Solid-state battery and method for manufacturing the same

Abstract

The present invention realizes a solid-state battery having excellent strength.　A solid-state battery (1) comprises a solid-state battery body (10) and a coating film (20). The solid-state battery body (10) includes: an electrolyte layer (13) containing a solid electrolyte; a positive electrode layer (11) that is provided to a portion of one primary surface (13a) of the electrolyte layer (13); and a negative electrode layer (12) that is provided to a portion of the other primary surface (13b) on the side opposite to the primary surface (13a) of the electrolyte layer (13). The coating film (20) has insulative properties, and covers the solid-state battery body (10) so that an area (11a) of the positive electrode layer (11) and an area (12a) of the negative electrode layer (12) are exposed. By using a film, as the coating film (20) having a higher hardness than that of the solid electrolyte included in the solid-state battery body (10), the strength of the solid-state battery (1) can be increased, and cracks or chips, as well as performance degradation caused by penetration of moisture, etc. due to such cracks or chips, can be suppressed.

Description

[Technical Field]

[0001] The present invention relates to a solid-state battery and a method for manufacturing a solid-state battery. [Background technology]

[0002] Solid-state batteries using a solid electrolyte instead of an electrolytic solution are known. Regarding solid-state batteries, a technology is known in which the surface of a battery element, in which a solid electrolyte layer is provided between opposing positive and negative electrode layers, is covered with a protective layer containing a polymer compound. Furthermore, a technology is known in which the surface of the battery element is covered with a protective layer made of an insulating material other than resin, which is less susceptible to cracking and shedding due to moisture and gas adsorption than a protective layer containing a polymer compound, has high bonding strength with the battery element, and is less susceptible to shedding due to vibration, impact, etc., and a technology is known in which glass or ceramics is used as such an insulating material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO2020 / 054544 Brochure [Patent Document 2] International Publication No. WO2020 / 054549 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] A solid-state battery is known in which a solid-state battery body having an electrolyte layer and a cathode layer and an anode layer partially provided on each of its main surfaces is covered with a protective layer using a solid electrolyte. However, such a solid-state battery using a solid electrolyte as a protective layer may not have sufficient strength depending on the mounting and usage environment. Insufficient strength of the solid-state battery may lead to cracks or chips in the protective layer, which may cause moisture or gas to enter the solid-state battery, thereby degrading the performance of the solid-state battery.

[0005] In one aspect, the present invention aims to realize a solid-state battery having excellent strength. [Means for solving the problem]

[0006] In one embodiment, an electrolyte layer including a solid electrolyte and a conductive film provided on a part of a first main surface of the electrolyte layer. It is not provided on the other part of the first main surface except for the part. a positive electrode layer and a second main surface of the electrolyte layer opposite to the first main surface; It is not provided on the other part of the second main surface except for the part. and an insulating coating film that covers the laminate so that a first portion of the positive electrode layer and a second portion of the negative electrode layer are exposed, and that has a higher hardness than the solid electrolyte.

[0007] In one embodiment, a method for producing the above solid-state battery is provided. [Effects of the Invention]

[0008] In one aspect, it becomes possible to realize a solid-state battery with excellent strength. The objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a solid-state battery. [Figure 2] FIG. 1 is a diagram (part 1) illustrating an example of the configuration of a solid-state battery. [Figure 3] FIG. 2 is a diagram (part 2) illustrating an example of the configuration of a solid-state battery. [Figure 4] 1A and 1B are diagrams illustrating an example of a coating film of a solid-state battery. [Figure 5] FIG. 10 is a diagram (part 1) illustrating an example of a process for forming a positive electrode layer part. [Figure 6] FIG. 10 is a diagram (part 2) illustrating an example of a process for forming a positive electrode layer part. [Figure 7]FIG. 10 is a diagram (part 1) illustrating an example of a process for forming a negative electrode layer part. [Figure 8] FIG. 10 is a diagram (part 2) illustrating an example of a process for forming a negative electrode layer part. [Figure 9] 1A to 1C are diagrams illustrating an example of a process for forming a structure. [Figure 10] 10A to 10C are diagrams (part 1) for explaining another example of the process for forming a structure. [Figure 11] FIG. 10 is a diagram (part 2) for explaining another example of the process for forming a structure. [Figure 12] 10A to 10C are diagrams illustrating an example of a cutting process for a structure. [Figure 13] 1A to 1C are diagrams illustrating an example of a heat treatment process for a structure. [Figure 14] 10A and 10B are diagrams (part 1) for explaining another example of the method for manufacturing a solid-state battery. [Figure 15] 10A and 10B are diagrams (part 2) for explaining another example of the method for manufacturing a solid-state battery. [Figure 16] 10A and 10B are diagrams (part 3) for explaining another example of the method for manufacturing a solid-state battery. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Solid battery] Figure 1 is a diagram illustrating an example of a solid-state battery. Figure 1(A) shows a schematic perspective view of a main part of an example of a solid-state battery. Figure 1(B) shows a schematic cross-sectional view taken along a chain line P1 in Figure 1(A), and Figure 1(C) shows a schematic cross-sectional view taken along a dotted line P2 in Figure 1(A).

[0011] 1(A) to 1(C) is an example of a chip-type battery. The solid-state battery 1 includes a solid-state battery body 10 and a coating film 20. The solid battery body 10 has a positive electrode layer 11 and a negative electrode layer 12 laminated on one main surface 13a (also referred to as the first main surface) and the other main surface 13b (also referred to as the second main surface) opposite thereto of an electrolyte layer 13. The solid battery body 10 is an example of a laminate of an electrolyte layer 13, a positive electrode layer 11, and a negative electrode layer 12.

[0012] The electrolyte layer 13 contains a solid electrolyte. An oxide solid electrolyte can be used for the solid electrolyte of the electrolyte layer 13. For example, LAGP, which is one type of NASICON (Na super ionic conductor)-type (also referred to as "NASICON type") oxide solid electrolyte, is used for the electrolyte layer 13. LAGP is an oxide solid electrolyte represented by the general formula Li 1+x Al x Ge 2-x (PO4)3 (0 < x ≤ 1), and is also referred to as aluminum-substituted lithium germanium phosphate gel, etc. For example, as the LAGP of the electrolyte layer 13, Li 1.5 Al 0.5 Ge 1.5 (PO4)3 with a composition ratio x = 0.5 is used.

[0013] The positive electrode layer 11 laminated on one main surface 13a of the electrolyte layer 13 contains a positive electrode active material. For example, lithium cobalt pyrophosphate (Li2CoP2O7, hereinafter referred to as "LCPO") is used for the positive electrode active material of the positive electrode layer 11. The positive electrode layer 11 may contain a solid electrolyte and a conductive assistant in addition to the positive electrode active material. For the solid electrolyte of the positive electrode layer 11, for example, the same type of material as the oxide solid electrolyte used for the electrolyte layer 13 is used. That is, in this example, LAGP is used as the oxide solid electrolyte of the positive electrode layer 11. For the conductive assistant of the positive electrode layer 11, for example, carbon materials such as carbon fiber, carbon black, graphite, graphene, and carbon nanotubes are used.

[0014] The anode layer 12 laminated on the other principal surface 13b of the electrolyte layer 13 includes an anode active material. The anode active material of the anode layer 12 is, for example, titanium oxide (TiO2). The anode layer 12 may include a solid electrolyte and a conductive additive in addition to the anode active material. The solid electrolyte of the anode layer 12 is, for example, the same material as the oxide solid electrolyte used in the electrolyte layer 13. That is, in this example, LAGP is used as the oxide solid electrolyte of the anode layer 12. The conductive additive of the anode layer 12 is, for example, a carbon material such as carbon fiber, carbon black, graphite, graphene, or carbon nanotubes.

[0015] In the solid-state battery body 10, which is a laminate of an electrolyte layer 13, a positive electrode layer 11, and a negative electrode layer 12, the positive electrode layer 11 is provided on a part of a main surface 13a of the electrolyte layer 13, the negative electrode layer 12 is provided on a part of a main surface 13b of the electrolyte layer 13, and the positive electrode layer 11 and the negative electrode layer 12 are provided so as to partially overlap each other with the electrolyte layer 13 interposed therebetween.

[0016] In the solid-state battery body 10, during charging, lithium ions are conducted from the positive electrode layer 11 through the electrolyte layer 13 to the negative electrode layer 12 and are taken up therein, and during discharging, lithium ions are conducted from the negative electrode layer 12 through the electrolyte layer 13 to the positive electrode layer 11 and are taken up therein. In the solid-state battery body 10, charge and discharge operations are realized by such lithium ion conduction.

