Solid-state battery

Abstract

Provided is a solid-state battery including a solid-state battery element provided with a positive electrode portion, a negative electrode portion, and a solid electrolyte portion interposed between the positive electrode portion and the negative electrode portion, wherein the solid-state battery includes a first insulating portion provided adjacent to an end of at least one electrode portion of the positive electrode portion and the negative electrode portion, and the first insulating portion has compressive stress when not in use.

Description

solid state battery

[0001] This disclosure relates to solid-state batteries.

[0002] Rechargeable batteries, which can be repeatedly charged and discharged, have long been used in a variety of applications. For example, rechargeable batteries are used as power sources for electronic devices such as smartphones and laptop computers.

[0003] In secondary batteries, a liquid electrolyte is generally used as a medium for ion transfer that contributes to charging and discharging. In other words, so-called electrolyte solutions are used in secondary batteries. However, safety is generally required in such secondary batteries in terms of preventing electrolyte leakage. Furthermore, since organic solvents used in electrolyte solutions are flammable substances, safety is also required in that respect.

[0004] Therefore, research is underway on solid-state batteries that use solid electrolytes instead of liquid electrolytes.

[0005] Japanese Patent Publication No. 2023-165328

[0006] Generally, in solid-state batteries, the electrode portion expands during charging and discharging, resulting in stress on the solid electrolyte portion adjacent to the electrode. This stress can cause cracks in the solid electrolyte portion. Therefore, a buffer layer is sometimes provided around the electrode portion to alleviate the stress. However, if the degree of expansion of the electrode portion is large, the buffer layer may not be able to withstand the stress, and cracks may occur in the solid electrolyte portion.

[0007] This disclosure has been made in view of the above issues. Specifically, the main object of this disclosure is to provide a solid-state battery that can relatively reduce the degree of expansion of the electrode portion during charging and suitably reduce the occurrence of cracks in the solid electrolyte portion and the like.

[0008] To achieve the above objective, one embodiment of the present disclosure provides a solid battery including a solid battery element comprising a positive electrode portion, a negative electrode portion, and a solid electrolyte portion interposed between the positive electrode portion and the negative electrode portion, wherein the solid battery includes a first insulating portion provided adjacent to the end of at least one of the electrode portions of the positive electrode portion and the negative electrode portion, and the first insulating portion has compressive stress when not in use.

[0009] Furthermore, in order to achieve the above objective, one embodiment of the present disclosure provides a solid battery comprising a solid battery element having a positive electrode portion, a negative electrode portion, and a solid electrolyte portion interposed between the positive electrode portion and the negative electrode portion, and an outer casing surrounding the solid battery element, further comprising a first insulating portion provided adjacent to the end of at least one electrode portion of the positive electrode portion and the negative electrode portion, and a second insulating portion provided between the solid battery element and the outer casing, wherein the second insulating portion has compressive stress when not in use.

[0010] According to one embodiment of the present disclosure, the degree of expansion of the electrode portion during charging of a solid-state battery can be relatively reduced, and the occurrence of cracks in the solid electrolyte portion and the like can be suitably reduced.

[0011] Figure 1 is a schematic cross-sectional view showing an unused solid-state battery according to the first embodiment of this disclosure. Figure 2 is a schematic cross-sectional view showing an unused solid-state battery according to a modified example of the first embodiment of this disclosure. Figure 3 is a schematic cross-sectional view showing an unused solid-state battery according to a further modified example of the first embodiment of this disclosure.

[0012] The solid-state battery of this disclosure will be described in detail below. While the description will be made with reference to the drawings as necessary, the illustrations are for illustrative purposes only to help understand this disclosure, and the appearance and dimensional ratios may differ from those of the actual product.

[0013] In this disclosure, "solid-state battery" broadly refers to a battery whose constituent elements are made of solids, and narrowly refers to an all-solid-state battery whose constituent elements (particularly preferably all constituent elements) are made of solids. In one preferred embodiment, the solid-state battery in this disclosure is a stacked solid-state battery configured such that each part constituting the battery constituent unit is stacked on top of each other, preferably such parts are made of fired material. The "solid-state battery" is a so-called "rechargeable battery" that can be repeatedly charged and discharged. The term "rechargeable battery" is not overly restrictive and may also include, for example, energy storage devices. In particular, the solid-state battery in this disclosure refers to a chip-type small battery. Such a chip-type battery may be a rectangular parallelepiped, with a length of about 2 mm to 10 mm and a volume of about 1 cm³.３ It could be a rectangular prism with a length of 10 mm, a width of 5 mm, and a height of 2 mm.

