Solid-state battery

Abstract

Provided is a solid-state battery in which the utilization rate of a negative electrode active material is sufficiently high even if the content of a conductive aid is less. The present invention relates to a solid-state battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer, at least one of the positive electrode layer or the negative electrode layer including a conductive aid (201) composed of a metal material, the conductive aid (201) being covered with a covering material (202) having a higher melting point than the conductive aid in the electrode layer.

Description

TECHNICAL FIELD

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

[0002] In recent years, demand for batteries has greatly increased as power sources for portable electronic devices such as mobile phones, portable personal computers, and the like. In batteries for such uses, an electrolyte (electrolytic solution) such as an organic solvent has been used as a medium for moving ions.

[0003] However, in the battery having the above-described structure, there is a risk of leakage of the electrolyte, and there is a problem that the organic solvent or the like for the electrolyte is a flammable substance. Therefore, the use of a solid electrolyte instead of the electrolyte has been proposed. In addition, development of a sintered solid-state secondary battery in which a solid electrolyte is used as an electrolyte and other constituent elements are also constituted by solids is being conducted.

[0004] From the viewpoint of improving electron conductivity, a technique of adding a carbon material as a conductive aid to an electrode layer such as a negative electrode layer and a positive electrode layer for a solid-state battery is known (Patent Literature 1). However, in such a technique, the sinterability of the carbon material is very low, and the sintering of the electrode layer is hindered at the time of co-sintering, and thus there is a problem that the utilization rate of the negative electrode active material decreases at the time of charge and discharge.

[0005] Therefore, attempts have been made to promote the sintering of the negative electrode layer by using a metal material as a conductive aid, and to improve the utilization rate of the negative electrode active material (Patent Literatures 2 and 3).

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent No. 5644951

[0009] Patent Literature 2: WO2019 / 044901

[0010] Patent Literature 3: WO2019 / 044902 SUMMARY

[0011] The present inventors and the like have found that the following problems exist in the prior art described above.

[0012] In the solid-state battery ideal in the prior art, since the electron conductivity of the electrode active material is low, as shown in Figure 5A the conductive path p' needs to be appropriately formed in the electrode layer such as the positive electrode layer 1' and the negative electrode layer 2' by the conductive aid 200'. However, in the case where a metal conductive aid 200' such as Ag and Cu is used, as shown in Figure 5BAs shown, the metal conductive aids 200' easily integrate with each other and spheroidize at the time of sintering, and thus it is difficult to form a continuous conductive path, and the electrode layer cannot have sufficient electronic conductivity. Therefore, in order to form a sufficient conductive path in the electrode layer, a large amount of metal conductive aids needs to be added. However, the large addition of metal conductive aids is not preferable in terms of improving the energy density of the solid-state battery. Therefore, a method of forming a proper and sufficient conductive path in the electrode layer with a smaller content of metal conductive aids is required. Figure 5A is a schematic cross-sectional view of an electrode layer for explaining a conductive path of an electrode layer in a solid-state battery ideal in the related art. Figure 5B is a schematic cross-sectional view of an electrode layer for explaining a conductive path of an electrode layer in a solid-state battery actual in the related art.

[0013] Under such circumstances, the inventors of the present application have further found that, in the case where the negative electrode layer contains a negative electrode active material having a Li / V ratio of 2 or more, the problem related to the utilization rate of the negative electrode active material due to the use of the above-described conductive aid composed of a metal material is significant. It is known that, when this negative electrode active material is used, the integration and spheroidization of the conductive aid at the time of sintering proceed particularly easily, and the breakage of the conductive path p' is particularly likely to occur. It is considered that this is because the wettability of the negative electrode active material having a Li / V ratio of 2 or more with the conductive aid (particularly, metal powder) is relatively low.

[0014] An object of the present application is to provide a solid-state battery in which the utilization rate of the negative electrode active material at the time of charge and discharge is sufficiently high even if the content of the conductive aid is smaller.

[0015] In addition, an object of the present application is to provide a solid-state battery in which the utilization rate of the negative electrode active material at the time of charge and discharge is sufficiently high even if the negative electrode layer contains a negative electrode active material having a Li / V ratio of 2 or more and the content of the conductive aid is smaller.

[0016] The present application relates to a solid-state battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer,

[0017] At least one of the electrode layers of the positive electrode layer or the negative electrode layer contains a conductive aid composed of a metal material,

[0018] The conductive aid is covered with a covering material having a higher melting point than the conductive aid in the electrode layer.

[0019] The inventors of the present application have researched a method of forming a proper conductive path in the electrode layer with a smaller content of conductive aid, and as a result, the following situation has been found:

[0020] It is known that, in the electrode layer, by covering the metal conductive aid with a high-melting-point material, integration and spheroidization at the time of sintering can be suppressed, and a proper conductive path can be formed in the electrode layer with a smaller content of the metal conductive aid, as a result of which the utilization rate of the electrode active material can be improved. Therefore, by using such an electrode layer, the energy density of the solid-state battery can be improved.

[0021] Further, in the negative electrode layer, by covering the metal conductive aid with a high-melting-point material, a conductive path can be effectively formed even in the case where the negative electrode layer contains a negative electrode active material having a Li / V ratio of 2 or more. Therefore, in the negative electrode layer, the metal conductive aid is covered with a high-melting-point material, whereby even if the negative electrode layer contains a negative electrode active material having a Li / V ratio of 2 or more and the content of the conductive aid is reduced, the utilization rate of the negative electrode active material can be improved, and high energy density of the solid-state battery can be achieved.

[0022] The solid-state battery of the present application has a sufficiently high utilization rate of the electrode active material even if the content of the conductive aid is smaller. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1A is a schematic cross-sectional view of a solid-state battery schematically showing a solid-state battery according to an embodiment of the present application.

[0024] Figure 1B is a schematic cross-sectional view of a solid-state battery schematically showing a solid-state battery according to another embodiment of the present application.

[0025] Figure 2A is a schematic cross-sectional view of an electrode layer for explaining a conductive path in an electrode layer in a solid-state battery according to the present application.

[0026] Figure 2B is a schematic cross-sectional view of a conductive aid schematically showing an example of a conductive aid and a covering material (particulate) contained in an electrode layer in a solid-state battery according to the present application.

[0027] Figure 2C is a schematic cross-sectional view of a conductive aid schematically showing an example of a conductive aid and a covering material (film-like) contained in an electrode layer in a solid-state battery according to the present application.

[0028] Figure 2D is a schematic cross-sectional view of a conductive aid schematically showing another example of a conductive aid and a covering material (particulate) contained in an electrode layer in a solid-state battery according to the present application.

[0029] Figure 2E is a schematic cross-sectional view of a conductive aid schematically showing another example of a conductive aid and a covering material (film-like) contained in an electrode layer in a solid-state battery according to the present application.

[0030] Figure 3A is a schematic cross-sectional view of an electrode layer for illustrating another example of a conductive path in an electrode layer in a solid-state battery of the present application.

[0031] Figure 3B is a schematic cross-sectional view of an electrode layer for illustrating an example of a conductive path in an electrode layer in a solid-state battery of the present application. Figure 3A is a schematic cross-sectional view of an electrode layer for illustrating another example of a conductive path in an electrode layer in a solid-state battery of the present application.

[0032] Figure 3C is a schematic cross-sectional view of an electrode layer for illustrating another example of a conductive path in an electrode layer in a solid-state battery of the present application. Figure 3A

[0033] Figure 4A is a schematic cross-sectional view of a solid-state battery for schematically showing a solid-state battery (main surface current collecting structure) related to one embodiment of the present application manufactured in an example.

[0034] Figure 4B is a schematic cross-sectional view of a solid-state battery for schematically showing a solid-state battery (end surface current collecting structure) related to another embodiment of the present application manufactured in an example.

[0035] Figure 5A is a schematic cross-sectional view of an electrode layer for illustrating a conductive path in an electrode layer in a solid-state battery ideal in the related art.

[0036] Figure 5B is a schematic cross-sectional view of an electrode layer for illustrating a conductive path in an electrode layer in a solid-state battery actual in the related art. DETAILED DESCRIPTION

[0037] < SOLID-STATE BATTERY >

[0038] The present application provides a solid-state battery. The "solid-state battery" in the present specification means a battery whose constituent elements (particularly, an electrolyte layer) are constituted of a solid in a broad sense, and means an "all-solid-state battery" whose constituent elements (particularly, all of the constituent elements) are constituted of a solid in a narrow sense. The "solid-state battery" in the present specification includes a so-called "secondary battery" capable of repeating charging and discharging, and a "primary battery" capable of discharging only. The "solid-state battery" is preferably a "secondary battery". The "secondary battery" is not excessively limited by its name, and for example, can include an "electrochemical device" such as a "power storage device".

[0039] As Figure 1A and Figure 1B ​As shown, the solid-state battery of the present invention includes a positive electrode layer 1, a negative electrode layer 2, and a solid electrolyte layer 3, typically having a stacked structure in which the positive electrode layer and the negative electrode layer are stacked with the solid electrolyte layer in between. The positive electrode layer and the negative electrode layer can each be stacked in two or more layers, provided that a solid electrolyte layer is present between them. The solid electrolyte layer is in contact with and sandwiched between the positive electrode layer and the negative electrode layer. The positive electrode layer and the solid electrolyte layer are integrally sintered to form sintered bodies, and / or the negative electrode layer and the solid electrolyte layer are integrally sintered to form sintered bodies. Integral sintering to form sintered bodies means that two or more adjacent or contacting components (especially layers) are joined by sintering. Here, the two or more components (especially layers) can all be sintered bodies and integrally sintered. Figure 1A as well as Figure 1B These are schematic cross-sectional views of a solid-state battery according to one embodiment of the present invention.

[0040] like Figure 1A as well as Figure 1B As shown, the solid-state battery of the present invention may also have a positive electrode current collector layer 11, a negative electrode current collector layer 21, a positive electrode current collector (not shown), a negative electrode current collector 22, electrode separation portions 15 and 25, a protective layer 5, and end face electrodes 10 and 20. Figure 1B In addition to the negative electrode layer 2 having an end-face current collection structure, the solid-state battery is similar to... Figure 1A It is the same as a solid-state battery. Figure 1B The end-face current collection structure of the negative electrode layer 2 refers to, as detailed later, a structure in which the end face of the negative electrode layer 2 is in contact with the negative electrode current collection section 22, and is electrically connected to the negative terminal 20 via the negative electrode current collection section 22. On the other hand, in Figure 1A In the solid-state battery, the negative electrode layer 2 has a main surface current collector structure. Figure 1A The main surface current collector structure of the negative electrode layer 2 refers to, as detailed later, a structure in which, while the main surface of the negative electrode layer 2 is in contact with the negative electrode current collector layer 21, it is primarily electrically connected to the negative terminal 20 via the negative electrode current collector layer 21. It should be noted that, in Figure 1A as well as Figure 1B In the middle, the positive electrode layer 1 has a main surface electrode structure, but is not limited to this, and may also have Figure 1B The negative electrode layer 2 has an end face collector structure.

[0041] [Electrode layer]

[0042] The electrode layer comprises a positive electrode layer 1 and a negative electrode layer 2. In this invention, at least one of the positive electrode layer 1 or the negative electrode layer 2 comprises a covering conductive additive, as described later. For example, only one of the positive electrode layer 1 or the negative electrode layer 2 may comprise a covering conductive additive, or both may comprise a covering conductive additive. In a preferred embodiment, it is preferable that at least the negative electrode layer, more preferably both the negative electrode layer and the positive electrode layer comprise a covering conductive additive. This is because, in the prior art, when the negative electrode layer contains a negative electrode active material with a Li / V ratio of 2 or higher, the problem of reduced utilization of the negative electrode active material due to integration and spheroidization caused by the use of conductive additives made of metallic materials is significant. Even in this case, the utilization of the negative electrode active material can be sufficiently improved. It should be noted that "conductive additive" can also be called "conductive material". Therefore, "covering conductive additive" can also be called "covering conductive material".

[0043] In capped conductive additives, the conductive additive (also known as the core material) is made of a metallic material and is capped by a capping material. The capping material has a higher melting point than the conductive additive (i.e., the core material). Therefore, as... Figure 2A As shown, when the negative electrode layer 2 (or positive electrode layer 1) contains a covering conductive additive 200, compared to the case where the conductive additive (i.e., the core material) is directly contained without being covered by the covering material, the integration and spheroidization of the conductive additive (i.e., the core material) caused by sintering can be suppressed. Specifically, by covering the conductive additive (i.e., a metal with high sinterability) used as the core material with a high-melting-point material (i.e., a difficult-to-sinter material), the contact between the core materials is physically suppressed, hindering the integration and spheroidization caused by the sintering of the core material. As a result, the conductive path p can be sufficiently ensured, and the utilization rate of the electrode active material during charging and discharging can be more fully improved even with a lower content of conductive additive.

[0044] When the melting point of the covering material is set as "Mpcv (°C)" and the melting point of the conductive additive (core material) is set as "Mpcr (°C)", "Mpcv-Mpcr" is usually above 50°C and below 4000°C. From the viewpoint of further suppressing the integration and spheroidization of the conductive additive (i.e., the core material), it is preferably above 100°C and below 4000°C, more preferably above 200°C and below 3000°C, even more preferably above 200°C and below 2000°C, particularly preferably above 200°C and below 1000°C, and most preferably above 200°C and below 800°C.

[0045] In the present specification, the melting point is based on the value of ChemIDplus or CRC Handbook of Chemistry and Physics. In detail, the melting point is based on the value of ChemIDplus, the melting point not recorded in ChemIDplus is based on the value of CRC Handbook of Chemistry and Physics, and the melting point not recorded in the above two documents is based on the value of Acer-NIST Phase Equilibria Diagrams.

[0046] The covering material is a material different from the material of the electrode active material and the solid electrolyte contained in the electrode layer containing the covering-type conductive aid. The electrode active material is the positive electrode active material in the positive electrode layer and the negative electrode active material in the negative electrode layer. The material different means that the chemical composition formula or the chemical structure formula is different. The reason for the integration and spheroidization of the core material is that the wettability between the electrode active material particle / core material (conductive aid) is low. By covering with an oxide different from the electrode active material particle, the wettability between the two can be improved, and as a result, the integration and spheroidization of the core material can be further suppressed.

[0047] The covering material can be, for example, a metal oxide, a metal nitride, or a metal carbide, or can also be a metal material. The metal material refers to a metal that is not oxidized. As specific examples of the covering material, for example, metal oxides such as Li2ZrO3, Li2SiO3, Li2TiO3, LiAlO2, CuO, Al2O3, ZrO2, etc.; metal nitrides such as ZrN, Si3N4, etc.; metal carbides such as WC, TaC, etc.; and metal materials such as Pd, W, Cu, etc. can be listed. From the viewpoint of improving the wettability between the electrode active material particle / core material (conductive aid) and further suppressing the integration and spheroidization of the core material, the covering material is preferably a metal oxide, and more preferably Li2ZrO3, CuO.

[0048] From the viewpoint of further suppressing the integration and spheroidization of the core material and the viewpoint of improving the utilization rate of the electrode, the covering material preferably contains an element that is not solid-soluble in the electrode active material. In detail, when the covering material is expressed in a chemical composition formula, as a metal element, it is preferable to contain only an element that is not solid-soluble in the electrode active material, or to contain only an element that is not solid-soluble in the electrode active material and Li. The element that is not solid-soluble in the electrode active material refers to an element that is not substituted or an element that is difficult to be substituted (preferably, an element that is not substituted) with respect to an element that constitutes the electrode active material (particularly, an element that participates in redox). This is because, in the case where the covering material contains an element that is solid-soluble in the negative electrode active material, a side reaction is easily performed between the negative electrode active material and the covering material, the covering effect at the time of sintering is weakened, and modification of the negative electrode active material is caused. The element that is not substituted or the element that is difficult to be substituted is selected based on the atomic radius, the valence number at the time of ionization, and the coordination number. In detail, the element that is not solid-soluble in the electrode active material can also be an element having a larger atomic radius than the element that constitutes the electrode active material (particularly, the element that participates in redox).

[0049] For example, in the negative electrode layer, the element that is not solid-soluble in the negative electrode active material refers to an element that is not substituted or an element that is difficult to be substituted with respect to V in the case where the negative electrode active material contains V. As the element that is not substituted or the element that is difficult to be substituted with respect to V, one or more elements selected from the group consisting of elements other than Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt) in the periodic table (i.e., long-period type periodic table) can be listed, and specifically, for example, one or more elements selected from the group consisting of Zr, Cu, Pd, Sc, Y, Nb, Ta, and B can be listed, and preferably, for example, one or more elements selected from the group consisting of Zr, Cu, and Pd can be listed.

