr, Hf, and Ti. In formula (A7), δ, a, x, and y satisfy -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6. Based on the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

[0100] Halogenated solid electrolytes can also be represented by the following compositional formula (A8).

[0101] Li3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y …Formula A8

[0102] In formula (A8), Me includes at least one selected from Ta and Nb. Me can also be at least one selected from Ta and Nb. In formula (A8), δ, a, x, and y satisfy -1 < δ < 1, 0 < a < 1.2, 0 < (3 - 3δ - 2a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x + y) ≤ 6. Based on the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

[0103] Examples of halide solid electrolytes include Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, and Li3(Al, Ga, In)X6. In these materials, element X is at least one selected from F, Cl, Br, and I. In this disclosure, "(Al, Ga, In)" means at least one element selected from the group of elements enclosed in parentheses. That is, "(Al, Ga, In)" is synonymous with "at least one selected from Al, Ga, and In". The same applies to other elements.

[0104] The X (i.e., anion) contained in halide solid electrolytes includes at least one selected from F, Cl, Br, and I, and may also include oxygen. Based on this composition, the ionic conductivity of halide solid electrolytes can be further improved.

[0105] Halogenated solid electrolytes can be represented by the compositional formula (1) as described above. Furthermore, halogenated solid electrolytes can also be made from Li... 6-3A M A X6 (where A satisfies 0 < A < 2, M is at least one of Y and In, and X is at least one of Cl and Br) represents a solid electrolyte.

[0106] In Li 6-3A M A In X6, when M is at least one of Y and In, A is greater than 0, and can be 0.75 or more, or 1 or more. On the other hand, A is less than 2, and can be 1.5 or less, or 1.25 or less. M is at least one of Y and In, preferably containing at least Y, but can also contain only Y. X is at least one of Cl and Br, but can also contain only Cl, only Br, or both Cl and Br.

[0107] Using Li 6-3A M AThe solid electrolyte represented by X6 can also have a first crystalline phase in which the arrangement of X is the same as the arrangement of Br in Li3ErBr6, which has a crystal structure belonging to space group C2 / m. In this case, characteristic peaks were observed in X-ray diffraction measurements using CuKα rays in the ranges of 2θ: 25°–28°, 29°–32°, 41°–46°, 49°–55°, and 51°–58°. Furthermore, the peak intensity of the first crystalline phase corresponding to the (200) plane in the crystal structure of Li3ErBr6 is denoted as I. 200 Let I denote the peak intensity of the first crystalline phase corresponding to the (110) plane. 110 In the case that I can also be satisfied 110 / I 200 ≤0.01. Furthermore, the half-width of the peak of the first crystalline phase on the (200) plane in the crystal structure of Li3ErBr6 is denoted as FWHM1, and the diffraction angle (peak center value) at the center of the aforementioned peak is denoted as 2θ. c1 Under the condition that FWHM1 / 2θ can also be satisfied c1 ≥0.015.

[0108] Using Li 6-3A M A The solid electrolyte represented by X6 can also have a second crystalline phase in which the arrangement of X is the same as that of Cl in Li3ErCl6, which has a crystal structure belonging to space group P-3m1. In this case, characteristic peaks were observed in X-ray diffraction measurements using CuKα rays in the ranges of 2θ: 29.8°–32°, 38.5°–41.7°, 46.3°–50.4°, and 50.8°–55.4°. Furthermore, the peak intensity of the second crystalline phase corresponding to the (303) face in the crystal structure of Li3ErCl6 is denoted as I. 303 The peak intensity of the second crystalline phase corresponding to the (110) plane is denoted as I′. 110 In the case that I′ can also be satisfied 110 / I 303 ≤0.3. Furthermore, the half-width of the peak of the second crystalline phase on the (303) plane in the crystal structure of Li3ErCl6 is denoted as FWHM2, and the diffraction angle (peak center value) at the center of the aforementioned peak is denoted as 2θ. c2 Under these conditions, FWHM2 / 2θ can also be satisfied. c2 ≥0.015.

