Battery

Abstract

Provided is a battery capable of improving discharge rate characteristics. A battery provided with a positive electrode, a solid electrolyte layer, and a negative electrode in this order, the negative electrode having a negative electrode current collector and a negative electrode layer in this order in a direction from the negative electrode toward the solid electrolyte layer side, the negative electrode layer comprising a Li-Mg-Al alloy layer, and the negative electrode layer comprising Li-Al alloy particles in the Li-Mg-Al alloy layer.

Description

Technical Field

[0001] This disclosure relates to batteries. Background Technology

[0002] Various technologies have been proposed regarding the battery disclosed in Patent Document 1.

[0003] Existing technical documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-184513 Summary of the Invention

[0005] Patent document 1 discloses a solid-state battery with a Li-Mg alloy at the negative electrode. During discharge of the solid-state battery, Li preferentially dissolves from the Li-Mg alloy near the solid electrolyte (SE) layer, increasing the Mg concentration near the solid electrolyte layer, which then becomes a resistive layer, thus reducing the discharge capacity.

[0006] This disclosure was made in view of the above circumstances, and its main objective is to provide a battery capable of improving discharge rate characteristics.

[0007] That is, this disclosure includes the following methods.

[0008] <1> A battery comprising, in sequence, a positive electrode, a solid electrolyte layer, and a negative electrode.

[0009] The negative electrode has a negative electrode current collector and a negative electrode layer in sequence in the direction from the negative electrode toward the solid electrolyte layer.

[0010] The negative electrode layer comprises a Li-Mg-Al alloy layer.

[0011] The negative electrode layer contains Li-Al alloy particles in the Li-Mg-Al alloy layer.

[0012] <2> According to the battery described in <1>, the average particle size of the Li-Al alloy particles is above 1 μm and below 3 μm.

[0013] <3> according to <1> or <2> In the battery described above, the thickness of the negative electrode layer is more than 1 μm and less than 15 μm.

[0014] <4> according to <1> ~ <3> In any one of the batteries, the solid electrolyte layer comprises a sulfide solid electrolyte.

[0015] <5> according to <1> ~ <4> In any one of the batteries, the negative electrode current collector is a Ni foil.

[0016] The battery disclosed herein can improve discharge rate characteristics. Attached Figure Description

[0017] Figure 1 This is a cross-sectional schematic diagram showing an example of a battery before its first charge according to the present disclosure.

[0018] Figure 2 This is a cross-sectional schematic diagram showing an example of a battery after its initial charging according to the present disclosure.

[0019] Figure 3 It is a graph showing the relationship between current density and discharge capacity of each unit in Example 1 (Mg, Al), Comparative Example 1 (Mg), and Comparative Example 2 (Al).

[0020] Explanation of reference numerals in the attached figures

[0021] 10 Positive Current Collector

[0022] 20 positive electrode layers

[0023] 30 Solid Electrolyte Layer

[0024] 40Al layers

[0025] 41Li-Mg-Al alloy layer

[0026] 50Mg layer

[0027] 51Li-Al alloy particles

[0028] 60 negative current collector

[0029] 100 batteries

[0030] 200 batteries Detailed Implementation

[0031] The embodiments of this disclosure will now be described. Furthermore, matters necessary for the implementation of this disclosure other than those specifically mentioned in this specification (e.g., the general structure and manufacturing process of a battery that are not features of this disclosure) can be grasped by those skilled in the art based on existing technology in the field. This disclosure can be implemented based on the content disclosed in this specification and common technical knowledge in the field.

[0032] In this disclosure, a fully charged battery refers to a battery with a State of Charge (SOC) of 100%. SOC represents the ratio of the battery's charge capacity to its full charge capacity, where full charge capacity is defined as SOC 100%.

[0033] SOC can also be estimated, for example, based on the battery's open circuit voltage (OCV).