[0014] In this specification, "cross-sectional view" refers to the state of a solid-state battery when viewed from a direction substantially perpendicular to the thickness direction based on the stacking direction of the active material constituting the solid-state battery. In this specification, "plan view" refers to the state of a solid-state battery when viewed from above or below along the thickness direction based on the stacking direction of the active material constituting the solid-state battery. Unless otherwise specified, the same reference numeral or symbol shall indicate the same component, part, or have the same meaning. In a preferred embodiment, the vertical downward direction (i.e., the direction in which gravity acts) can be considered as "downward direction," and the opposite direction can be considered as "upward direction."

[0015] [Basic Configuration of Solid-State Battery] Figure 1 is a schematic cross-sectional view of a solid-state battery in unused condition according to the first embodiment of this disclosure. Figure 2 is a schematic cross-sectional view of a solid-state battery in unused condition according to a modified example of the first embodiment of this disclosure. A solid-state battery has at least positive electrode and negative electrode portions and a solid electrolyte portion. Specifically, as shown in Figures 1 and 2, solid-state batteries 200, 200A include a solid-state battery element 100 which includes a battery component unit consisting of a positive electrode portion 10, a negative electrode portion 20, and a solid electrolyte portion 30 interposed between them.

[0016] The solid-state battery 200 according to this disclosure is typically a laminated solid-state battery 200 having at least one battery component unit along the stacking direction L, each unit comprising a positive electrode portion 10, a negative electrode portion 20, and a solid electrolyte portion 30 interposed between them; and also having a positive electrode end face electrode portion 40A and a negative electrode end face electrode portion 40B provided on opposing sides of the laminated solid-state battery 200. In the laminated solid-state battery 200, the positive electrode portion 10 and the negative electrode portion 20 are alternately stacked via the solid electrolyte portion 30.

[0017] Solid-state batteries may have their constituent parts formed by firing, and the positive electrode, negative electrode, and solid electrolyte may form fired parts. Preferably, the positive electrode, negative electrode, and solid electrolyte are each fired integrally with each other, and therefore the laminated solid-state battery is a single fired body.

[0018] The positive electrode portion is an electrode portion containing at least a positive electrode active material. The positive electrode portion may further contain a solid electrolyte. In one preferred embodiment, the positive electrode portion is composed of a sintered body containing at least positive electrode active material particles and solid electrolyte particles. On the other hand, the negative electrode portion is an electrode portion containing at least a negative electrode active material. The negative electrode portion may further contain a solid electrolyte. In one preferred embodiment, the negative electrode portion is composed of a sintered body containing at least negative electrode active material particles and solid electrolyte particles. Positive and negative electrode portions having such configurations can also be referred to as a "composite positive electrode" and a "composite negative electrode," respectively.

[0019] The positive electrode active material and the negative electrode active material are substances involved in ion transfer in a solid-state battery. Ions move (conduce) between the positive electrode and the negative electrode via the solid electrolyte, and charging and discharging occur through the transfer of electrons. It is particularly preferable that each electrode portion of the positive electrode and the negative electrode is capable of intercalating and deintercalating lithium ions or sodium ions. In other words, it is preferable that the solid-state battery is an all-solid-state secondary battery in which charging and discharging of the battery occurs by the movement of lithium ions or sodium ions between the positive electrode and the negative electrode via the solid electrolyte.

[0020] (Positive electrode section) (Positive electrode active material) The positive electrode active material included in the positive electrode section may be at least one selected from the group consisting of lithium-containing phosphate compounds having a NASICON-type structure, lithium-containing phosphate compounds having an olivine-type structure, lithium-containing layered oxides, and lithium-containing oxides having a spinel-type structure. An example of a lithium-containing phosphate compound having a NASICON-type structure is Li ３ V ２ (PO ４ ) ３ Examples include Li ３ Fe２ (PO ４ ) ３ , LiFePO ４ , and / or LiMnPO ４ , and the like. Examples of lithium-containing layered oxides include LiCoO ２ , and / or LiCo １／３ Ni １／３ Mn １／３ O ２ , and the like. Examples of lithium-containing oxides having a spinel structure include LiMn ２ O ４ , and / or LiNi ０．５ Mn １．５ O ４ , and the like. The type of lithium compound is not particularly limited, and may be, for example, a lithium transition metal composite oxide or a lithium transition metal phosphate compound. A lithium transition metal composite oxide is a general term for oxides containing lithium and one or more transition metal elements as constituent elements, and a lithium transition metal phosphate compound is a general term for phosphate compounds containing lithium and one or more transition metal elements as constituent elements. The type of transition metal element is not particularly limited, and examples thereof include cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe).