[0017] The coating film 20 covers the solid-state battery body 10 so that a portion of the positive electrode layer 11 and a portion of the negative electrode layer 12 of the solid-state battery body 10 are exposed. In this example, a portion 11a (also referred to as a first portion) on the side surface of the positive electrode layer 11 and a portion 12a (also referred to as a second portion) on the side surface of the negative electrode layer 12 are exposed. The portion 11a of the positive electrode layer 11 and the portion 12a of the negative electrode layer 12 are positioned opposite each other in a direction perpendicular to the stacking direction of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12. The portion 11a of the positive electrode layer 11 and the portion 12a of the negative electrode layer 12 exposed from the coating film 20 are used for electrical connection to the outside of the solid-state battery body 10. Here, the side surface of the solid-state battery 1 from which the portion 11a of the positive electrode layer 11 is exposed from the coating film 20 is referred to as a positive-electrode drawn-out surface 1a, and the side surface from which the portion 12a of the negative electrode layer 12 is exposed from the coating film 20 is referred to as a negative-electrode drawn-out surface 1b.

[0018] The coating film 20 covers the solid-state battery body 10 so as to be in contact with the other part of the main surface 13a of the electrolyte layer 13, which has the positive electrode layer 11 provided on part of the main surface 13a, and the surface of the positive electrode layer 11 excluding the part 11a exposed from the positive-electrode-extracted surface 1a. The coating film 20 covers the solid-state battery body 10 so as to be in contact with the other part of the main surface 13b of the electrolyte layer 13, which has the negative electrode layer 12 provided on part of the main surface 13b, and the surface of the negative electrode layer 12 excluding the part 12a exposed from the negative-electrode-extracted surface 1b. Furthermore, the coating film 20 covers the solid-state battery body 10 so as to be in contact with the side surface of the electrolyte layer 13 (the surface connecting the main surface 13a and the main surface 13b), excluding the positive-electrode-extracted surface 1a and the negative-electrode-extracted surface 1b.

[0019] The coating film 20 covers the solid-state battery body 10 so that a portion 11a of the positive electrode layer 11 and a portion 12a of the negative electrode layer 12 are exposed from the positive electrode drawn-out surface 1a and the negative electrode drawn-out surface 1b of the solid-state battery 1, respectively. An insulating coating film 20 having a hardness higher than that of the solid electrolyte used in the solid-state battery body 10 is used. For example, an insulating coating film 20 having a hardness higher than that of the solid electrolyte used in the electrolyte layer 13 is used. Alternatively, an insulating coating film 20 having a hardness higher than that of the solid electrolyte used in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 is used. The insulating property of the coating film 20 refers to a property that has no or a sufficiently low effect on the lithium ion conduction and electron conduction of the solid-state battery body 10. The insulating coating film 20 having a hardness higher than that of the solid electrolyte used in the solid-state battery body 10 is made of, for example, glass or ceramics.

[0020] The coating film 20 has the function of protecting the solid-state battery body 10 from external forces and the external environment. Therefore, the coating film 20 has the hardness and insulating properties described above, as well as low permeability to moisture or gases such as hydrogen and oxygen, and is capable of achieving good sealing. Furthermore, the coating film 20 preferably has a thermal expansion coefficient similar to that of each of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 of the solid-state battery body 10, and also preferably has good adhesion to each layer. Glass or ceramics is one type of material that can combine these properties, and is suitable as a material for forming the coating film 20 that covers the solid-state battery body 10.

[0021] The solid-state battery 1 having the above-described configuration is manufactured, for example, by the following procedure. First, a structure is formed including a solid-state battery body 10 having an electrolyte layer 13 and a positive electrode layer 11 and a negative electrode layer 12 laminated on its main surface 13a and main surface 13b, respectively, and a material (referred to as a "coating material") that covers the solid-state battery body 10 so that a portion 11a of the positive electrode layer 11 and a portion 12a of the negative electrode layer 12 for electrical connection with the outside are exposed. Then, this structure is fired at a predetermined temperature (also referred to as a first temperature). This firing sinters the coating material covering the solid-state battery body 10, and an insulating coating film 20 having a higher hardness than the solid electrolyte used in the solid-state battery body 10 is formed from the coating material.

[0022] During this firing, for example, the solid electrolyte used in the solid battery body 10 may be sintered, and the coating material covering the solid battery body 10 may be sintered to form the coating film 20. That is, materials having the same, equivalent, or similar sintering temperatures may be used for the solid electrolyte used in the solid battery body 10 and the coating material covering the solid battery body 10, and the solid electrolyte and the coating material may be sintered together by firing under a single condition.

[0023] As described above, in the solid-state battery 1, the solid-state battery body 10 is covered with the coating film 20 having a higher hardness than the solid electrolyte used therefor, such that the portion 11a of the positive electrode layer 11 is exposed on the positive-electrode drawn-out surface 1a and the portion 12a of the negative electrode layer 12 is exposed on the negative-electrode drawn-out surface 1b. By using such a coating film 20 as a protective layer for the solid-state battery body 10, the occurrence of cracks or chips due to externally applied force is suppressed compared to, for example, when a solid electrolyte is used as the protective layer, and degradation of the performance of the solid-state battery 1, such as the intrusion of moisture or gas through the cracked or chipped portion and the resulting short circuit or increased resistance, is effectively suppressed.

[0024] In the solid-state battery 1, a portion of the coating film 20 having high hardness as described above is provided on a portion of the main surface 13a of the electrolyte layer 13 where the positive electrode layer 11 is not provided and on a portion of the main surface 13b where the negative electrode layer 12 is not provided, i.e., a portion recessed inward from the side surface of the electrolyte layer 13. By providing the coating film 20 on the irregularities formed on the surface of the solid-state battery body 10, the bonding strength of the coating film 20 to the solid-state battery body 10 is increased, and peeling of the coating film 20 from the solid-state battery body 10 is effectively suppressed.

[0025] By using the coating film 20 as described above as a protective layer for the solid state battery body 10 as described above, a solid state battery 1 having excellent strength and environmental resistance is realized. Furthermore, in the solid-state battery 1, the coating film 20 is made of a material having a thermal expansion coefficient similar to that of each layer of the solid-state battery body 10, thereby preventing delamination due to expansion and contraction of each layer caused by the external temperature environment. Furthermore, in the solid-state battery 1, the coating film 20 is made of a material having good adhesion to each layer of the solid-state battery body 10, thereby preventing delamination of the coating film 20 from the solid-state battery body 10 when an external force is applied or when each layer expands and contracts. Furthermore, in the solid-state battery 1, the coating film 20 is made of a material having a relatively low sintering temperature, such as 900°C or less, that is the same as, equivalent to, or approximately the same as the sintering temperature of the solid electrolyte, such as 650°C or less, thereby preventing thermal degradation of the solid-state battery body 10 caused by the formation of the coating film 20. Furthermore, the simultaneous sintering of the coating material and the solid electrolyte prevents an increase in the number of steps. Such a coating film 20 also realizes a solid-state battery 1 having excellent strength and environmental resistance, and also enables efficient production of such a solid-state battery 1.

[0026] [Solid-state battery configuration example] Next, an example of the configuration of a solid-state battery will be described. 2 and 3 are diagrams illustrating an example of the configuration of a solid-state battery. Fig. 2(A) is a schematic perspective view of a main part of an example of a solid-state battery, and Fig. 2(B) is a schematic cross-sectional view taken along the chain line P3 in Fig. 2(A). Fig. 3(A) is a schematic perspective view of a main part of an example of a solid-state battery, and Fig. 3(B) is a schematic cross-sectional view taken along the dotted line P4 in Fig. 3(A). Figs. 2 and 3 are diagrams illustrating the same solid-state battery and are intended to explain cross-sectional structures at different positions of the same solid-state battery.

[0027] The solid-state battery 1A shown in Figures 2(A), 2(B), 3(A), and 3(B) is an example of a chip-type battery. The solid-state battery 1A includes a solid-state battery body 10A, a coating film 20A, an external electrode 31 (also referred to as a first external electrode), and an external electrode 32 (also referred to as a second external electrode).

