SOLID-STATE BATTERY AND SOLID-STATE ELECTROLYTE

Abstract

The present disclosure provides an all-solid-state battery comprising: a positive electrode active material layer; a negative electrode active material layer; and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains a solid electrolyte; and the solid electrolyte contains a Li element, an Al element, an M element (M is at least one kind of B, Ga, In, and Tl), and a halogen element, and the halogen element is a main component of an anion.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present disclosure relates to a solid-state battery and a solid-state electrolyte. 2. Description of the related art

[0002] In recent years, battery development has been actively pursued. For example, the automotive industry has pushed forward with the development of a battery used in a battery electric vehicle (BEV), a plug-in hybrid electric vehicle (PHEV), or a hybrid electric vehicle (HEV). Furthermore, the development of an element and a material used in the aforementioned batteries has been advanced.

[0003] For example, Japanese Unexamined Patent Application Laid-Open No. 2023-120474 discloses a lithium-ion conductor containing LiBI4 as a solid electrolyte used in the battery. SUMMARY OF THE INVENTION

[0004] From the perspective of improving battery performance, it is desirable that the charge-discharge efficiency (Coulombic efficiency) be high. The present disclosure was made in consideration of the above circumstance and has a primary objective of providing an all-solid-state battery having high charge-discharge efficiency. [1] A solid-state battery comprising: a positive electrode active material layer; a negative electrode active material layer; and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein: at least one of the positive electrode active material layer, the negative electrode active material layer and the solid electrolyte layer contains a solid electrolyte; and the solid electrolyte contains a Li element, an Al element, an M element (M is at least one of B, Ga, In and Tl) and a halogen element, and the halogen element is the main component of an anion. [2] The all-solid-state battery according to [1], wherein the ratio of the M element to the total of the Al element and the M element in the solid electrolyte is 10% or more and 80% or less. [3] The solid-state battery according to [1] or [2], wherein the solid-state electrolyte contains an I element as a halogen element. [4] The solid-state battery according to any one of [1] to [3], wherein the negative electrode active material layer contains a Si-based negative electrode active material. [5] Solid electrolyte used in a solid-state battery, where the solid electrolyte contains a Li element, an Al element, an M element (M is at least one of B, Ga, In and Tl) and a halogen element, and the halogen element is the main component of an anion.

[0005] The present disclosure provides a solid-state battery having high charge-discharge efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Features, advantages and technical and industrial significance of embodiments of the invention are described below with reference to the accompanying drawings, in which like characters designate like elements and wherein: Fig. 1 is a schematic sectional view of a solid-state battery according to the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0007] A solid-state battery and a solid-state electrolyte in the present disclosure are described in detail below. A. Solid-state battery

[0008] Fig. 1 is a schematic sectional view showing an all-solid-state battery of the present disclosure. Fig. 1 schematically shows the solid-state battery of the present disclosure, and to facilitate understanding, the sizes and shapes of the individual sections are exaggerated where appropriate. Fig.The all-solid-state battery 10 shown in Figure 1 comprises a positive electrode active material layer 1, a negative electrode active material layer 2, and a solid electrolyte layer 3 disposed between the positive electrode active material layer 1 and the negative electrode active material layer 2. The all-solid-state battery 10 further includes a positive electrode current collector 4 that collects electrons in the positive electrode active material layer 1 and a negative electrode current collector 5 that collects electrons in the negative electrode active material layer 2. Specifically, in the all-solid-state battery 10, at least one of the positive electrode active material layer 1, the negative electrode active material layer 2, and the solid electrolyte layer 3 contains a solid electrolyte.The solid electrolyte contains a Li element, an Al element, an M element (M is at least one of B, Ga, In and Tl) and a halogen element, and the halogen element is the main component of an anion.

[0009] In the present disclosure, at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains a predetermined solid electrolyte, so that the all-solid-state battery has a high charge-discharge efficiency.