[0021] Further, examples of the positive electrode active material capable of inserting and extracting sodium ions include at least one selected from the group consisting of sodium-containing phosphate compounds having a NASICON structure, sodium-containing phosphate compounds having an olivine structure, sodium-containing layered oxides, and sodium-containing oxides having a spinel structure. For example, in the case of a sodium-containing phosphate compound, Na ３ V ２ (PO ４ ) ３ , NaCoFe ２ (PO ４ ) ３ , Na ２ Ni ２ Fe(PO ４ ) ３ , Na ３ Fe ２ (PO ４ )３ Na ２ FeP ２ O ７ Na ４ Fe ３ (PO ４ ) ２ (P ２ O7), and NaFeO as a sodium-containing layered oxide. ２ At least one selected from the group consisting of the following can be mentioned.

[0022] In addition, the positive electrode active material may be, for example, an oxide, disulfide, chalcogenide, or conductive polymer. Oxides may be, for example, titanium oxide, vanadium oxide, or manganese dioxide. Disulfides may be, for example, titanium disulfide or molybdenum sulfide. Chalcogenides may be, for example, niobium selenide. Conductive polymers may be, for example, disulfide, polypyrrole, polyaniline, polythiophene, polyparastyrene, polyacetylene, or polyacene.

[0023] (Negative electrode section) Examples of negative electrode active materials included in the negative electrode section include at least one selected from the group consisting of oxides containing at least one element selected from the group consisting of titanium (Ti), silicon (Si), tin (Sn), chromium (Cr), iron (Fe), niobium (Nb), and molybdenum (Mo), carbon materials such as graphite, graphite-lithium compounds, lithium alloys, lithium-containing phosphate compounds having a NASCICON-type structure, lithium-containing phosphate compounds having an olivine-type structure, and lithium-containing oxides having a spinel-type structure. An example of a lithium alloy is Li-Al. An example of a lithium-containing phosphate compound having a NASCICON-type structure is Li ３ V ２ (PO ４ ) ３ , and / or LiTi ２ (PO ４ ) ３ Examples include Li ３ Fe ２ (PO ４ ) ３ , and / or LiCuPO４ Examples include Li ４ Ti ５ O １２ These are some examples.

[0024] Furthermore, examples of negative electrode active materials capable of intercalating and deintercalating sodium ions include at least one selected from the group consisting of sodium-containing phosphate compounds having a nasicone-type structure, sodium-containing phosphate compounds having an olivine-type structure, and sodium-containing oxides having a spinel-type structure.

[0025] In addition, in a solid-state battery, the positive electrode and the negative electrode may be made of the same material.

[0026] The positive electrode and / or negative electrode may contain a conductive material. Examples of conductive materials included in the positive and negative electrode include at least one metallic material such as silver, palladium, gold, platinum, aluminum, copper, and nickel, as well as carbon.

[0027] Furthermore, the positive electrode and / or negative electrode may contain a sintering aid. Examples of sintering aids include at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide.

[0028] The thickness of the positive electrode and the negative electrode is not particularly limited, but for example, they may be 1 μm or more and 50 μm or less, and more particularly 1 μm or more and 15 μm or less, respectively.

[0029] (Positive electrode current collector / Negative electrode current collector) Although not essential elements of the electrode section, the positive electrode section and the negative electrode section may each be equipped with a positive electrode current collector and a negative electrode current collector, respectively. The positive electrode current collector and the negative electrode current collector may each be in the form of foil. However, if greater emphasis is placed on aspects such as improved electronic conductivity through integral firing, reduction of manufacturing costs for solid-state batteries, and / or reduction of internal resistance of solid-state batteries, the positive electrode current collector and the negative electrode current collector may each be in the form of a fired body.

[0030] It is preferable to use materials with high conductivity for the positive electrode current collector constituting the positive electrode current collector section and the negative electrode current collector constituting the negative electrode current collector section. For example, silver, palladium, gold, platinum, aluminum, copper, and / or nickel may be used. The positive electrode current collector and the negative electrode current collector may each have an electrical connection part for electrical connection to the outside, and may be configured to be electrically connectable to the end face electrode section.

[0031] Furthermore, if the positive electrode current collector and the negative electrode current collector are in the form of a fired body, they may be composed of a fired body containing a conductive material and a sintering aid. The conductive material included in the positive electrode current collector and the negative electrode current collector may be selected from materials similar to those that may be included in the positive electrode and the negative electrode. The sintering aid included in the positive electrode current collector and the negative electrode current collector may be selected from materials similar to those that may be included in the positive electrode and the negative electrode.