[0050] In the covering-type conductive aid 200, the covering layer formed of the covering material 202 around the conductive aid (core material) 201 can have a granular form as illustrated in FIG. 1, or can have a form in which the covering material 202 is deposited on the surface of the conductive aid (core material) 201 as illustrated in FIG. 2. Figure 2B The covering layer formed of the covering material 202 around the conductive aid (core material) 201 can have a granular form as illustrated in FIG. 1, or can have a form in which the covering material 202 is deposited on the surface of the conductive aid (core material) 201 as illustrated in FIG. 2. Figure 2CThe film-like form, or a composite thereof. In detail, the cover layer can have a granular form, a film-like form, or a composite thereof in a cross-sectional view. The "cross-sectional view" in the present specification means a form when the solid-state battery is observed from a direction substantially perpendicular to a thickness direction based on a stacking direction of layers constituting the solid-state battery (in short, a form when a plane parallel to the thickness direction is cut), including a cross-sectional view. In particular, the "cross-sectional view" can also mean a form when a plane parallel to a thickness direction based on a stacking direction of layers constituting the solid-state battery, that is, a plane perpendicular to the positive electrode terminal and the negative electrode terminal is cut, and for example, a cross-sectional view as illustrated in Figure 1A and Figure 1B illustrated cross-sectional view. Therefore, the "SEM image showing the stacking structure (cross-sectional structure) of the solid-state battery" for various measurements can also be an image based on the above-described cross-sectional view.

[0051] The cover layer having a granular form means that the cover layer is composed of a granular cover material as illustrated in Figure 2B The cover layer having a granular form in the solid-state battery can be obtained by manufacturing the solid-state battery using a cover-type conductive aid raw material obtained by mixing a granular conductive aid (core material) 201 and a granular cover material 202, and electrostatically adhering the granular cover material 202 to the surface of the granular conductive aid (core material) 201.

[0052] The cover layer having a film-like form means that the cover layer is composed of a film-like cover material as illustrated in Figure 2C The cover layer having a film-like form in the solid-state battery can be obtained by manufacturing the solid-state battery using a cover-type conductive aid raw material obtained by forming a film of the cover material 202 on the surface of the granular conductive aid (core material) 201 by a film formation method such as a sputtering method, an evaporation method, an ion plating method, a sol-gel method, and the like.

[0053] In the case where the cover layer has a granular form, or in the case where it has a film-like form, the cover layer does not necessarily have to be formed continuously around the conductive aid as illustrated in Figure 2B and Figure 2C In detail, the conductive aid (core material) 201 can have a portion where the cover layer 202 is not formed (for example, a portion where the conductive aid 201 is not covered with the cover material 202 (that is, a portion where it is exposed)) 210 as illustrated in Figure 2D and Figure 2E

[0054] ​The form of the covering layer 202 in the solid-state battery is generally maintained before sintering for manufacturing the solid-state battery.

[0055] For example, in the case where the covering-type conductive aid 200 has a covering layer with a granular form before sintering, the covering layer also has a granular form after sintering. At this time, the covering layer 202 after sintering can have an exposed portion 210 of the core material 201 as shown in FIG. 2A, or can not have an exposed portion of the core material 201 as shown in FIG. 2B. Figure 2D Figure 2B In the present application, the covering layer 202 having a granular form after sintering means that the average of the aspect ratios of all the covering materials in contact with the core material 201 is less than 1.5 (for example, 1 or more and less than 1.5), regardless of whether the core material 201 has an exposed portion. In detail, with respect to each of any 100 core materials 201 in the electrode layer, when the average of the aspect ratios of all the covering materials in contact with the core material 201 is within the above range, the covering layer (or the covering materials constituting the covering layer) has a granular form.

[0056] In addition, for example, in the case where the covering-type conductive aid 200 has a covering layer with a film form before sintering, the covering layer also has a film form after sintering. At this time, the covering layer 202 after sintering can have an exposed portion 210 of the core material 201 as shown in FIG. 2A, or can not have an exposed portion of the core material 201 as shown in FIG. 2B. Figure 2E Figure 2C In the present application, the covering layer 202 having a film form after sintering means that the average of the aspect ratios of all the covering materials in contact with the core material 201 is 1.5 or more, regardless of whether the core material 201 has an exposed portion. In detail, with respect to each of any 100 core materials 201 in the electrode layer, when the average of the aspect ratios of all the covering materials in contact with the core material 201 is within the above range, the covering layer (or the covering materials constituting the covering layer) has a film form.

[0057] Here, for example, Figure 2E The aspect ratio of the covering material is the ratio of the maximum length L of the covering material to the length t in the direction perpendicular to the direction in which the maximum length L is defined, in a cross-sectional view. The length t in the direction perpendicular to the direction in which the maximum length L is defined can also be the size t' of the covering material in the direction perpendicular to the surface (or the contact portion thereof) of the conductive aid with which the covering material is in contact. In particular, as shown in FIG. 2A, in the case where one covering film material 202 is arranged along the surface of the core material 201, the maximum length L is the maximum value of the length along the surface of the core material 201. Figure 2E

[0058] ​​​The covering material 202 is disposed in contact with the electrically conductive aid 201 around the electrically conductive aid 201, and generally has a size t' (refer to FIG. 2) of 500 nm or less (e.g., 1 nm or more and 500 nm or less). Figures 2B-2E That is, the covering material is a covering material disposed in contact with the electrically conductive aid (core material) around the electrically conductive aid, and is a covering material having the above-described prescribed size. The covering material having the above-described prescribed size t' means that the covering material has the above-described prescribed size t' in a direction perpendicular to the surface (or the contact portion thereof) of the electrically conductive aid with which the covering material is in contact. Thus, even a substance (or material) disposed in contact with the electrically conductive aid, a substance having a size exceeding the above-described prescribed size in a direction perpendicular to the surface of the electrically conductive aid is not included in the covering material in the present application. The above-described size t' is the maximum length in a direction perpendicular to the surface (or the contact portion thereof) of the electrically conductive aid with which the covering material is in contact. In the case where the covering layer has a granular form, the above-described size t' is the size of each covering material particle constituting the covering layer. In the case where the covering layer has a film form, the above-described size t' is the thickness dimension of the covering layer. From the viewpoint of further suppressing the integration and spheroidization of the electrically conductive aid (core material) and further improving the utilization rate of the electrode active material at the time of charge and discharge of the solid-state battery, the size t' is preferably 1 nm or more and 400 nm or less, more preferably 1 nm or more and 200 nm or less, further preferably 1 nm or more and 100 nm or less, particularly preferably 1 nm or more and 50 nm or less, and most preferably 1 nm or more and 30 nm or less.

[0059] For example, in the case where the covering material constitutes a covering layer in a granular form, each covering material particle has the above-described prescribed size t' in a direction perpendicular to the surface of the electrically conductive aid with which the covering material is in contact, while being disposed in contact with the electrically conductive aid.

[0060] In addition, for example, in the case where the covering material constitutes a covering layer in a film form, the covering material film has the above-described prescribed size (i.e., prescribed thickness) in a direction perpendicular to the surface of the electrically conductive aid with which the covering material is in contact (i.e., the thickness direction), while being disposed in contact with the electrically conductive aid.

[0061] In either of the case where the covering material constitutes a covering layer in a granular form and the case where the covering material constitutes a covering layer in a film form, the average thickness of the covering layer measured at any 100 in a cross-sectional view is preferably within the range of the above-described size t'.

[0062] The area ratio of the covering material is generally 0.1% or more and 15% or less relative to the conductive additive (core material) constituting the covering conductive additive. From the viewpoint of further suppressing the integration and spheroidization of the conductive additive (core material) and further improving the utilization rate of the electrode active material during the charging and discharging of the solid battery, it is preferably 0.8% or more and 8% or less, and more preferably 0.8% or more and 4% or less.

[0063] The area ratio of the covering material is the ratio of the area of ​​the covering material having the specified dimensions to the conductive additive (core material) in the covering material disposed around and in contact with the conductive additive.

[0064] In this specification, the area ratio of the covering material is represented by a value based on the following ratio: in cross-sectional observation, the area of ​​any 100 selected conductive additives (core materials) and the area of ​​the covering material in each of these conductive additives are measured, and the total area of ​​the covering material is divided by the total area of ​​the conductive additives.

[0065] The coverage of the conductive additive (core material) by the covering material only needs to reach the coverage ratio of the area of ​​the covering material mentioned above.

[0066] The conductive additive (core material) of the covered conductive additive is composed of a metallic material. The metallic material refers to an unoxidized metal. There is no particular limitation on the metallic material constituting the core material; for example, it may be composed of one or more metallic materials selected from the group consisting of Ag (silver), Au (gold), Pd (palladium), Pt (platinum), Cu (copper), Sn (tin), Ni (nickel), and their alloys. From the viewpoint of further suppressing the integration and spheroidization of the conductive additive (core material) and further improving the utilization rate of electrode active materials during the charging and discharging of solid-state batteries, the conductive additive is preferably composed of one or more metallic materials selected from the group consisting of Ag, Cu, and their alloys.

[0067] The shape of the conductive additive (core material) constituting the covering conductive additive is not particularly limited. The conductive additive (core material) can be, for example, an elongated conductive additive, a spherical conductive additive, or a mixture thereof. From the viewpoint of further suppressing the integration and spheroidization of the conductive additive (core material) and further improving the utilization rate of the electrode active material during the charging and discharging of the solid battery, the conductive additive (core material) constituting the covering conductive additive preferably includes an elongated conductive additive.

[0068] like Figure 3A As shown, elongated conductive additives refer to conductive additives that have an elongated shape when viewed in cross-section of the electrode layer. Therefore, an elongated shape can also be described as "exhibiting an elongated shape when viewed in cross-section". Figure 3AThis is a schematic cross-sectional view of an electrode layer used to illustrate the conductive path in an example of an electrode layer containing a cover-type conductive additive that uses an elongated conductive additive. For example, the conductive additive with an elongated shape has a shape with an elongated direction in the cross-sectional view of the electrode layer.

[0069] As a conductive additive that can have an elongated shape, for example, a flat conductive additive, a fibrous conductive additive, or a mixture thereof can be used. In the solid-state battery of the present invention, the conductive additive that appears to have an elongated shape in cross-section corresponds to any one of the flat conductive additive, the fibrous conductive additive, or a mixture thereof, and can be easily identified by disassembling the solid-state battery.

[0070] In simple terms, a flat shape is the shape of particles that have been flattened; it is also known as a "scale-like" or "flat" shape.

[0071] Fibrous refers to shapes that include “wire-like” or “rod-like” shapes, such as those found in so-called metal nanowires.

[0072] Specifically, regarding elongated conductive additives, in the electrode layer, such as... Figure 3B As shown, in cross-sectional observation, a conductive additive 200a has a shape defined by the longest dimension a and the short side length (thickness dimension) b, and its depth length c (i.e. Figure 3B The dimensions in the inward and outward directions (not shown) are not particularly limited. The longest dimension 'a' is the dimension with the maximum length specified in the sectional view. The short side length 'b' is the dimension with the maximum length (or maximum thickness) specified in the sectional view in the direction perpendicular to the longest dimension 'a'. The short side length 'b' generally satisfies a > b. The depth length 'c' is the dimension with the maximum length specified in the direction perpendicular to the sectional view, generally satisfying c ≥ 2b in the case of flattened shapes (especially 2a ≥ c ≥ 2b), and 2b > c in the case of fibrous shapes (especially 2b > c > 0.5b). Specifically, an elongated shape refers to a shape with a / b ratio of 2.0 or higher (especially 2.0 or higher and 20.0 or lower). Figure 3B This is a schematic cross-sectional view of an example of an elongated conductive additive that may be included in the electrode layer of the solid-state battery of the present invention.

[0073] Elongated shapes include curved elongated shapes that give rise to curved portions. Specifically, curved elongated shapes include... Figure 3C As shown, in cross-sectional observation, one of the conductive additives 200b in the electrode layer has more than one bend 201, and its shape is defined by the longest dimension a and the short side length (thickness dimension) b, with a depth length c (i.e. Figure 3CThe dimension in the top-bottom direction (not shown) is not particularly limited. In the curved elongated shape as well, the longest dimension a is a dimension that defines the maximum length in a cross-sectional view. The short side length b is a dimension that defines the maximum length (or maximum thickness) in a direction perpendicular to the longest dimension a in a cross-sectional view. The depth length c is a dimension that defines the maximum length in a plan view perpendicular to the cross-sectional view. The a, b, c, and their relationships in the curved elongated shape (for example Figure 3C ) are the same as those in the simple cross-sectional view elongated shape (for example Figure 3B ). Figure 3C is a schematic cross-sectional view of a conductive aid schematically showing another example of a cross-sectional view elongated shape of a conductive aid that can be contained in an electrode layer in a solid-state battery of the present application.

[0074] With respect to the elongated shape of the conductive aid in the electrode layer, the average aspect ratio (the longest dimension a / the short side length b) is generally 2.0 or greater (particularly 2.0 or greater and 20.0 or less), and from the viewpoint of further improving the utilization rate of the electrode active material, it is preferably 2.0 or greater and 15.0 or less, more preferably 2.5 or greater and 10.0 or less, and further preferably 3.0 or greater and 8.0 or less.

[0075] The average aspect ratio (a / b) of the elongated shape of the conductive aid is an average value of any 100 cross-sectional view elongated shapes of the conductive aid confirmed in the electrode layer based on the SEM image (photograph) showing the laminated structure (cross-sectional structure) of the solid-state battery. The cross-sectional view can also be the SEM image (photograph) showing the laminated structure (cross-sectional structure) of the solid-state battery.

[0076] In the elongated shape of the conductive aid in the electrode layer, the average short side length (average short side thickness) b is not particularly limited, and from the viewpoint of further improving the utilization rate of the electrode active material, it is preferably 0.1 μm or greater and 4.0 μm or less, more preferably 0.1 μm or greater and 2.0 μm or less, further preferably 0.1 μm or greater and 1.5 μm or less, and particularly preferably 0.1 μm or greater and 1.0 μm or less.

[0077] The average short side length b of the elongated shape of the conductive aid is an average value of any 100 elongated shapes of the conductive aid confirmed in the electrode layer based on the SEM image (photograph) showing the laminated structure (cross-sectional structure) of the solid-state battery.

[0078] The average depth length c of the elongated conductive aid in the electrode layer is not particularly limited, and can be, for example, 0.1 μm or more and 10.0 μm or less. For example, in the case where a flat conductive aid is used as the conductive aid, the average depth length c of the elongated conductive aid in the electrode layer is usually 0.1 μm or more and 20 μm or less. In addition, for example, in the case where a fibrous conductive aid is used, the average depth length c of the elongated conductive aid in the electrode layer is usually 0.1 μm or more and 10.0 μm or less.

[0079] The average depth length c of the elongated conductive aid can be an average value based on any 100 elongated conductive aids observed in a cross section, which are confirmed in the electrode layer of a three-dimensional image generated from 100 SEM images taken at 0.1 μm intervals showing the laminated structure (cross-sectional structure) of the solid-state battery.

[0080] In detail, the spherical conductive aid is a conductive aid having a shape in which, in cross-sectional observation, as with the elongated conductive aid, when a longest dimension of a prescribed maximum length is set to "a" and a short side length of a prescribed maximum length in a direction perpendicular to the longest dimension a direction is set to "b", their ratio (a / b) is less than 2.0 (particularly 1.5 or less).

[0081] The average size of the conductive aid (core material) constituting the coated conductive aid is not particularly limited, and is usually 0.1 μm or more and 10 μm or less, and from the viewpoint of further suppressing the integration and spheroidization of the conductive aid (core material) and further improving the utilization rate of the electrode active material at the time of charge and discharge of the solid-state battery, it is preferably 0.3 μm or more and 2 μm or less, and more preferably 0.5 μm or more and 2 μm or less.

[0082] The average size of the conductive aid (core material) constituting the coated conductive aid is an average value of the size of a prescribed maximum length, and is an average value of the size corresponding to the longest dimension a of the elongated and spherical conductive aids.

[0083] The average size of the conductive aid (core material) constituting the coated conductive aid is an average value based on any 100 coated conductive aids confirmed in the electrode layer of the SEM image (photograph) showing the laminated structure (cross-sectional structure) of the solid-state battery.