[0010] For example, a LiAl halide salt such as LiAlI4 has been studied as a solid electrolyte used in the all-solid-state battery. Meanwhile, the inventor is aware that the charge-discharge efficiency (cycle characteristic) decreases in the all-solid-state battery using the LiAl halide salt. Although details are unknown, it is estimated that repeated charging and discharging of the battery causes the reductive decomposition of the LiAl halide salt. In this regard, as a result of careful research, the inventor has found that an all-solid-state battery with high charge-discharge efficiency can be obtained by using a solid electrolyte in which a Group 13 element other than Al is added to the LiAl halide salt.Although details are unknown, it is believed that the addition of the Group 13 element other than Al forms a stable product on the surface of the solid electrolyte and limits the reductive decomposition of the entire solid electrolyte. 1. Solid-state electrolyte

[0011] The solid electrolyte in the present disclosure contains the Li element, the Al element, the M element (M is at least one of B, Ga, In, and Tl), and the halogen element, and contains the halogen element as the main component of the anion. The solid electrolyte in the present disclosure corresponds to a so-called LiAl halide-based salt.

[0012] The ratio of the total amount of the Li element, the Al element, the halogen element, and the M element to all elements contained in the solid electrolyte may be 100 mol% or less than 100 mol%. For example, the ratio of the total amount of the Li element, the Al element, the halogen element, and the M element is 70 mol% or more, and may be 80 mol% or more or 90 mol% or more.

[0013] Examples of the halogen element are F, Cl, B, and I. The solid electrolyte may contain one type of halogen element, but may also contain two or more types of halogen elements. It is particularly preferable that the solid electrolyte contain at least element I. Furthermore, the above-mentioned halogen element is contained as the main component of the anion. "Contained as the main component of the anion component" means that the ratio of the above halogen element to all the anion components contained in the solid electrolyte is 50 mol% or more. The ratio of the above halogen element to all the anion components may be 100 mol% and may be less than 100 mol%.

[0014] The M element is at least one of B, Ga, In, and Tl. The solid electrolyte may contain one type of M element, but may also contain two or more types of M elements. In particular, it is preferable that the solid electrolyte contains at least Ga. Further, in the solid electrolyte, the ratio (molar ratio) of the M element to the total amount of the Al element and the M element is, for example, 10% or more, and may be 20% or more, 30% or more, or 40% or more. On the other hand, the ratio of the M element is, for example, 80% or less, and may be 60% or less, or 50% or less. If the ratio of the M element is too small, there is a fear that the effect of restricting the reductive decomposition of the solid electrolyte cannot be sufficiently achieved. If the ratio of the M element is too large, there is a fear that it is not possible to achieve high ionic conductivity.

[0015] It is preferable that the solid electrolyte in the present disclosure does not contain a sulfur element (S element). This is because the water resistance of the solid electrolyte becomes high.

[0016] An example of the composition of the solid electrolyte is LiAl 1-a M a X4 (0.1 ≤ a ≤ 0.8). M is the element M described above, and X is the halogen element described above. Further, a may be 0.2 or more, 0.3 or more, or 0.4 or more. On the other hand, a may be 0.7 or less, 0.6 or less, or 0.5 or less. The solid electrolyte in the above composition can be regarded as a salt in which the element M replaces part of the Al in the LiAl halide salt.

[0017] The melting point of the solid electrolyte is, for example, 300°C or lower, and may be 200°C or lower, or 150°C or lower. On the other hand, the melting point is, for example, 10°C or higher, and may be 50°C or higher. The melting point can be measured by differential scanning calorimetry (DSC measurement). A solid electrolyte with a melting point of 100°C or lower is also called a molten salt. At the time of charge and discharge, the solid electrolyte in the present disclosure may be in a molten state or in a solid state.

[0018] The ionic conductivity of the solid electrolyte at 25 °C is not particularly limited, but should preferably be high. For example, the ionic conductivity is 1.0 × 10 -6 S / cm or more and 1.0 × 10 -4 S / cm or less.

[0019] The solid electrolyte can contain only one crystal phase, but also two or more crystal phases. Examples of the crystalline phase in the former case include a crystalline phase expressed as the composition described above. Examples of crystal phases in the latter case are the crystal phase in the composition described above, a crystal phase with a LiAl halide, such as LiAlI4, and a crystal phase with a LiM halide, such as LiGaI4.

[0020] Furthermore, in the all-solid-state battery of the present disclosure, the solid electrolyte is contained in at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer. The solid electrolyte may be contained in one layer of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer, may be contained in two layers, or may be contained in three layers. 2. Positive electrode active material layer

[0021] The positive electrode active material layer contains at least one positive electrode active material.