[0028] 2(B) and 3(B), the solid-state battery body 10A has a plurality of electrolyte layers 13, a plurality of positive electrode layers 11, and a plurality of negative electrode layers 12. The plurality of electrolyte layers 13, the plurality of positive electrode layers 11, and the plurality of negative electrode layers 12 of the solid-state battery body 10A are stacked such that one electrolyte layer 13 is interposed between a pair of positive electrode layers 11 and negative electrode layers 12. That is, the solid-state battery body 10A shown in this example has a structure in which, from bottom to top, the negative electrode layer 12, the electrolyte layer 13, the positive electrode layer 11, the electrolyte layer 13, the negative electrode layer 12, the electrolyte layer 13, and the positive electrode layer 11 are stacked. In the solid-state battery main body 10A, each positive electrode layer 11 is provided on a part of the main surface 13a (also referred to as the first main surface) of the electrolyte layer 13 on which it is stacked, and each negative electrode layer 12 is provided on a part of the main surface 13b (also referred to as the second main surface) of the electrolyte layer 13 on which it is stacked, and a pair of positive electrode layer 11 and negative electrode layer 12 facing each other with one electrolyte layer 13 interposed therebetween are provided so as to partially overlap each other with the electrolyte layer 13 interposed therebetween. The solid-state battery main body 10A is an example of a laminate in which a plurality of electrolyte layers 13, a plurality of positive electrode layers 11, and a plurality of negative electrode layers 12 are stacked in this manner.

[0029] Each electrolyte layer 13 of the solid battery body 10A contains, for example, an LAGP oxide solid electrolyte. Each positive electrode layer 11 of the solid battery body 10A contains, for example, LCPO as a positive electrode active material, LAGP as an oxide solid electrolyte, and a carbon material as a conductive additive. Each negative electrode layer 12 of the solid battery body 10A contains, for example, TiO2 as a negative electrode active material, LAGP as an oxide solid electrolyte, and a carbon material as a conductive additive.

[0030] In the solid-state battery body 10A, during charging, lithium ions are conducted from the positive electrode layer 11 to the negative electrode layer 12 via the electrolyte layer 13 and are taken up, and during discharging, lithium ions are conducted from the negative electrode layer 12 to the positive electrode layer 11 via the electrolyte layer 13 and are taken up. In the solid-state battery body 10A, charge and discharge operations are realized by such lithium ion conduction between the opposing positive electrode layer 11 and negative electrode layer 12 and the electrolyte layer 13 interposed therebetween.

[0031] 2(B), the coating film 20A covers the solid battery main body 10A so as to expose a portion 11a (also referred to as a first portion) on the side surface of each positive electrode layer 11 and a portion 12a (also referred to as a second portion) on the side surface of each negative electrode layer 12 of the solid battery main body 10A. The side surface of the solid battery 1A from which the portion 11a of the positive electrode layer 11 is exposed through the coating film 20A becomes a positive electrode extraction surface 1Aa, and the side surface of the solid battery 1A from which the portion 12a of the negative electrode layer 12 is exposed through the coating film 20A becomes a negative electrode extraction surface 1Ab.

[0032] 2(B) and 3(B), the coating film 20A covers the solid-state battery main body 10A so as to be in contact with the other part of the main surface 13a of the electrolyte layer 13, which has the positive electrode layer 11 provided on part of the main surface 13a, and the surface of the positive electrode layer 11 excluding the part 11a exposed from the positive-electrode-extracted surface 1Aa. The coating film 20A covers the solid-state battery main body 10A so as to be in contact with the other part of the main surface 13b of the electrolyte layer 13, which has the negative electrode layer 12 provided on part of the main surface 13b, and the surface of the negative electrode layer 12 excluding the part 12a exposed from the negative-electrode-extracted surface 1Ab. Furthermore, the coating film 20A covers the solid-state battery main body 10A so as to be in contact with the side surfaces of the electrolyte layer 13 excluding the positive-electrode-extracted surface 1Aa and the negative-electrode-extracted surface 1Ab. In the solid state battery 1A, a portion of the coating film 20A is provided on a portion of the main surface 13a of the electrolyte layer 13 where the positive electrode layer 11 is not provided and on a portion of the main surface 13b where the negative electrode layer 12 is not provided, i.e., on a portion recessed inward from the side surface of the electrolyte layer 13.

[0033] The coating film 20A is an insulating coating film 20A having a higher hardness than the solid electrolyte used in the solid battery body 10A, for example, the solid electrolyte of the electrolyte layer 13, or the solid electrolytes used in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12. The coating film 20A has high hardness and insulating properties, and is low in permeability to moisture and gas, enabling good sealing. Furthermore, the coating film 20A preferably has a thermal expansion coefficient similar to that of each layer constituting the solid battery body 10A, and preferably has good adhesion to each layer. The coating film 20A is made of, for example, glass or ceramics.

[0034] As shown in FIG. 2(B), the external electrode 31 is provided on the positive electrode drawn-out surface 1Aa of the solid-state battery 1A, and is connected to a portion 11a of the positive electrode layer 11 of the solid-state battery main body 10A exposed from the positive electrode drawn-out surface 1Aa (and in this example, a portion of the side surface of the electrolyte layer 13). As shown in FIG. 2(B), the external electrode 32 is provided on the negative electrode drawn-out surface 1Ab of the solid-state battery 1A, and is connected to a portion 12a of the negative electrode layer 12 of the solid-state battery main body 10A exposed from the negative electrode drawn-out surface 1Ab (and in this example, a portion of the side surface of the electrolyte layer 13). Various conductive materials can be used for the external electrodes 31 and 32. For example, the external electrodes 31 and 32 can be formed by drying and hardening a conductive paste containing conductive particles such as metal particles (e.g., silver (Ag)) or carbon particles, or by depositing various metals using a method such as sputtering or plating.

[0035] As described above, in the solid-state battery 1A, the solid-state battery body 10A, excluding the positive electrode drawn surface 1Aa and the negative electrode drawn surface 1Ab, is covered with the coating film 20A having a hardness higher than that of the solid electrolyte used therein. This prevents cracks or chips in the coating film 20A due to externally applied force, and effectively prevents moisture or gas from entering through cracked or chipped areas, resulting in a decrease in performance of the solid-state battery 1A, such as a short circuit or increased resistance.

[0036] In the solid state battery 1A, a part of the coating film 20A is provided in a portion recessed inward from the side surface of the electrolyte layer 13, thereby exerting an anchor effect and effectively suppressing peeling of the coating film 20A from the solid state battery main body 10A.

[0037] Furthermore, on the positive electrode extraction surface 1Aa, a portion of the coating film 20A is provided in a region recessed inward from the side surfaces of a pair of electrolyte layers 13 facing each other with the negative electrode layer 12 interposed therebetween. This increases the strength between the pair of electrolyte layers 13 and strengthens support for the positive electrode layers 11 stacked on each of them. This increases the strength of the positive electrode layer 11 on the positive electrode extraction surface 1Aa and reduces the occurrence of cracks or chips. Similarly, on the negative electrode extraction surface 1Ab, a portion of the coating film 20A is provided in a region recessed inward from the side surfaces of a pair of electrolyte layers 13 facing each other with the positive electrode layer 11 interposed therebetween. This increases the strength between the pair of electrolyte layers 13 and strengthens support for the negative electrode layers 12 stacked on each of them. This increases the strength of the negative electrode layer 12 on the negative electrode extraction surface 1Ab and reduces the occurrence of cracks or chips.

[0038] By using the coating film 20A as described above as a protective layer for the solid battery body 10A as described above, a solid battery 1A with excellent strength and environmental resistance is realized. Furthermore, in the solid-state battery 1A, by using for the coating film 20A a material having a thermal expansion coefficient similar to that of each layer of the solid-state battery body 10A, delamination between layers due to expansion and contraction of each layer caused by the external temperature environment is suppressed. Furthermore, in the solid-state battery 1A, by using for the coating film 20A a material having good adhesion to each layer of the solid-state battery body 10A, delamination of the coating film 20A from the solid-state battery body 10A when an external force is applied or when each layer expands and contracts. Such a coating film 20A also realizes a solid-state battery 1A having excellent strength and environmental resistance.