[0084] The area ratio of the electrically conductive agent (core material) constituting the covering-type electrically conductive agent with respect to the electrode layer is a value of the area ratio of the electrically conductive agent (core material) confirmed in the electrode layer in the SEM image (photograph) showing the laminated structure (cross-sectional structure) of the solid-state battery. In more detail, the area ratio of the electrically conductive agent (core material) constituting the covering-type electrically conductive agent with respect to the electrode layer is an average value of the values measured at 10 arbitrary places in cross-sectional observation, and is expressed as the area ratio with respect to the electrode layer (i.e., the total area of each field of view in the electrode layer).

[0085] The area ratio of the electrically conductive agent (core material) constituting the covering-type electrically conductive agent with respect to the electrode layer is a value of the area ratio of the electrically conductive agent (core material) confirmed in the SEM image (photograph) showing the laminated structure (cross-sectional structure) of the solid-state battery. In more detail, the area ratio of the electrically conductive agent (core material) constituting the covering-type electrically conductive agent with respect to the electrode layer is an average value of the values measured at 10 arbitrary places in cross-sectional observation, and is expressed as the area ratio with respect to the electrode layer (i.e., the total area of each field of view in the electrode layer).

[0086] (Negative electrode layer)

[0087] The negative electrode layer 2 contains a negative electrode active material, and can also contain a solid electrolyte. In the case where the negative electrode layer 2 contains a covering-type electrically conductive agent, the negative electrode layer 2 contains a covering-type electrically conductive agent and a negative electrode active material, and can also contain a solid electrolyte. In the negative electrode layer, it is preferable that the covering-type electrically conductive agent, the negative electrode active material, and the solid electrolyte each have the form of a sintered body. For example, in the case where the negative electrode layer contains a covering-type electrically conductive agent, a negative electrode active material, and a solid electrolyte, the negative electrode layer preferably has the form of a sintered body in which the negative electrode active material particles are bound by the covering-type electrically conductive agent and the solid electrolyte, and the covering-type electrically conductive agent, the negative electrode active material particles, and the solid electrolyte are joined by mutual sintering therebetween.

[0088] The negative electrode layer can also contain other electrically conductive agents in addition to the covering-type electrically conductive agent. As the other electrically conductive agents, for example, there can be mentioned an electrically conductive agent composed of the same metal material as the metal material constituting the electrically conductive agent (core material) of the above-described covering-type electrically conductive agent, acetylene black, Ketjen black, Super P (registered trademark), VGCF (registered trademark), a carbon nanotube, or the like.

[0089] The negative electrode layer is a layer capable of intercalating and deintercalating metal ions, and preferably a layer capable of intercalating and deintercalating lithium ions or sodium ions (particularly lithium ions). The negative electrode active material capable of intercalating and deintercalating lithium ions contained in the negative electrode layer is not particularly limited, and for example, can be a carbon material such as graphite. From the viewpoint of further improving the utilization rate of the negative electrode active material and increasing the discharge capacity, it is preferable that the negative electrode active material contain Li (lithium) and V (vanadium) in a molar ratio of 2.0 or greater (particularly 2 or greater and 10 or less). From the viewpoint of further improving the utilization rate of the negative electrode active material, the molar ratio of Li to V in the negative electrode active material is preferably 2 or greater and 6 or less (particularly 2 or greater and 4 or less). The present application is particularly effective when the negative electrode layer contains a negative electrode active material having such a molar ratio. In the case where the negative electrode layer contains a negative electrode active material having such a molar ratio, since the wettability with the conductive aid is low, the integration and spheroidization (e.g., spheronization) of the conductive aid is particularly likely to proceed at the time of sintering, and the breakage of the conductive path is particularly likely to occur, and the utilization rate of the negative electrode active material is further reduced. However, in the present application, even in the case where the negative electrode layer contains such a negative electrode active material, the breakage of the conductive path can be sufficiently suppressed, and as a result, the utilization rate of the negative electrode active material at the time of charge and discharge can be more sufficiently improved by a smaller amount of the conductive aid. Therefore, in the case where the negative electrode layer contains a negative electrode active material having the above-described molar ratio, the effect of forming the form of the conductive aid into the covering type is particularly remarkable in the present application.

[0090] In the present application, by the negative electrode layer containing a negative electrode active material having a molar ratio of Li to V in the above-described range, and the solid electrolyte layer containing a solid electrolyte having a garnet structure or a LISICON structure as described later, good jointability between the solid electrolyte layer and the negative electrode layer can be obtained. Furthermore, the side reaction at the time of co-sintering between the negative electrode active material contained in the negative electrode layer and the garnet solid electrolyte or the LISICON solid electrolyte in the solid electrolyte layer can be suppressed, and the reversible capacity of the solid battery can be increased. As a result, the utilization rate of the negative electrode active material at the time of charge and discharge can be more sufficiently improved.

[0091] From the viewpoint of further improving the utilization rate of the negative electrode active material, the negative electrode active material preferably has an average chemical composition represented by the following general formula (1).

[0092] [Chemical Formula 1]

[0093] (Li [3-ax+(5-b)(1-y)] A x )(V y B 1-y )O4 (1)

[0094] By adopting such a composition, the reactivity with the LISICON-type solid electrolyte in the solid electrolyte layer can be further reduced. In addition, the negative electrode active material used in the present application more fully exhibits a capacity through the oxidation and reduction of V. Therefore, in order to obtain a sufficient reversible capacity, the amount y of V is preferably 0.5≤y≤1.0 as described later. In the case where the negative electrode active material has the above-described composition, as long as the average composition described above is adopted in the thickness direction of the negative electrode layer, the chemical composition can also vary in the thickness direction of the negative electrode layer.

[0095] In formula (1), A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), and Zn (zinc).

[0096] B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt).

[0097] x has a relationship of 0≤x≤1.0, preferably a relationship of 0≤x≤0.5, more preferably a relationship of 0≤x≤0.1, and further preferably 0.

[0098] y has a relationship of 0.5≤y≤1.0, preferably a relationship of 0.55≤y≤1.0, more preferably a relationship of 0.8≤y≤1.0, and further preferably 1.

[0099] a is the average valence number of A. For the average valence number of A, as A, for example, in the case where an element X having a valence number a+ is n1, an element Y having a valence number b+ is n2, and an element Z having a valence number c+ is n3, it is a value represented by (n1×a+n2×b+n3×c) / (n1+n2+n3).

[0100] b is the average valence number of B. For the average valence number of B, as B, for example, in the case where an element X having a valence number a+ is n1, an element Y having a valence number b+ is n2, and an element Z having a valence number c+ is n3, it is the same value as the average valence number of A described above.

[0101] In formula (1), from the viewpoint of improving the ease of obtaining the negative electrode active material and further improving the utilization rate of the negative electrode active material, in the preferred embodiment, as described below:

[0102] A is one or more elements selected from the group consisting of Al and Zn.

[0103] B is one or more, particularly two elements, selected from the group consisting of Si and P.

[0104] x has a relationship of 0 < x < 0.06, more preferably 0.

[0105] y has a relationship of 0.55 < y < 1.0, more preferably 0.8 < y < 1.0, further preferably 1.

[0106] a is the average valence number of A.

[0107] b is the average valence number of B.

[0108] As specific examples of the negative electrode active material, for example, Li3VO4, Li 3.2 (V 0.8 Si 0.2 )O4, (Li 3.1 Al 0.03 )(V 0.8 Si 0.2 )O4, (Li 3.1 Zn 0.05 )(V 0.8 Si 0.2 )O4, Li 3.3 (V 0.6 P 0.1 Si 0.3 )O4, Li 3.18 (V 0.77 P 0.05 Si 0.18 )O4, Li 3.07 (V 0.90 P 0.03 Si 0.07 )O4, Li 3.22 (V 0.72 P 0.06 Si 0.22 )O4, and the like can be listed.

[0109] The chemical composition of the negative electrode active material can be an average chemical composition. The average chemical composition of the negative electrode active material refers to the average value of the chemical composition of the negative electrode active material in the thickness direction of the negative electrode layer. The average chemical composition of the negative electrode active material can be analyzed and measured by breaking the solid-state battery, using SEM-EDX (energy dispersive X-ray spectroscopy), and performing composition analysis using EDX in a case where the entire thickness direction of the negative electrode layer is included in the field of view.

[0110] In the negative electrode layer, the average chemical composition of the negative electrode active material and the average chemical composition of the solid electrolyte described later can be automatically distinguished and measured according to these compositions in the above composition analysis.

[0111] The negative electrode active material can be produced, for example, as follows. First, a raw material compound containing a prescribed metal atom is weighed, the chemical composition is made to be a prescribed chemical composition, water is added and mixed to obtain a slurry. The slurry is dried, pre-fired at a temperature of 700°C or higher and 1000°C or lower for 4 hours or more and 6 hours or less, and then pulverized, whereby a negative electrode active material can be obtained.

[0112] As for the chemical composition of the negative electrode active material, in the case of high-speed sintering at 750°C for about 1 minute together with the solid electrolyte layer, the chemical composition of the negative electrode active material used at the time of production is directly reflected, but in the case of long-time sintering at 750°C for about 1 hour, the elements diffuse into the solid electrolyte layer, and the amount of V generally decreases.

[0113] From the viewpoint of further improving the utilization rate of the negative electrode active material, the negative electrode active material preferably has a β II -Li3VO4-type structure or γ II -Li3VO4-type structure. By having such a crystal structure, the reversibility of charge and discharge is improved, and stable cycle characteristics can be obtained. In addition, by the active material adopting a γ II -Li3VO4-type structure, the adhesion to the LISICON-type solid electrolyte in the solid electrolyte layer is improved, and thus is more preferable.

[0114] The negative electrode active material has a β II -Li3VO4-type structure means that the negative electrode active material (particularly, the particles thereof) has a β II -Li3VO4-type crystal structure, refers to a crystal structure that can be recognized by those skilled in the art in the field of solid-state batteries as a β II -Li3VO4-type crystal structure. In a narrow sense, the negative electrode active material has a β II -Li3VO4-type structure means that the negative electrode active material (particularly, the particles thereof) shows, in X-ray diffraction, one or more main peaks corresponding to the Miller indices inherent to the so-called β II -Li3VO4-type crystal structure. As the negative electrode active material having a β II -Li3VO4-type structure, for example, ICDD Card No. 01-073-6058 can be cited.

[0115] The negative electrode active material has a γ II -Li3VO4-type structure means that the negative electrode active material (particularly, the particles thereof) has a γ II -Li3VO4-type crystal structure, refers to a crystal structure that can be recognized by those skilled in the art in the field of solid-state batteries as a γ IIcrystal structure of the crystal structure of the Li3VO4type. In a narrow sense, the negative electrode active material has a crystal structure of the Li3VO4type II The Li3VO4type structure means that the negative electrode active material (particularly, a particle thereof) shows a peak corresponding to the so-called γ II The Li3VO4type crystal structure has one or more main peaks corresponding to the Miller indices. As the negative electrode active material having the γ II An example of the negative electrode active material of the Li3VO4type structure can be exemplified by ICDD Card No. 01-073-2850.

[0116] The average chemical composition and the crystal structure of the negative electrode active material in the negative electrode layer are generally changed by the diffusion of elements at the time of sintering. The negative electrode active material preferably has the above-described average chemical composition and the crystal structure in the solid-state battery after sintering together with the positive electrode layer and the solid electrolyte layer.

[0117] As the negative electrode active material capable of intercalating and deintercalating sodium ions, at least one selected from the group consisting of a sodium-containing phosphoric acid compound having a NASICON type structure, a sodium-containing phosphoric acid compound having an olivine type structure, and a sodium-containing oxide having a spinel type structure, and the like can be exemplified.

[0118] The average particle diameter of the negative electrode active material is not particularly limited, and can be, for example, 0.01 μm or more and 20 μm or less, and preferably 0.1 μm or more and 5 μm or less.

[0119] The average particle diameter of the negative electrode active material can be, for example, obtained by randomly selecting 10 or more and 100 or less particles from a SEM image, and simply averaging the particle diameters thereof (arithmetic mean).

[0120] The particle diameter is the diameter of a spherical particle assuming that the particle is a perfect sphere. Such a particle diameter can be obtained, for example, by cutting a cross section of the solid-state battery, taking a cross-sectional SEM image using an SEM, and calculating the cross-sectional area S of the particle using image analysis software (for example, "Azokun" (manufactured by Asahi Chemical Industry Co., Ltd.)) and then calculating the particle diameter R by the following equation.

[0121] [Mathematical Formula 1]

[0122] R = 2 x (S / π) 1 / 2

[0123] Note that the average particle diameter of the negative electrode active material in the negative electrode layer can be measured automatically by determining the negative electrode active material at the time of measurement of the above-described average chemical composition.

[0124] The volume ratio of the negative electrode active material in the negative electrode layer is not particularly limited, and is preferably 20% or greater and 80% or less, more preferably 30% or greater and 75% or less, and further preferably 30% or greater and 60% or less, from the viewpoint of further improving the utilization rate of the negative electrode active material.

[0125] The volume ratio of the negative electrode active material in the negative electrode layer can be measured from the SEM image after FIB cross-section processing. In detail, the cross-section of the negative electrode layer is observed using SEM-EDX. The portion where V is detected by EDX is determined to be the negative electrode active material, and the volume ratio of the negative electrode active material can be measured by calculating the area ratio of the above portion.

[0126] The particle shape of the negative electrode active material in the negative electrode layer is not particularly limited, and can be any of a spherical shape, a flat shape, and an irregular shape, for example.

[0127] The negative electrode layer preferably further contains a solid electrolyte, and particularly a solid electrolyte having a garnet structure. By causing the negative electrode layer to contain a garnet solid electrolyte, the ionic conductivity of the negative electrode layer can be increased, and high-rate capability can be expected. In addition, since the side reaction at the time of co-firing with a negative electrode active material having a Li / V ratio of 2 or greater can be suppressed, the utilization rate of the negative electrode can be expected to be improved. As described later, the solid electrolyte layer also preferably further contains a solid electrolyte, and particularly a solid electrolyte having a garnet structure. This is because, by causing the solid electrolyte layer to contain a garnet solid electrolyte, the insulating property of the solid electrolyte layer can be improved. It is considered that this is because the garnet solid electrolyte is difficult to be reduced in charge and discharge, and thus electrons are difficult to be injected, and the degree of curvature of the LISICON-type solid electrolyte in the solid electrolyte increases, and the electron resistance increases. In addition, since the side reaction at the time of co-firing with a negative electrode active material having a Li / V ratio of 2 or greater can be suppressed, the utilization rate of the negative electrode can be expected to be improved. Therefore, at least one of the negative electrode layer or the solid electrolyte layer, and particularly both, preferably contains a solid electrolyte having a garnet structure. At least one of the negative electrode layer or the solid electrolyte layer containing a solid electrolyte having a garnet structure means that one of the negative electrode layer or the solid electrolyte layer can contain a solid electrolyte having a garnet structure, or both can contain a solid electrolyte having a garnet structure.

[0128] The solid electrolyte having a garnet structure means that the solid electrolyte has a crystal structure of a garnet type, and broadly means a crystal structure that can be recognized as a crystal structure of a garnet type by those skilled in the art in the field of solid-state batteries. In a narrow sense, the solid electrolyte having a garnet structure means that the solid electrolyte shows one or more main peaks corresponding to the Miller indices inherent to the crystal structure of a so-called garnet type in X-ray diffraction at a prescribed incident angle.

[0129] In the negative electrode layer, the solid electrolyte having the garnet structure preferably has an average chemical composition represented by the following general formula (2).

[0130] [Chemical Formula 2]

[0131] (Li (7-ax-(b-4)y] A x )La3Zr 2-y B y O 12 (2)

[0132] By including the solid electrolyte having the above average chemical composition in the negative electrode layer, further improvement of the utilization rate of the negative electrode active material can be achieved.

[0133] In formula (2), A is one or more elements selected from the group consisting of Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc), and Sc (scandium).

[0134] B is one or more elements selected from the group consisting of Nb (niobium), Ta (tantalum), W (tungsten), Te (tellurium), Mo (molybdenum), and Bi (bismuth).

[0135] x has a relationship of 0 ≤ x ≤ 0.5.

[0136] y has a relationship of 0 ≤ y ≤ 2.0.

[0137] a is the average valence number of A, which is the same as the average valence number of A in formula (1).

[0138] b is the average valence number of B, which is the same as the average valence number of B in formula (1).

[0139] In formula (2), from the viewpoint of further improving the utilization rate of the negative electrode active material, in the preferable embodiment, the following is satisfied:

[0140] A is one or more elements selected from the group consisting of Ga and Al.

[0141] B is one or more elements selected from the group consisting of Nb, Ta, W, Mo, and Bi.