[0109] Using Li 6-3A M AThe solid electrolyte represented by X6 can also have a third crystalline phase in which the arrangement of X is the same as the arrangement of Cl in Li3YbCl6, which has a crystal structure belonging to space group Pnma. In this case, characteristic peaks were observed in X-ray diffraction measurements using CuKα rays in the ranges of 2θ: 29.8°–32°, 38.5°–41.7°, 46.3°–50.4°, and 50.8°–55.4°. Furthermore, the half-width of the peak of the third crystalline phase corresponding to the (231) plane in the crystal structure of Li3YbCl6 is denoted as FWHM3, and the diffraction angle (peak center value) at the center of the above peak is denoted as 2θ. c3 Under these conditions, FWHM3 / 2θ can also be satisfied. c3 ≥0.015.

[0110] Using Li 6-3A M A X6 represents a solid electrolyte in which X at least contains Br, and may also have a fourth crystalline phase with peaks observed in X-ray diffraction measurements using CuKα rays within the ranges of 2θ: 13.1°–14.5°, 26.6°–28.3°, 30.8°–32.7°, 44.2°–47.1°, 52.3°–55.8°, and 54.8°–58.5°. Furthermore, the half-width of the peak observed within the range of 2θ: 26.6°–28.3° is denoted as FWHM4, and the diffraction angle (peak center value) at the center of the aforementioned peak is denoted as 2θ. c4 Under these conditions, FWHM4 / 2θ can also be satisfied. c4 ≥0.015. Furthermore, if the intensity of the aforementioned peak observed in the range of 2θ being 26.6° to 28.3° is denoted as I1, and the intensity of the peak observed in the range of 2θ being denoted as I2, then I2 / I1 ≤ 0.1, or I2 / I1 ≤ 0.01. Moreover, if no peak is observed in the range of 2θ being 15.0° to 16.0°, then I2 = 0.

[0111] Using Li 6-3A M A X6 represents a solid electrolyte in which X contains at least Cl, and may also have a fifth crystalline phase with peaks observed in X-ray diffraction measurements using CuKα rays within the ranges of 2θ: 15.3°–16.3°, 29.8°–32°, 38.5°–41.7°, 46.3°–50.4°, and 50.8°–55.4°. Furthermore, the half-width of the peak observed within the 2θ range of 29.8°–32° is denoted as FWHM5, and the diffraction angle (peak center value) at the center of the aforementioned peak is denoted as 2θ. c5Under these conditions, FWHM5 / 2θ can also be satisfied. c5 ≥0.015. In addition, if the intensity of the above peak observed in the range of 2θ of 29.8° to 32° is denoted as I3 and the intensity of the above peak observed in the range of 2θ of 15.3° to 16.3° is denoted as I4, then I4 / I3≤0.3 can also be satisfied.

[0112] Halide solid electrolytes can also be chloride solid electrolytes. Chloride solid electrolytes are electrolytes that contain at least Cl as a halogen element. Halide solid electrolytes can also contain Cl as the main halogen element. The term "main halogen element" refers to the halogen element with the highest proportion among all halogen elements contained in the halide solid electrolyte. The proportion of Cl element in the first solid electrolyte layer relative to all halogen elements can be, for example, 30 mol% or more, 50 mol% or more, 70 mol% or more, or 90 mol% or more.

[0113] The proportion of halide solid electrolyte in the first solid electrolyte layer is, for example, 80% by volume or more, and can be 90% by volume or more. Furthermore, the halide solid electrolyte can be obtained, for example, by mechanically milling the raw material composition. For example, when the raw material composition contains LiCl and YCl3 in a molar ratio of LiCl:YCl3 = 3:1, a halide solid electrolyte represented as Li3YCl6 can be obtained by mechanical milling.

[0114] The first solid electrolyte layer may also contain a binder. Since the binder is the same as described in "1. Negative Electrode" above, it will not be described here. The thickness of the first solid electrolyte layer is, for example, 0.1 μm or more and 500 μm or less.