[0039] In manufacturing the solid state battery 1A, for example, first, a structure is formed including a solid state battery body 10A having an electrolyte layer 13 and a positive electrode layer 11 and a negative electrode layer 12 laminated on its main surface 13a and main surface 13b, respectively, and a coating material covering the solid state battery body 10A so that a portion 11a of the positive electrode layer 11 and a portion 12a of the negative electrode layer 12 connected to the external electrode 31 and the external electrode 32, respectively, are exposed. Then, this structure is fired at a predetermined temperature (also referred to as a first temperature), whereby the coating material covering the solid state battery body 10A is sintered to form a coating film 20A. Here, using a coating material with a relatively low sintering temperature of 900°C or less, for example, a sintering temperature of 650°C or less, can suppress thermal degradation of the solid state battery body 10A accompanying the formation of the coating film 20A. Furthermore, if a coating material having a sintering temperature that is the same as, or equivalent to, or approximately the same as the sintering temperature of the solid electrolyte used in the solid battery body 10A is used, it becomes possible to sinter the solid electrolyte and the coating material together by firing under a single condition. The details of the manufacturing method of the solid battery 1A will be described later.

[0040] The coating film 20A formed by firing the coating material is made of, for example, glass or ceramics. The coating film 20A may take various forms, such as glass, crystallized glass, polycrystal, or single crystal. The coating film 20A may be made of one material phase, or may contain two or more material phases. The coating film 20A may contain two or more material phases with different physical properties, for example, two or more material phases with different hardness.

[0041] Figure 4 is a diagram illustrating an example of a coating film of a solid-state battery. Figure 4(A) shows a schematic cross-sectional view of a main part of an example of a solid-state battery (a cross-sectional view taken along dotted line P4 in Figure 3(A)), and Figure 4(B) shows a schematic enlarged view of part Q1 in Figure 4(A).

[0042] The coating film 20A covering the solid-state battery body 10A of the solid-state battery 1A shown in FIG. 4(A) may include, for example, two types of material phases: a material phase 21 (also referred to as a first material phase) and a material phase 22 (also referred to as a second material phase), as shown in FIG. 4(B). As an example, the coating film 20A includes a material phase 21 made of glass or ceramic having a predetermined hardness (also referred to as a first hardness) and a material phase 22 having a hardness (also referred to as a second hardness) higher than that of the material phase 21. For example, ceramics is used as the material phase 22 having a higher hardness than that of the material phase 21. For example, aluminum oxide (Al2O3) is used as the ceramic material phase 22. The material phase 22 is contained in the material phase 21 in the form of particles, for example, as shown in FIG. 4(B). Note that the particulate material phase 22 does not necessarily need to be uniformly dispersed within the material phase 21. Although FIG. 4(B) shows a particulate material phase 22, the material phase 21 may contain a fiber-like or sheet-like material phase having a higher hardness, or may contain material phases of multiple types.

[0043] By configuring the coating film 20A so that the glass or ceramic material phase 21 contains the material phase 22 having a higher hardness than the glass or ceramic material phase 21, it is possible to further increase the hardness of the coating film 20A compared to a case where only the material phase 21 is used. By covering the solid state battery main body 10A with such a coating film 20A, a solid state battery 1A having even greater strength and environmental resistance is realized.

[0044] [Solid-state battery manufacturing method] Next, a method for manufacturing a solid-state battery having the above-described structure will be described. First, examples of forming the electrolyte paste, the positive electrode paste, the negative electrode paste, and the coating material paste and coating material sheet will be described.

[0045] (electrolyte paste) An electrolyte paste containing a solid electrolyte, a binder, a plasticizer, a dispersant, and a diluent is prepared. For example, an electrolyte paste using LAGP, which is an oxide solid electrolyte, as the solid electrolyte is prepared.

[0046] (positive electrode paste) A positive electrode paste containing a positive electrode active material, a solid electrolyte, a conductive additive, a binder, a plasticizer, a dispersant, and a diluent is prepared. For example, a positive electrode paste using LCPO as the positive electrode active material, LAGP (a solid oxide electrolyte) as the solid electrolyte, and carbon nanofiber as the conductive additive is prepared.

[0047] (negative electrode paste) A negative electrode paste containing a negative electrode active material, a solid electrolyte, a conductive additive, a binder, a plasticizer, a dispersant, and a diluent is prepared. For example, a negative electrode paste using TiO2 as the negative electrode active material, LAGP (a solid oxide electrolyte) as the solid electrolyte, and carbon nanofiber as the conductive additive is prepared.

[0048] (Coating material paste and coating material sheet) A glass paste containing a glass component is prepared as the coating material paste. For example, a glass paste containing a glass component called low-melting-point glass, which is melted and sintered by firing at around 600°C, is prepared. The prepared glass paste is applied and dried to form a glass sheet as the coating material sheet. The coating material paste and the coating material sheet are one form of coating material that is formed into the coating film 20A by firing.

[0049] The coating material paste and coating material sheet are used such that the hardness after firing is higher than the hardness of the solid electrolyte contained in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 after firing. Furthermore, the coating material paste and coating material sheet are preferably used such that the thermal expansion coefficient after firing is similar to that of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 after firing. Furthermore, the coating material paste and coating material sheet are preferably used such that good adhesion is achieved between the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 after firing. Furthermore, a ceramic material such as particulate Al2O3 may be added to the coating material paste and coating material sheet. In this case, the glass component contained in the coating material paste and coating material sheet constitutes a first material phase, and the ceramic material such as particulate Al2O3 constitutes a second material phase.

[0050] Next, a first example of forming a structure using the electrolyte paste, positive electrode paste, negative electrode paste, coating material paste, and coating material sheet prepared as described above will be described with reference to FIGS.

[0051] <First example> (Formation of positive electrode layer parts) 5 and 6 are diagrams illustrating an example of a process for forming a positive electrode layer part. FIG. 5(A) is a schematic perspective view of a key portion of an example of a support preparation process. FIG. 5(B) is a schematic perspective view of a key portion of an example of a positive electrode layer formation process. FIG. 5(C) is a schematic perspective view of a key portion of an example of a first coating material layer formation process. FIG. 5(D) is a schematic perspective view of a key portion of an example of an electrolyte layer formation process. FIG. 5(E) is a schematic perspective view of a key portion of an example of a second coating material layer formation process. FIG. 6(A) is a schematic perspective view of a key portion of an example of a positive electrode layer part, corresponding to FIG. 5(E). FIG. 6(B) is a schematic cross-sectional view taken along the dashed line P3a in FIG. 6(A). FIG. 6(C) is a schematic cross-sectional view taken along the dotted line P4a in FIG. 6(A).

[0052] For example, a polyethylene terephthalate (PET) film is used for the support 50 shown in FIG. 5(A). A positive electrode paste is applied by screen printing onto a portion of the prepared support 50 shown in FIG. 5(A), and the applied positive electrode paste is dried to form the positive electrode layer 11, as shown in FIG. 5(B). After the positive electrode layer 11 is formed, a coating material paste is applied by screen printing around the positive electrode layer 11 formed on the portion of the support 50, as shown in FIG. 5(C), and the applied coating material paste is dried to form a coating material layer 24. The coating material layer 24 is also referred to as a buried layer.

[0053] Next, an electrolyte paste is applied by screen printing onto the positive electrode layer 11 and onto a portion of the coating material layer 24 formed around it, as shown in Fig. 5(D), and the applied electrolyte paste is dried to form the electrolyte layer 13. After the electrolyte layer 13 is formed, a coating material paste is applied by screen printing onto a portion of the coating material layer 24 that is not covered by the electrolyte layer 13, as shown in Fig. 5(E), and the applied coating material paste is dried to form the coating material layer 24 (embedded layer).

[0054] For example, by the steps shown in FIGS. 5(A) to 5(E), a part is formed that has a cross-sectional structure as shown in FIG. 6(B) at the position of the chain line P3a shown in FIG. 6(A) and a cross-sectional structure as shown in FIG. 6(C) at the position of the dotted line P4a shown in FIG. 6(A). Parts such as those shown in FIGS. 6(A) to 6(C) (and FIG. 5(E)) can be used as positive electrode layer parts. Alternatively, a part such as that shown in FIGS. 6(A) to 6(C) from which the support 50 has been peeled can also be used as a positive electrode layer part. Furthermore, a part such as that shown in FIG. 5(C) before the formation of the electrolyte layer 13, or a part from which the support 50 has been peeled, can also be used as a positive electrode layer part.

[0055] When forming the positive electrode layer part, the application of the positive electrode paste onto the support 50 and the application of the coating material paste around it may be alternately repeated multiple times to adjust the thickness and active material amount of the positive electrode layer 11. In this case, the positive electrode paste and the coating material paste may be dried after each application, or may be dried all at once after multiple applications of the positive electrode paste and the coating material paste.