[0142] x has a relationship of 0 ≤ x ≤ 0.3, and is preferably 0.

[0143] y has a relationship of 0 ≤ y ≤ 1.0, preferably a relationship of 0 ≤ y ≤ 0.7, more preferably a relationship of 0.3 ≤ y ≤ 0.7, and is preferably 0.5.

[0144] a is the average valence number of A.

[0145] b is the average valence number of B.

[0146] As a specific example of the solid electrolyte represented by General Formula (2), for example, (Li 6.4 Ga 0.05 Al 0.15 )La3Zr2O 12 、(Li 6.4 Ga 0.2 )La3Zr2O 12 、Li 6.4 La3(Zr 1.6 Ta 0.4 )O 12 、(Li 6.4 Al 0.2 )La3Zr2O 12 、Li 6.5 La3(Zr 1.5 Mo 0.25 )O 12 、Li 6.5 La3(Zr 1.5 Ta 0.5 )O 12 .

[0147] The average chemical composition of the solid electrolyte in the negative electrode layer (particularly, the solid electrolyte having a garnet structure) refers to the average value of the chemical composition of the solid electrolyte in the thickness direction of the negative electrode layer. The average chemical composition of the solid electrolyte can be analyzed and measured by breaking the solid battery, using SEM-EDX (energy dispersive X-ray spectroscopy), and performing composition analysis using EDX with the entire thickness direction of the negative electrode layer being in the field of view.

[0148] In the negative electrode layer, the average chemical composition of the negative electrode active material and the average chemical composition of the solid electrolyte can be automatically distinguished and measured in the above composition analysis.

[0149] For the solid electrolyte of the negative electrode layer, in addition to using a raw material compound containing a prescribed metal atom, it can be obtained by the same method as the negative electrode active material, or it can be obtained as a commercially available product.

[0150] The average chemical composition and the crystal structure of the solid electrolyte in the negative electrode layer generally vary depending on the element diffusion at the time of sintering. It is preferable that the solid electrolyte have the above average chemical composition and crystal structure in the solid battery after sintering together with the positive electrode layer and the solid electrolyte layer.

[0151] The volume ratio of the solid electrolyte in the negative electrode layer, particularly the solid electrolyte having a garnet structure, is not particularly limited, and is preferably 10% or more and 50% or less, more preferably 20% or more and 40% or less, from the viewpoint of further improving the utilization rate of the negative electrode active material and the balance of high energy density of the solid battery.

[0152] The volume ratio of the solid electrolyte in the negative electrode layer can be measured by the same method as the volume ratio of the negative electrode active material. The garnet solid electrolyte is based on the portion where Zr and / or La are detected by EDX.

[0153] The negative electrode layer can contain, for example, a sintering aid and a conductive aid, in addition to the negative electrode active material and the solid electrolyte.

[0154] By including a sintering aid in the negative electrode layer, densification can be achieved even at a lower temperature when sintering, and the diffusion of elements at the negative electrode active material / solid electrolyte layer interface can be suppressed. The sintering aid can use a sintering aid known in the field of solid batteries. From the viewpoint of further improving the utilization rate of the negative electrode active material, the present inventors and others have conducted research, and as a result, it has been found that the composition of the sintering aid preferably contains at least Li (lithium), B (boron), and O (oxygen), and the molar ratio of Li to B (Li / B) is 2.0 or more. These sintering aids have low melting properties, and by performing liquid phase sintering, the negative electrode layer can be densified at a lower temperature. It has also been found that by using the above composition, the side reaction of the sintering aid with the LISICON-type solid electrolyte used in the present application during co-sintering can be further suppressed. As a sintering aid that satisfies these requirements, for example, Li3BO3, (Li 2.7 Al 0.3 )BO3, Li 2.8 (B 0.8 C 0.2 )O3, and the like can be listed. Among these, (Li 2.7 Al 0.3 )BO3, which has particularly high ion conductivity, is particularly preferable.

[0155] The volume ratio of the sintering aid in the negative electrode layer is not particularly limited, and is preferably 0.1 or more and 10% or less, more preferably 1% or more and 7% or less, from the viewpoint of further improving the utilization rate of the negative electrode active material and the balance of high energy density of the solid battery.

[0156] The volume ratio of the sintering aid in the negative electrode layer can be measured by the same method as the volume ratio of the negative electrode active material. As the detected element in EDX that is judged to be the sintering aid region, B can be considered.

[0157] The porosity of the negative electrode layer is not particularly limited, and is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less from the viewpoint of further improving the utilization rate of the negative electrode active material.

[0158] The porosity of the negative electrode layer is measured using a SEM image after FIB cross-sectioning.

[0159] The negative electrode layer generally has a thickness of 2 μm or more and 100 μm or less, and particularly 2 μm or more and 50 μm or less.

[0160] The negative electrode layer 2 can have an end-face current collecting structure as shown in Figure 1B , or can have a main-face current collecting structure as shown in Figure 1A . From the viewpoint of further improving the capacity density (e.g., energy density), the negative electrode layer preferably has an end-face current collecting structure.

[0161] The negative electrode layer 2 having an end-face current collecting structure means that the negative electrode layer 2 has a structure in which the end face 2a (particularly, only the end face) of the negative electrode layer 2 on the negative electrode terminal 20 side collects electricity. In detail, the negative electrode layer 2, for example, Figure 1B , can be electrically connected to the negative electrode terminal 20 via the negative electrode current collecting portion 22 while the end face 2a (particularly, only the end face) of the negative electrode layer 2 on the negative electrode terminal 20 side is in contact with the negative electrode current collecting portion 22, or can be directly and electrically connected to the negative electrode terminal 20 while the end face 2a (particularly, only the end face) of the negative electrode layer 2 on the negative electrode terminal 20 side is in contact with the negative electrode terminal 20. From the viewpoint of more sufficiently ensuring electrical connection to the negative electrode terminal 20, the negative electrode layer 2 preferably, Figure 1B , is electrically connected to the negative electrode terminal 20 via the negative electrode current collecting portion 22 while the end face 2a (particularly, only the end face) of the negative electrode layer 2 on the negative electrode terminal 20 side is in contact with the negative electrode current collecting portion 22.

[0162] In the end-face current collecting structure of the negative electrode layer 2, in the case where the negative electrode layer 2 is electrically connected to the negative electrode terminal 20 via the negative electrode current collecting portion 22, the negative electrode layer 2 and the negative electrode current collecting portion 22 are in contact with each other at the end faces, and as a result, have a structure in which they are adjacent to each other in a direction perpendicular to the stacking direction in a cross-sectional view. The negative electrode layer 2 and the negative electrode current collecting portion 22 have a structure in which they are adjacent to each other in a direction perpendicular to the stacking direction in a plan view.

[0163] In the end surface current collecting structure of the negative electrode layer 2, in the case where the negative electrode layer 2 is electrically connected to the negative electrode terminal 20 via the negative electrode current collecting portion 22, the negative electrode current collecting portion 22 generally has an upper surface 22b flush with the upper surface 2b of the negative electrode layer 2 in the stacking direction L of the negative electrode layer 2, and has a lower surface 22c flush with the lower surface 2c of the negative electrode layer 2 in the stacking direction L of the negative electrode layer 2. By the term "flush", it is meant a state where there is no difference in level between the two surfaces. The two surfaces are the upper surface 2b of the negative electrode layer 2 and the upper surface 22b of the negative electrode current collecting portion 22, and the lower surface 2c of the negative electrode layer 2 and the lower surface 22c of the negative electrode current collecting portion 22.

[0164] The negative electrode layer 2 having the main surface current collecting structure means that the negative electrode layer 2 has a structure in which current is collected from the main surface of the negative electrode layer. In detail, as shown in FIG. 1, the negative electrode layer 2 is in contact with the negative electrode current collecting layer 21 on the main surface 2x of the negative electrode layer 2, and is electrically connected to the negative electrode terminal 20 via the negative electrode current collecting layer 21. Figure 1A In the main surface current collecting structure of the negative electrode layer 2, the negative electrode current collecting layer 21 can be laminated on the main surface of the negative electrode layer 2, and / or the negative electrode layer 2 can be laminated on the main surface of the negative electrode current collecting layer 21. The main surface means a surface having a relatively large area, and in detail means an upper surface and / or a lower surface perpendicular to the stacking direction. By the term "current is collected from the main surface", it is meant that mainly electrons enter and exit from the main surface. In the main surface current collecting structure of the negative electrode layer 2, the negative electrode layer 2 can be in direct electrical connection with the negative electrode terminal 20 on the side of the negative electrode terminal 20, but can also be electrically connected to the negative electrode terminal 20 via the negative electrode current collecting portion as in the end surface current collecting structure of the negative electrode layer. Figure 1A In the main surface current collecting structure of the negative electrode layer 2, the negative electrode current collecting layer 21 can be laminated on the main surface of the negative electrode layer 2, and / or the negative electrode layer 2 can be laminated on the main surface of the negative electrode current collecting layer 21. The main surface means a surface having a relatively large area, and in detail means an upper surface and / or a lower surface perpendicular to the stacking direction. By the term "current is collected from the main surface", it is meant that mainly electrons enter and exit from the main surface. In the main surface current collecting structure of the negative electrode layer 2, the negative electrode layer 2 can be in direct electrical connection with the negative electrode terminal 20 on the side of the negative electrode terminal 20, but can also be electrically connected to the negative electrode terminal 20 via the negative electrode current collecting portion as in the end surface current collecting structure of the negative electrode layer. Figure 1A In the main surface current collecting structure of the negative electrode layer 2, the negative electrode current collecting layer 21 can be laminated on the main surface of the negative electrode layer 2, and / or the negative electrode layer 2 can be laminated on the main surface of the negative electrode current collecting layer 21. The main surface means a surface having a relatively large area, and in detail means an upper surface and / or a lower surface perpendicular to the stacking direction. By the term "current is collected from the main surface", it is meant that mainly electrons enter and exit from the main surface. In the main surface current collecting structure of the negative electrode layer 2, the negative electrode layer 2 can be in direct electrical connection with the negative electrode terminal 20 on the side of the negative electrode terminal 20, but can also be electrically connected to the negative electrode terminal 20 via the negative electrode current collecting portion as in the end surface current collecting structure of the negative electrode layer.

[0165] The negative electrode current collecting layer 21 and the negative electrode current collecting portion 22 of the negative electrode layer 2 can be composed of at least a conductive material. The negative electrode current collecting layer 21 and the negative electrode current collecting portion 22 can further be composed of a solid electrolyte. In one preferred mode, the negative electrode current collecting layer 21 and the negative electrode current collecting portion 22 are composed of a sintered body containing at least a conductive material and a solid electrolyte. The conductive material that can be contained in the negative electrode current collecting layer 21 and the negative electrode current collecting portion 22 is generally a material having a relatively high electrical conductivity, and for example, at least one selected from the group consisting of carbon materials, silver, palladium, gold, platinum, aluminum, copper and nickel is preferably used. The solid electrolyte that can be contained in the negative electrode current collecting layer 21 and the negative electrode current collecting portion 22 can be selected from the same solid electrolytes as those that can be contained in the negative electrode layer.

[0166] The negative current collector layer 21 and the negative current collector portion 22 preferably have the form of a sintered body from the viewpoint of reducing the manufacturing cost of the solid-state battery and reducing the internal resistance of the solid-state battery by integral sintering. In the case where the negative current collector layer 21 and the negative current collector portion 22 have the form of a sintered body, for example, the negative current collector layer 21 and the negative current collector portion 22 can be composed of a sintered body containing a sintering aid in addition to the above-described electrically conductive material and the solid electrolyte. The sintering aid contained in the negative current collector layer 21 and the negative current collector portion 22 can be selected, for example, from the same material as the sintering aid that can be contained in the negative electrode layer.

[0167] The thickness of the negative current collector layer is not particularly limited and can be, for example, 1 μm or more and 5 μm or less, and is particularly preferably 1 μm or more and 3 μm or less.

[0168] The thickness of the negative current collector portion can generally have the same thickness as the negative electrode layer.

[0169] The negative electrode layer is a layer that can be referred to as a "negative electrode active material layer".

[0170] (Polar Layer)

[0171] The positive electrode layer 1 contains a positive electrode active material and can also contain a solid electrolyte. In the case where the positive electrode layer 1 contains a covering-type electrically conductive aid, the positive electrode layer 1 contains a covering-type electrically conductive aid and a positive electrode active material and can also contain a solid electrolyte. From the viewpoint of further improving the utilization rate of the positive electrode active material, the positive electrode layer preferably contains a covering-type electrically conductive aid. In the positive electrode layer, it is preferable that the covering-type electrically conductive aid, the positive electrode active material, and the solid electrolyte all have the form of a sintered body. For example, in the case where the positive electrode layer contains a covering-type electrically conductive aid, a positive electrode active material, and a solid electrolyte, the positive electrode layer preferably has the form of a sintered body in which the positive electrode active material particles are bound by the covering-type electrically conductive aid and the solid electrolyte, and the covering-type electrically conductive aid, the positive electrode active material particles, and the solid electrolyte are joined by sintering among them.

[0172] The positive electrode layer is a layer capable of intercalating and deintercalating metal ions, and is preferably a layer capable of intercalating and deintercalating lithium ions or sodium ions, particularly lithium ions. The positive electrode active material is not particularly limited, and a positive electrode active material known in the field of solid-state batteries can be used. As a positive electrode active material capable of intercalating and deintercalating lithium ions, for example, there can be mentioned lithium-containing phosphoric acid compound particles having a NASICON-type structure, lithium-containing phosphoric acid compound particles having an olivine-type structure, lithium-containing layered oxide particles, lithium-containing oxides having a spinel-type structure, and the like. As a specific example of the lithium-containing phosphoric acid compound having a NASICON-type structure that is preferably used, there can be mentioned Li3V2(PO4)3and the like. As a specific example of the lithium-containing phosphoric acid compound having an olivine-type structure that is preferably used, there can be mentioned Li3Fe2(PO4)3, LiMnPO4, and the like. As a specific example of the lithium-containing layered oxide particles that is preferably used, there can be mentioned LiCoO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, and the like. As a specific example of the lithium-containing oxides having a spinel-type structure that is preferably used, there can be mentioned LiMn2O4, LiNi 0.5 Mn 1.5 O4, and the like. From the viewpoint of reactivity upon co-sintering with the LISICON-type solid electrolyte used in the present application, as the positive electrode active material, LiCoO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, and the like lithium-containing layered oxides are more preferably used. Note that one of these positive electrode active material particles can be used alone, or a plurality of them can be used in admixture.

[0173] That the positive electrode active material in the positive electrode layer has a NASICON-type structure means that the positive electrode active material (particularly the particles thereof) has a crystal structure of the NASICON type, and in a broad sense means a crystal structure that can be recognized by those skilled in the art in the field of solid-state batteries as a crystal structure of the NASICON type. In a narrow sense, that the positive electrode active material in the positive electrode layer has a NASICON-type structure means that the positive electrode active material (particularly the particles thereof) shows one or more main peaks corresponding to the Miller indices inherent to the so-called crystal structure of the NASICON type in X-ray diffraction at a prescribed incident angle. As the positive electrode active material having a NASICON-type structure that is preferably used, there can be mentioned the above-mentioned compounds exemplified.

[0174] The positive electrode active material in the positive electrode layer having an olivine-type structure means that the positive electrode active material (particularly, particles thereof) has a crystal structure of the so-called olivine-type. In a broad sense, it means that the positive electrode active material has a crystal structure which can be recognized by those skilled in the art in the field of solid-state batteries as a crystal structure of the olivine-type. In a narrow sense, the positive electrode active material in the positive electrode layer having an olivine-type structure means that the positive electrode active material (particularly, particles thereof) shows one or more main peaks corresponding to Miller indices inherent to the crystal structure of the so-called olivine-type in X-ray diffraction at a prescribed incident angle. As the positive electrode active material having an olivine-type structure which is preferably used, the above-mentioned exemplified compounds can be cited.

[0175] As the positive electrode active material capable of intercalating and deintercalating sodium ions, at least one selected from the group consisting of a sodium-containing phosphoric acid compound having a NASICON-type structure, a sodium-containing phosphoric acid compound having an olivine-type structure, a sodium-containing layered oxide, and a sodium-containing oxide having a spinel-type structure, and the like can be cited.

