Solid state battery

Abstract

To solve a problem in which a foreign matter such as a positive electrode migrates to a solid electrolyte layer, making it difficult to achieve stable battery performance.SOLUTION: The particle size of a solid electrolyte contained in a solid electrolyte layer is smaller than the particle size of the solid electrolyte contained in a positive electrode layer and a negative electrode layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a solid-state battery.

Background Art

[0002] In recent years, the importance of secondary batteries has been increasing, and in addition to secondary batteries equipped with an electrolytic solution, the development of solid-state batteries using a solid electrolyte has been promoted. An all-solid-state battery, which is an example of a solid-state battery, is a battery having a solid electrolyte layer instead of an electrolytic solution, and since it does not use a flammable organic solvent, simplification of safety devices can be achieved, and it is excellent in manufacturing cost and productivity. Patent Document 1 discloses that a solid electrolyte and an active material have an active material layer in which they are continuously arranged vertically, and that the solid electrolyte has a particle diameter less than the film thickness of the electrode, specifically, the particle diameter of the solid electrolyte is less than 50 μm. According to Patent Document 1, it is stated that the mobility of Li ions in the electrode is improved.

[0003] Further, Patent Document 2 discloses that in an electrode including an active material layer containing active material particles and solid electrolyte particles, the average particle diameter of the solid electrolyte particles is smaller than the average particle diameter of the active material particles. According to Patent Document 2, it is possible to improve the contact between the active material particles and the solid electrolyte particles in the active material layer, and it is stated that the Li ion conductivity in the active material layer is improved compared to the conventional one.

[0004] Furthermore, Patent Document 3 discloses an all-solid-state battery including a solid electrolyte layer and a heat-resistant resin layer having ion conductivity in order to prevent a short circuit due to the generation of dendrites. According to Patent Document 3, it is stated that the heat-resistant resin layer functions as a short-circuit prevention layer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] By the way, in a solid-state battery in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order, it may be difficult to exhibit stable battery performance because foreign matter present in the positive electrode and / or the negative electrode moves to the solid electrolyte layer. Therefore, in view of such circumstances, an object of the present disclosure is to provide a solid-state battery that can suppress the movement of foreign matter to the solid electrolyte layer even if foreign matter is present in the positive electrode and / or the negative electrode, and thereby exhibit stable battery performance.

MEANS FOR SOLVING THE PROBLEMS

[0007] The present disclosure that has achieved the above object includes the following. <1> A solid-state battery including a positive electrode layer containing a positive electrode active material and a solid electrolyte, a negative electrode layer containing a negative electrode active material and a solid electrolyte, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the particle size of the solid electrolyte contained in the solid electrolyte layer is smaller than the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer. <2> The solid-state battery according to <1>, wherein the particle size of the solid electrolyte contained in the solid electrolyte layer is 0.5 or less when the smaller particle size of the solid electrolytes contained in the positive electrode layer and the negative electrode layer is set to 1. <3> The solid-state battery according to <1>, wherein the particle size of the solid electrolyte contained in the solid electrolyte layer is 0.2 or less when the smaller particle size of the solid electrolytes contained in the positive electrode layer and the negative electrode layer is set to 1.

EFFECTS OF THE INVENTION

[0008] In the solid-state battery according to the present disclosure, the movement of foreign matter present in the positive electrode layer and / or the negative electrode layer to the solid electrolyte layer is suppressed, and thereby stable battery performance can be exhibited.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] The solid battery according to the present disclosure includes a positive electrode layer containing a positive electrode active material and a solid electrolyte, a negative electrode layer containing a negative electrode active material and a solid electrolyte, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The particle size of the solid electrolyte contained in the solid electrolyte layer is smaller than the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer.

[0011] In the solid battery according to the present disclosure, since the particle size of the solid electrolyte contained in the solid electrolyte layer is smaller than the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer, when foreign matter exists in the positive electrode layer or the negative electrode layer, it is possible to prevent the foreign matter from moving to the solid electrolyte layer. As a result, if the foreign matter is a conductive substance such as a metal piece, it is possible to prevent a short - circuit between the positive electrode layer and the negative electrode layer. Also, if the foreign matter is a non - conductive substance, it is possible to prevent an inhibition of ion conductivity in the solid electrolyte layer. Thus, in the solid battery according to the present disclosure, as a result of suppressing the movement of foreign matter to the solid electrolyte layer, stable battery performance can be exhibited.