[0034] In this disclosure, an example of a method for calculating the average particle size is as follows. First, for a single particle, the particle size is calculated by considering it as spherical in a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image at an appropriate magnification (e.g., 50,000 to 1,000,000 times). This particle size calculation based on TEM or SEM observations is performed on 2 to 300 particles of the same type, and the average value of these particles is taken as the average particle size.

[0035] This disclosure provides a battery that sequentially comprises a positive electrode, a solid electrolyte layer, and a negative electrode.

[0036] The negative electrode has a negative electrode current collector and a negative electrode layer in sequence in the direction from the negative electrode toward the solid electrolyte layer.

[0037] The negative electrode layer comprises a Li-Mg-Al alloy layer.

[0038] The negative electrode layer contains Li-Al alloy particles in the Li-Mg-Al alloy layer.

[0039] In this disclosure, by containing Li-Al alloy particles in the Li-Mg-Al alloy layer, the Li diffusion coefficient in the negative electrode layer can be increased. The discharge rate characteristics can be improved by supplying Li to the solid electrolyte layer interface and by suppressing the rise of Mg concentration near the solid electrolyte layer in the negative electrode layer through the supply of Li from the Li-Al alloy particles.

[0040] The battery disclosed herein comprises a positive electrode, a solid electrolyte layer, and a negative electrode in sequence.

[0041] Figure 1 This is a cross-sectional schematic diagram showing an example of a battery before its first charge according to the present disclosure.

[0042] like Figure 1 As shown, the battery 100 before the first charge sequentially comprises a positive current collector 10, a positive electrode layer 20, a solid electrolyte layer 30, an Al layer 40, a Mg layer 50, and a negative current collector 60.

[0043] Figure 2 This is a cross-sectional schematic diagram showing an example of a battery after its initial charging according to the present disclosure.

[0044] like Figure 2 As shown, the battery 200 after initial charging sequentially comprises a positive current collector 10, a positive electrode layer 20, a solid electrolyte layer 30, a Li-Mg-Al alloy layer 41, and a negative current collector 60.

[0045] Upon initial charging, the Al layer 40 and Mg layer 50 become a Li-Mg-Al alloy layer 41. The negative electrode layer contains Li-Al alloy particles 51 within the Li-Mg-Al alloy layer 41.

[0046] exist Figures 1-2 The orientation of the three-dimensional orthogonal coordinate system is also shown. Here, the xy plane is the horizontal plane, the z-axis direction is the vertical direction, and the positive direction of the z-axis is up.

[0047] [negative electrode]

[0048] The negative electrode has a negative current collector and a negative electrode layer in sequence in the direction from the negative electrode toward the solid electrolyte layer.

[0049] The negative current collector can be made of materials that are not alloyed with Li, such as SUS, aluminum, copper, nickel, iron, titanium, and carbon. The form of the negative current collector can be, for example, foil or plate. The top-view shape of the negative current collector is not particularly limited; for example, it can be circular, elliptical, rectangular, or any polygonal shape. Furthermore, the thickness of the negative current collector varies depending on its shape, for example, it can be in the range of 1 μm to 50 μm, or in the range of 5 μm to 20 μm. The negative current collector can be a structure with a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on its surface.

[0050] The negative electrode layer contains a Li-Mg-Al alloy layer.

[0051] The negative electrode layer contains Li-Al alloy particles in the Li-Mg-Al alloy layer.

[0052] The proportion of aluminum in the Li-Mg-Al alloy layer can be 0.1 atomic% to 5 atomic%, the proportion of magnesium can be 0.3 atomic% to 54.9 atomic%, and the proportion of lithium can be 45 atomic% to 99.6 atomic%.

[0053] The proportion of aluminum in Li-Al alloy particles can be 0.1 atomic% to 15 atomic%, and the proportion of lithium can be 85 atomic% to 99.9 atomic%.

[0054] The average particle size of Li-Al alloy particles can be above 1 μm and below 3 μm.

[0055] The thickness of the negative electrode layer can be greater than 1 μm and less than 15 μm.