[0115] (2) Second solid electrolyte layer

[0116] The second solid electrolyte layer is a layer that contains at least a sulfide solid electrolyte as a solid electrolyte. Preferably, the second solid electrolyte layer contains a sulfide solid electrolyte as the main component of the solid electrolyte. This is because it improves ionic conductivity. The definition of "main component of the solid electrolyte" is the same as described above. The proportion of the sulfide solid electrolyte in the second solid electrolyte layer relative to the total solid electrolyte is, for example, 50% by volume or more, 70% by volume or more, or 90% by volume or more.

[0117] Alternatively, the second solid electrolyte layer may contain only a sulfide solid electrolyte. On the other hand, if the second solid electrolyte layer contains a solid electrolyte other than a sulfide solid electrolyte, examples of such solid electrolytes include inorganic solid electrolytes such as oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. Furthermore, the second solid electrolyte layer may not contain a halide solid electrolyte. In this case, performance degradation caused by the reductive decomposition of the halide solid electrolyte can be prevented.

[0118] Sulfide solid electrolytes preferably contain Li and M. 2 (M 2 It is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In, and S. Additionally, M... 2 Preferably, it contains at least P. Furthermore, the sulfide solid electrolyte may also contain at least one of O and a halogen. Examples of halogens include F, Cl, Br, and I.

[0119] Sulfide solid electrolytes preferably contain ion conductors having Li, P, and S. The ion conductor preferably has PS4. 3- The structure is an anionic structure. Compared to all anionic structures in ion conductors, PS4... 3- The proportion of the structure can be, for example, 50 mol% or more, 70 mol% or more, or 90 mol% or more. PS4 3- The proportions of the structure can be determined by methods such as Raman spectroscopy, NMR, and XPS.

[0120] The sulfide solid electrolyte preferably comprises an ion conductor having Li, P, and S and at least one selected from LiBr and LiI. Preferably, at least a portion of LiBr and LiI are incorporated into the structure of the ion conductor as LiBr and LiI components, respectively. The proportions of LiBr and LiI contained in the sulfide solid electrolyte are, for example, 1 mol% or more and 30 mol% or less, and can be 5 mol% or more and 20 mol% or less.

[0121] The sulfide solid electrolyte preferably has a composition represented by (100-ab)(Li3PS4)-aLiBr-bLiI. a, for example, satisfies 1≤a≤30, or 5≤a≤20. b, for example, satisfies 1≤b≤30, or 5≤b≤20.

[0122] The sulfide solid electrolyte preferably possesses a crystalline phase (crystalline phase A) with peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in X-ray diffraction measurements using CuKα rays. This is because crystalline phase A has high ionic conductivity. Crystalline phase A typically also has peaks at 2θ = 29.4° ± 0.5°, 37.8° ± 0.5°, 41.1° ± 0.5°, and 47.0° ± 0.5°. Furthermore, a small half-width (FWHM) is preferred for the peak at 2θ = 20.2° ± 0.5°. The FWHM is, for example, 0.51° or less, 0.45° or less, or 0.43° or less.

[0123] Sulfide solid electrolytes can also possess a crystalline phase (crystalline phase B) with peaks at 2θ = 21.0° ± 0.5° and 28.0° ± 0.5° in X-ray diffraction using CuKα rays, but it is preferable not to possess crystalline phase B. This is because the ionic conductivity of crystalline phase B is lower than that of crystalline phase A. Crystalline phase B typically also has peaks at 2θ = 32.0° ± 0.5°, 33.4° ± 0.5°, 38.7° ± 0.5°, 42.8° ± 0.5°, and 44.2° ± 0.5°. The peak intensity of crystalline phase A at 2θ = 20.2° ± 0.5° is denoted as I. 20.2 The peak intensity at 2θ = 21.0° ± 0.5° for crystalline phase B is denoted as I. 21.0 In the case of I 21.0 / I 20.2 For example, it can be below 0.4, below 0.2, or 0.