[0022] Examples of the positive electrode active material include an oxide active material. Examples of an oxide active material are a salt bed type active material such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and LiNi 0,8 Co0,15 Al 0,05 O2, a spinel-type active material such as LiMn2O4, and an olivine-type active material such as LiFePO4. Sulfur (S) can also be used as a positive electrode active material.

[0023] The shape of the positive electrode active material is, for example, a particle shape. The average particle diameter (D 50 ) of the positive electrode active material is, for example, 0.5 µm or more and 50 µm or less. The average particle diameter (D 50 ) is a volume-accumulated particle diameter measured using a laser diffraction-diffusion particle size distribution measurement device. The proportion of the positive electrode active material in the positive electrode active material layer is, for example, 50 wt% or more and 80 wt% or less.

[0024] The positive electrode active material layer may contain at least an electrolyte, a conductive material, and a binder as needed. Preferably, the positive electrode active material layer contains the solid electrolyte described in "1. Solid Electrolyte" as the electrolyte. Furthermore, the positive electrode active material may contain an electrolyte other than the solid electrolyte described above. The other electrolyte is described in "4. Solid Electrolyte Layer." The proportion of the solid electrolyte in the positive electrode active material layer is, for example, 30 wt% or more and 80 wt% or less.

[0025] Examples of the conductive material include a carbon material. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs). The proportion of the conductive material in the positive electrode active material layer is, for example, 0.01 wt% or more and 10 wt% or less.

[0026] The thickness of the positive electrode active material layer is not particularly limited and is, for example, 0.1 μm or more and 1000 μm or less. 3. Negative electrode active material layer

[0027] The negative electrode active material layer contains at least one negative electrode active material.

[0028] Examples of the negative electrode active material include a Si-based active material. The Si-based active material is an active material containing a Si element. Examples of the Si-based active material include elemental Si, a Si alloy, and a Si oxide. Preferably, the Si alloy contains the Si element as a main component. The content of the Si element in the Si alloy is, for example, 50 mol% or more, and may be 70 mol% or more or 90 mol% or more. On the other hand, the content of the Si element in the Si alloy is, for example, 99 mol% or less. Examples of a Si alloy are a Si-Al alloy, a Si-Sn alloy, a Si-In alloy, a Si-Ag alloy, a Si-Pb alloy, a Si-Sb alloy, a Si-Bi alloy, a Si-Mg alloy, a Si-Ca alloy, a Si-Ge alloy and a Si-Pb alloy.The Si alloy can be a two-component alloy or a multi-component alloy containing three or more components. Examples of Si oxide include SiO.

[0029] Furthermore, the Si-based active material may contain a diamond-type crystal phase, a clathrate I-type crystal phase, or a clathrate II-type crystal phase. In the clathrate I crystal phase or the clathrate II crystal phase, a polyhedron (cage) with a pentagon or hexagon is formed by a plurality of Si elements. This polyhedron has a space capable of accommodating metal ions, such as Li ions, within the polyhedron and can therefore restrict volume changes due to charge and discharge. Furthermore, the Si-based active material may contain a void inside a primary particle. This void can restrict the volume change of the active material and prevent cracks in the negative electrode active material layer. The void content is not particularly limited and is, for example, 4% or more and 40% or less.Whether the primary particle contains the void and the void ratio can be confirmed by observation with a scanning electron microscope (SEM).

[0030] The negative electrode active material layer may contain at least an electrolyte, a conductive material, and a binder as needed. The contents of the conductive material and the binder are the same as those described in "2. Positive Electrode Active Material Layer." Furthermore, it is preferable that the negative electrode active material layer contain the solid electrolyte described in "1. Solid Electrolyte" as the electrolyte. Furthermore, another electrolyte may also be contained as the electrolyte. The ratio of the solid electrolyte and the other electrolyte is the same as that described in "2. Positive Electrode Active Material Layer."

[0031] The thickness of the negative electrode active material layer is not particularly limited and is, for example, 0.1 µm or more and 1000 µm or less. 4. Solid electrolyte layer

[0032] The solid electrolyte layer is a layer disposed between the positive electrode active material layer and the negative electrode active material layer and contains at least one solid electrolyte. Preferably, the solid electrolyte layer contains the solid electrolyte described in "1. Solid Electrolyte."

[0033] In addition, the solid electrolyte layer may contain another electrolyte. Examples of the other electrolyte include an inorganic solid electrolyte such as a sulfide solid electrolyte. Preferably, the sulfide solid electrolyte contains sulfur (S) as the main component of an anion element.