[0056] Furthermore, when forming the positive electrode layer part, the application of the electrolyte paste and the application of the outer coating material paste may be alternately repeated multiple times to adjust the thickness of the electrolyte layer 13. In this case, the electrolyte paste and the coating material paste may be dried after each application, or may be dried all at once after multiple applications of the electrolyte paste and the coating material paste.

[0057] 5(A) to 5(E) and 6(A) to 6(C) show an example in which the positive electrode layer 11 and the surrounding coating material layer 24 are formed on the support 50, and then the electrolyte layer 13 and the outer coating material layer 24 are formed, but this order can also be reversed. That is, the electrolyte layer 13 and the outer coating material layer 24 may be formed on the support 50 according to the above example, and then the positive electrode layer 11 and the surrounding coating material layer 24 may be formed.

[0058] (Formation of negative electrode layer parts) 7 and 8 are diagrams illustrating an example of a process for forming an anode layer part. FIG. 7(A) is a schematic perspective view of a main part of an example of a support preparation process. FIG. 7(B) is a schematic perspective view of a main part of an example of a process for forming an anode layer. FIG. 7(C) is a schematic perspective view of a main part of an example of a process for forming a first coating material layer. FIG. 7(D) is a schematic perspective view of a main part of an example of a process for forming an electrolyte layer. FIG. 7(E) is a schematic perspective view of a main part of an example of a process for forming a second coating material layer. FIG. 8(A) is a schematic perspective view of a main part of an example of an anode layer part, corresponding to FIG. 7(E). FIG. 8(B) is a schematic cross-sectional view taken along the dashed line P3b in FIG. 8(A). FIG. 8(C) is a schematic cross-sectional view taken along the dotted line P4b in FIG. 8(A).

[0059] As shown in Fig. 7(A), a negative electrode paste is applied by screen printing onto a portion of a support 50 such as a PET film, and the applied negative electrode paste is dried to form a negative electrode layer 12, as shown in Fig. 7(B). After the negative electrode layer 12 is formed, a coating material paste is applied by screen printing around the negative electrode layer 12 formed on the portion of the support 50, as shown in Fig. 7(C), and the applied coating material paste is dried to form a coating material layer 24 (embedded layer).

[0060] Next, an electrolyte paste is applied by screen printing onto the negative electrode layer 12 and onto a portion of the coating material layer 24 formed around it, as shown in Fig. 7(D), and the applied electrolyte paste is dried to form the electrolyte layer 13. After the electrolyte layer 13 is formed, a coating material paste is applied by screen printing onto a portion of the coating material layer 24 that is not covered by the electrolyte layer 13, as shown in Fig. 7(E), and the applied coating material paste is dried to form the coating material layer 24 (embedded layer).

[0061] For example, by the steps shown in FIGS. 7(A) to 7(E), a part is formed that has a cross-sectional structure as shown in FIG. 8(B) at the position of the chain line P3b shown in FIG. 8(A) and a cross-sectional structure as shown in FIG. 8(C) at the position of the dotted line P4b shown in FIG. 8(A). Parts such as those shown in FIGS. 8(A) to 8(C) (and FIG. 7(E)) can be used as negative electrode layer parts. Alternatively, a part such as that shown in FIGS. 8(A) to 8(C) from which the support 50 has been peeled can also be used as a negative electrode layer part. Furthermore, a part such as that shown in FIG. 7(C) before the formation of the electrolyte layer 13, or a part from which the support 50 has been peeled, can also be used as a negative electrode layer part.

[0062] When forming the negative electrode layer part, the application of the negative electrode paste onto the support 50 and the application of the coating material paste around it may be alternately repeated multiple times to adjust the thickness and active material amount of the negative electrode layer 12. In this case, the negative electrode paste and the coating material paste may be dried after each application, or may be dried all at once after multiple applications of the negative electrode paste and the coating material paste.

[0063] Furthermore, when forming the negative electrode layer part, the application of the electrolyte paste and the application of the outer coating material paste may be alternately repeated multiple times to adjust the thickness of the electrolyte layer 13. In this case, the electrolyte paste and the coating material paste may be dried after each application, or may be dried all at once after multiple applications of the electrolyte paste and the coating material paste.

[0064] 7(A) to 7(E) and 8(A) to 8(C) show an example in which the negative electrode layer 12 and the surrounding coating material layer 24 are formed on the support 50, and then the electrolyte layer 13 and the outer coating material layer 24 are formed, but this order can also be reversed. That is, the electrolyte layer 13 and the outer coating material layer 24 may be formed on the support 50 according to the above example, and then the negative electrode layer 12 and the surrounding coating material layer 24 may be formed.

[0065] (Structure formation) 9A and 9B are diagrams illustrating an example of a process for forming a structure. Fig. 9A shows a schematic cross-sectional view of a main part of an example of a process for stacking a group of parts. Fig. 9B shows a schematic cross-sectional view of a main part of an example of a process for stacking a coating material sheet. Figs. 9A and 9B show schematic cross sections of the group of parts corresponding to the positions of the chain line P3a in Fig. 6A and the chain line P3b in Fig. 8A.

[0066] The positive electrode layer part and the negative electrode layer part having the predetermined shape obtained as described above are stacked, for example, as shown in FIG. 9(A). In this example, the positive electrode layer part shown in FIG. 6(B) from which the support 50 has been peeled is stacked on the negative electrode layer part with the support 50 shown in FIG. 8(B). On top of that, the negative electrode layer part shown in FIG. 8(B) from which the support 50 has been peeled is stacked, and on top of that, the positive electrode layer part shown in FIG. 5(C) from which the support 50 has been peeled is stacked. Then, the support 50 is peeled from the structure shown in FIG. 9(A), and coating material sheets 23 are stacked on the bottom and top layers, or coating material sheets 23 are formed using a coating material paste. These are then thermocompressed under predetermined pressure and temperature conditions to form the structure 5 shown in FIG. 9(B).

[0067] When the structure 5 is formed in this manner, the positive electrode layer part and the negative electrode layer part are laminated so that the negative electrode layer 12 and the positive electrode layer 11, which face each other with the electrolyte layer 13 interposed therebetween, partially overlap in the cross section shown in Figures 9(A) and 9(B). Alternatively, in the step of forming the positive electrode layer part and the negative electrode layer part, coating is performed so that when they are laminated, the negative electrode layer 12 and the positive electrode layer 11, which face each other with the electrolyte layer 13 interposed therebetween, partially overlap in the cross section shown in Figures 9(A) and 9(B).

[0068] 9(A) and 9(B), the positive electrode layer part and the negative electrode layer part are laminated so that the negative electrode layer 12 and the positive electrode layer 11, which face each other with the electrolyte layer 13 interposed therebetween, entirely overlap each other. Alternatively, in the process of forming the positive electrode layer part and the negative electrode layer part, coating is performed so that when they are laminated, the negative electrode layer 12 and the positive electrode layer 11, which face each other with the electrolyte layer 13 interposed therebetween, entirely overlap each other in a cross section orthogonal to the cross section shown in FIG. 9(A) and 9(B).

[0069] For example, by the steps shown in FIGS. 9(A) and 9(B), a structure 5 is formed, which includes a laminate (basic structure of the solid-state battery body 10A) having a positive electrode layer 11, a negative electrode layer 12, and an electrolyte layer 13 interposed therebetween, and a coating material sheet 23 and a coating material layer 24 (basic structure of the coating film 20A) provided so as to cover the laminate.

[0070] Next, a second example of forming a structure using the electrolyte paste, positive electrode paste, negative electrode paste, and coating material paste and coating material sheet prepared as described above will be described with reference to FIGS. 10 and 11.

[0071] <Second example> 10 and 11 are diagrams illustrating another example of the steps of forming a structure. Figures 10(A) to 10(D) and 11(A) to 11(D) each show a schematic cross-sectional view of a main part of an example of each step of forming a structure.

[0072] In this second example, first, as shown in Fig. 10(A), a negative electrode paste is applied to a portion of the coating material sheet 23 and dried to form the negative electrode layer 12. Thereafter, as shown in Fig. 10(A), a coating material paste is applied to the periphery of the negative electrode layer 12 formed on the portion of the coating material sheet 23 and dried to form a coating material layer 24 (embedded layer).

[0073] Next, as shown in FIG. 10(B), an electrolyte paste is applied to the negative electrode layer 12 and a portion of the surrounding coating material layer 24, and then dried to form the electrolyte layer 13. Although not shown here, after the formation of the electrolyte layer 13, a coating material paste is applied by screen printing to a portion of the coating material layer 24 that is not covered by the electrolyte layer 13, and then dried to form the coating material layer 24 (embedded layer). Then, as shown in FIG. 10(C), a positive electrode paste is applied to a portion of the electrolyte layer 13, and then dried to form the positive electrode layer 11. Thereafter, as shown in FIG. 10(D), a coating material paste is applied to the periphery of the positive electrode layer 11 formed on the portion of the electrolyte layer 13, and then dried to form the coating material layer 24 (embedded layer).