[0124] Sulfide solid electrolytes can also have crystalline phases such as Thio-LISICON type, LGPS type, and argyrodite type.

[0125] The shape of sulfide solid electrolytes can be, for example, particulate. Furthermore, the average particle size (D) of sulfide solid electrolytes... 50 For example, the particle size is greater than 0.1 μm and less than 50 μm. Average particle size (D) 50 The particle size distribution can be determined based on the results of particle size distribution measurements using laser diffraction scattering. Furthermore, sulfide solid electrolytes preferably have high ionic conductivity. For example, the ionic conductivity at 25°C is 1 × 10⁻⁶. -4 For values ​​above S / cm, it can be 1×10 -3 S / cm or higher.

[0126] Sulfide solid electrolytes can be obtained, for example, by mechanically grinding a raw material composition containing Li₂S and P₂S₅ to form a sulfide glass, followed by heat treatment of the sulfide glass. In the raw material composition, the proportion of Li₂S relative to the total of Li₂S and P₂S₅ is, for example, 70 mol% or more, 72 mol% or more, or 74 mol% or more. On the other hand, the aforementioned proportion of Li₂S is, for example, 80 mol% or less, 78 mol% or less, or 76 mol% or less. The raw material composition may also further contain at least one of LiBr and LiI.

[0127] The second solid electrolyte layer may also contain a binder. Since the binder is the same as described in "1. Negative Electrode" above, it will not be described here. The thickness of the second solid electrolyte layer is, for example, 0.1 μm or more and 500 μm or less.

[0128] (3) Solid electrolyte layer

[0129] The solid electrolyte layer in this disclosure has a first solid electrolyte layer and a second solid electrolyte layer disposed between the first solid electrolyte layer and the negative electrode active material layer.

[0130] The solid electrolyte layer in this disclosure may have a first solid electrolyte layer and a second solid electrolyte layer, each consisting of only one layer, or may have two or more first solid electrolyte layers and second solid electrolyte layers. The first solid electrolyte layer may or may not be in contact with the positive electrode active material layer. The first solid electrolyte layer and the second solid electrolyte layer may or may not be in contact. The second solid electrolyte layer may or may not be in contact with the positive electrode active material layer.

[0131] Furthermore, the thickness of the first solid electrolyte layer is denoted as T. F The thickness of the second solid electrolyte layer is denoted as T. S In the case of T F It can be greater than T S It can also be used with T S The same, or less than T S The so-called T F Greater than T S It refers to T F With T S The difference is greater than 3 μm. Under these conditions, a solid electrolyte layer with high ionic conductivity can be obtained. The so-called T... F With T S Same refers to T F With T SThe absolute value of the difference is less than 3 μm. Under these conditions, a solid electrolyte layer with a good balance between ion conductivity and safety against heating can be obtained. The so-called T... F Less than T S It refers to T S With T F The difference is greater than 3 μm. Under these conditions, a solid electrolyte layer with high safety against heat generation can be obtained.

[0132] 3. Positive electrode

[0133] The positive electrode of this disclosure has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer 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 conductive material, a solid electrolyte, and a binder, as needed.

[0134] Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other layered active substances in rock salt, LiMn2O4, Li4Ti5O 12 Li(Ni) 0.5 Mn 1.5 Spinel-type active substances such as O4, and olivine-type active substances such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0135] A protective layer containing a Li-ion-conducting oxide can also be formed on the surface of the oxide active material. This is because it can inhibit 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, 1 nm or more and 30 nm or less.

[0136] The shape of a positive electrode active material can be, for example, particulate. The average particle size (D) of the positive electrode active material... 50 The size is not specifically limited; for example, it can be 10 nm or larger, or even 100 nm or larger. On the other hand, the average particle size (D) of the positive electrode active material... 50 For example, it can be below 50μm, or below 20μm.