[0034] Preferably, the sulfide solid electrolyte contains the Li element, an X element (X is at least one of P, Sn, Al, Zn, In, Ge, Si, Sb, Ga, and Bi), and the S element. Furthermore, the sulfide solid electrolyte may contain a halogen element such as F, Cl, Br, and I. Furthermore, in the sulfide solid electrolyte, an O element may replace some of the S elements.

[0035] Examples of the sulfide solid electrolyte are Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m and n are positive values, and Z is one of Ge, Zn and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li x MO y (x and y are positive values, and M is one of P, Si, Ge, B, Al, Ga and In).

[0036] Other examples of the other electrolyte include an organic solid-state electrolyte, such as a gel electrolyte, and an electrolyte solution. Materials commonly used in the battery field can be considered as organic solid-state electrolyte and electrolyte solution.

[0037] Furthermore, the solid electrolyte layer may optionally contain a binder. The content of the binder is the same as that described in "2. Positive Electrode Active Material Layer." The thickness of the solid electrolyte layer is not particularly limited and is, for example, 0.1 μm or more and 1000 μm or less. 5. Other configurations

[0038] Preferably, the all-solid-state battery of the present disclosure includes a positive electrode current collector that receives the electric current from the positive electrode active material layer and a negative electrode current collector that receives the electric current from the negative electrode active material layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0039] The all-solid-state battery in the present disclosure may further include a confining device that applies confining pressure in a thickness direction to the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer. The confining pressure is, for example, 0.1 MPa or more, and may be 1 MPa or more, or 5 MPa or more. On the other hand, the confining pressure is, for example, 100 MPa or less, and may be 50 MPa or less, or 20 MPa or less. 6. Solid-state battery

[0040] The type of all-solid-state battery in the present disclosure is not particularly limited and is typically a lithium-ion battery. Furthermore, the all-solid-state battery in the present disclosure may be a semi-solid-state battery or an all-solid-state battery. Generally, the all-solid-state battery is a solid-state battery in which all the electrolytes constituting the solid electrolyte layer are inorganic solid electrolytes. Furthermore, the all-solid-state battery in the present disclosure may be a primary battery or a secondary battery, preferably a secondary battery. This is because the secondary battery allows repeated charge and discharge and is useful, for example, as a vehicle battery.

[0041] The all-solid-state battery is used, for example, as an electric power source of a vehicle such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a battery electric vehicle (BEV), a gasoline vehicle, and a diesel vehicle. It is particularly preferred that the all-solid-state battery be used as an electric power source for driving the hybrid electric vehicle (HEV), the plug-in hybrid electric vehicle (PHEV), or the battery electric vehicle (BEV). Furthermore, the all-solid-state battery can be used as an electric power source of a non-vehicle moving body (e.g., a train, a ship, or an aircraft) or as an electric power source of an electrical product such as an information processing device. B. Solid-state electrolyte

[0042] In the present disclosure, it is possible to provide a solid electrolyte used in the all-solid-state battery. The solid electrolyte contains the Li element, the Al element, the M element (M is at least one of B, Ga, In, and Tl), and a halogen element, and contains the above halogen element as a main component of the anion. The contents of the all-solid-state battery and the solid electrolyte are the same as those described in "A. All-solid-state Battery."

[0043] The present disclosure is not limited to the above embodiment. The above embodiment is an example, and the technical scope of the present disclosure includes all embodiments that are substantially identical to the technical ideas described in the claims of the present disclosure and that exert the same functional effects. Example 1: Preparation of a solid-state electrolyte

[0044] As raw materials, LiI and AlI3 (10 g total) and heptane (100 g) were weighed, placed in a Fritsch ball mill (size: 500 ml, used ball: 5 mm ZrO2), and ball milled at 300 rpm for 20 h. This yielded LiAlI4. Furthermore, ball milling was performed with LiI and GaCl3 as raw materials, similar to the above, to yield LiGaI4. The resulting LiAlI4 and LiGaI4 were weighed in a molar ratio of 90:10, and ball milled. This yielded a solid electrolyte with a composition of LiAl. 0,9 Ga 0,1 I4. Manufacturing of the battery for evaluation