[0032] As mentioned above, positive and negative electrode current collectors are not essential for solid-state batteries, and solid-state batteries without such collectors are also conceivable.

[0033] (Solid Electrolyte) The solid electrolyte is a material that can conduct lithium ions or sodium ions. In particular, the solid electrolyte portion that forms the battery component unit in a solid-state battery may form a portion that can conduct lithium ions between the positive electrode portion and the negative electrode portion. The solid electrolyte portion only needs to be provided between the positive electrode portion and the negative electrode portion. In other words, the solid electrolyte portion may exist around the positive electrode portion and / or negative electrode portion so as to protrude from between the positive electrode portion and the negative electrode portion. Specific solid electrolytes include, for example, one or more types from among crystalline solid electrolytes, glass-based solid electrolytes, and glass-ceramic solid electrolytes.

[0034] Crystalline solid electrolytes include, for example, oxide-based crystalline materials and sulfide-based crystalline materials. Examples of oxide-based crystalline materials include lithium-containing phosphate compounds having a nasicone structure, oxides having a perovskite structure, oxides having a garnet-type or garnet-type similar structure, and oxide glass-ceramic lithium-ion conductors.

[0035] Examples of the lithium-containing phosphate compound having a NASICON structure include Li ｘ M ｙ (PO ４ ) ３ (1≦x≦2, 1≦y≦2, and M is at least one selected from the group consisting of titanium (Ti), germanium (Ge), aluminum (Al), gallium (Ga) and zirconium (Zr)). Examples of the lithium-containing phosphate compound having a NASICON structure include, for instance, Li １．２ Al ０．２ Ti １．８ (PO ４ ) ３ and the like. Examples of oxides having a perovskite structure include La ０．５ 5Li ０．３５ TiO ３ and the like. Examples of oxides having a garnet-type or garnet-like similar structure include Li ７ La ３ Zr ２ O １２ and the like. Further, examples of sulfide-based crystalline materials include thio-LISICON, for example, Li ３．２５ Ge ０．２５ P ０．７５ S ４ and Li １０ GeP ２ S １２ and the like. The crystalline solid electrolyte may contain a polymer material (e.g., polyethylene oxide (PEO) etc.).

[0036] Glass-based solid electrolytes include, for example, oxide-based glass materials and sulfide-based glass materials. The oxide-based glass materials include, for example, 50Li ４ SiO ４ ·50Li ３ BO ３ and the like. Further, the sulfide-based glass materials include, for example, 30Li ２ S·26B ２ S ３ ·44LiI, 63Li ２ S·36SiS ２ ·1Li ３ PO ４ , 57Li ２ S·38SiS２ ・5Li ４ SiO ４ , 70Li ２ S・30P ２ S ５ and 50Li ２ S・50GeS ２ and the like.

[0037] Glass-ceramic solid electrolytes are, for example, oxide glass-ceramic materials and sulfide glass-ceramic materials. As the oxide glass-ceramic material, for example, a phosphate compound containing lithium, aluminum and titanium as constituent elements (LATP), and a phosphate compound containing lithium, aluminum and germanium as constituent elements (LAGP) can be used. LATP is, for example, Li １．０７ Al ０．６９ Ti １．４６ (PO ４ ) ３ and the like. Also, LAGP is, for example, Li １．５ A ｌ０．５ Ge １．５ (PO ４ ) and the like. Also, as the sulfide glass-ceramic material, for example, Li ７ P ３ S １１ and Li ３．２５ P ０．９５ S ４ and the like.

[0038] Further, examples of the solid electrolyte capable of conducting sodium ions include a sodium-containing phosphate compound having a NASICON structure, an oxide having a perovskite structure, and an oxide having a garnet-type or garnet-type similar structure. As the sodium-containing phosphate compound having a NASICON structure, Na ｘ M ｙ (PO ４ ) ３ (1≦x≦2, 1≦y≦2, M is at least one selected from the group consisting of Ti, Ge, Al, Ga and Zr).

[0039] The solid electrolyte portion may contain a sintering aid. The sintering aid included in the solid electrolyte portion may be selected from materials similar to those used for sintering aids included in the positive electrode portion and the negative electrode portion.

[0040] The thickness of the solid electrolyte portion is not particularly limited. The thickness of the solid electrolyte portion located between the positive electrode portion and the negative electrode portion may be, for example, 1 μm or more and 15 μm or less, and particularly 1 μm or more and 10 μm or less.