[0056] The thickness of the negative electrode layer can be greater than 10μm and less than 15μm during a full charge after the initial charge of the battery.

[0057] The thickness of the negative electrode layer can be greater than 1 μm and less than 4 μm when the battery is fully discharged after its initial charge (SOC: 0%).

[0058] The negative electrode layer can sequentially include, from the solid electrolyte layer side, an Al layer containing elemental Al and a Mg layer containing elemental Mg, which serve as precursors to the Li-Mg-Al alloy layer, before the first charge of the battery.

[0059] A Mg layer can be formed, for example, on the negative electrode current collector. Methods for forming the film include placing and pressing Mg particles, vapor deposition, sputtering, PVD, and electroplating. Vapor deposition or sputtering is one such method. Improved adhesion between the Mg layer and the negative electrode current collector helps suppress increases in the negative electrode's resistance.

[0060] Regarding the Al layer, it can also be formed on either the negative electrode current collector side or the solid electrolyte layer side using the same method described above. Specifically, it can be formed on the solid electrolyte layer side. By forming the film on the solid electrolyte layer side, the adhesion between the Al layer and the solid electrolyte layer becomes higher.

[0061] The negative electrode layer can be a Li-Mg-Al alloy layer formed by alloying elemental Li, an Al layer, and a Mg layer after the battery's initial charging.

[0062] In the Li-Mg-Al alloy layer, Li-Al alloy phases containing Li-Al alloy particles can be dispersed.

[0063] The charging and discharging conditions for a battery in which an Al layer and a Mg layer are disposed between the negative electrode current collector and the solid electrolyte layer to form a Li-Mg-Al alloy layer containing Li-Al alloy particles are not particularly limited. For example, the Li-Mg-Al alloy layer containing Li-Al alloy particles is formed by charging and discharging for a predetermined time at a predetermined current density.

[0064] [positive electrode]

[0065] The positive electrode has a positive electrode layer and, if necessary, a positive electrode current collector.

[0066] The positive electrode layer contains positive electrode active material, and may contain solid electrolyte, conductive material, binder, thickener, etc. as needed.

[0067] The positive electrode layer can be formed by coating a positive electrode slurry onto at least one side of a support such as a positive electrode current collector and drying it.

[0068] The positive electrode slurry contains positive electrode active material and solvent, and may contain solid electrolyte, conductive material, binder, thickener, solvent, etc. as needed.

[0069] There are no particular limitations on the coating method of the positive electrode paste. Examples include doctor blade coating, metal mask printing, electrostatic coating, dip coating, spray coating, roller coating, gravure coating, and screen printing.

[0070] As a support, a self-supporting support can be appropriately selected without any particular limitation. For example, metal foils such as Cu and Al can be used.

[0071] Examples of positive electrode active materials include oxide active materials. For example, LiNi can be listed as an oxide active material. 0.8 Co 0.15 Al 0.05 O2, LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMn2O4, Li(Ni) 0.5 Mn 1.5 )O4, LiFePO4, LiMnPO4, LiNiPO4, LiCuPO4, etc.

[0072] The positive electrode active material can be positive electrode active material particles.

[0073] The average particle size of the positive electrode active material is not particularly limited and can range from 1 nm to 100 μm.

[0074] There is no particular limitation on the content of the positive electrode active material in the positive electrode layer, which can be 50.00 to 99.00% by mass.

[0075] The positive electrode active material can be coated with a lithium-ion conductive compound on at least a portion of its surface.

[0076] The lithium-ion conductive compound can be coated on at least a portion of the surface of the above-mentioned positive electrode active material, or it can be coated on the entire surface of the positive electrode active material.