[0012] <Solid Electrolyte> In the present disclosure, the particle sizes of the solid electrolytes contained in the solid electrolyte layer, the positive electrode layer, and the negative electrode layer can be compared in terms of the particle sizes defined by the average particle size D50. Note that the solid electrolytes contained in the solid electrolyte layer, the positive electrode layer, and the negative electrode layer may have the same composition or different compositions from each other. D50 indicating the average particle size is also referred to as the median diameter and represents the particle size at which the cumulative frequency from the smaller particle size side reaches 50% in the particle size distribution based on volume. D50 for particles such as solid electrolytes is a value measured by the laser diffraction method and can be measured using a laser diffraction scattering intensity distribution measuring device.

[0013] In the present disclosure, the particle size of the solid electrolyte contained in the solid electrolyte layer may be significantly smaller compared to the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer. Here, "significant" means that there is a statistical significant difference. The statistical significant difference can be determined according to a method such as comparing the data obtained by measuring the particle size of the solid electrolyte contained in the solid electrolyte layer multiple times with the data obtained by measuring the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer multiple times, for example, by t-test. If the particle size of the solid electrolyte contained in the solid electrolyte layer is significantly smaller than the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer, foreign substances contained in the positive electrode or the negative electrode are less likely to move into the solid electrolyte layer compared to the case where solid electrolytes of the same particle size are used for the solid electrolyte, the positive electrode, and the negative electrode.

[0014] In particular, when the particle size of the solid electrolyte contained in the solid electrolyte layer is set with the smaller particle size among the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer as 1, it is preferably 0.9 or less, preferably 0.8 or less, preferably 0.7 or less, preferably 0.6 or less, preferably 0.5 or less, preferably 0.4 or less, preferably 0.3 or less, preferably 0.2 or less, preferably 0.1 or less. Among these, when the particle size of the solid electrolyte contained in the solid electrolyte layer is set with the smaller particle size among the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer as 1, it is more preferably 0.5 or less, more preferably 0.4 or less, more preferably 0.3 or less, more preferably 0.2 or less, more preferably 0.1 or less. Further, when the particle size of the solid electrolyte contained in the solid electrolyte layer is set with the smaller particle size among the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer as 1, it is most preferably 0.2 or less, most preferably 0.1 or less. When the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer are the same, the particle size of the solid electrolyte contained in the solid electrolyte layer is within the above range with the said particle size as 1.

[0015] When the particle size of the solid electrolyte contained in the solid electrolyte layer is within the above range with respect to the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer, when a foreign substance is present in the positive electrode layer or the negative electrode layer, it is possible to more reliably prevent the foreign substance from moving to the solid electrolyte layer.

[0016] The average particle size D50 of the solid electrolytes contained in the positive electrode layer and the negative electrode layer is not particularly limited, but can be 0.7 μm or more and 2.0 μm or less, can be 0.8 μm or more and 1.8 μm or less, and can be 0.9 μm or more and 1.5 μm or less.

[0017] The average particle diameter D50 of the solid electrolyte contained in the solid electrolyte layer is not limited as long as it is smaller than the average particle diameter D50 of the solid electrolyte contained in the positive electrode layer and the negative electrode layer. For example, it can be 0.35 μm or more and 1.0 μm or less, it can be 0.4 μm or more and 0.9 μm or less, and it can be 0.45 μm or more and 0.75 μm or less. In particular, the average particle diameter D50 of the solid electrolyte contained in the solid electrolyte layer is not limited as long as it is smaller than the average particle diameter D50 of the solid electrolyte contained in the positive electrode layer and the negative electrode layer. For example, it can be 0.14 μm or more and 0.4 μm or less, it can be 0.16 μm or more and 0.36 μm or less, and it can be 0.19 μm or more and 0.3 μm or less.

[0018] The solid electrolyte with a predetermined particle diameter used in the solid electrolyte layer and the solid electrolytes used in the positive electrode layer and the negative electrode layer with different particle diameters can be produced by appropriately applying known grinding methods. Examples of the grinding method include media grinding method, jet grinding method, cavitation grinding method, etc. Also, the grinder is not particularly limited, and examples include bead mill, planetary ball mill, etc. The grinding conditions can be appropriately set so as to obtain a solid electrolyte having a desired average particle diameter.