[0074] Next, as shown in FIG. 11(A), an electrolyte paste is applied to the positive electrode layer 11 and a portion of the surrounding coating material layer 24, and then dried to form the electrolyte layer 13. Although not shown here, after the formation of the electrolyte layer 13, a coating material paste is applied by screen printing to a portion of the coating material layer 24 that is not covered by the electrolyte layer 13, and then dried to form the coating material layer 24 (embedded layer). Then, as shown in FIG. 11(B), a negative electrode paste is applied to a portion of the electrolyte layer 13, and then dried to form the negative electrode layer 12. Thereafter, as shown in FIG. 11(C), a coating material paste is applied to the periphery of the negative electrode layer 12 formed on the portion of the electrolyte layer 13, and then dried to form the coating material layer 24 (embedded layer).

[0075] Thereafter, using the same procedure as above, as shown in FIG. 11(D), an electrolyte layer 13 is formed using the electrolyte paste on the negative electrode layer 12 and a portion of the surrounding coating material layer 24, and a coating material layer 24 (embedded layer, not shown) is formed on the outside of the electrolyte layer 13 using the coating material paste. A positive electrode layer 11 is then formed on a portion of the electrolyte layer 13 using the positive electrode paste. Furthermore, a coating material layer 24 (embedded layer) is formed using the coating material paste around the positive electrode layer 11 formed on a portion of the electrolyte layer 13. Then, a coating material sheet 23 is formed using the coating material paste on the positive electrode layer 11 and the surrounding coating material layer 24, or a previously prepared coating material sheet 23 is laminated. This forms a structure 5 as shown in FIG. 11(D).

[0076] The application of the negative electrode paste and the coating material paste onto the coating material sheet 23 (FIG. 10(A)), and the application of the negative electrode paste and the coating material paste onto the electrolyte layer 13 (FIGS. 11(B) and 11(C)) may be alternately repeated multiple times to adjust the thickness and the amount of active material of the negative electrode layer 12. In this case, the negative electrode paste and the coating material paste may be dried after each application, or may be dried all at once after multiple applications of the negative electrode paste and the coating material paste.

[0077] Furthermore, the application of the positive electrode paste and the application of the coating material paste onto the electrolyte layer 13 (FIGS. 10(C), 10(D), and 11(D)) may be alternately repeated multiple times to adjust the thickness and the amount of active material of the positive electrode layer 11. In this case, the positive electrode paste and the coating material paste may be dried after each application, or may be dried all at once after multiple applications of the positive electrode paste and the coating material paste.

[0078] For example, by the steps shown in FIGS. 10(A) to 10(D) and 11(A) to 11(D), a structure 5 may be formed that includes a laminate (the basic structure of the solid-state battery body 10A) having a positive electrode layer 11, a negative electrode layer 12, and an electrolyte layer 13 interposed therebetween, and a coating material sheet 23 and a coating material layer 24 (the basic structure of the coating film 20A) that are provided so as to cover the laminate.

[0079] (Cutting of structure) 12A and 12B are diagrams illustrating an example of a cutting process for a structure, in which a cross-sectional view of a main part of an example of a cutting process for a structure is shown.

[0080] The structure 5 formed by the method shown in the first example (FIGS. 5 to 9) or the second example (FIGS. 10 and 11) is cut at predetermined positions C1 and C2 as shown in FIG. 12(A). The structure 5 is cut at position C1 so that an end face of the positive electrode layer 11 is exposed on one cut surface, and at position C2 so that an end face of the negative electrode layer 12 is exposed on the other cut surface. By cutting at positions C1 and C2, a structure 5a is formed in which the end faces of the positive electrode layer 11 and the negative electrode layer 12 are exposed on the cut surfaces, as shown in FIG. 12(B). The cut surfaces of the structure 5a at which the end faces of the positive electrode layer 11 and the negative electrode layer 12 are exposed become a positive electrode drawn surface 1Aa and a negative electrode drawn surface 1Ab, respectively, as described below.

[0081] (Heat treatment of structure) 13A and 13B are diagrams illustrating an example of a heat treatment process for a structure, in which a cross-sectional view of a main part of an example of a heat treatment process for a structure is shown.

[0082] As shown in FIG. 13(A), the structure 5a obtained by cutting is transferred to a heat treatment furnace 40 and heat-treated under predetermined conditions of atmosphere, temperature, and time. For example, the structure 5a transferred to the heat treatment furnace 40 is subjected to a heat treatment for degreasing, which mainly burns off organic components such as binders, and a heat treatment for firing, which mainly sinters the solid electrolyte and coating material. As an example, the heat treatment for degreasing can be performed under conditions of holding at 500°C for 10 hours in an oxygen-containing atmosphere. The heat treatment for firing can be performed under conditions of holding at 600°C for 2 hours in an atmosphere containing nitrogen or oxygen. If a coating material having a sintering temperature that is the same as, equivalent to, or approximately the same as the sintering temperature of the solid electrolyte contained in the structure 5a is used, the solid electrolyte and the coating material can be sintered together by firing under a single condition.

[0083] The heat treatment for firing sinters the solid electrolyte in the electrolyte layer 13 included in the structure 5a. Also, the solid electrolyte in the positive electrode layer 11 and the negative electrode layer 12 included in the structure 5a is sintered. As a result, a solid battery body 10A is formed, which has the positive electrode layer 11, the negative electrode layer 12, and the electrolyte layer 13 interposed therebetween, as shown in FIG. 13(B).

[0084] Furthermore, the heat treatment for firing sinters the coating materials in the coating material sheet 23 and the coating material layer 24 included in the structure 5a, and they are integrated with each other. As a result, an insulating coating film 20A is formed from the coating material sheet 23 and the coating material layer 24, as shown in Fig. 13(B), which covers the solid battery body 10A and has a higher hardness than the fired solid electrolyte included therein.

[0085] The coating film 20A formed by firing may take various forms, such as glass, crystallized glass, polycrystalline, or single crystal. It may consist of a single material phase or two or more material phases with different physical properties. When a ceramic material such as particulate Al2O3 is added to the coating material of the coating film 20A, the coating film 20A may have higher hardness than when a coating material without such a material is used. The coating film 20A is bonded to the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 of the solid-state battery body 10A by this heat treatment. Depending on the properties of the coating material used, the coating film 20A obtained by firing may have a thermal expansion coefficient similar to that of each layer of the solid-state battery body 10A and may have good adhesion to each layer.

[0086] 13(B), the cut surface at which the end face of the positive electrode layer 11 is exposed, i.e., the cut surface at the position C1, is the positive electrode drawn surface 1Aa, and the end face of the positive electrode layer 11 exposed from the positive electrode drawn surface 1Aa is the portion 11a to be connected to the external electrode 31. The cut surface at which the end face of the negative electrode layer 12 is exposed, i.e., the cut surface at the position C2, is the negative electrode drawn surface 1Ab, and the end face of the negative electrode layer 12 exposed from the negative electrode drawn surface 1Ab is the portion 12a to be connected to the external electrode 32.

[0087] After the heat treatment, an external electrode 31 is formed on the positive electrode drawn surface 1Aa of the structure 5a, and an external electrode 32 is formed on the negative electrode drawn surface 1Ab. For example, the external electrodes 31 and 32 are formed on the positive electrode drawn surface 1Aa and the negative electrode drawn surface 1Ab of the structure 5a after the heat treatment by using a method such as applying, drying, and curing a conductive paste, or by depositing a metal by sputtering or plating. This results in a solid state battery 1A as shown in FIGS. 2(A) and 2(B) (and FIGS. 3(A) and 3(B)).

[0088] In the solid-state battery 1A, the solid-state battery body 10A, excluding the positive-electrode extraction surface 1Aa and the negative-electrode extraction surface 1Ab, is covered with a coating film 20A having a hardness greater than that of the solid electrolyte used therein. This effectively prevents cracks and chips in the coating film 20A, the resulting infiltration of moisture and gas, and degradation of the performance of the solid-state battery 1A. Furthermore, in the solid-state battery 1A, a portion of the coating film 20A is provided as an embedded layer in a portion recessed inward from the side surface of the electrolyte layer 13. This effectively prevents peeling of the coating film 20A due to an anchor effect, and also enhances support and strength for the positive electrode layer 11 on the positive-electrode extraction surface 1Aa and the negative electrode layer 12 on the negative-electrode extraction surface 1Ab.