[0176] The positive electrode active material in the positive electrode layer having a spinel-type structure means that the positive electrode active material (particularly, particles thereof) has a crystal structure of the so-called spinel-type. In a broad sense, it means that the positive electrode active material has a crystal structure which can be recognized by those skilled in the art in the field of solid-state batteries as a crystal structure of the spinel-type. In a narrow sense, the positive electrode active material in the positive electrode layer having a spinel-type structure means that the positive electrode active material (particularly, particles thereof) shows one or more main peaks corresponding to Miller indices inherent to the crystal structure of the so-called spinel-type in X-ray diffraction at a prescribed incident angle. As the positive electrode active material having a spinel-type structure which is preferably used, the above-mentioned exemplified compounds can be cited.

[0177] The chemical composition of the positive electrode active material can also be an average chemical composition. The average chemical composition of the positive electrode active material means an average value of the chemical composition of the positive electrode active material in the thickness direction of the positive electrode layer. The average chemical composition of the positive electrode active material can be analyzed and measured by breaking the solid-state battery and performing composition analysis using EDX in a case where the entire thickness direction of the positive electrode layer is included in the field of view using SEM-EDX (energy dispersive X-ray spectroscopy).

[0178] The positive electrode active material can be obtained by the same method as the negative electrode active material, or can be obtained as a commercial product, in addition to using a raw compound containing a prescribed metal atom.

[0179] The chemical composition and the crystal structure of the positive electrode active material in the positive electrode layer generally vary depending on the element diffusion at the time of sintering. The positive electrode active material preferably has the above-mentioned chemical composition and crystal structure in the solid-state battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0180] The average particle diameter of the positive electrode active material is not particularly limited, and can be, for example, 0.01 μm or more and 10 μm or less, and is preferably 0.05 μm or more and 4 μm or less.

[0181] The average particle diameter of the positive electrode active material in the positive electrode layer can be obtained by the same method as the average particle diameter of the negative electrode active material in the negative electrode layer.

[0182] The average particle diameter of the positive electrode active material in the positive electrode layer generally directly reflects the average particle diameter of the positive electrode active material used at the time of production. This is directly reflected particularly in the case where LiCoO2is used in the positive electrode particle.

[0183] The particle shape of the positive electrode active material in the positive electrode layer is not particularly limited, and can be, for example, any of a spherical shape, a flat shape, and an irregular shape.

[0184] The volume ratio of the positive electrode active material in the positive electrode layer is not particularly limited, and is preferably 30% or more and 90% or less, and more preferably 40% or more and 70% or less, from the viewpoint of further improving the utilization rate of the negative electrode active material.

[0185] The positive electrode layer can contain, in addition to the positive electrode active material, for example, a solid electrolyte, a sintering aid, and a conductive aid, and the like.

[0186] The kind of the solid electrolyte contained in the positive electrode layer is not particularly limited. As the solid electrolyte contained in the positive electrode layer, for example, a solid electrolyte having a garnet structure (Li 6.4 Ga 0.2 )La3Zr2O 12 , Li 6.4 La3(Zr 1.6 Ta 0.4 )O 12 , (Li 6.4 Al 0.2 )La3Zr2O 12 , Li 6.5 La3(Zr 1.5 Mo 0.25 )O 12 , a solid electrolyte having a LISICON structure Li 3+x (V 1-x Si x )O4, a solid electrolyte having a perovskite structure La 2 / 3-x Li 3xTiO3, a solid electrolyte having an amorphous structure such as Li3BO3-Li4SiO4, and the like. Among them, from the viewpoint of reactivity at the time of co-sintering with the LISICON-type solid electrolyte used in the present application, it is particularly preferable to use a solid electrolyte having a garnet structure, a solid electrolyte having a LISICON-type structure.

[0187] As for the solid electrolyte of the positive electrode layer, in addition to using a raw compound containing a prescribed metal atom, it can be obtained by the same method as the negative electrode active material, or it can also be obtained as a commercial product.

[0188] The average chemical composition and the crystal structure of the solid electrolyte in the positive electrode layer generally vary depending on the element diffusion at the time of sintering. It is preferable that the solid electrolyte have the above-described average chemical composition and crystal structure in the solid battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0189] The volume ratio of the solid electrolyte in the positive electrode layer is not particularly limited, and from the viewpoint of further improving the utilization rate of the positive electrode active material and the balance of high energy density of the solid battery, it is preferable to be 20% or more and 60% or less, and more preferably 30% or more and 45% or less.

[0190] As the sintering aid in the positive electrode layer, the same compound as the sintering aid in the negative electrode layer can be used.

[0191] The volume ratio of the sintering aid in the positive electrode layer is not particularly limited, and from the viewpoint of further improving the utilization rate of the negative electrode active material and the balance of high energy density of the solid battery, it is preferable to be 0.1% or more and 20% or less, and more preferably 1% or more and 10% or less.

[0192] The positive electrode layer can also contain other conductive aids other than the covering-type conductive aid. The other conductive aid that can be contained in the positive electrode layer can use all the conductive aids known in the field of solid batteries. As such a conductive aid, for example, metal materials such as Ag (silver), Au (gold), Pd (palladium), Pt (platinum), Cu (copper), Sn (tin), Ni (nickel), and the like; and carbon materials such as acetylene black, Ketjen black, Super P (registered trademark), VGCF (registered trademark) carbon nanotubes, and the like can be listed.

[0193] The volume ratio of the conductive aid in the positive electrode layer is not particularly limited, and from the viewpoint of further improving the utilization rate of the positive electrode active material and the balance of high energy density of the solid battery, it is preferable to be 10% or more and 50% or less, and more preferably 20% or more and 40% or less.

[0194] The porosity of the positive electrode layer is not particularly limited, and is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less from the viewpoint of further improving the utilization rate of the negative electrode active material.

[0195] The porosity of the positive electrode layer is measured by the same method as the porosity of the negative electrode layer.

[0196] As shown in Figure 1A and Figure 1B , the positive electrode layer 1 can have a main surface current collecting structure, or can have an end surface current collecting structure. From the viewpoint of reducing manufacturing costs, the positive electrode layer preferably has a main surface current collecting structure.

[0197] The positive electrode layer 1 having a main surface current collecting structure means that the positive electrode layer 1 has a structure in which current is collected from the main surface of the positive electrode layer. In detail, as shown in Figure 1A and Figure 1B , the positive electrode layer 1 contacts the positive electrode current collecting layer 11 on the main surface 1x of the positive electrode layer 1, and is electrically connected to the positive electrode terminal 10 via the positive electrode current collecting layer 11. In the main surface current collecting structure of the positive electrode layer 1, the positive electrode current collecting layer 11 can be laminated on the main surface of the positive electrode layer 1, and / or the positive electrode layer 1 can be laminated on the main surface of the positive electrode current collecting layer 11. The main surface means a surface having a relatively large area, and in detail means an upper surface and / or a lower surface perpendicular to the lamination direction. By the current being collected from the main surface, it mainly means that electrons enter and exit from the main surface. In Figure 1A , the positive electrode layer 1 is directly electrically connected to the positive electrode terminal 10 on the positive electrode terminal 10 side, but can also be electrically connected to the positive electrode terminal 10 via the positive electrode current collecting portion as in the positive electrode layer having an end surface current collecting structure described later. In the case where the positive electrode layer 1 has a main surface current collecting structure, as shown in Figure 1A and Figure 1B , the positive electrode layer 1 can be laminated on both main surfaces of the positive electrode current collecting layer 11, or can be laminated on one main surface.

[0198] The positive electrode layer 1 having an end surface current collecting structure means that the positive electrode layer 1 has a structure in which current is collected from the end surface (particularly only the end surface) of the positive electrode layer 1 on the positive electrode terminal 10 side. In detail, the positive electrode layer 1 can contact the positive electrode current collecting portion on the end surface (particularly only the end surface) of the positive electrode layer 1 on the positive electrode terminal 10 side, and be electrically connected to the positive electrode terminal 10 via the positive electrode current collecting portion, or can directly and electrically connect to the positive electrode terminal 10 on the end surface (particularly only the end surface) of the positive electrode layer 1 on the positive electrode terminal 10 side.

[0199] The positive electrode current collecting layer 11 and the positive electrode current collecting portion can be composed of at least a conductive material. The positive electrode current collecting layer 11 and the positive electrode current collecting portion can also be composed of a solid electrolyte. In one preferred embodiment, the positive electrode current collecting layer 11 and the positive electrode current collecting portion are composed of a sintered body including at least a conductive material and a solid electrolyte. The conductive material included in the positive electrode current collecting layer 11 and the positive electrode current collecting portion is generally a material having a relatively high electrical conductivity, and can be selected from the same conductive materials as those included in the negative electrode current collecting layer and the negative electrode current collecting portion. The solid electrolyte included in the positive electrode current collecting layer 11 and the positive electrode current collecting portion can be selected from the same solid electrolytes as those included in the negative electrode layer.

[0200] From the viewpoint of reducing the manufacturing cost of the solid-state battery and reducing the internal resistance of the solid-state battery by sintering in one step, the positive electrode current collecting layer 11 and the positive electrode current collecting portion preferably have the form of a sintered body. In the case where the positive electrode current collecting layer 11 and the positive electrode current collecting portion have the form of a sintered body, for example, the positive electrode current collecting layer 11 and the positive electrode current collecting portion can be composed of a sintered body including a sintering aid in addition to the aforementioned conductive material and solid electrolyte. The sintering aid included in the positive electrode current collecting layer 11 and the positive electrode current collecting portion can be selected from the same materials as those included in the negative electrode layer.

[0201] The thickness of the positive electrode current collecting layer is not particularly limited, and can be, for example, 1 μm or more and 5 μm or less, particularly 1 μm or more and 3 μm or less.

[0202] The thickness of the positive electrode current collecting portion can generally be the same as the thickness of the positive electrode layer.

[0203] The positive electrode layer is a layer that can be referred to as a "positive electrode active material layer".

[0204] [Solid electrolyte layer]

[0205] In the present application, the solid electrolyte layer 3 is not particularly limited, and is, for example, a material capable of conducting lithium ions or sodium ions, particularly lithium ions. As a solid electrolyte capable of conducting lithium ions, the solid electrolyte layer 3 can include, for example, one or more materials selected from a solid electrolyte having a LISICON-type structure (e.g., the first solid electrolyte described below), a solid electrolyte having a garnet-type structure (e.g., the second solid electrolyte described below), and an oxide glass-ceramic lithium ion conductor. From the viewpoint of further improving the utilization rate of the electrode active material, the solid electrolyte layer 3 preferably includes one of the first solid electrolyte or the second solid electrolyte described below, or both. From the same viewpoint and other viewpoints (e.g., the viewpoint of manufacturing cost), the solid electrolyte layer 3 preferably includes only the second solid electrolyte.

[0206] The first solid electrolyte is a solid electrolyte having a LISICON-type structure and containing at least V. The LISICON-type structure possessed by the first solid electrolyte in the solid electrolyte layer includes a β I -type structure, a β II -type structure, a β II '-type structure, a T I -type structure, a T II -type structure, a γ II -type structure, and a γ0-type structure. That is, the solid electrolyte layer can contain one or more kinds of solid electrolytes having a β I -type structure, a β II -type structure, a β II '-type structure, a T I -type structure, a T II -type structure, a γ II -type structure, a γ0-type structure, or a composite structure thereof. From the viewpoint of further improving the utilization rate of the electrode active material, the LISICON-type structure possessed by the first solid electrolyte layer is preferably a γ II -type structure.

[0207] In the solid electrolyte layer, the first solid electrolyte has a γ II -type structure means that the solid electrolyte has a crystal structure of the γ II -type, and broadly means a crystal structure that can be recognized by those skilled in the art in the field of solid-state batteries as a crystal structure of the γ II -type. In the narrow sense, the first solid electrolyte in the solid electrolyte layer has a γ II -type structure means that the solid electrolyte shows one or more main peaks corresponding to the Miller indices inherent to the so-called γ II -Li3VO4-type crystal structure in X-ray diffraction at a prescribed incident angle. A compound (i.e., a solid electrolyte) having a γ II -type structure is described, for example, in the literature "J. solid state chem" (A. R. West et. al, J. solid state chem., 4, 20-28 (1972)), and as an example thereof, ICDD Card No. 01-073-2850 can be cited.

[0208] In the solid electrolyte layer, the first solid electrolyte has a β I -type structure means that the solid electrolyte has a crystal structure of the β I -type, and broadly means a crystal structure that can be recognized by those skilled in the art in the field of solid-state batteries as a crystal structure of the β I -type. In the narrow sense, the first solid electrolyte in the solid electrolyte layer has a β IThe β-type structure refers to the solid electrolyte exhibiting a similar appearance to the so-called β-type structure in X-ray diffraction at a specified incident angle. I The crystal structure of the Li3VO4 type inherently contains more than one major peak corresponding to the Miller index. It possesses β... I Compounds with this type of structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)). As an example, the XRD data (Miller index corresponding to the surface spacing d value) described in the following table are shown.

[0209] [Table 1]

[0210]

[0211] The first solid electrolyte in the solid electrolyte layer has β II Type structure refers to the solid electrolyte having β II A β-type crystal structure, broadly speaking, refers to a crystal structure that can be identified by those skilled in the art of solid-state batteries as β. II A crystal structure of type β. In a narrow sense, the first solid electrolyte in the solid electrolyte layer has a β-type crystal structure. II The β-type structure refers to the solid electrolyte exhibiting a similar appearance to the so-called β-type structure in X-ray diffraction at a specified incident angle. II The crystal structure of the Li3VO4 type inherently contains more than one major peak corresponding to the Miller index. It possesses β... II Compounds with this type of structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)). As an example, ICDD Card No. 00-024-0675 can be cited.

[0212] The first solid electrolyte in the solid electrolyte layer has β II '-type structure refers to the solid electrolyte having β II A β-type crystal structure, broadly speaking, refers to a crystal structure that can be identified by those skilled in the art of solid-state batteries as a β-type crystal. II A crystal structure of the '-type. In a narrow sense, the first solid electrolyte in the solid electrolyte layer has a β-type crystal structure. II The 'type' structure refers to the solid electrolyte exhibiting a similar appearance to the so-called β-type structure in X-ray diffraction at a specified incident angle. II The '-Li3VO4 type crystal structure inherently contains more than one major peak corresponding to the Miller indices. It possesses β... IICompounds with a '-type structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)). As an example, the XRD data (Miller index corresponding to the surface spacing d value) described in the following table are shown.

[0213] [Table 2]

[0214]

[0215] The first solid electrolyte in the solid electrolyte layer has T I Type-type structure refers to the solid electrolyte having T I A type of crystal structure, broadly speaking, refers to a structure that can be identified by those skilled in the art of solid-state batteries as a T-type crystal. I A crystal structure of type T. In a narrow sense, the first solid electrolyte in the solid electrolyte layer has a T... I The type structure refers to the solid electrolyte exhibiting a similar appearance to the so-called To structure in X-ray diffraction at a specified incident angle. I The crystal structure of the Li3VO4 type inherently contains more than one major peak corresponding to the Miller indices. It has T... I Compounds with this type of structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)). As an example, ICDD Card No. 00-024-0668 can be cited.

[0216] The first solid electrolyte in the solid electrolyte layer has T II Type-type structure refers to the solid electrolyte having T II A type of crystal structure, broadly speaking, refers to a structure that can be identified by those skilled in the art of solid-state batteries as a T-type crystal. II A crystal structure of type T. In a narrow sense, the first solid electrolyte in the solid electrolyte layer has a T... II The type structure refers to the solid electrolyte exhibiting a similar appearance to the so-called To structure in X-ray diffraction at a specified incident angle. II The crystal structure of the Li3VO4 type inherently contains more than one major peak corresponding to the Miller indices. It has T... IIA compound having a γ0-type structure (i.e., a solid electrolyte) is described, for example, in the literature "J. solid state chem" (A.R. West et. al, J. solid state chem., 4, 20-28 (1972)), and as one example thereof, for example, ICDD Card No. 00-024-0669 can be cited.

[0217] The first solid electrolyte in the solid electrolyte layer having a γ0-type structure means that the solid electrolyte has a crystal structure of a γ0-type, and in a broad sense, means a crystal structure that can be recognized by a person skilled in the art in the field of solid batteries as a crystal structure of a γ0-type. In a narrow sense, the first solid electrolyte in the solid electrolyte layer having a γ0-type structure means that the solid electrolyte shows one or more main peaks corresponding to Miller indices inherent to a crystal structure of a so-called γ0-Li3VO4-type in X-ray diffraction at a prescribed incident angle. A compound having a γ0-type structure (i.e., a solid electrolyte) is described, for example, in the literature "J. solid state chem" (A.R. West et. al, J. solid state chem., 4, 20-28 (1972)), and as one example thereof, for example, XRD data (Miller indices corresponding to interplanar spacing d values) described in the following table are shown.