[0019] The solid electrolyte can usually be used without limiting the solid electrolyte used in the solid battery. As such a solid electrolyte, crystalline nitrides, oxides, sulfides and oxoacid salts, and amorphous glass structure materials can be used. Specifically, examples of the sulfide solid electrolyte that can be used as the solid electrolyte include at least one selected from the group consisting of LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, Li3PS4, LiCl-LiBr-Li3PS4, LiCl-LiBr-Li2S-P2S5 and LiCl-LiBr-Li2S-SiS2. Also, as the oxide-based solid electrolyte, for example, Li 0.34 La 0.56TiO3, Li 3 / 8 Sr 7 / 16 Ta 3 / 4 M 1 / 4 O3 (M = Zr or Hf), Li7La3Zr2O 12 Li 1.3 Al 0.7 Ti 1.3 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 3.5 Ge 0.5 V 0.5 O, Li 2.88 PO 3.73 N 0.14 and Li 2.9 Si 0.45 PO 1.6 N 1.3 can be mentioned. In addition to these, as the solid electrolyte, a complex hydrogenated lithium ion conductor or a halide-based lithium ion conductor may also be used.

[0020] <Active material> In the present disclosure, the positive electrode active material is not particularly limited, and conventionally known materials can be appropriately used. Examples of the positive electrode active material include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. Note that in "Li(NiCoMn)O2", "(NiCoMn)" indicates that the total of the composition ratios in the parentheses is 1. As long as the total is 1, the individual component amounts are arbitrary. Also, as the positive electrode active material, Li(NiCoMn)O2 may include, for example, Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2, Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, Li(Ni 0.8 Co 0.1 Mn 0.1 )O2, etc. Note that the positive electrode active material particles may be Hi-Nickel (positive electrode active material with a high Ni ratio) or a ternary positive electrode active material.

[0021] In the present disclosure, the negative electrode active material is not particularly limited, and conventionally known materials can be appropriately used. Examples of the negative electrode active material include graphite, Si, SiOx (0 < x < 2), and Li4Ti5O 12 can be mentioned.

[0022] Further, in the present disclosure, a coating layer (which may also be referred to as a coating layer or a protective layer) may be formed on at least a part of the surface, preferably the entire surface, of the positive electrode active material and / or the negative electrode active material. The coating layer is not particularly limited, but for example, a Li-ion conductive oxide can be used. A coating layer can be formed by coating the surface of the active material with a Li-ion conductive oxide.

[0023] <Other components> In the present disclosure, the solid electrolyte layer, the positive electrode layer, and the negative electrode layer constituting the solid-state battery can contain other components in addition to the above-described solid electrolyte and active material. Examples of other components include conductive aids. The conductive aid can be appropriately selected from among conductive aids applicable to solid-state batteries. Examples of the conductive aid include carbon black, vapor-grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake. Further, as the conductive aid, carbon materials such as acetylene black and ketjen black, or metal materials such as nickel, aluminum, and stainless steel may be used.

[0024] Also, in the present disclosure, examples of other components include binders. As the binder, conventionally known materials used for electrodes of solid-state batteries can be arbitrarily used. Examples of the binder include butadiene rubber (BR), isobutylene rubber (IIR), acrylate butadiene rubber (ABR), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), and the like.

[0025] <Fabrication of solid-state battery> In the present disclosure, a solid-state battery having a solid electrolyte layer, a positive electrode layer, and a negative electrode layer can be manufactured by a conventionally known method using the above-described solid electrolyte, active material, and other components as materials. The solid electrolyte layer, the positive electrode layer, and the negative electrode layer may be formed, for example, by a dry film-forming method that does not use a solvent or a wet film-forming method that uses a solvent. As the dry film-forming method, for example, the materials constituting each layer may be mixed and pressed for production. Further, as the dry film-forming method, after dispersing the materials constituting each layer in a dispersant to form a slurry, the slurry may be applied to a predetermined substrate and dried to manufacture an electrode.

[0026] As an example, for a method of manufacturing a positive electrode layer using a slurry, first, a slurry is prepared by stirring and mixing a positive electrode active material, a solid electrolyte, a conductive assistant, etc. in a solvent (also referred to as a dispersion medium). The solvent is not particularly limited, and examples thereof include 1,2,3,4-tetrahydronaphthalene, butyl acetate, butyl butyrate, mesitylene, tetralin, heptane, and N-methyl-2-pyrrolidone (NMP). Then, the obtained slurry is applied to a substrate by a conventionally known method. The substrate to which the slurry is applied is not particularly limited and may be a metal foil, a current collector, or a solid electrolyte layer. The coating method can be carried out by a known method. For example, general methods such as a doctor blade method, a die coating method, a gravure coating method, a spray coating method, an electrostatic coating method, and a bar coating method can be mentioned.