[0137] Regarding the conductive materials, solid electrolyte, and binder used in the positive electrode active material layer, since the content is the same as described in "1. Negative Electrode" above, it will not be described here. The thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less. In addition, materials used as positive electrode current collectors include, for example, stainless steel (SUS), aluminum, nickel, iron, titanium, and carbon.

[0138] 4. Battery

[0139] The battery disclosed herein has at least one power generation unit, and may also have two or more power generation units, wherein the power generation unit has a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. In the case of a battery with multiple power generation units, these units may be connected in parallel or in series. Furthermore, batteries that use a solid electrolyte (especially an inorganic solid electrolyte) instead of a liquid electrolyte are equivalent to all-solid-state batteries.

[0140] Figure 3 This is a schematic cross-sectional view illustrating the battery in this disclosure, showing a schematic cross-sectional view of two power generation units connected in parallel. Furthermore, in Embodiment 1 described later, a battery with... Figure 3 The battery structure shown. Figure 3 The battery 10 shown has a negative current collector 5, a negative active material layer 4a, a second solid electrolyte layer 3ya, a first solid electrolyte layer 3xa, a positive active material layer 2a and a positive current collector 1a arranged sequentially from one side s1 of the negative current collector 5, and a negative active material layer 4b, a second solid electrolyte layer 3yb, a first solid electrolyte layer 3xb, a positive active material layer 2b and a positive current collector 1b arranged sequentially from the other side s2 of the negative current collector 5.

[0141] Figure 3 The battery 10 shown has the following advantages. That is, for batteries using inorganic solid electrolytes such as halide solid electrolytes and sulfide solid electrolytes, very high pressure is required to suppress the power generation elements in order to form a good ion conduction pathway. Figure 3 The battery 10 shown has a symmetrical configuration of other layers with respect to the negative electrode current collector 5, thus suppressing stress in the negative electrode current collector caused by the difference in elasticity between the positive and negative electrode active material layers. Furthermore, although not specifically illustrated, the battery of this disclosure can also have a structure with a symmetrical configuration of other layers with respect to the positive electrode current collector.

[0142] The battery disclosed herein has an outer casing housing a positive electrode, a solid electrolyte layer, and a negative electrode. The type of outer casing is not particularly limited; for example, a laminated exterior body can be cited.

[0143] The battery disclosed herein may also include a confining jig that applies confining pressure to the positive electrode, solid electrolyte layer, and negative electrode along the thickness direction. By applying confining pressure, good ion conduction pathways and electron conduction pathways can be formed. The confining pressure may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. On the other hand, the confining pressure may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0144] The battery disclosed herein is typically a lithium-ion secondary battery. Its application is not particularly limited; examples include power sources for hybrid electric vehicles, electric vehicles, gasoline vehicles, and diesel vehicles. It is particularly preferred for use as a power source for driving hybrid electric vehicles or electric vehicles. Furthermore, the battery disclosed herein can also be used as a power source for mobile bodies other than vehicles (e.g., trains, ships, airplanes), and as a power source for electrical products such as information processing devices.

[0145] Furthermore, this disclosure is not limited to the above-described embodiments. The above embodiments are illustrative examples. Any solution that has a substantially the same structure as the technical concept described in the claims of this disclosure and achieves the same effect is included within the technical scope of this disclosure, regardless of the solution.

[0146] Example

[0147] [Comparative Example 1]

[0148] (Preparation of negative electrode active material)

[0149] 0.65 g of Si particles (high-purity chemically produced) and 0.60 g of Li metal (Honjo Metals produced) were mixed in an agate mortar under an Ar atmosphere to obtain a LiSi precursor. 250 ml of ethanol (made by Nakalitesk) at 0°C was added to 1.0 g of the obtained LiSi precursor, and the mixture was reacted in a glass reactor under an Ar atmosphere for 120 minutes. Subsequently, the liquid and solid reactants were separated by suction filtration, and the solid reactants were recovered. 50 ml of acetic acid (made by Nakalitesk) was added to 0.5 g of the recovered solid reactants, and the mixture was reacted in a glass reactor under atmospheric atmosphere for 60 minutes. Subsequently, the liquid and solid reactants were separated by suction filtration, and the solid reactants were recovered. The recovered solid reactants were dried under vacuum at 100°C for 2 hours to obtain the negative electrode active material (nanoporous Si particles).