[0218] [Table 3]

[0219]

[0220] In the solid electrolyte layer, the first solid electrolyte is more preferably of an average chemical composition represented by the following general formula (3).

[0221] [Chemical Formula 3]

[0222] (Li [3ax+(5-b)(1-y)] A x )(V y B 1-y )O4 (3)

[0223] In formula (3), A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), and Zn (zinc).

[0224] B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt).

[0225] x has a relationship of 0 ≤ x ≤ 1.0, particularly 0 ≤ x ≤ 0.2, and is preferably 0.

[0226] y has a relationship of 0 < y < 1.0, particularly 0.05 ≤ y < 0.93, and preferably has a relationship of 0.4 ≤ y ≤ 0.9, more preferably 0.6 ≤ y ≤ 0.9, from the viewpoint of further improving the utilization rate of the electrode active material.

[0227] a is the average valence number of A, which is the same as the average valence number of A in formula (1).

[0228] b is the average valence number of B, which is the same as the average valence number of B in formula (1).

[0229] In formula (3), from the viewpoint of further improving the utilization rate of the electrode active material, in the preferred embodiment, the following is satisfied:

[0230] A is Al.

[0231] B is one or more elements selected from the group consisting of Si, Ge, and P.

[0232] x has a relationship of 0 ≤ x ≤ 0.2, particularly 0 ≤ x ≤ 0.1, and is preferably 0.

[0233] y has a relationship of 0.7 ≤ y ≤ 0.9, and is preferably 0.8.

[0234] The average chemical composition of the first solid electrolyte in the solid electrolyte layer refers to the average value of the chemical composition of the first solid electrolyte in the thickness direction of the solid electrolyte layer. The average chemical composition of the first solid electrolyte can be analyzed and measured by breaking the solid battery, using SEM-EDX (energy dispersive X-ray spectroscopy), and performing composition analysis using EDX while the entire solid electrolyte layer in the thickness direction is included in the field of view.

[0235] The average chemical composition of the first solid electrolyte of the LISICON type structure and the average chemical composition of the solid electrolyte of the garnet type structure in the solid electrolyte layer described later can be automatically distinguished and measured in the above composition analysis according to these compositions. For example, the site of the first solid electrolyte (i.e., the solid electrolyte of the LISICON type structure) can be separated by identification based on V detection, and the site of the second solid electrolyte (e.g., the garnet type solid electrolyte) can be separated by identification based on La and Zr according to SEM-EDX analysis.

[0236] For the first solid electrolyte of the solid electrolyte layer, in addition to using a raw material compound containing a prescribed metal atom, it can be obtained by the same method as the negative electrode active material, or it can also be obtained as a commercial product.

[0237] The chemical composition and crystal structure of the first solid electrolyte in the solid electrolyte layer generally change due to element diffusion at the time of sintering. The first solid electrolyte preferably has the above-described chemical composition and crystal structure in the solid battery after sintering together with the negative electrode layer and the positive electrode layer. In particular, the chemical composition of the first solid electrolyte directly reflects the chemical composition of the solid electrolyte used at the time of production in the case of high-speed sintering at 750°C for about 1 minute together with the negative electrode layer, but the amount of V generally increases due to the diffusion of the element of the negative electrode active material from the negative electrode layer in the case of long-time sintering at 750°C for about 1 hour.

[0238] The volume ratio of the first solid electrolyte in the solid electrolyte layer is not particularly limited, and is preferably 0% or more and 80% or less, more preferably 0% or more and 60% or less, and further preferably 30% or more and 60% or less from the viewpoint of further improving the utilization rate of the electrode active material.

[0239] The volume ratio of the first solid electrolyte in the solid electrolyte layer can be measured by the same method as the volume ratio of the positive electrode active material.

[0240] The second solid electrolyte is a solid electrolyte having a garnet structure. By including the second solid electrolyte in the solid electrolyte layer, the insulating property of the solid electrolyte layer can be improved. It is considered that this is because the second solid electrolyte is difficult to be reduced and thus difficult to inject electrons in charge and discharge. In the case of using both the first solid electrolyte and the second solid electrolyte, the degree of bending of the first solid electrolyte in the solid electrolyte layer increases, and the electron resistance increases due to the second solid electrolyte.

[0241] The second solid electrolyte is the same as the solid electrolyte having a garnet structure preferably included in the negative electrode layer, and can also be selected from the same range as the solid electrolyte having a garnet structure described in the description of the negative electrode layer. In the case where the solid electrolyte layer and the negative electrode layer each include a solid electrolyte having a garnet structure, the solid electrolyte having a garnet structure included in the solid electrolyte layer and the solid electrolyte having a garnet structure included in the negative electrode layer can have the same chemical composition, or can also have different chemical compositions from each other.

[0242] The solid electrolyte preferred for the solid electrolyte layer B is a solid electrolyte having the following chemical composition in the formula (2):

[0243] A is an element selected from one or more species (particularly two species) of the group consisting of Ga and Al.

[0244] B is an element selected from one or more species of the group consisting of Nb, Ta, W, Mo, and Bi.

[0245] x has a relationship of 0≤x≤0.3, preferably 0.2.

[0246] y has a relationship of 0≤y≤1.0, preferably a relationship of 0≤y≤0.7, more preferably a relationship of 0≤y≤0.3, further preferably 0.

[0247] a is the average valence number of A.

[0248] b is the average valence number of B.

[0249] The average chemical composition of the second solid electrolyte in the solid electrolyte layer refers to the average value of the chemical composition of the second solid electrolyte in the thickness direction of the solid electrolyte layer. The average chemical composition of the second solid electrolyte can be analyzed and measured by breaking the solid battery, using SEM-EDX (energy dispersive X-ray spectroscopy), and performing composition analysis using EDX in a case where the entire solid electrolyte layer in the thickness direction is included in the field of view.

[0250] The volume ratio of the second solid electrolyte in the solid electrolyte layer is not particularly limited, and from the viewpoint of further improving the utilization rate of the electrode active material, it is preferably 20% or more and 100% or less, more preferably 40% or more and 100% or less, and further preferably 40% or more and 70% or less.

[0251] The volume ratio of the second solid electrolyte in the solid electrolyte layer can be measured by the same method as the volume ratio of the positive electrode active material.

[0252] As the oxide glass ceramic lithium ion conductor, for example, a phosphoric acid compound (LATP) containing lithium, aluminum, and titanium in the constituent elements, and a phosphoric acid compound (LAGP) containing lithium, aluminum, and germanium in the constituent elements can be used.

[0253] As the solid electrolyte capable of conducting sodium ions, for example, a sodium-containing phosphoric acid compound having a NASICON structure, an oxide having a perovskite structure, an oxide having a garnet-type or garnet-type similar structure, and the like can be listed. As the sodium-containing phosphoric acid compound having a NASICON structure, Na x M y (PO4)3 (1≤x≤2, 1≤y≤2, M is at least one selected from the group consisting of Ti, Ge, Al, Ga, and Zr).

[0254] In addition to the solid electrolyte, the solid electrolyte layer may also contain, for example, sintering aids. From the viewpoint of further improving the utilization rate of the electrode active material, it is preferable that at least one of the negative electrode layer or the solid electrolyte layer also contains a sintering aid, and preferably both of them also contain a sintering aid. "At least one of the negative electrode layer or the solid electrolyte layer also contains a sintering aid" means that either one of the negative electrode layer or the solid electrolyte layer may contain a sintering aid, or both of them may contain a sintering aid.

[0255] As a sintering aid in the solid electrolyte layer, the same compound as the sintering aid in the negative electrode layer can be used.

[0256] The volume ratio of sintering aid in the solid electrolyte layer is not particularly limited. From the viewpoint of further improving the utilization rate of electrode active materials and balancing the high energy density of solid batteries, it is preferably 0.1% or more and 20% or less, and more preferably 1% or more and 10% or less.

[0257] The thickness of the solid electrolyte layer is typically 0.1–30 μm, and from the viewpoint of making the solid electrolyte layer thinner, it is preferably 20–1 μm.

[0258] The thickness of the solid electrolyte layer was calculated using the average of the thickness measured at any 10 points in the SEM image.

[0259] In the solid electrolyte layer, the porosity is not particularly limited, but from the viewpoint of further improving the utilization rate of the electrode active material, it is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less.

[0260] The porosity of the solid electrolyte layer is measured using the same method as that used for the porosity of the negative electrode layer.

[0261] The chemical composition of the solid electrolyte layer does not need to be homogeneous; for example, the chemical composition can vary along the thickness direction. In particular, insulation can be improved by ensuring that the average composition of the first solid electrolyte in the solid electrolyte layer meets the above conditions.

[0262] [Protective Layer]

[0263] like Figure 1A As shown on the paper, the protective layer 5 is formed at least on the top and bottom surfaces of the solid-state battery, and preferably also on all sides of the solid-state battery. The protective layer 5 is used to electrically, physically, and chemically protect the solid-state battery (especially battery elements such as the positive electrode layer, negative electrode layer, and solid electrolyte layer).

[0264] The protective layer 5 is typically composed of an insulating substance. The insulating substance refers to a substance that does not have ion conductivity and electron conductivity. Thus, the insulating substance refers to an inorganic substance that does not have ion conductivity and electron conductivity. The inorganic substance that does not have ion conductivity refers to an inorganic substance having ion conductivity of 1 x 10 -7 S / cm or less. From the viewpoint of more long-term inhibition of battery deterioration, the ion conductivity is preferably 1 x 10 -10 S / cm or less. The inorganic substance that does not have electron conductivity refers to an inorganic substance having electron conductivity of 1 x 10 -7 S / cm or less. From the viewpoint of more long-term inhibition of battery deterioration, the electron conductivity is preferably 1 x 10 -10 S / cm or less.

[0265] When the protective layer 5 is composed of such an insulating substance, the protective layer 5 has excellent moisture resistance, environmental resistance, and durability. In detail, the protective layer 5 can be a protective layer having high adhesion strength to the battery element, as compared with a protective layer including a resin (e.g., a high molecular compound). As a result, the protective layer 5 can more sufficiently prevent expansion and shrinkage of the solid-state battery, and as a result, can more sufficiently inhibit reduction in battery performance, as compared with a protective layer including a high molecular compound.

[0266] The insulating substance that constitutes the protective layer 5 is not particularly limited, and for example, glass, ceramic can be cited. As the glass, quartz glass (Si02), or a composite oxide-based glass in which Si02is combined with at least one selected from the group consisting of PbO, B203, MgO, ZnO, Bi203, Na20, Al203, and the like can be cited. As the ceramic, alumina, cordierite, mullite, talc, forsterite, and the like can be cited. The protective layer can be composed of one or more materials selected from the group consisting of these substances. The protective layer can include a material having electron conductivity (e.g., a metal) as long as the battery element is not short-circuited. In the case where the protective layer includes a material having electron conductivity, the content ratio of the electron conductivity material can be, for example, 1% by volume or less. By including an electron conductivity material (e.g., a metal) in the protective layer, heat generated due to a battery reaction can be smoothly released to the outside.

[0267] The protective layer is preferably composed of a sintered body including the above-described insulating substance particles. The sintered body that constitutes the protective layer has pores between the insulating substance particles, but has a degree of density that can inhibit adsorption, absorption, and permeation of moisture and gas (carbon dioxide) in the thickness direction (e.g., the stacking direction L).

[0268] The protective layer can contain a resin such as a high molecular compound, and for example, a high molecular compound used at the time of production and / or a thermal decomposition product thereof can remain. The content of the high molecular compound and the thermal decomposition product thereof and the like as a residue in the protective layer is usually 0.1% by mass or less, and particularly preferably 0.01% by mass or less, relative to the total amount of the protective layer. Note that, in the positive electrode layer, the positive electrode current collector layer, the positive electrode current collecting portion, the negative electrode layer, the negative electrode current collector layer, the negative electrode current collecting portion, the solid electrolyte layer, and the electrode separation portion described later, a residue can also remain as in the protective layer. For example, the content of the residue in each layer or each portion of the positive electrode layer, the positive electrode current collector layer, the positive electrode current collecting portion, the negative electrode layer, the negative electrode current collector layer, the negative electrode current collecting portion, the solid electrolyte layer, and the electrode separation portion can be in the same range as the content of the residue in the protective layer.

[0269] The porosity of the protective layer can be, for example, 0.1% by volume or more and 20% by volume or less, and particularly preferably 1% by volume or more and 10% by volume or less. The porosity is a value measured by a gravimetric porosimetry method, a computed tomography method using CT scanning, an immersion method, or the like.

[0270] The oxygen permeability in the thickness direction of the protective layer can be, for example, 10 -1 cc / m 2 / day / atmospheric pressure or less, and particularly preferably 10 -3 cc / m 2 / day / atmospheric pressure or less.

[0271] The H2O permeability in the thickness direction of the protective layer can be, for example, 10 -2 g / m 2 / day or less, and particularly preferably 10 -4 g / m 2 / day or less. The H2O permeability is a value measured by a carrier gas method, a pressurization method, a Ca corrosion method at 25°C.

[0272] The protective layer can contain, in addition to the insulating substance, for example, a sintering aid or the like. The protective layer preferably further contains a sintering aid. As the sintering aid in the protective layer, the same compound as the sintering aid in the negative electrode layer can be used.

[0273] From the viewpoint of further suppressing a decrease in battery performance, the thickness of the thickest portion of the protective layer is preferably 500 μm or less, more preferably 100 μm or less, still more preferably 50 μm or less, and most preferably 20 μm or less. From the viewpoint of further suppressing a decrease in battery performance due to adsorption, absorption, and permeation of moisture and gas (carbon dioxide), the average thickness of the protective layer is preferably 1 μm or more, and more preferably 5 μm or more.

[0274] The thickness of the thickest portion of the protective layer and the average thickness are the maximum thickness and the average thickness of the thicknesses of 100 arbitrary points, respectively.

[0275] The protective layer covers the upper and lower surfaces of the solid-state battery. The protective layer can be in direct contact with the upper and lower surfaces of the battery element covered by the protective layer as shown in Figure 1A and Figure 1B The protective layer can also be in indirect contact via a layer other than the layer constituting the battery element. The protective layer being in direct contact with the upper and lower surfaces of the battery element means that a layer other than the layer constituting the battery element is not interposed between the protective layer and the battery element, and the surface of the protective layer is in direct contact with the surface of the battery element.

[0276] The protective layer preferably forms an integral sintering of the upper and lower surfaces of the battery element covered by the protective layer and the sintered body with each other. The protective layer and the upper and lower surfaces of the battery element covered by the protective layer forming an integral sintering of the sintered bodies with each other means that the protective layer and the upper and lower surfaces of the battery element covered by the protective layer are joined by sintering. In detail, the protective layer and the upper and lower surfaces of the battery element covered by the protective layer are both sintered bodies, and are sintered integrally. For example, the protective layer and the battery element preferably adopt an integral sintering structure. Note that it is not necessary for the protective layer and the upper and lower surfaces of the battery element covered by the protective layer to be integrally sintered throughout, and a portion thereof can not be integrally sintered. It is sufficient that the protective layer and the upper and lower surfaces of the battery element covered by the protective layer are integrally sintered as a whole.

[0277] The upper and lower surfaces of the battery element covered by the protective layer are usually the surfaces of the outermost layer of the battery element. The outermost layer of the battery element means the uppermost layer disposed at the highest position and the lowermost layer disposed at the lowest position among the layers constituting the battery element. The surfaces of the outermost layer are the upper surface of the uppermost layer and the lower surface of the lowermost layer.

[0278] [Electrode separation portion]

[0279] The solid-state battery of the present application usually also has an electrode separation portion (also referred to as a "margin layer" or a "margin portion") 15, 25.

[0280] The electrode separation portion 15 (i.e., the positive electrode separation portion) is disposed around the positive electrode layer 1, thereby separating the positive electrode layer 1 from the negative electrode terminal 20. The electrode separation portion 25 (i.e., the negative electrode separation portion) is also disposed around the negative electrode layer 2, thereby separating the negative electrode layer 2 from the positive electrode terminal 10.

[0281] The electrode separation portions 15, 25 are preferably composed of, for example, one or more materials selected from the group consisting of solid electrolytes, insulating substances, and mixtures thereof.

[0282] The solid electrolyte that can constitute the electrode separation portions 15, 25 can use the same material as the solid electrolyte that can constitute the solid electrolyte layer.

[0283] The insulating substance that can constitute the electrode separation portions 15, 25 can use the same material as the insulating substance that can constitute the protective layer.