[0027] Next, the slurry applied to the substrate is dried. At this time, the slurry may be heated in the range of 50°C to 200°C or lower, or the atmosphere may be set to an inert atmosphere or a reduced-pressure atmosphere. Note that the negative electrode layer can be manufactured in the same manner as the positive electrode layer except that a negative electrode active material is used instead of the positive electrode active material. Also, the solid electrolyte layer can be manufactured in the same manner as the positive electrode layer except that no active material is used and the solid electrolyte used for the above-described solid electrolyte layer is used.

[0028] The structure of the solid-state battery has a stacked structure of a positive electrode layer / solid electrolyte layer / negative electrode layer. The solid-state battery includes so-called all-solid-state batteries that use a solid electrolyte as the electrolyte, and the solid electrolyte may contain an electrolytic solution of less than 10% by mass with respect to the total amount of the electrolyte. Note that the solid electrolyte may be a composite solid electrolyte including an inorganic solid electrolyte and a polymer electrolyte.

[0029] As one embodiment in the present disclosure, a schematic configuration diagram of the main part of the all-solid-state battery is shown in FIG. 1. As shown in FIG. 1, the all-solid-state battery 11 according to this embodiment includes a solid electrolyte layer 12, a positive electrode layer 13 and a negative electrode layer 14 disposed via the solid electrolyte layer 12, and a positive electrode current collector foil 15 which is an example of a positive electrode current collector disposed on a surface of the positive electrode layer 13 opposite to the surface in contact with the solid electrolyte layer 12, and a negative electrode current collector foil 16 which is an example of a negative electrode current collector disposed on a surface of the negative electrode layer 14 opposite to the surface in contact with the solid electrolyte layer 12. Note that although not shown, the all-solid-state battery 11 shown in this embodiment includes configurations such as a positive electrode tab lead electrically connected to the positive electrode current collector foil 15 and a negative electrode tab lead electrically connected to the negative electrode current collector foil 16, and other packaging materials.

[0030] In the embodiment shown in FIG. 1, an all-solid-state battery having a single-cell structure with the solid electrolyte layer 12, the positive electrode layer 13, and the negative electrode layer 14 as one unit is shown. However, the solid-state battery according to the present disclosure is not limited to the embodiment shown in FIG. 1. For example, it may be an all-solid-state battery having a structure in which a plurality of units with the solid electrolyte layer 12, the positive electrode layer 13, and the negative electrode layer 14 as one unit are stacked in the thickness direction. The all-solid-state battery may be a monopolar type laminated battery (parallel-connected laminated battery) or a bipolar type laminated battery (series-connected laminated battery). Examples of the shape of the all-solid-state battery include a coin type, a laminate type, a cylindrical type, and a rectangular type, and the all-solid-state battery according to the present disclosure is not limited to a specific shape.

[0031] The positive current collector foil 15 and the negative current collector foil 16 can have any configuration in the solid battery according to the present disclosure. The materials of the positive current collector foil 15 and the negative current collector foil 16 are not particularly limited and can be appropriately selected from known materials. Examples of the positive current collector foil 15 and the negative current collector foil 16 include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like. The thickness of the positive current collector foil 15 and the negative current collector foil 16 is not particularly limited and can be, for example, in the range of 0.1 μm or more and 1 mm or less.

[0032] The all-solid-state battery shown in the above embodiments uses the positive electrode layer 13 and the negative electrode layer 14 manufactured as described above and a separately manufactured solid electrolyte layer 12. The solid electrolyte layer 12 is disposed between the positive electrode layer 13 and the negative electrode layer 14, and these positive electrode layer 13, solid electrolyte layer 12, and negative electrode layer 14 are laminated so as to be sandwiched between the positive current collector foil 15 and the negative current collector foil 16, thereby manufacturing can be achieved. As an example, a method is as follows: after laminating the positive electrode layer 13, the solid electrolyte layer 12, and the negative electrode layer 14 in this order, press them by a predetermined method, and then dispose the positive current collector foil 15 and the negative current collector foil 16. Also, it is possible to press the positive electrode layer 13, the solid electrolyte layer 12, and the negative electrode layer 14 in a state where they are sandwiched between the positive current collector foil 15 and the negative current collector foil 16 by a predetermined method. The pressing method is not particularly limited, and examples include roll pressing and flat pressing. The linear pressure applied during roll pressing can be, for example, 1 t / cm 2 or more, and may be 10 t / cm 2 or less. The surface pressure applied during flat pressing can be, for example, 800 MPa or more, and may be 3000 MPa or less.