[0150] (Making the negative electrode)

[0151] The obtained negative electrode active material (nanoporous Si particles, average particle size 0.5 μm), sulfide solid electrolyte (10LiI·15LiBr·75(0.75Li2S·0.25P2S5), average particle size 0.5 μm), conductive material (VGCF-H), and binder (SBR) were weighed in a weight ratio of negative electrode active material: sulfide solid electrolyte: conductive material: binder = 47.0: 44.6: 7.0: 1.4 and mixed with a dispersion medium (diisobutyl ketone). The mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by ESMOT Corporation) to obtain a slurry. The slurry was applied to one surface of the negative electrode current collector (Ni foil, thickness 22 μm) using a scraper coating method with an applicator and dried at 100°C for 30 minutes. Subsequently, the same coating and drying process was performed on the other surface of the negative current collector. This resulted in a negative electrode having a negative current collector and negative active material layers formed on both sides of the negative current collector. The thickness (single-sided thickness) of the negative active material layer was 60 μm.

[0152] (Fabrication of components for the positive electrode)

[0153] The positive electrode active material (LiNi) coated with LiNbO3 using a rolling flow granulation coating device 0.8 Co 0.15 Al 0.05 O2 (average particle size 10 μm), sulfide solid electrolyte (10LiI·15LiBr·75 (0.75Li2S·0.25P2S5), average particle size 0.5 μm), conductive material (VGCF-H), and binder (SBR) were weighed in a weight ratio of positive electrode active material: sulfide solid electrolyte: conductive material: binder = 83.3:14.4:2.1:0.2 and mixed with a dispersion medium (diisobutyl ketone). The mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by ESMOT Corporation) to obtain a slurry. The slurry was then coated onto an Al foil (15 μm thick) using a doctor blade coating method and dried at 100°C for 30 minutes. This yielded a positive electrode component having an Al foil and a positive electrode active material layer. The thickness of the positive electrode active material layer was 100 μm.

[0154] (Fabrication of components for solid electrolyte layers)

[0155] A sulfide solid electrolyte (10LiI·15LiBr·75 (0.75Li2S·0.25P2S5), average particle size 2.0 μm) and a binder (SBR) were weighed at a weight ratio of sulfide solid electrolyte: binder = 99.6:0.4, and mixed with a dispersion medium (diisobutyl ketone). The mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by ESMOT Corporation) to obtain a slurry. The slurry was then applied to an Al foil (15 μm thick) using a doctor blade coating method and dried at 100°C for 30 minutes. This yielded a component for a solid electrolyte layer having an Al foil and a solid electrolyte layer. The thickness of the solid electrolyte layer was 50 μm.

[0156] (Battery manufacturing)

[0157] First, the negative electrode and solid electrolyte layer are cut into components measuring 7.2cm × 7.2cm. Meanwhile, the positive electrode is cut into components measuring 7.0cm × 7.0cm.

[0158] Next, the negative electrode active material layer on one surface of the negative electrode is brought into contact with the solid electrolyte layer of the solid electrolyte layer component, and the negative electrode active material layer on the other surface of the negative electrode is also brought into contact with the solid electrolyte layer of the solid electrolyte layer component. The resulting laminate is pressed using a rolling method at a linear pressure of 1.6 tons / cm. Then, the Al foil is peeled off from each solid electrolyte layer, exposing the solid electrolyte layer.