[0284] The electrode separation portion preferably further contains a sintering aid. As the sintering aid in the electrode separation portion, the same compound as the sintering aid in the negative electrode layer can be used.

[0285] [Electrode terminal]

[0286] The solid-state battery of the present application has electrode terminals 10, 20 that are electrically connected to the positive electrode layer or the negative electrode layer on two opposing sides, respectively. The electrode terminal electrically connected to the positive electrode layer is referred to as a positive electrode terminal, and the electrode terminal electrically connected to the negative electrode layer is referred to as a negative electrode terminal 20. In addition, the electrode terminal is a component also referred to as an end face electrode. The solid-state battery of the present application has electrode terminals 10, 20 that are parallel to each other and also parallel to the stacking direction L. The electrode terminal preferably contains an electrically conductive material having a large electrical conductivity. As a specific material for constituting the electrode terminal, there is no particular limitation, but from the viewpoint of electrical conductivity, for example, at least one electrically conductive metal (i.e., a metal or an alloy) selected from the group consisting of gold, silver, copper, platinum, tin, palladium, aluminum, titanium, nickel, oxygen-free copper, a Cu-Sn alloy, a Cu-Zr alloy, a Cu-Fe alloy, a Cu-Cr-Sn-Zn alloy, a 42 alloy (a Ni-Fe alloy, a Kovar iron-nickel-cobalt alloy) can be listed.

[0287] The thickness of the electrode terminals 10, 20 is not particularly limited, and can be, for example, 1 μm or more and 1 mm or less, particularly 10 μm or more and 100 μm or less.

[0288] <Method for manufacturing a solid-state battery>

[0289] The solid-state battery can be manufactured, for example, by a so-called green sheet method, a printing method, or a method combining these methods.

[0290] The green sheet method will be described.

[0291] First, a paste is prepared by appropriately mixing a solvent, a resin, and the like in the positive electrode active material. By applying the paste on a sheet and drying it, a green sheet for constituting the positive electrode layer is formed. The positive electrode layer green sheet can also contain a solid electrolyte, an electrically conductive aid, and / or a sintering aid, and the like. The electrically conductive aid of the positive electrode layer can also contain a covering-type electrically conductive aid.

[0292] A paste is prepared by appropriately mixing a solvent, a resin, and the like in the negative electrode active material. A green sheet for constituting the negative electrode layer is formed by coating the paste on a sheet and drying it. A solid electrolyte, a conductive aid, and / or a sintering aid, and the like can also be contained in the negative electrode layer green sheet. The conductive aid of the negative electrode layer can contain a covering-type conductive aid.

[0293] A paste is prepared by appropriately mixing a solvent, a resin, and the like in the solid electrolyte. A green sheet for constituting the solid electrolyte layer is formed by coating the paste and drying it. A sintering aid, and the like can also be contained in the solid electrolyte layer green sheet.

[0294] A paste is prepared by appropriately mixing a solvent, a resin, and the like in the insulating substance. A green sheet for constituting the protective layer is formed by coating the paste and drying it. A sintering aid, and the like can also be contained in the protective layer green sheet.

[0295] A paste is prepared by appropriately mixing a solvent, a resin, and the like in the solid electrolyte and / or the insulating substance. A green sheet for constituting the electrode separation portion is formed by coating the paste and drying it. A sintering aid, and the like can also be contained in the electrode separation portion green sheet.

[0296] An electrode terminal paste is prepared by appropriately mixing a solvent, a resin, and the like in the conductive material.

[0297] Next, a laminate is produced by appropriately layering the green sheets obtained by the above method. The produced laminate can be subjected to pressing. As a preferred pressing method, isopressing and the like can be cited.

[0298] Then, the electrode terminal paste is coated on a prescribed arrangement in the laminate, and sintering at, for example, 600 to 800°C is performed, and a solid-state battery can be obtained.

[0299] The printing method is described.

[0300] The printing method is the same as the green sheet method except for the following matters.

[0301] • In addition to making the mixed amount of the solvent and the resin a mixed amount suitable for use as an ink, an ink of each layer having the same composition as the paste used to obtain each layer of the green sheet is prepared.

[0302] • Printing and layering are performed using the ink of each layer, and a laminate is produced.

[0303] Hereinafter, the present application is described in more detail based on specific examples, but the present application is not limited to any of the following examples, and can be appropriately changed and implemented within a range not changing the gist thereof.

[0304] Example

[0305] [Manufacture of materials]

[0306] In the following (1) to (3), a positive electrode active material, a negative electrode active material, a solid electrolyte, and a sintering aid for manufacturing a positive electrode layer and a negative electrode layer were manufactured; and a first and a second solid electrolyte and a sintering aid for manufacturing a solid electrolyte layer were manufactured so as to have the compositions described later.

[0307] (1) Manufacture of garnet-type solid electrolyte powder (solid electrolyte powder for negative electrode layer and second solid electrolyte powder for solid electrolyte layer)

[0308] The garnet-type solid electrolyte powder used in the following examples and comparative examples was manufactured as follows.

[0309] As raw materials, lithium hydroxide monohydrate LiOH-H20, lanthanum hydroxide La(OH)3, zirconium oxide Zr02, gallium oxide Ga203, aluminum oxide Al203, niobium oxide Nb205, tantalum oxide Ta205, and molybdenum oxide M0O3 were used.

[0310] Each raw material was weighed so as to have a chemical composition of a predetermined chemical composition, water was added, and the raw materials were mixed by being enclosed in a 100-ml polyethylene tank and being rotated at 150 rpm on a tank stand for 16 hours. In addition, in consideration of Li deficiency at the time of sintering, lithium hydroxide monohydrate LiOH-H20 as a Li source was added in an amount exceeding the target composition by 3 wt%.

[0311] After the obtained slurry was evaporated and dried, pre-sintering was performed at 900°C for 5 hours, whereby the target phase was obtained.

[0312] A toluene-acetone mixed solvent was added to the obtained pre-sintered powder, and the powder was pulverized for 6 hours using a planetary ball mill.

[0313] The pulverized powder was dried to produce a solid electrolyte powder. The above powder was measured by ICP, and it was confirmed that there was no composition deviation.

[0314] (2) Manufacture of positive electrode active material powder, negative electrode active material powder, and LISICON-type solid electrolyte powder (first solid electrolyte powder for solid electrolyte layer)

[0315] The positive electrode active material powder, the negative electrode active material powder, and the first solid electrolyte powder used in the following examples and comparative examples were manufactured as follows.

[0316] As raw materials, lithium hydroxide monohydrate LiOH-H20, vanadium pentoxide V205, and silicon (Si) were used.

[0317] Each raw material was weighed appropriately so that the chemical composition became the prescribed chemical composition, water was added, and the raw materials were mixed in a 100-ml polyethylene tank, which was rotated at 150 rpm on a tank stand for 16 hours.

[0318] The obtained slurry was evaporated and dried, and then pre-fired at 800°C for 5 hours in air.

[0319] To the obtained pre-fired powder, alcohol was added, and the powder was again mixed in a 100-ml polyethylene tank, which was rotated at 150 rpm on a tank stand for 16 hours, and then pulverized.

[0320] The pulverized powder was again subjected to main firing at 900°C for 5 hours.

[0321] Then, to the obtained main fired powder, a mixed solvent of toluene-acetone was added, and the powder was pulverized for 6 hours using a planetary ball mill, and then dried, to obtain a negative electrode active material powder and a first solid electrolyte powder. The powder was measured by ICP, and no deviation in composition was confirmed.

[0322] (3) Production of sintering aid powder

[0323] The sintering aid powder used in the examples and comparative examples was produced as follows.

[0324] As raw materials, lithium hydroxide monohydrate (LiOH-H2O), boron oxide (B2O3), and aluminum oxide (Al2O3) were used.

[0325] Each raw material was weighed appropriately so that the chemical composition became the prescribed chemical composition, and then mixed in a mortar at 650°C for 5 hours.

[0326] Then, the pre-fired powder was again pulverized in the mortar, mixed, and then subjected to main firing at 680°C for 40 hours.

[0327] To the obtained main fired powder, a mixed solvent of toluene-acetone was added, and the powder was pulverized for 6 hours using a planetary ball mill, and then dried, to obtain a sintering aid powder. The powder was measured by ICP, and no deviation in composition was confirmed.

[0328] (4) Production of conductive aid

[0329] • Conductive aid Al (uncoated Ag powder)

[0330] As the conductive aid Al, spherical Ag powder (average primary particle diameter 0.8 μm, manufactured by Showa Denko K.K.) was used.

[0331] • Conductive aids Bl to B5 (particulate layer-coated Ag powder)

[0332] As a method of supporting the covering material on the conductive aid, powder barrel sputtering was used. Using a prescribed covering material (Li2ZrO3) as a target, the conductive aid particles Al as a core material were covered. In addition, by varying the sputtering time, conductive aid particles in which the particle diameter (thickness) and the covering amount of the covering material were varied were obtained. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material / Ag particles. Note that by lowering the sputtering rate, a film-shaped covering material can be obtained.

[0333] • Conductive aid Cl (granular layer-covered Ag powder)

[0334] By subjecting spherical Ag powder (average primary particle diameter 2 μm, manufactured by Showa Denko K.K.) to bead mill treatment, flat Ag powder having an aspect ratio (a / b) of 4.5 and a b value of 0.9 μm was obtained.

[0335] Except that flat Ag powder was used as the core material, granular layer-covered Ag powder in which a granular Li2ZrO3 layer was covered on the surface of the flat Ag powder was obtained by the same method as that of the conductive aid Bl. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material / Ag particles.

[0336] • Conductive aid Dl (granular layer-covered Ag powder)

[0337] Except that Li2SiO3 was used as the covering material (target), granular layer-covered Ag powder in which a granular Li2SiO3 layer was covered on the surface of the spherical Ag powder was obtained by the same method as that of the conductive aid Bl. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material / Ag particles and a prescribed average thickness of the covering material.

[0338] • Conductive aid El (granular layer-covered Ag powder)

[0339] Except that Li2TiO3 was used as the covering material (target), granular layer-covered Ag powder in which a granular Li2TiO3 layer was covered on the surface of the spherical Ag powder was obtained by the same method as that of the conductive aid Bl. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material / Ag particles and a prescribed average thickness of the covering material.

[0340] • Conductive aid Fl (granular layer-covered Ag powder)

[0341] Except that CuO was used as the covering material (target), granular layer-covered Ag powder in which a granular CuO layer was covered on the surface of the spherical Ag powder was obtained by the same method as in the conductive aid B1. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material to the Ag particles and a prescribed average thickness of the covering material.

[0342] • Conductive aid G1 (granular layer-covered Cu powder)

[0343] Except that spherical Cu powder was used as the core material, granular layer-covered Cu powder in which a granular Li2ZrO3 layer was covered on the surface of the spherical Cu powder was obtained by the same method as in the conductive aid B1. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material to the Cu particles and a prescribed average thickness of the covering material.

[0344] • Conductive aid H1 (granular layer-covered Ag powder)

[0345] Except that Si3N4 was used as the covering material (target), granular layer-covered Ag powder in which a granular ZrN layer was covered on the surface of the spherical Ag powder was obtained by the same method as in the conductive aid B1. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material to the Ag particles and a prescribed average thickness of the covering material.

[0346] • Conductive aid J1 (granular layer-covered Ag powder)

[0347] Except that WC was used as the covering material (target), granular layer-covered Ag powder in which a granular WC layer was covered on the surface of the spherical Ag powder was obtained by the same method as in the conductive aid B1. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material to the Ag particles and a prescribed average thickness of the covering material.

[0348] • Conductive aids K1 to K2 (film layer-covered Ag powder)

[0349] Except that the sputtering rate was lowered, film layer-covered Ag powder in which a film-like Li2ZrO3 layer was covered on the surface of the spherical Ag powder was obtained by the same method as in the conductive aid B1. The ratio of the core material to the covering material and the sputtering time were adjusted so that the electrode layer obtained in each example had a prescribed area ratio of the covering material to the Ag particles and a prescribed average thickness of the covering material.

[0350] • Conductive aid L1 (film layer-covered Ag powder)

[0351] In addition to using Pd as the capping material (target), a film-like layer of Pd was obtained on the surface of spherical Ag powder using the same method as for conductive additive K1. The ratio of core material to capping material and the sputtering time were adjusted so that the electrode layers obtained in each embodiment had a specified area ratio of capping material to Ag particles and a specified average thickness of capping material.

[0352] • Conductive additive M1 (film-like layer covering Ag powder)

[0353] In addition to using W as the cover material (target), a film-like layer of W was obtained on the surface of spherical Ag powder using the same method as for conductive additive K1. The ratio of core material to cover material and sputtering time were adjusted so that the electrode layers obtained in each embodiment had a specified area ratio of cover material to Ag particles and a specified average thickness of cover material.

[0354] [Example 1]

[0355] (The manufacture of solid-state batteries)

[0356] It was manufactured using the following method. Figure 4A The solid-state battery shown is a solid-state battery for unipolar evaluation.

[0357] • Raw sheet for negative electrode layer

[0358] Weigh Li3VO4(β) as the negative electrode active material. Ⅱ Li3VO4 type), as a solid electrolyte powder 6.5 La3(Zr 1.5 Ta 0.5 )O 12 Garnet-type, conductive additive B2 (i.e., granular Ag powder covering the layer), and Li3BO3 as a sintering aid are mixed with butyral resin, alcohol, and binder to prepare a slurry for the negative electrode layer. The volume ratio of the negative electrode active material, solid electrolyte, conductive additive, and sintering aid is (60-x):35:x:5 (10≤x≤25). In Example 1, x=20.

[0359] The negative electrode layer slurry sheet is formed on a PET film using a doctor blade method, then dried and peeled off to obtain a raw negative electrode layer sheet.

[0360] • Raw sheet for solid electrolyte layer

[0361] Weigh Li as the first solid electrolyte 3.2 (V 0.8 Si 0.2 O4(γ) Ⅱ (type), as the second solid electrolyte (Li)6.4 Ga 0.05 Al 0.15 )La3Zr2O 12 (garnet type) and Li3BO3 as a sintering aid, and mixed with a butyral resin, an alcohol, and a binder to prepare a slurry for a solid electrolyte layer. The volume ratio of the first solid electrolyte, the second solid electrolyte, and the sintering aid powder was 47.5:47.5:5.

[0362] A sheet of the slurry for a solid electrolyte layer was formed on a PET film using a doctor blade method, dried, and peeled to obtain a sheet for a solid electrolyte layer.

[0363] Next, the green sheet for a negative electrode layer and the green sheet for a solid electrolyte layer were stacked on each other, and a laminate was obtained by pressure bonding.

[0364] The laminate was cut into a square shape (plan view shape) having a plan view size of 10 mm x 10 mm. Then, as shown in FIG. 1, an Ag paste coating layer for a negative electrode current collector layer 21 was formed on the side of the green sheet for a negative electrode layer opposite to the green sheet for a solid electrolyte layer. The obtained laminate was sandwiched with two porous holding plates, and sintering was performed at 750°C after removing the binder at 400°C. Note that, in order to suppress oxidation reaction of the covering material, sintering was performed in a N2 / H2 mixed atmosphere. Figure 4A

[0365] Then, Li metal 50 was attached to the side of the solid electrolyte layer opposite to the negative electrode layer as a counter electrode and a reference electrode, and WIP (Warm Isostatic Pressing) treatment was performed at 60°C and 200 MPa, whereby a solid-state battery was manufactured. Then, the solid-state battery was sealed with a 2032 type coin cell, and evaluation was performed.

[0366] The thickness of the solid electrolyte layer 3, the negative electrode layer 2, and the negative electrode current collector layer 21 was confirmed using a scanning electron microscope, and the results were 100 μm, 15 μm, and 5 μm, respectively. The porosity of the solid electrolyte layer and the negative electrode layer was 10% or less, and it was confirmed that sintering was sufficiently performed.

[0367] Such a solid-state battery has a main surface current collecting structure, and as shown in FIG. 1, current is collected from the electrode layer in the arrow direction. In the solid-state battery of the present embodiment, the electron diffusion path in the negative electrode layer 2 is 15 μm. Figure 4A Figure 4A

[0368] In addition, the plan view size (size in the X and Y directions) after sintering was 8 mm x 8 mm. The solid-state battery of the present embodiment shrinks as the voids decrease through the sintering process.