[0041] (End Electrode Sections) The solid-state battery 200 of this disclosure is generally provided with end electrode sections 40 (40A, 40B). In particular, the positive and negative end electrode sections 40A and 40B are provided in pairs on the side surface of the solid-state battery 200. More specifically, the positive electrode side end electrode section 40A, which is connected to the positive electrode section 10, and the negative electrode side end electrode section 40B, which is connected to the negative electrode section 20, are provided in pairs (see Figure 1). The end electrode sections 40 (40A, 40B) can be made of a material with high conductivity. The material of the end electrode section 40 is not particularly limited, but at least one conductive material selected from the group consisting of silver, gold, platinum, aluminum, copper, tin, and nickel can be used.

[0042] The end electrode portions 40 (40A, 40B) may further contain a sintering aid. Examples of sintering aids include materials similar to those used in the positive electrode portion 10.

[0043] In one preferred embodiment, the end face electrode portion 40 (40A, 40B) is composed of a sintered body containing at least a conductive material and a sintering aid.

[0044] (Exterior portion) An exterior portion 60 may be provided that covers or surrounds at least a part of the outer surface of at least one battery component unit, excluding the end electrode portion. The exterior portion 60 is formed on the outermost part of the solid battery and is intended to protect the solid battery element 100 electrically, physically, and chemically. The material constituting the exterior portion 60 is preferably excellent in insulating properties, durability, moisture resistance, and environmental safety. For example, glass, ceramics, thermosetting resin, photocurable resin, etc., are preferably used.

[0045] [Features of the Solid-State Battery of This Disclosure] After considering the basic configuration of the solid-state battery, the following describes the features of a solid-state battery according to one embodiment of this disclosure.

[0046] The inventors of the present invention have diligently studied solutions to suitably reduce the occurrence of cracks on the peripheral edge of the solid electrolyte portion 30 during charging of a solid battery 200, when the solid electrolyte portion 30 is provided without gap between the opposing positive electrode portion 10 and negative electrode portion 20 and is in contact with the end portion 70 (the side not connected to the end face electrode 40) of the electrode portion (positive electrode portion 10 / negative electrode portion 20). As a result, the inventors of the present invention have newly discovered a characteristic configuration in the interface region between the end portion 70 (the side not connected to the end face electrode 40) of the electrode portion and the solid electrolyte portion 30.

[0047] Specifically, the inventors of the present invention have come up with the technical idea of ​​"providing a first insulating portion in the solid battery 200 that is provided adjacent to at least one end of the positive electrode portion 10 and the negative electrode portion 20 in a cross-sectional view, and that has compressive stress when not in use." By having such a first insulating portion 50, it is possible to suppress the degree of expansion of the electrode portion (positive electrode portion 10 / negative electrode portion 20) during charging, and to provide a solid battery 200 that can suitably reduce the occurrence of cracks in the solid electrolyte portion 30, etc. of the solid battery 200.

[0048] More specifically, when not in use, the first insulating portion 50, which has been pre-applied with compressive stress, is positioned in cross-sectional view between at least one end 70 (the side not connected to the end face electrode 40) of the electrode portion (positive electrode portion 10 / negative electrode portion 20) and the end face electrode portions 40A and 40B. With this arrangement of the first insulating portion 50, even if the electrode portion expands outward when the solid battery 200 is in use, the direction of action of the compressive stress that was present before use is inward, opposite to the outward direction in which the electrode portion expands. Therefore, the outward expansion of the electrode portion can be relatively mitigated by the inward-acting compressive stress of the first insulating portion 50. As a result, the effect of the expansion of the electrode portion during use can be physically suppressed, and the occurrence of cracks in the solid electrolyte portion 30, etc., can be more effectively reduced. Accordingly, damage to the solid battery 200 and deterioration of its electrical characteristics can be suitably reduced.

[0049] In this specification, "outward direction" refers to the direction acting outward from the center or inside of the solid-state battery 200 (for example, the stacking direction and / or width direction), and "inward direction" refers to the direction opposite to the outward direction, i.e., the direction acting toward the center of the solid-state battery 200. Furthermore, "when not in use" as used herein refers to the state before the solid-state battery 200 is connected to another electrical device for use. On the other hand, "when in use" refers to the state in which the solid-state battery 200 is connected to another electrical device and charging and discharging are performed, and may also be simply described as "during charging and discharging."