[0089] By the manufacturing method described above, it is possible to manufacture a solid state battery 1A that is excellent in strength and environmental resistance. In addition, the following method shown in FIGS. 14 to 16 can also be used to manufacture the solid state battery.

[0090] 14 to 16 are diagrams illustrating another example of a method for manufacturing a solid-state battery. Here, FIGS. 14 and 15 are diagrams illustrating an example of a process for forming an electrode layer part. FIG. 14(A) is a schematic perspective view of a main part of an example of a support preparation process. FIG. 14(B) is a schematic perspective view of a main part of an example of a process for forming an electrode layer. FIG. 14(C) is a schematic perspective view of a main part of an example of a process for forming a first coating material layer. FIG. 14(D) is a schematic perspective view of a main part of an example of a process for forming an electrolyte layer. FIG. 14(E) is a schematic perspective view of a main part of an example of a process for forming a second coating material layer. FIG. 15(A) is a schematic perspective view of a main part of an example of an electrode layer part, corresponding to FIG. 14(E). FIG. 15(B) is a schematic cross-sectional view taken along the chain line P3c in FIG. 15(A). Fig. 15(C) is a schematic illustration of an example of a cross-sectional view taken along dotted line P4c in Fig. 15(A). Fig. 16 is a diagram illustrating an example of a process for forming a structure and external electrodes. Fig. 16(A) is a schematic illustration of a cross-sectional view of a key portion of an example of a process for stacking a group of parts. Fig. 16(B) is a schematic illustration of a cross-sectional view of a key portion of an example of a process for cutting a structure. Fig. 16(C) is a schematic illustration of a cross-sectional view of a key portion of an example of a process for forming external electrodes on a structure after heat treatment.

[0091] As shown in Fig. 14(A), a positive electrode paste or a negative electrode paste (also referred to as "electrode paste") is applied by screen printing onto a portion of a support 50 such as a PET film, and the applied positive electrode paste or negative electrode paste is dried to form a positive electrode layer 11 or a negative electrode layer 12 (also referred to as "electrode layer"), as shown in Fig. 14(B). After the electrode layer of the positive electrode layer 11 or the negative electrode layer 12 is formed, a coating material paste is applied by screen printing around the electrode layer formed on the portion of the support 50, as shown in Fig. 14(C), and the applied coating material paste is dried to form a coating material layer 24 (embedded layer).

[0092] Next, an electrolyte paste is applied by screen printing onto the electrode layer of the positive electrode layer 11 or the negative electrode layer 12 and onto a portion of the coating material layer 24 formed therearound, as shown in FIG. 14(D), and the applied electrolyte paste is dried to form the electrolyte layer 13. The electrolyte layer 13 is formed so that the coating material layer 24 remains around the entire periphery thereof, not covered by the electrolyte layer 13. After the formation of the electrolyte layer 13, a coating material paste is applied by screen printing onto the entire periphery thereof, as shown in FIG. 14(E), and the applied coating material paste is dried to form the coating material layer 24 (embedded layer).

[0093] For example, by the steps shown in FIGS. 14(A) to 14(E), a part is formed that has a cross-sectional structure as shown in FIG. 15(B) at the position of the chain line P3c shown in FIG. 15(A) and a cross-sectional structure as shown in FIG. 15(C) at the position of the dotted line P4c shown in FIG. 15(A). The parts shown in FIGS. 15(A) to 15(C) (and FIG. 14(E)) can be used as positive electrode layer parts or negative electrode layer parts (also referred to as "electrode layer parts") depending on the type of electrode layer. Alternatively, parts such as those shown in FIGS. 15(A) to 15(C) from which the support 50 has been peeled can also be used as electrode layer parts. Furthermore, parts such as those shown in FIG. 14(C) before the formation of the electrolyte layer 13, or parts from which the support 50 has been peeled, can also be used as electrode layer parts.

[0094] When a positive electrode layer part is formed as an electrode layer part, the positive electrode layer 11 and the electrolyte layer 13 are formed so that a part of the positive electrode layer 11 (a part that will be on the side of a positive electrode drawn-out surface 1Ba described later) protrudes outside the electrolyte layer 13. When a negative electrode layer part is formed as an electrode layer part, the negative electrode layer 12 and the electrolyte layer 13 are formed so that a part of the negative electrode layer 12 (a part that will be on the side of a negative electrode drawn-out surface 1Bb described later) protrudes outside the electrolyte layer 13.

[0095] 14(A) to 14(E) and 15(A) to 15(C) show an example in which an electrode layer of the positive electrode layer 11 or the negative electrode layer 12 and the surrounding coating material layer 24 are formed on the support 50, and then an electrolyte layer 13 and the surrounding coating material layer 24 are formed, but this order can also be reversed. That is, the electrolyte layer 13 and the surrounding coating material layer 24 may be formed on the support 50 according to the above example, and then an electrode layer of the positive electrode layer 11 or the negative electrode layer 12 and the surrounding coating material layer 24 may be formed.

[0096] The electrode layer parts thus formed are used, and according to the method shown in the first example (FIGS. 5 to 9) above, positive electrode layer parts and negative electrode layer parts of predetermined shapes and a coating material sheet 23 are stacked and thermocompressed to form a structure 7, as shown in FIG. 16(A).

[0097] Furthermore, in the method shown in the second example (FIGS. 10 and 11), the structure 7 shown in FIG. 16(A) may be obtained by forming the positive electrode layer 11 or the negative electrode layer 12, forming the coating material layer 24 around it, forming the electrolyte layer 13 thereon, and forming the coating material layer 24 around it, according to the example shown in FIGS. 14(A) to 14(E) and 15(A) to 15(C).

[0098] 16(A), a structure 7 is formed at a position where the end surfaces of the positive electrode layer 11 and the negative electrode layer 12 are exposed, thereby forming a structure 7a as shown in FIG. 16(B). In the structure 7a, of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12, only the positive electrode layer 11 (a portion 11a) is exposed from the positive electrode extracted surface 1Ba, and neither the negative electrode layer 12 nor the electrolyte layer 13 is exposed from the positive electrode extracted surface 1Ba. In the structure 7a, of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12, only the negative electrode layer 12 (a portion 12a) is exposed from the negative electrode extracted surface 1Bb, and neither the positive electrode layer 11 nor the electrolyte layer 13 is exposed from the negative electrode extracted surface 1Bb.

[0099] Then, the cut structure 7a, as shown in Fig. 16(B), is subjected to a heat treatment for degreasing and firing, whereby organic components such as the binder are burned off and the solid electrolyte and coating material are sintered. As a result, as shown in Fig. 16(C), a solid-state battery body 10B is formed, which has a positive electrode layer 11, a negative electrode layer 12, and an electrolyte layer 13 interposed therebetween, and a coating film 20B that covers the solid-state battery body 10B and has a hardness greater than that of the solid electrolyte used therein. Thereafter, an external electrode 31 and an external electrode 32 are formed on the positive electrode drawn-out surface 1Ba and the negative electrode drawn-out surface 1Bb, respectively, to obtain a solid-state battery 1B as shown in Fig. 16(C).

[0100] In the solid state battery 1B, only the positive electrode layer 11 (a portion 11a) of the solid state battery main body 10B is exposed on the positive electrode extraction surface 1Ba, and the positive electrode layer 11 is supported by a portion of the coating film 20B having a higher hardness than the electrolyte layer 13. On the negative electrode extraction surface 1Bb, only the negative electrode layer 12 (a portion 12a) of the solid state battery main body 10B is exposed, and the negative electrode layer 12 is supported by a portion of the coating film 20B having a higher hardness than the electrolyte layer 13. This further enhances the support and strength of the positive electrode layer 11 on the positive electrode extraction surface 1Ba and the negative electrode layer 12 on the negative electrode extraction surface 1Bb in the solid state battery 1B.

[0101] [Evaluation of coating film] Next, we will explain the results of evaluating the hardness of the coating film used in the solid-state battery. The results are shown in Table 1.