[0077] Examples of lithium-ion conductive compounds include B₂O₃, Li₂B₄O₇, LiBPO₄, Li₃PO₄, LiPO₃, and LiNbO₃. The thickness of the lithium-ion conductive compound coating is, for example, 0.1 nm or more, and may also be 1 nm or more. Alternatively, the thickness of the lithium-ion conductive compound may be, for example, 100 nm or less, and may also be 20 nm or less. The coating percentage of the lithium-ion conductive compound on the positive electrode active material is, for example, 70% or more, may also be 90% or more, and may also be 100%. The coating method for the lithium-ion conductive compound is not particularly limited, and conventionally known methods may be appropriately used.

[0078] As solid electrolytes, examples of solid electrolytes contained in solid electrolyte layers, which will be described later, can be listed.

[0079] There is no particular limitation on the proportion of solid electrolyte in the positive electrode layer.

[0080] 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); and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs).

[0081] There is no particular limitation on the proportion of conductive material in the positive electrode layer.

[0082] Examples of adhesives include acrylonitrile butadiene rubber (ABR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and styrene butadiene rubber (SBR).

[0083] There is no particular limitation on the proportion of binder in the positive electrode layer.

[0084] Examples of thickeners include carboxymethyl cellulose (CMC) and methyl cellulose polysaccharides.

[0085] Examples of solvents include aqueous solvents and organic solvents. Aqueous solvents refer to water or a mixture of water and a polar organic solvent. For example, an appropriate solvent can be selected based on the type of positive electrode active material, binder, etc.

[0086] Water is preferred as an aqueous solvent for ease of handling. Examples of polar organic solvents that can be used in mixed solvents include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone; and ethers such as tetrahydrofuran.

[0087] Examples of organic solvents include 1,2,3,4-tetrahydronaphthalene, n-heptane, butyl butyrate, diisobutyl ketone, and N-methyl-2-pyrrolidone (NMP).

[0088] Materials used as positive current collectors include, for example, metals such as aluminum, copper, SUS, and nickel. The thickness of the positive current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the positive current collector can be sheet-like or the like. The positive current collector can be a structure with a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on its surface.

[0089] [Solid electrolyte layer]

[0090] The solid electrolyte layer contains at least a solid electrolyte.

[0091] There is no particular limitation on the thickness of the solid electrolyte layer, which is usually above 0.1 μm and below 1 mm.

[0092] As the solid electrolyte contained in the solid electrolyte layer, a known solid electrolyte suitable for use in solid-state batteries can be appropriately used, such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. In order to suppress the peeling of the positive and negative electrode layers from the solid electrolyte layer, a relatively soft sulfide solid electrolyte can be used as the solid electrolyte.

[0093] Examples of sulfide solid electrolytes include those containing Li, M (where M is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. Furthermore, sulfide solid electrolytes may further contain at least one of O and a halogen.

[0094] Examples of sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-SiS₂, LiX-Li₂S-SiS₂, LiX-Li₂S-P₂S₅, LiX-Li₂O-Li₂S-P₂S₅, LiX-Li₂S-P₂O₅, LiX-Li₃PO₄-P₂S₅, and Li₃PS₄. Furthermore, the description of "Li₂S-P₂S₅" refers to a material formed using a raw material composition containing Li₂S and P₂S₅, and the other descriptions are similar.

[0095] Furthermore, the "X" in LiX represents a halogen. Examples of halogens include F, Cl, Br, and I. The raw material composition containing the aforementioned LiX may contain one or more types of LiX. When containing two or more types of LiX, the mixing ratio of the two or more types is not particularly limited.

[0096] The molar ratio of each element in a sulfide solid electrolyte can be controlled by adjusting the content of each element in the raw materials. Furthermore, the molar ratio and composition of each element in the sulfide solid electrolyte can be determined, for example, by ICP-based luminescence analysis.

[0097] Sulfide solid electrolytes can be sulfide glasses, crystallized sulfide glasses (glass ceramics), or crystalline materials obtained through solid-state reaction treatment of raw material compositions.

[0098] The crystalline state of sulfide solid electrolytes can be confirmed, for example, by powder X-ray diffraction using CuKα rays.

[0099] Sulfide glasses can be obtained by amorphous treatment of a raw material composition (e.g., a mixture of Li2S and P2S5). Examples of amorphous treatments include mechanical polishing.