[0050] In a plan view, the first insulating portion 50 is partially adjacent to the ends 70 of the positive electrode portion 10 and the negative electrode portion 20, and is configured such that the positive electrode portion 10 and the negative electrode portion 20 are surrounded by the first insulating portion 50 and the end face electrode portions 40A and 40B.

[0051] Based on the above technical concept, a first insulating portion 50 is provided adjacent to the end 70 of the electrode portion (positive electrode portion 10 / negative electrode portion 20) and having compressive stress. Specifically, as shown in Figure 1, in a cross-sectional view, the positive electrode portion 10 and the negative electrode portion 20 are configured to face each other via the solid electrolyte portion 30. In a plan view, the first insulating portion 50 is adjacent to the end 70 of the electrode portion (positive electrode portion 10 / negative electrode portion 20), and the electrode portion (positive electrode portion 10 / negative electrode portion 20) is configured to be surrounded by the first insulating portion 50 and the end face electrode portion 40 (specifically, the positive end face electrode portion 40A / negative end face electrode portion 40B).

[0052] Figure 1 is a schematic cross-sectional view showing the internal structure of a solid-state battery 200 in unused condition according to the first embodiment of the present disclosure. The solid-state battery 200 of the present disclosure is provided with "a first insulating portion 50 that, in cross-sectional view, is provided adjacent to the end of at least one of the electrode portions of the positive electrode portion 10 and the negative electrode portion 20, and has compressive stress when not in use," thereby allowing compressive stress to be applied to the electrode portions (for example, the first insulating portion 50A adjacent to the positive electrode portion is on the positive electrode portion, and the first insulating portion 50B adjacent to the negative electrode portion is on the negative electrode portion). That is, since compressive stress can be applied in the inward direction of the solid-state battery 200, the effect of expansion of the electrode portions due to charging can be reduced. This is characterized in that the stress on the solid electrolyte portion 30, etc. due to the expansion of the electrode portions can be effectively relieved.

[0053] The compressive stress of the first insulating portion 50 is determined by the difference between the thermal expansion coefficients of the adjacent solid battery element 100, i.e., the positive electrode portion 10 or the negative electrode portion 20 and the solid electrolyte portion 30, and the thermal expansion coefficient of the first insulating portion. Specifically, in the positive electrode portion 10, compressive stress is generated in the first insulating portion 50A based on the difference between the thermal expansion coefficients of the adjacent solid electrolyte portion 30 and the positive electrode portion 10 and the thermal expansion coefficient of the first insulating portion 50A. Similarly, in the negative electrode portion 20, compressive stress is generated in the first insulating portion 50B due to the difference between the thermal expansion coefficients of the adjacent solid electrolyte portion 30 and the negative electrode portion 20 and the thermal expansion coefficient of the first insulating portion 50B.

[0054] The compressive stress σ is influenced by three factors: the difference between the elastic modulus and thermal expansion coefficient of the materials, and the rate of temperature change, as shown in the following equation. In the formula, E is Young's modulus (Pa), α is the coefficient of thermal expansion (1 / °C), and T is the temperature (°C). α refers to the difference in the coefficient of thermal expansion between the solid battery element 100 and the adjacent solid battery element 100, and T is the difference between the maximum firing temperature of the solid battery 200 and the temperature before use (e.g., 25°C, room temperature, etc.).

[0055] From the above formula, the compressive stress applied to the first insulating portion 50 is caused by the difference between the thermal expansion coefficient of the adjacent solid battery element 100 and the thermal expansion coefficient of the first insulating portion 50. In other words, the first insulating portion 50 has a different thermal expansion coefficient from at least one of the adjacent electrode portion (positive electrode portion 10 / negative electrode portion 20) and the solid electrolyte portion 30.

[0056] In the above formula, the relationship between the thermal expansion coefficient α, temperature T, and the generation of compressive stress σ will be explained. When multiple materials having different thermal expansion coefficients (for example, the first insulating part 50, the solid electrolyte part 30, and the electrode part (positive electrode part 10 / negative electrode part 20)) come into contact, each material exhibits different expansion behavior in response to temperature changes, and as a result, compressive stress is generated at the contact surface of each material.

[0057] For example, if the negative electrode portion 20 and the solid electrolyte portion 30 are in contact with the first insulating portion 50B, and the first insulating portion 50B has a smaller coefficient of thermal expansion than the negative electrode portion 20 and the solid electrolyte portion 30, then during cooling, the amount of contraction of the adjacent negative electrode portion 20 and the solid electrolyte portion 30 may be relatively larger. Therefore, due to the contact between the negative electrode portion 20 and the solid electrolyte portion 30 and the first insulating portion 50B, the first insulating portion 50B may have an effect of suppressing (or restricting) their free contraction. As a result, compressive stress is applied to the first insulating portion 50B.