[0159] Subsequently, the exposed solid electrolyte layers were brought into contact with the positive electrode active material layers of the positive electrode components. The resulting laminate was pressed using a rolling method at a linear pressure of 1.6 tons / cm. Next, the Al foil was peeled off from each positive electrode active material layer to expose the positive electrode active material layer, and then pressed using a rolling method at a linear pressure of 5 tons / cm. Next, a positive electrode current collector (Al foil, 15 μm thick) with a carbon coating was disposed on the rolled positive electrode active material layer. Furthermore, the carbon coating was formed by applying a slurry to the positive electrode current collector (Al foil) and drying it. The slurry was obtained by weighing conductive material (furnace black, manufactured by Tokai Carbon) and PVDF (manufactured by Kreha) at a volume ratio of conductive material:PVDF = 85:15, and mixing them with N-methylpyrrolidone (NMP). Next, by setting tabs for current collection on the positive and negative current collectors respectively, and then laminating and sealing them, the battery is obtained smoothly.

[0160] [Comparative Example 2]

[0161] (Fabrication of components for solid electrolyte layers)

[0162] A halide solid electrolyte (Li3YBr2Cl4, average particle size 0.5 μm) and a binder (SEBS) were weighed at a weight ratio of halide solid electrolyte: binder = 100:3, and mixed with a dispersion medium (tetralin and p-chlorotoluene). The mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by ESMOT Corporation) to obtain a slurry. The slurry was then applied to an Al foil (15 μm thick) using a doctor blade coating method and dried at 100°C for 30 minutes. This yielded a component for a first solid electrolyte layer having an Al foil and a first solid electrolyte layer. The thickness of the first solid electrolyte layer was 25 μm.

[0163] In addition, a sulfide solid electrolyte (10LiI·15LiBr·75 (0.75Li2S·0.25P2S5), with an average particle size of 2.0 μm) and a binder (SBR) were weighed at a weight ratio of sulfide solid electrolyte: binder = 99.6:0.4, and mixed with a dispersion medium (diisobutyl ketone). The mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by ESMOT Corporation) to obtain a slurry. The slurry was then applied to an Al foil (15 μm thick) using a doctor blade coating method and dried at 100°C for 30 minutes. This yielded a component for a second solid electrolyte layer having an Al foil and a second solid electrolyte layer. The thickness of the second solid electrolyte layer was 50 μm.

[0164] (Battery manufacturing)

[0165] The negative electrode and positive electrode components were prepared in the same manner as in Comparative Example 1. The negative electrode, the component for the first solid electrolyte layer, and the component for the second solid electrolyte layer were cut to a size of 7.2 cm × 7.2 cm. On the other hand, the positive electrode component was cut to a size of 7.0 cm × 7.0 cm.

[0166] The negative electrode active material layer on one surface of the negative electrode is brought into contact with the second solid electrolyte layer of the second solid electrolyte layer component, and the negative electrode active material layer on the other surface of the negative electrode is also brought into contact with the second solid electrolyte layer of the second solid electrolyte layer component. The resulting laminate is pre-pressed using a rolling press to peel off Al foil from each second solid electrolyte layer, exposing the second solid electrolyte layer. Next, the exposed second solid electrolyte layers are brought into contact with the first solid electrolyte layer of the first solid electrolyte layer component, and pressed using a rolling press at a linear pressure of 1.6 tons / cm. Next, Al foil is peeled off from each first solid electrolyte layer, exposing the first solid electrolyte layer. Next, the exposed first solid electrolyte layers are brought into contact with the positive electrode active material layer of the positive electrode component. The resulting laminate is pressed using a rolling press at a linear pressure of 1.6 tons / cm. Then, the same process as in Comparative Example 1 is performed to obtain a battery.

[0167] [Comparative Example 3]

[0168] LTO particles (Li4Ti5O) 12 LTO particles (with an average particle size of 0.7 μm) and binder (SBR) were weighed at a weight ratio of 95:5 and mixed with a dispersion medium (diisobutyl ketone). The mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by ESMOT Corporation) to obtain a slurry. The slurry was applied to one surface of a negative electrode current collector (Ni foil, 22 μm thick) using a doctor blade coating method and dried at 100°C for 30 minutes. Subsequently, the same coating and drying process was performed on the other surface of the negative electrode current collector. Thus, a negative electrode current collector with coatings on both sides was obtained. The coating thickness (thickness on one side) was 5 μm. Except for using the obtained negative electrode current collector, the same procedure as Comparative Example 1 was performed to obtain a battery.