[0369] ​​​(Measurement and evaluation)

[0370] • Area ratio of conductive aid (core material)

[0371] SEM images (photographs) showing the laminated structure (cross-sectional structure) of the solid-state battery were taken by the image analysis software "Azokun" (manufactured by Asahi Chemical Industry Co., Ltd.). The cross section of the solid-state battery for which the SEM image was taken was a cross section parallel to the laminated direction L of the positive electrode layer (in the present example, the counter electrode and reference electrode), the solid electrolyte layer, and the negative electrode layer, and perpendicular to the positive electrode terminal and the negative electrode terminal, and was a cross section passing through the center of gravity of the solid-state battery in the plan view. The center of gravity of the solid-state battery in the plan view refers to the point at which the solid-state battery (plan view) is supported in balance when an equivalent material (for example, paper) is cut out along the outline of the solid-state battery and supported at the point. The area ratio of the conductive aid identified in the negative electrode layer of the SEM image was calculated. The area ratio was an average of values measured at 10 arbitrary points, and was the ratio of the area of the conductive aid (core material) to the total area of each field of view.

[0372] • Area ratio of covering material / core material (Ag particles or Cu particles)

[0373] The area of the covering material and the core material identified in the negative electrode layer of the TEM image taken by the measurement method of the area ratio of the conductive aid was calculated to obtain the area ratio thereof. In detail, the area ratio of the covering material / core material was an average of values measured at 10 arbitrary points, and was calculated as the area ratio with respect to the core material (Ag particles or Cu particles) of the conductive aid in the negative electrode layer.

[0374] • Average thickness of covering material

[0375] The average of the thickness of the covering material identified in the negative electrode layer of the TEM image taken by the measurement method of the area ratio of the conductive aid was calculated. In detail, the thickness of the covering material was calculated as an average of values measured at 100 arbitrary points.

[0376] • Utilization rate of negative electrode active material

[0377] For the solid-state battery, the electric quantity was measured at a current density corresponding to 0.05 C in the voltage range 0.2 V to 3.0 V (vs. Li / Li+) by the constant current charge-discharge test, and the reversible capacity was calculated.

[0378] The initial reversible capacity was calculated by dividing the initial reversible electric quantity obtained by the constant current charge-discharge test by the weight of the negative electrode active material. In addition, the capacity when V (vanadium) in the negative electrode active material undergoes 2-electron reaction was taken as the theoretical capacity, and the above initial reversible capacity was divided by the theoretical capacity, whereby the utilization rate R was calculated.

[0379] ◎: 90% < R < 100% (best);

[0380] O: 80% < R < 90% (good);

[0381] Δ: 70% < R < 80% (fair) (there is no problem in practical use);

[0382] X: R < 70% (poor) (there is a problem in practical use).

[0383] [Examples 2-3]

[0384] Except for changing the content of the coated conductive aid, the manufacture, measurement, and evaluation of the solid batteries were performed by the same method as Example 1.

[0385] [Comparative Examples 1-2]

[0386] Except for using the conductive aid Al (uncoated conductive aid, spherical Ag powder, average primary particle diameter 0.8 μm, manufactured by Showa Denko K.K.) instead of the coated conductive aid, and changing the content of the conductive aid Al, the manufacture, measurement, and evaluation of the solid batteries were performed by the same method as Example 1.

[0387] [Table 4]

[0388]

[0389] Comparative Examples 1-2 relate to solid batteries manufactured using an uncoated conductive aid and changing the content of the uncoated conductive aid.

[0390] From Comparative Examples 1-2, it was found that by containing the uncoated conductive aid and reducing the content thereof, the utilization rate of the active material was significantly reduced. It is considered that this is because the uncoated conductive aid is integrated and spheroidized during firing, resulting in a discontinuation of the conductive path and a failure to supply electrons, and there is active material that does not contribute to charge and discharge.

[0391] Examples 1-3 relate to solid batteries manufactured using a coated conductive aid subjected to coating with a high-melting-point material, and changing the content of the coated conductive aid.

[0392] From Examples 1-3, it was found that by containing the coated conductive aid subjected to coating with a high-melting-point material as the conductive aid, even if the content of the conductive aid is reduced, the reversible capacity can be maintained at a high level. It is considered that this is because, by using the coated conductive aid, integration and spheroidization during firing can be suppressed, and therefore, even if the content is the same, the conductive paths in the negative electrode layer are easily connected compared to the uncoated conductive aid.

[0393] In addition, when the area ratio of the electrically conductive aid as the core material is reduced, the reversible capacity is found to decrease. From this, it is understood that even in the case of containing the covering electrically conductive aid, there is a preferable content range in which a higher utilization rate can be achieved.

[0394] In the solid-state battery obtained in Comparative Example 2, the average aspect ratio (a / b) of the core material (electrically conductive aid) was 1.1, and the average short side length b was 3.1 μm.

[0395] In the solid-state battery obtained in Example 2, the average aspect ratio (a / b) of the core material (electrically conductive aid) was 1.8, and the average short side length b was 1.2 μm.

[0396] From the comparison between Comparative Example 2 and Example 2, it is understood that by using the covering electrically conductive aid, the average aspect ratio of the core material increases, and the average short side length decreases. It is considered that this is because, by using the covering electrically conductive aid, the integration and spheroidization of the core particles at the time of sintering are suppressed. It is considered that, by thus suppressing the integration and spheroidization of the core particles at the time of sintering, the connectivity of the electrically conductive aid in the electrode layer improves, and the contact area with the active material increases, and the utilization rate improves.

[0397] [Examples 4 to 7]

[0398] Except for changing the kind and content of the covering electrically conductive aid, the production, measurement, and evaluation of the solid-state battery were performed by the same method as in Example 1.

[0399] [Table 5]

[0400]

[0401] Examples 4 to 7 relate to solid-state batteries produced by changing the covering amount of the high-melting-point material.

[0402] From Examples 4 to 7, it is understood that when the area ratio (%) of the covering material / core material (electrically conductive aid) is 0.8% or more and 8% or less (particularly 0.8% or more and 4% or less), the utilization rate is higher, and is more preferable.

[0403] It is considered that this is due to the following phenomena:

[0404] • When the content of the covering electrically conductive aid is small, the effect of suppressing the integration and spheroidization at the time of sintering becomes weak;

[0405] • If the content is too much, although the suppressing effect of the integration and spheroidization is exhibited, the covering particles hinder the movement of electric charges between the active material and the electrically conductive aid.

[0406] [Examples 8 to 10]

[0407] Except for changing the type and content of the conductive additives used, the solid-state battery was manufactured, measured, and evaluated using the same method as in Example 1.

[0408] In the solid-state battery obtained in Example 10, the average aspect ratio (a / b) of the core material (conductive additive) was 4.3, and the average short side length b was 1.2 μm.

[0409] [Table 6]

[0410]

[0411] Examples 2, 8-10 relate to solid-state batteries fabricated by altering the shape of the core material (conductive additive) and the morphology and average thickness of the covering material.

[0412] As can be seen from Examples 8 and 9, even when the covering material is in the form of a film, a high level of effectiveness can be achieved. It is clear that when the covering material is in the form of a film, reducing the thickness of the covering material improves the utilization rate of the active substance, which is preferable.

[0413] A comparison of Examples 2 and 10 shows that using a flat conductive additive improves the utilization rate of the active material, which is preferable. This can be attributed to the fact that a flat shape makes it easier to form conductive paths compared to a spherical shape.

[0414] [Examples 11-18]

[0415] Except for changing the type and content of the conductive additives used, the solid-state battery was manufactured, measured, and evaluated using the same method as in Example 1.

[0416] In Example 13 only, sintering was carried out in the atmosphere.

[0417] [Example 19]

[0418] Except for the use of an end-face current collection structure that does not form a negative electrode current collector layer and forms a negative electrode layer that is in contact with the negative electrode current collector while being electrically connected to the negative terminal via the negative electrode current collector, the solid-state battery was manufactured, measured and evaluated using the same method as in Example 1.

[0419] The resulting solid-state battery has Figure 4B The cross-sectional structure shown.

[0420] In detail, such as Figure 4B As shown, in addition to forming an Ag paste coating layer for the negative electrode current collector 210 on the end face of the green sheet in the negative electrode layer, by interacting with... Figure 4A The same method used to manufacture solid-state batteries was used to manufacture... Figure 4B Solid-state batteries.

[0421] Such a solid battery has a face collecting structure, as shown in Figure 4B electrons are collected from the electrode layer in the arrow direction. In Figure 4B In the solid battery of Example 1, the electron diffusion path in the negative electrode layer 2 was 15 μm.

[0422] In addition, the planar dimension (dimension in the X and Y directions) after sintering was measured, and the result was 8 mm x 8 mm. The solid battery of this example was shrunk with the reduction of voids by the sintering process.

[0423] [Table 7]

[0424]

[0425] Examples 11 to 18 relate to solid batteries produced by changing the composition of the conductive aid (core material) and the covering material.

[0426] As is apparent from Table 7, even if the composition of the covering material is changed in various ways, a high utilization rate can be obtained.

[0427] As is apparent from Examples 14 and 16 to 18, the use of a metal material, metal nitride, or metal carbide as the covering material also gives a result, but the use of an oxide as the covering material gives a higher utilization rate. It is considered that this is because the effect of improving the wettability between the active material and the conductive aid is higher when an oxide is used as the covering material.

[0428] As is apparent from the comparison of Examples 2, 11 to 15, the use of a covering material containing the elements Zr, Cu, and Pb, which are difficult to substitute for V contained in the active material, gives a particularly high effect.

[0429] As is apparent from Example 15, even in the case where Cu is used as the conductive aid, the use of a covering material gives a high utilization rate, as in the case where Ag is used.

[0430] [Example 20 and Comparative Example 3]

[0431] Except that the kind and content of the covering conductive aid were changed, and Li 1.1 V 0.9 The production, measurement, and evaluation of the solid battery were performed by the same method as in Example 1, except that the kind and content of the covering conductive aid were changed, and Li

[0432] [Table 8]

[0433]

[0434] Example 20 and Comparative Example 3 relate to solid batteries in which the composition of the electrode active material was changed.

[0435] As is apparent from Table 8, in the case where the active material having a Li / V ratio of 3 was used, the effect of coverage by the high-melting-point material was particularly obtained, as compared with the case where the active material having a Li / V ratio of 1.2 was used. It is considered that this is because the active material having a Li / V ratio of 3 has a particularly low wettability with the metal conductive aid, has a property of easily being integrated and spheroidized, and easily obtains the effect of suppressing spheroidization by coverage with the oxide.

[0436] Industrial applicability

[0437] The solid-state battery according to one embodiment of the present application can be applied to various fields in which use of a battery or electric power storage is assumed. Although only examples are illustrated, the solid-state battery according to one embodiment of the present application can be applied to the field of electronic mounting. The solid-state battery according to one embodiment of the present application can also be applied to the field of electrical / information / communication using mobile devices and the like (for example, the field of electrical / electronic devices or the field of mobile devices including mobile phones, smartphones, smartwatches, notebook computers, digital cameras, activity meters, arm computers, electronic paper, wearable devices, RFID tags, card-type electronic money, smartwatches, and the like); the field of household / small industrial use (for example, the field of electric power tools, golf carts, household / attendant / industrial robots); the field of large industrial use (for example, the field of forklifts, elevators, port cranes); the field of transportation systems (for example, the field of hybrid cars, electric cars, buses, electric trains, electric power-assisted bicycles, electric motorcycles, and the like); the field of electric power systems (for example, the field of various power generation, load regulators, smart grids, household stationary power storage systems, and the like); the field of medical use (for example, the field of medical devices such as earphones and hearing aids); the field of pharmaceutical use (for example, the field of medication management systems); the field of IoT; the field of space / deep sea use (for example, the field of space probes, submersible survey vessels, and the like); and the like.

[0438] Explanation of reference numerals

[0439] 200: covering conductive aid

[0440] 201: conductive aid (core material)

[0441] 202: covering material.

Claims

1. A solid-state battery, comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The electrode layer of at least one of the positive or negative electrode layers contains a conductive additive made of a metallic material. The conductive additive is covered in the electrode layer by a covering material with a higher melting point than the conductive additive. The covering material is a metal oxide, metal nitride, or metal carbide, or the covering material is a metallic material. The electrode layer also includes electrode active materials and solid electrolyte. The covering material is a material different from the electrode active material and the solid electrolyte. The covering material contains elements that are not dissolved in the electrode active material, and contains elements that are not replaced by the elements constituting the electrode active material or are difficult to replace by the elements constituting the electrode active material.

2. A solid-state battery, comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The electrode layer of at least one of the positive or negative electrode layers contains a conductive additive made of a metallic material. The conductive additive is covered in the electrode layer by a covering material with a higher melting point than the conductive additive. The covering material comprises at least one of the following materials: metal oxides comprising Li2ZrO3, Li2SiO3, Li2TiO3, LiAlO2, CuO, Al2O3, and ZrO2; metal nitrides comprising ZrN and Si3N4; metal carbides comprising WC and TaC; metallic materials comprising Pd, W, and Cu; and covering materials comprising one or more elements selected from Zr, Cu, and Pd.

3. A solid-state battery, comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The electrode layer of at least one of the positive or negative electrode layers contains a conductive additive made of a metallic material. The conductive additive is covered in the electrode layer by a covering material with a higher melting point than the conductive additive. The covering material is a metal oxide, metal nitride, or metal carbide, or the covering material is a metallic material. The conductive additive content is such that, in a cross-sectional view of the electrode layer, the conductive additive accounts for 18% or more and 28% or less of the area of ​​the electrode layer.

4. The solid-state battery according to any one of claims 1 to 3, wherein, The covering material forms a covering layer around the conductive additive. The covering layer has a granular or film-like morphology.

5. The solid-state battery according to any one of claims 1 to 3, wherein, The covering material is disposed around and in contact with the conductive additive, and has a size of less than 500 nm. The dimension is the maximum length in the direction perpendicular to the surface of the conductive additive that is in contact with the covering material.

6. The solid-state battery according to any one of claims 1 to 3, wherein, The area ratio of the covering material is more than 0.1% and less than 15% relative to the conductive additive.

7. The solid-state battery according to any one of claims 1 to 3, wherein, The conductive additive is composed of one or more metallic materials selected from the group consisting of silver (Ag), gold (Au), palladium (Pd), platinum (Pt), copper (Cu), tin (Sn), nickel (Ni), and their alloys.

8. The solid-state battery according to any one of claims 1 to 3, wherein, The conductive additive is an elongated conductive additive, a spherical conductive additive, or a mixture thereof.

9. The solid-state battery according to any one of claims 1 to 3, wherein, The conductive additive is an elongated conductive additive with an average short side thickness of 0.1 μm or more and 4.0 μm or less.

10. The solid-state battery according to any one of claims 1 to 3, wherein, The electrode layer has an end face current collection structure that contacts the electrode current collection part at its end face and is electrically connected to the electrode terminal via the electrode current collection part.

11. The solid-state battery according to claim 10, wherein, The electrode current collector has an upper surface that is flush with the upper surface of the electrode layer and a lower surface that is flush with the lower surface of the electrode layer in the stacking direction of the positive electrode layer, the solid electrolyte layer and the negative electrode layer.

12. The solid-state battery according to any one of claims 1 to 3, wherein, The electrode layer is a negative electrode layer. The negative electrode layer contains a negative electrode active material in which the molar ratio of Li to vanadium V is 2.0 or higher.

13. The solid-state battery according to claim 12, wherein, The negative electrode active material has an average chemical composition represented by the following general formula (1), In formula (1), A is one or more elements selected from the group consisting of Na, K, Mg, Ca and Zn; B is one or more elements selected from the group consisting of Zn, Al, Ga, Si, Ge, Sn, P, As, Ti, Mo, W, Fe, Cr and Co; 0≤x≤1.0; 0.5≤y≤1.0; a is the average valence of A; b is the average valence of B.

14. The solid-state battery according to claim 12, wherein, The negative electrode active material has β Ⅱ -Li3VO4 type crystal structure or γ Ⅱ -Li3VO4 type crystal structure.

15. The solid-state battery according to claim 12, wherein, The negative electrode layer has a thickness of more than 2 μm and less than 50 μm.

16. The solid-state battery according to claim 12, wherein, At least one of the negative electrode layer or the solid electrolyte layer further comprises a sintering aid. The sintering aid is a compound having the following chemical composition: containing Li, B and O, and the molar ratio of Li to B, Li / B, is 2.0 or higher.

17. The solid-state battery according to any one of claims 1 to 3, wherein, The positive electrode layer and the negative electrode layer are layers capable of inserting and de-inserting lithium ions.

18. The solid-state battery according to any one of claims 1 to 3, wherein, The solid electrolyte layer, the positive electrode layer, and the negative electrode layer are sintered together as a single sintered body.

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