[0058] On the other hand, during cooling, the first insulating portion 50B is relatively more prone to expansion (i.e., less prone to contraction) than the negative electrode portion 20 and the solid electrolyte portion 30, so the negative electrode portion 20 and the solid electrolyte portion 30 may suppress the expansion of the first insulating portion 50B. As a result, tensile stress is applied to the negative electrode portion 20 and the solid electrolyte portion 30 as a reaction to the above. In other words, a material adjacent to a material to which compressive stress is applied experiences opposing tensile stress due to the difference in thermal expansion coefficients. Thus, in the process of cooling from a high temperature to a low temperature, compressive stress is generated in materials with a small thermal expansion coefficient.

[0059] The solid-state battery 200 according to this disclosure has compressive stress when not in use. Specifically, after the sintering process in the manufacturing process of the solid-state battery 200, during the cooling process of the solid-state battery 200 to room temperature, compressive stress is generated in the first insulating portion 50 due to the difference in the thermal expansion coefficients of each component, and this compressive stress is maintained even when not in use. In particular, the fact that the first insulating portion 50 has compressive stress acting inward when not in use suppresses or reduces the degree of expansion of the electrode portion during charging and discharging. As a result, it is possible to reduce the occurrence of interfacial delamination and cracks in the solid electrolyte portion 30, etc., caused by volume changes.

[0060] Therefore, in order for the first insulating portion 50 to have compressive stress during the process from the sintering process to room temperature, it is preferable that the thermal expansion coefficient of the first insulating portion 50 is smaller than that of at least one of the thermal expansion coefficients of the electrode portion (positive electrode portion 10 / negative electrode portion 20) and the solid electrolyte portion 30, and it is even more preferable that it is smaller than both the electrode portion and the solid electrolyte portion. As a result, during the cooling process to room temperature after the sintering process, the first insulating portion 50 maintains compressive stress, thereby dispersing and easing internal stress caused by the difference in thermal expansion with adjacent constituent materials. This can reduce the tensile stress applied to the electrode portion (positive electrode portion 10 / negative electrode portion 20) and the solid electrolyte portion 30, thereby improving the mechanical stability of the solid battery 200.

[0061] Furthermore, as described above, compressive stress is generated in the first insulating portion 50 with temperature changes, and this compressive stress increases as the difference in thermal expansion coefficients between adjacent constituent materials increases. Therefore, by selecting a material with a large difference in thermal expansion coefficient with respect to the first insulating portion 50, the degree of expansion of the solid-state battery 200 can be further suppressed. On the other hand, if the compressive stress of the first insulating portion 50 exceeds a predetermined range, it can cause deformation that exceeds the compressive strength and buckling limit of the material of the first insulating portion 50, potentially causing cracks in the solid-state battery element 100. Therefore, it is important to set the difference in thermal expansion coefficients of adjacent materials and select materials within a range in which the solid-state battery 200 can exhibit appropriate battery characteristics at room temperature (e.g., 25°C, or before use). By setting an appropriate range for the difference in thermal expansion coefficients, the durability of the solid-state battery element 100 against temperature changes can be ensured, contributing to improved reliability of the solid-state battery 200.

[0062] The temperature change in the solid-state battery 200 of this disclosure refers to the temperature change from the high temperature state during sintering to the temperature when not in use (before use). For example, after firing at 700°C or higher, compressive stress is generated in the first insulating part 50 during the cooling process to room temperature (e.g., 25°C). This compressive stress increases as the temperature difference between the firing temperature and the temperature when not in use (before use) increases.

[0063] Each material constituting the solid-state battery element 100 generally expands significantly when sintered at high temperatures, but contracts when cooled after sintering. During this expansion and contraction process, an imbalance occurs in the expansion and contraction of each material due to the difference in the thermal expansion coefficients of the different materials. At this time, because adjacent materials are in contact, the free expansion and contraction of each material may be constrained, and this imbalance manifests as internal stress. This imbalance increases in proportion to the temperature change (ΔT), and as a result, the compressive stress applied to the first insulating part 50 may increase. Therefore, it is desirable to design the solid-state battery 200 considering the sintering temperature and the difference in thermal expansion between adjacent materials, within a range in which the solid-state battery 200 can exhibit appropriate battery characteristics at room temperature (e.g., 25°C, or during use). By appropriately setting the sintering temperature and selecting the materials used, the accumulation of stress due to temperature changes can be suppressed, and the structural stability and long-term reliability of the solid-state battery 200 can be improved.