[0169] [Example 1]

[0170] The same procedure as in Comparative Example 3 was followed to obtain a negative electrode current collector with coatings on both sides. A battery was obtained by proceeding in the same manner as in Comparative Example 2, except that the obtained negative electrode current collector was used.

[0171] [evaluate]

[0172] (Prick test)

[0173] The batteries obtained in Example 1 and Comparative Examples 1-3 were charged and subjected to puncture tests. Specifically, the batteries were constant-size confined at 5 MPa and subjected to constant current charging (current value 1 / 3C, charging termination voltage 4.05V) and constant voltage charging (voltage value 4.05V, current value 20A). In constant voltage charging, an iron nail with a diameter of 3.0 mm and a tip angle of 30° was punctured from the side of the battery at a speed of 0.1 mm / s to induce an internal short circuit. Punctures were continued until the battery temperature reached 300°C, and the short-circuit area at that point was measured. The "short-circuit area" refers to the cross-sectional area of ​​the hole created by the nail's penetration. Due to the angle at the nail tip, the short-circuit area increases as the nail is driven deeper. The short-circuit area was calculated by observing the size of the puncture hole on the battery after the puncture test using a microscope. See Table 1 and... Figure 4 The results are shown below. Furthermore, the short-circuit area is a relative value when Comparative Example 1 is set to 1.00.

[0174] Table 1

[0175]

[0176] As shown in Table 1 and Figure 4 As shown, the short-circuit area of ​​Example 1 is larger than that of Comparative Examples 1-3. Specifically, the short-circuit area of ​​Comparative Example 2 is the same as that of Comparative Example 1, while the short-circuit area of ​​Comparative Example 3 is slightly increased. In contrast, it was confirmed that the short-circuit area of ​​Example 1 is significantly increased compared to Comparative Example 1. This is presumably due to the synergistic effect obtained by the coating blocking the inflow current during short circuits and the good thermal stability of the halide solid electrolyte.

Claims

1. A battery comprising, sequentially along its thickness direction, a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector. The surface of the negative electrode current collector on the side of the negative electrode active material layer has a coating containing an oxide active material. The solid electrolyte layer has a first solid electrolyte layer and a second solid electrolyte layer disposed between the first solid electrolyte layer and the negative electrode active material layer. The first solid electrolyte layer contains a halide solid electrolyte. The second solid electrolyte layer contains a sulfide solid electrolyte. The oxide active material contains Li4Ti5O as lithium titanate. 12 The coating contains at least one of Li4TiO4, Li2TiO3, and Li2Ti3O7, wherein the proportion of the oxide active material in the coating is 50% by weight or more.

2. The battery according to claim 1, The halide solid electrolyte is represented by the following compositional formula (1). Li α M β X γ ⋯ Formula (1) α, β, and γ are values ​​greater than 0. M contains at least one selected from metallic and half-metallic elements other than Li. X contains at least one selected from F, Cl, Br and I.

3. The battery according to claim 2, The halide solid electrolyte uses Li 6-3A M A X6 indicates that, among which, A satisfies 0 < A < 2, M is at least one of Y and In, and X is at least one of Cl and Br.

4. The battery according to claim 1, The halide solid electrolyte is a chloride solid electrolyte.

5. The battery according to claim 1, The sulfide solid electrolyte contains Li, P, and S.

6. The battery according to claim 1, The negative electrode active material layer contains a negative electrode active material, which is an active material whose total volume expansion rate due to charging is more than 14%.

7. The battery according to claim 1, The negative electrode active material is a Si-based active material.

8. The battery according to claim 1, The thickness of the coating is more than 3% and less than 20% of the thickness of the negative electrode active material layer.

9. The battery according to claim 1, wherein the coating contains an adhesive, and the content of the adhesive in the coating is more than 1% by weight and less than 10% by weight.

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