[0100] Glass ceramics can be obtained, for example, by heat treatment of sulfide glass.

[0101] The heat treatment temperature can be any temperature higher than the crystallization temperature (Tc) observed by thermal analysis of the sulfide glass, typically above 195°C. On the other hand, there is no particular upper limit to the heat treatment temperature.

[0102] The crystallization temperature (Tc) of sulfide glass can be determined by differential calorimetry (DTA).

[0103] There is no particular limitation on the heat treatment time as long as it is sufficient to achieve the desired crystallinity of the glass ceramic, for example, it can be in the range of 1 minute to 24 hours, of which the range of 1 minute to 10 hours can be cited.

[0104] There are no particular limitations on the heat treatment method; for example, the use of a firing furnace can be cited.

[0105] Examples of oxide solid electrolytes include substances with a garnet-type crystal structure, wherein the garnet-type crystal structure contains the elements Li, La, A (A being at least one of Zr, Nb, Ta, and Al), and O. Examples of oxide solid electrolytes include Li₂O-B₂O₃-P₂O₅, Li₂O-SiO₂, Li₂O-B₂O₃, and Li₂O-P₂O₅. 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 Li7La3Zr2O 12 Li6BaLa2Ta2O 12 Li 3.6 Si 0.6 P 0.4 O4, Li4SiO4, Li3PO4 and Li 3+x PO 4-x N x (1≤x≤3) etc.

[0106] As a halide solid electrolyte, it can be, for example, a solid electrolyte containing Li, M and X (M represents at least one of Ti, Al and Y, and X represents F, Cl or Br).

[0107] From an operational point of view, solid electrolytes can be in the form of particles.

[0108] In addition, the average particle size (D50) of the solid electrolyte is not particularly limited and can be from 1 nm to 100 μm.

[0109] Solid electrolytes can be used alone or in combination with two or more types. Furthermore, when using two or more solid electrolytes, they can be mixed, or they can form two or more layers of solid electrolyte to create a multilayer structure.

[0110] The proportion of solid electrolyte in the solid electrolyte layer is not particularly limited; for example, it can be 50% or more by mass, or it can be in the range of 60% or more and less than 100% by mass, or it can be in the range of 70% or more and less than 100% by mass, or it can be 100% by mass. The solid electrolyte can contain less than 10% by mass of electrolyte relative to the total electrolyte volume. Furthermore, the solid electrolyte can be a composite solid electrolyte comprising inorganic solid electrolyte and polymer electrolyte.

[0111] From the viewpoint of exhibiting plasticity, the solid electrolyte layer may also contain a binder. Examples of such a binder include materials used as binders in the aforementioned positive electrode layer. However, to facilitate high output, and from the viewpoint of forming a solid electrolyte layer that prevents excessive aggregation of the solid electrolyte and provides uniform dispersion, the binder contained in the solid electrolyte layer may be 5% by mass or less.

[0112] There are no particular restrictions on the type of battery; for example, lithium-ion batteries can be listed. Batteries can be primary or secondary. Batteries can also be solid-state batteries.

[0113] Furthermore, in this disclosure, a solid-state battery refers to a battery containing a solid electrolyte. A solid-state battery can be a semi-solid-state battery containing both a solid electrolyte and liquid materials, or a fully solid-state battery not containing liquid materials. The shape of the battery is not particularly limited; for example, it can be coin-shaped, cylindrical, square, sheet-shaped, button-shaped, flat, or stacked.

[0114] Batteries are used in various applications, including as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. They can also be used as power sources for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Furthermore, batteries can be used as power sources for mobile bodies other than vehicles (such as railways, ships, and aircraft), and also as power sources for electrical products such as information processing devices.