[0045] Using the above solid electrolyte, a Fig.1 was prepared as a battery for evaluation. A layer containing a Si-based negative electrode active material (elemental Si), a binder (PVdF-based binder), the above solid electrolyte, and a conductive material (VGCF) was used as the negative electrode active material layer. A layer containing a positive electrode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2), a binder (PVdF-based binder), the above-mentioned solid electrolyte, and a conductive material (VGCF) was used as the positive electrode active material layer. In addition, a layer containing a binder (butadiene rubber) and the above-mentioned solid electrolyte was used as the solid electrolyte layer. Furthermore, an Al foil was used as the positive electrode current collector and a Ni foil as the negative electrode current collector. Furthermore, the battery under investigation was enclosed at a pressure of 6 N. Examples 2-4

[0046] Solid electrolytes with the compositions shown in Table 1 were obtained by mixing LiAlI4 and LiGaI4 in a molar ratio of 80:20, a molar ratio of 60:40, and a molar ratio of 20:80, respectively. The batteries to be tested were prepared in a similar manner to Example 1, except that the solid electrolytes were used. Comparative examples 1-2

[0047] The batteries for evaluation were prepared similarly to Example 1, except that LiAlI4 or LiGaI4 was used as the solid electrolyte instead of the solid electrolyte in Example 1. Reference example

[0048] A battery to be evaluated was prepared similarly to Example 1, except that a sulfide solid electrolyte (Li2S-P2S5 sulfide solid electrolyte) was used as the solid electrolyte instead of the solid electrolyte in Example 1. Rating charge-discharge efficiency

[0049] For each battery under evaluation, a CCCV charge-discharge cycle was repeated at a charge-discharge rate of 1 / 3 C at room temperature for 50 cycles. The ratio of the discharge capacity after 5 cycles to the initial discharge capacity and the ratio of the discharge capacity after 50 cycles to the initial discharge capacity were calculated as the "charge-discharge efficiency." The results are presented in Table 1. [Table 1] Solid-state electrolyte M / (Al + M)(%) Charge-discharge efficiency (%) after 5 cycles after 50 cycles Reference example Sulfide solid electrolyte - 93 86 Comparative Example 1 LiAlI4 0 68 31 Example 1 LiAl 0,9 Ga 0.1 I4 10 85 78 Example 2 LiAl 0,8 Ga 0,2 I4 20 95 92 Example 3 LiAl 0,6 Ga 0,4 I4 40 94 91 Example 4 LiAl 0,2 Ga 0,8 I4 80 88 80 Comparative Example 2 LiGaI4 100 84 56

[0050] As shown in Table 1, the all-solid-state batteries in Examples 1 to 3 had higher charge-discharge efficiencies after 5 cycles, and especially higher charge-discharge efficiencies after 50 cycles, compared with Comparative Examples 1 and 2. Therefore, it was suspected that the decomposition of the solid electrolyte during battery charge and discharge was restrained in the all-solid-state batteries of the present disclosure. Furthermore, it is known that the sulfide solid electrolyte used in Reference Example is a solid electrolyte that inhibits the occurrence of oxidation-reduction reactions and has high ionic conductivity. However, the sulfide solid electrolyte tends to have poor water resistance because it contains sulfur.In contrast, for the all-solid-state batteries in Examples 1 to 3, it was confirmed that the charge-discharge efficiencies are comparable to those of the all-solid-state battery in the Reference Example, and it was suggested that the water resistance is also high because the sulfur element is not included. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-120474

[0003]

Claims

[1] Solid-state battery, comprising: a positive electrode active material layer; a negative electrode active material layer; and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer; wherein: at least one of the positive electrode active material layer, the negative electrode active material layer and the solid electrolyte layer contains a solid electrolyte; and the solid electrolyte contains a Li element, an Al element, an M element (M is at least one of B, Ga, In and Tl) and a halogen element, and the halogen element is the main component of an anion. [2] The all-solid-state battery according to claim 1, wherein the ratio of the M element to the total amount of the Al element and the M element in the solid electrolyte is 10% or more and 80% or less. [3] The all-solid-state battery according to claim 1, wherein the solid electrolyte contains an I element as a halogen element. [4] The all-solid-state battery according to any one of claims 1 to 3, wherein the negative electrode active material layer contains a Si-based negative electrode active material. [5] A solid electrolyte used in a solid-state battery, wherein the solid electrolyte contains a Li element, an Al element, an M element (M is at least one of B, Ga, In, and Tl), and a halogen element, and the halogen element is a main component of an anion.

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