[0102] [Table 1]

[0103] To evaluate the hardness of the coating film, samples were prepared by applying, drying, and heat-treating the coating material paste used to form the coating films 20A and 20B of the solid-state batteries 1A and 1B under the same conditions as those used to manufacture the solid-state batteries 1A and 1B. Here, samples were prepared by applying, drying, and heat-treating two types of coating material paste containing different glass components under predetermined conditions ("Glass 1" and "Glass 2" in Table 1). Furthermore, samples were prepared by adding 10 wt.% Al2O3 particles to two types of coating material paste containing different glass components ("Glass 1 + 10 wt.% Al2O3" and "Glass 2 + 10 wt.% Al2O3" in Table 1). For comparison, a sample was prepared by applying, drying, and heat-treating the electrolyte paste used to form the electrolyte layer 13 of the solid-state batteries 1A and 1B under the same conditions as those used to manufacture the solid-state batteries 1A and 1B ("Electrolyte" in Table 1). Each of the five samples prepared was subjected to a mirror finish, and then measurements were taken five or more times using a Vickers hardness tester at loads of 200g, 500g, and 1000g, and the average value was calculated as the Vickers hardness [GPa].

[0104] Table 1 confirms that the samples formed from two types of coating material pastes containing different glass components ("Glass 1" and "Glass 2") have higher Vickers hardness than the sample formed from the electrolyte paste ("Electrolyte"). Furthermore, it was confirmed that the samples formed from two types of coating material pastes containing different glass components, each with 10 wt% Al2O3 particles added ("Glass 1 + 10 wt.% Al2O3" and "Glass 2 + 10 wt.% Al2O3") have higher Vickers hardness than the samples without Al2O3 particles ("Glass 1" and "Glass 2").

[0105] From these evaluation results, it can be said that by using a coating material paste containing a glass component or a coating material paste to which Al2O3 particles are further added as a material for forming the coating films 20A, 20B of the solid state batteries 1A, 1B, it is possible to cover the solid state battery bodies 10A, 10B with coating films 20A, 20B having a higher hardness than the solid electrolyte used therein.

[0106] [Variations] In the above description, an example has been shown in which the solid battery body 10 including one positive electrode layer 11 and one negative electrode layer 12 is covered with the coating film 20, and the solid battery bodies 10A, 10B including two positive electrode layers 11 and two negative electrode layers 12 are covered with the coating films 20A, 20B. The number of positive electrode layers 11 and negative electrode layers 12 included in the solid battery body covered with the coating film is not limited to the above example, and a solid battery body including three or more layers of each may also be covered with the above coating film.

[0107] In the above description, the coating material sheet 23 and the coating material layer 24 serving as the embedded layer may be formed from coating material pastes having different compositions. For example, as long as the coating material sheet 23 and the coating material layer 24 are sintered and integrated by the heat treatment to obtain coating films 20A, 20B having a higher hardness than the solid electrolyte used in the solid battery bodies 10A, 10B, the coating material sheet 23 and the coating material layer 24 may be formed from coating material pastes having different compositions. Furthermore, when the coating material layer 24 is formed by applying the coating material paste multiple times, different coating material pastes may be used in different applications.

[0108] In the above description, an example was shown in which an oxide solid electrolyte is used for the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12, and LAGP is used as the oxide solid electrolyte. However, for LAGP, in addition to amorphous LAGP, crystalline LAGP, or both crystalline and amorphous LAGP can be used.

[0109] The LAGP of the electrolyte layer 13 contains Li 1.5 Al 0.5 Ge 1.5 (PO4)3 is not limited to this composition, and other compositions of NASICON-type LAGP such as Li 1.4 Al 0.4 Ge 1.6 (PO4)3 may be used. In addition to LAGP, for the electrolyte layer 13, NASICON-type LATP (general formula Li 1+z Al z Ti 2-z (PO4)3, 0 < z ≤ 1), one type of Li 1.3 Al 0.3 Ti 1.7 (PO4)3, garnet-type lithium lanthanum zirconate (Li7La3Zr2O 12 , hereinafter referred to as "LLZ"), perovskite-type lithium lanthanum titanate (Li 0.5 La 0.5 TiO3, hereinafter referred to as "LLT"), partially nitrided lithium phosphate (γ-Li3PO4, hereinafter referred to as "LiPON"), and other oxide solid electrolytes may be used.

[0110] For the positive electrode layer 11 and the negative electrode layer 12, as long as a certain performance can be achieved in combination with the active material used, in addition to LAGP, other oxide solid electrolytes such as LATP, LLZ, LLT, and LiPON may be used.

[0111] For example, for the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12, a NASICON-type oxide solid electrolyte represented by the general formula Li 1+y Al y M 2-y (PO4)3 is suitable. Here, the composition ratio y is in the range of 0 < y ≤ 1, and M is one or both of germanium (Ge) and titanium (Ti).

[0112] The electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 may each use the same type of oxide solid electrolyte, or different types of oxide solid electrolytes. The electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 may each use one type of oxide solid electrolyte, or two or more types of oxide solid electrolytes.

[0113] In the above description, LCPO is exemplified as the positive electrode active material contained in the positive electrode layer 11, but other positive electrode active materials may be used, such as lithium cobalt phosphate (LiCoPO4), lithium vanadium phosphate (Li3V2(PO4)3, hereinafter referred to as "LVP"), etc. The positive electrode layer 11 may use one type of material as the positive electrode active material, or two or more types of materials.

[0114] In the above description, TiO2 is exemplified as the negative electrode active material contained in the negative electrode layer 12, but LATP, LVP, niobium oxide (Nb2O5), metal silicide such as nickel (Ni), etc. may also be used as the negative electrode active material.

[0115] Further, since numerous variations and modifications are possible to those skilled in the art, the present invention is not limited to the exact construction and application shown and described above, and all corresponding modifications and equivalents are deemed to be within the scope of the present invention as defined by the appended claims and their equivalents. [Explanation of symbols]

[0116] 1,1A,1B solid state battery 1a,1Aa,1Ba Positive electrode extraction surface 1b,1Ab,1Bb Negative electrode extraction surface 5,5a,7,7a structure 10,10A,10B solid battery body 11 Positive electrode layer 11a,12a parts 12 negative electrode layer 13 Electrolyte layer 13a,13b Main surface 20, 20A, 20B coating film 21,22 Material phase 23 Coating material sheet 24 coating material layer 31,32 External electrode 40 Heat treatment furnace 50 Support

Claims

1. a laminate including an electrolyte layer containing a solid electrolyte, a positive electrode layer provided on a part of a first main surface of the electrolyte layer and not provided on any other part of the first main surface excluding the part, and a negative electrode layer provided on a part of a second main surface of the electrolyte layer opposite to the first main surface and not provided on any other part of the second main surface excluding the part; an insulating coating film that covers the laminate so that a first portion of the positive electrode layer and a second portion of the negative electrode layer are exposed, and that has a hardness higher than that of the solid electrolyte; A solid-state battery comprising:

2. The solid-state battery according to claim 1 , wherein the coating film contains glass or ceramics.

3. the coating film is provided in contact with the other portion of the first main surface of the electrolyte layer on which the positive electrode layer is provided and with a surface of the positive electrode layer excluding the first portion exposed from the laminate, the other portion of the first main surface not being provided with the positive electrode layer, and 2. The solid-state battery according to claim 1, wherein the coating film is provided so as to be in contact with the other part of the second main surface of the electrolyte layer on which the anode layer is provided and the surface of the anode layer excluding the second portion exposed from the laminate, where the other part of the second main surface is not provided with the anode layer.

4. a first external electrode in contact with the first portion of the positive electrode layer and the coating film; a second external electrode in contact with the second portion of the negative electrode layer and the coating film; The solid-state battery according to claim 1 ,

5. 2. The solid-state battery according to claim 1, wherein the coating film includes a first material phase having a first hardness and a second material phase having a second hardness higher than the first hardness.

6. a laminate including an electrolyte layer containing a solid electrolyte, a positive electrode layer provided on a part of a first main surface of the electrolyte layer and not provided on any other part of the first main surface excluding the part, and a negative electrode layer provided on a part of a second main surface of the electrolyte layer opposite to the first main surface and not provided on any other part of the second main surface excluding the part; a coating material that covers the laminate so that a first portion of the positive electrode layer and a second portion of the negative electrode layer are exposed; forming a structure comprising: firing the structure at a first temperature to form an insulating coating film from the coating material, the coating film having a hardness greater than that of the solid electrolyte; A method for manufacturing a solid-state battery, comprising:

7. 7. The method for manufacturing a solid-state battery according to claim 6, wherein in the step of firing the structure at the first temperature, the solid electrolyte is sintered and the coating film is formed at the same time.

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