[0033] The solid electrolyte layer 12 is disposed between the positive electrode layer 13 and the negative electrode layer 14 and is a layer containing at least a solid electrolyte. As described above, the solid electrolyte layer 12 contains a solid electrolyte that is smaller than the particle sizes of the solid electrolytes contained in the positive electrode layer 13 and the negative electrode layer 14. Thereby, even if foreign matter exists in the positive electrode layer 13 or the negative electrode layer 14, it is possible to prevent the foreign matter from moving to the solid electrolyte layer 12.

[0034] For example, when the positive electrode layer 13 is located above the solid electrolyte layer 12 (above with respect to the gravitational direction), if foreign matter exists in the positive electrode layer 13, the foreign matter moves in the direction of the solid electrolyte layer 12 along with vibrations or the like. However, in the solid battery according to the present disclosure, since the particle size of the solid electrolyte contained in the solid electrolyte layer 12 is smaller than the particle size of the solid electrolyte contained in the positive electrode layer 13, even if the foreign matter can move in the positive electrode layer 13 in the direction of the solid electrolyte layer 12, a greater force is required to progress into the solid electrolyte layer 12. Therefore, in the solid battery according to the present disclosure, it is possible to suppress the foreign matter existing in the positive electrode layer 13 from progressing into the solid electrolyte layer 12. Similarly, even when the negative electrode layer 14 is located above the solid electrolyte layer 12 (above with respect to the gravitational direction), it is possible to suppress the foreign matter existing in the negative electrode layer 14 from progressing into the solid electrolyte layer 12.

[0035] Note that the foreign matter existing in the positive electrode layer 13 or the negative electrode layer 14 means that it includes dust, metal pieces, dendrites of metallic lithium generated on the negative electrode layer 14 side, etc. mixed in during the manufacturing process of the all-solid-state battery. Therefore, foreign matter is something that may exist in the positive electrode layer 13 and / or the negative electrode layer 14, and is not an element constituting the solid battery according to the present disclosure.

[0036] As foreign matter that may exist in the positive electrode layer 13 and / or the negative electrode layer 14, conductive substances such as metal pieces can be considered. Even if a conductive substance exists as foreign matter in the positive electrode layer 13 and / or the negative electrode layer 14, in the solid battery according to the present disclosure, it is possible to suppress the conductive substance from moving into the solid electrolyte layer 12, so that a short circuit between the positive electrode layer 13 and the negative electrode layer 14 can be prevented. Also, even if the foreign matter that may exist in the positive electrode layer 13 and / or the negative electrode layer 14 is a non-conductive substance, in the solid battery according to the present disclosure, it is possible to suppress the conductive substance from moving into the solid electrolyte layer 12, so that partial loss of the solid electrolyte layer 12 can be prevented. Thus, the solid battery according to the present disclosure can avoid problems such as voltage drop caused by a short circuit between the positive electrode layer 13 and the negative electrode layer 14 and loss of the solid electrolyte layer 12, and can exhibit excellent battery performance.

[0037] Regarding the solid-state battery according to the present disclosure, as described above, whether problems such as voltage drop due to short circuit or the like occur, or whether the occurrence of such problems can be avoided, can be determined by the method described in the examples to be described later in detail. Generally speaking, a method can be exemplified in which a state in which a short circuit due to foreign matter is likely to occur is created by a method such as a vibration load test, and the voltage change of the solid-state battery in that state is measured.

Example

[0038] Hereinafter, the solid-state battery according to the present disclosure will be described by way of examples. However, the technical scope of the present disclosure is not limited to the following examples.

[0039] <Examples 1 to 2, Comparative Example 1> In this example, a plurality of types of solid electrolytes with different particle sizes were used as the solid electrolyte used for the solid electrolyte layer. In addition, in all the solid-state batteries fabricated in this example, a metal piece (foreign matter) of 200 μm × 200 μm × 1 μm was encapsulated in the positive electrode layer (located above the solid electrolyte layer in the gravitational direction). Using these solid electrolytes, a foreign matter short circuit test was conducted.

[0040] More specifically, all solid-state batteries were fabricated as follows.