[0115] [Example]

[0116] (Example 1)

[0117] [Positive electrode production]

[0118] LiNi, which is used as a positive electrode active material 1 / 3 Co 1 / 3 Mn 1 / 3 A positive electrode slurry consisting of O2, a binder, and a solvent is applied to one side of an Al current collector foil that serves as the positive electrode current collector and then dried to obtain a positive electrode having a positive electrode layer on the positive electrode current collector.

[0119] [Solid Electrolyte Layer Fabrication]

[0120] As a sulfide solid electrolyte, a mixture of Li2S-P2S5-based materials containing LiBr and LiI, a binder, and a solvent is prepared. This mixture is then coated onto a release film. The coated mixture is then dried. The release film is peeled off from the dried solid electrolyte film to obtain a solid electrolyte layer.

[0121] [Negative electrode fabrication]

[0122] Using Al material prepared as a raw material for the modification layer and a magnetron sputtering apparatus, Al is deposited on one side of the solid electrolyte layer to form an Al layer (i.e., the modification layer) with a thickness of 100 nm.

[0123] Using an electron beam evaporation apparatus, Mg is deposited on one side of a Ni foil that serves as the negative electrode current collector, forming a Mg layer with a thickness of 1000 nm.

[0124] A Ni foil with a Mg layer on one side is disposed in surface contact with a solid electrolyte layer containing an Al layer. This results in a negative electrode with both Mg and Al layers on the negative current collector.

[0125] [Unit Production]

[0126] On the side opposite to the surface where the Al layer is located, the positive electrode is positioned in contact with the solid electrolyte layer. These are then subjected to cold isostatic pressing (CIP) at a rate of 4 tons / cm². 2 The solid-state battery is formed by pressing under pressure to obtain a unit (solid-state battery). The solid-state battery has, in sequence, a positive current collector, a positive electrode layer, a solid electrolyte layer, an Al layer, a Mg layer, and a negative current collector.

[0127] [Negative electrode layer of a solid-state battery]

[0128] A solid-state battery was charged at 0.15 mA, causing Li to precipitate in the negative electrode layer, thus forming the structure of the battery during operation. The cross-section of the charged solid-state battery was processed, and the negative electrode layer was observed using a secondary electron microscope (SEM). The thickness of the negative electrode layer was confirmed. Using energy-dispersive X-ray diffraction (EDX) analysis, based on elemental mapping and spectral analysis of the negative electrode layer, the types and concentrations of metal species, the thickness of the Li-Mg-Al alloy layer, and the particle size of the Li-Al alloy particles were estimated. Therefore, it is concluded that the negative electrode layer of Example 1 in its charged state contains Li-Al alloy particles within the Li-Mg-Al alloy layer.

[0129] The solid-state battery in the discharged state was also subjected to cross-sectional processing, and the negative electrode layer was observed using a secondary electron microscope (SEM). The thickness of the Li-Mg-Al alloy layer and the particle size of the Li-Al alloy are described below.

[0130] <Charging Status>

[0131] Li-Mg-Al alloy layer thickness: 12.5μm

[0132] Average particle size of Li-Al alloy: 1.5 μm

[0133] <Discharge State>

[0134] Li-Mg-Al alloy layer thickness: 2μm

[0135] Average particle size of Li-Al alloy: 1.5 μm (no change)

[0136] (Comparative Example 1)

[0137] In the [negative electrode fabrication] process, no Al layer was formed; otherwise, the cell was fabricated using the same method as in Example 1. It is known that the negative electrode layer of Comparative Example 1 in the state of charge contains a Li-Mg alloy layer.

[0138] (Comparative Example 2)

[0139] In the [negative electrode fabrication] process, no Mg layer was formed; otherwise, the cell was fabricated using the same method as in Example 1. It is evident that the negative electrode layer of Comparative Example 2 in the state of charge comprises a Li-Al alloy layer.