[0041] First, a positive electrode layer (thickness: 70 μm) was fabricated using lithium cobaltate (particle size (D50): 5 μm) as the positive electrode active material and a Li2S-P2S5 compound (particle size (D50): 1 μm) as the solid electrolyte. Also, a negative electrode layer (thickness: 50 μm) was fabricated using lithium titanate (particle size (D50): 1.2 μm) as the negative electrode active material and a Li2S-P2S5 compound (particle size (D50): 1 μm) as the solid electrolyte. As the solid electrolyte layer, three types of solid electrolytes (Li2S-P2S5 compounds) with an average particle size D50 of 1 μm, 0.5 μm, and 0.2 μm were prepared, and solid electrolyte layers with a thickness of 15 μm were fabricated using each solid electrolyte. Also, a positive electrode foil made of aluminum (Al) was attached to the outside of the positive electrode layer, and a negative electrode foil made of copper (Cu) was attached to the outside of the negative electrode layer.

[0042] A all-solid-state battery with a solid electrolyte layer using a solid electrolyte having an average particle size D50 of 1 μm was used as Comparative Example 1. Also, a all-solid-state battery with a solid electrolyte layer using a solid electrolyte having an average particle size D50 of 0.5 μm was used as Example 1. Furthermore, a all-solid-state battery with a solid electrolyte layer using a solid electrolyte having an average particle size D50 of 0.2 μm was used as Example 2.

[0043] Using the all-solid-state batteries of Comparative Example 1, Example 1, and Example 2 prepared as described above, a foreign object short-circuit test was conducted as follows. First, while applying a vibration load of 4G to the fabricated all-solid-state battery in the direction in which the positive electrode layer, solid electrolyte layer, and negative electrode layer were laminated, the voltage was measured as shown in Figure 2. In this test, a vibration load of 4G was applied under the conditions of a frequency of 25 Hz and a time of 600 seconds, and the voltage change during the test period was detected. Note that when a metal piece progresses into the solid electrolyte layer and a short circuit occurs, a voltage drop accompanied by an initial spike (instantaneous voltage drop) occurs. Therefore, it can be determined that a short circuit has occurred when an instantaneous voltage drop occurs.

[0044] Table 1 shows the results of the foreign object short-circuit test conducted using the all-solid-state batteries of Comparative Example 1, Example 1, and Example 2. The foreign object short-circuit test was performed 10 times for the all-solid-state batteries of Comparative Example 1, Example 1, and Example 2 by changing the position of the metal piece. Specifically, the foreign object short-circuit test was performed 2 times for each of the all-solid-state batteries of Comparative Example 1, Example 1, and Example 2 at a total of 5 locations where the position of the metal piece was near the center on the upper surface of the all-solid-state battery or near the four corners on the upper surface of the all-solid-state battery.

[0045]

Table 1

[0046] As shown in Table 1, it has been clarified that by making the particle size of the solid electrolyte in the solid electrolyte layer smaller than the particle size of the solid electrolyte used in the positive electrode layer and / or the negative electrode layer, it is possible to prevent a short circuit caused by foreign matter present in the positive electrode layer. In Example 1 where the particle size of the solid electrolyte in the solid electrolyte layer was set to 0.5 when the particle size of the solid electrolyte used in the positive electrode layer and / or the negative electrode layer was set to 1, although some voltage drop was observed, an effect of preventing internal short circuit of the battery was recognized. In particular, when the particle size of the solid electrolyte in the solid electrolyte layer was set to 0.2 or less when the particle size of the solid electrolyte used in the positive electrode layer and / or the negative electrode layer was set to 1, it has been clarified that a short circuit caused by foreign matter present in the positive electrode layer can be more reliably prevented.

Explanation of Signs

[0047] 11…All-solid battery, 12…Solid electrolyte layer, 13…Positive electrode layer, 14…Negative electrode layer, 15…Positive electrode current collector foil, 16…Negative electrode current collector foil

Claims

1. a positive electrode layer containing a positive electrode active material and a solid electrolyte; a negative electrode layer containing a negative electrode active material and a solid electrolyte; a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, a solid-state battery, wherein the particle size of the solid electrolyte contained in the solid electrolyte layer is smaller than the particle sizes of the solid electrolytes contained in the positive electrode layer and the negative electrode layer.

2. The solid-state battery according to claim 1, wherein the particle size of the solid electrolyte contained in the solid electrolyte layer is 0.5 or less when the smaller particle size of the solid electrolytes contained in the positive electrode layer and the negative electrode layer is taken as 1.

3. The solid-state battery according to claim 1, wherein the particle size of the solid electrolyte contained in the solid electrolyte layer is 0.2 or less when the smaller particle size of the solid electrolytes contained in the positive electrode layer and the negative electrode layer is taken as 1.

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