[0140] <Changes in Mg concentration near the solid electrolyte layer of the negative electrode>

[0141] For the units of Example 1 and Comparative Example 1, under conditions of 25°C and 0.4C rate, with a discharge charge of 15% (SOC 77%) 20 minutes after the start of discharge, the change in Mg concentration near the solid electrolyte layer of the negative electrode layer after discharge relative to before discharge was calculated. The results are shown in Table 1. "Near the solid electrolyte layer of the negative electrode layer" refers to the region of the negative electrode layer within a predetermined distance from the solid electrolyte layer. "Near the negative current collector of the negative electrode layer" refers to the region of the negative electrode layer within a predetermined distance from the negative current collector. The predetermined distance is less than half the thickness of the negative electrode layer.

[0142] Table 1

[0143]

[0144] As shown in Table 1, in Example 1, the Mg concentration near the solid electrolyte layer of the negative electrode layer increased by 13.3% after discharge compared to before discharge.

[0145] As shown in Table 1, in Comparative Example 1, the Mg concentration near the solid electrolyte layer of the negative electrode layer increased by 56.8% after discharge compared to before discharge.

[0146] It is known that an increase in local Mg concentration near the solid electrolyte layer of the negative electrode layer causes an increase in resistance during discharge. Therefore, it is preferable that the Mg concentration during discharge is uniform. Compared with Comparative Example 1, Example 1 can suppress the increase in Mg concentration after discharge.

[0147] As shown in the SEM and reflectance electron images of Example 1, Al is dispersed near the solid electrolyte layer of the negative electrode layer and within the negative electrode layer. The slight change in Mg concentration near the solid electrolyte layer of the negative electrode layer before and after discharge is presumably due to the function of the Li-Al alloy particles as a buffer.

[0148] Furthermore, a comparison of the Mg concentration during the 90-minute recovery period after discharge cessation with that immediately after discharge cessation shows that the Mg concentration near the negative electrode current collector during the recovery period changes only slightly compared to immediately after discharge cessation. This is presumably because the diffusion path of Mg is reduced by Al.

[0149] [Discharge Evaluation]

[0150] For each unit of Example 1 and Comparative Examples 1-2, the discharge capacity at a high discharge rate (1C) was compared to that at a normal discharge rate (0.2C).

[0151] Calculate the current density of each unit as 3 mA / cm². 2 (1C) Discharge capacity relative to a current density of 0.6 mA / cm² 2 The percentage of discharge capacity at (0.2C) discharge. The results are shown in Table 2.

[0152] Table 2

[0153] negative electrode layer 1C / 0.2C discharge capacity ratio (％) Comparative Example 1 Li-Mg alloy layer 40.8 Comparative Example 2 Li-Al alloy layer 27.3 Example 1 Li-Mg-Al alloy layer + Li-Al alloy particles 58.6

[0154] Figure 3 It is a graph showing the relationship between current density and discharge capacity of each unit in Example 1 (Mg, Al), Comparative Example 1 (Mg), and Comparative Example 2 (Al).

[0155] like Figure 3 As shown in Table 2, it can be seen that the discharge capacity of Example 1 at high rate (1C) is significantly improved compared with Comparative Examples 1 to 2.

[0156] As can be seen from this disclosure, when Mg and Al alloys are configured in the negative electrode layer, the discharge rate characteristics are significantly improved compared with only one alloy.

Claims

1. A battery comprising, in sequence, a positive electrode, a solid electrolyte layer, and a negative electrode. The negative electrode has a negative electrode current collector and a negative electrode layer in sequence in the direction from the negative electrode toward the solid electrolyte layer. The negative electrode layer comprises a Li-Mg-Al alloy layer. The negative electrode layer contains Li-Al alloy particles in the Li-Mg-Al alloy layer.

2. The battery according to claim 1, wherein the average particle size of the Li-Al alloy particles is greater than 1 μm and less than 3 μm.

3. The battery according to claim 1, wherein the thickness of the negative electrode layer is more than 1 μm and less than 15 μm.

4. The battery according to claim 1, wherein the solid electrolyte layer comprises a sulfide solid electrolyte.

5. The battery according to claim 1, wherein the negative electrode current collector is a Ni foil.

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