[0064] The first insulating portion 50 having compressive stress stably supports the positive electrode portion 10 and the negative electrode portion 20 when not in use, and can reduce the stress caused by the deformation of the positive electrode portion 10 and the negative electrode portion 20 during charging and discharging. That is, the amount of deformation caused by the expansion of the electrode portion (positive electrode portion 10 / negative electrode portion 20) during charging and discharging can be made relatively small, so that the stress changes applied to them can also be kept to a minimum. Accordingly, the stress acting on the solid electrolyte portion 30 adjacent to the electrode portion (positive electrode portion 10 / negative electrode portion 20) can also be kept to a minimum, and the occurrence of cracks can be suitably reduced.

[0065] As described above, compressive stress is generated in the first insulating part 50 during the cooling process from high temperature (during sintering) to low temperature (when not in use, before use). Therefore, the first insulating part 50 can be made of an oxide-based ceramic that can withstand these temperature changes. Oxide-based ceramics have high heat resistance and a stable coefficient of thermal expansion, and exhibit excellent durability against thermal stress caused by rapid temperature changes. In addition, oxide-based ceramics generally have high chemical stability, and therefore have the characteristic of not degrading easily even in oxidizing and high-temperature environments. Due to these characteristics, the reliability of the structure can be improved by using oxide-based ceramics as the first insulating part 50. Accordingly, by using oxide-based ceramics, compressive stress may be generated during the cooling of the solid-state battery 200 due to the difference in the coefficient of thermal expansion between the oxide ceramic and the adjacent material. As described later, the solid-state battery 200 of this disclosure has its electrodes and insulating parts integrally formed by co-sintering. Therefore, as described above, from the viewpoint of being able to withstand the sintering process in a high-temperature environment, it is preferable that the first insulating part 50 be made of an oxide-based ceramic.

[0066] In one embodiment of the present invention, the compressive stress of the first insulating portion 50 of the chip-type solid battery 200 can be 300 MPa or less. When the compressive stress of the first insulating portion 50 is 300 MPa or less, the occurrence of cracks in the solid electrolyte 30 can be reduced, and in particular, when it is 100 MPa or less, the occurrence of cracks can be suppressed.

[0067] On the other hand, the compressive stress of the first insulating portion 50 can be 10 MPa or more in order to suitably suppress the expansion of the electrode portion during charging. In this case, a compressive stress of 10 MPa or more can reduce the occurrence of cracks in the solid electrolyte 30, and a compressive stress of 20 MPa or more can suppress the occurrence of cracks. By setting the optimal temperature change and selecting the material of the solid battery element 100 in order to apply compressive stress to the first insulating portion 50 within such an appropriate range of compressive stress, the load and deformation on the material during charging and discharging can be minimized. As a result, damage and crack occurrence of the electrode portion (positive electrode portion 10 / negative electrode portion 20) and / or solid electrolyte portion 30 can be reduced.

[0068] Furthermore, the compressive stress can vary depending on the type of adjacent materials (electrode portion, solid electrolyte portion 30, first insulating portion 50) as well as their contact area. Since the compressive stress is determined based on the magnitude and area of ​​the applied force, the larger the contact area between adjacent materials, the greater the area where deformation is constrained, and the easier it is to suppress expansion.

[0069] Furthermore, the film thickness of each component of the solid-state battery element 100 is also an important factor in ensuring that the first insulating portion 50 has a predetermined range of compressive stress. For example, if the film thickness of the solid electrolyte portion 30 is too thick, compressive stress cannot be applied uniformly to the entire adjacent material (electrode portion and first insulating portion 50), and internal stress may tend to concentrate at specific locations within the solid electrolyte portion 30. On the other hand, if the film thickness of the solid electrolyte portion 30 is too thin, sufficient mechanical strength cannot be obtained, and it may not be able to follow the expansion and contraction of the electrode portion (positive electrode portion 10 / negative electrode portion 20), potentially causing delamination between the electrode portion and the first insulating portion 50. Therefore, it is important to set the film thickness of the solid electrolyte portion 30 to a range that ensures uniformity of compressive stress while maintaining sufficient mechanical strength.

[0070] Similarly, the film thickness of the electrode portion (positive electrode portion 10 / negative electrode portion 20) also needs to be appropriately adjusted from the viewpoint of ion conductivity and mechanical stability. Specifically, if the film thickness of the electrode portion (positive electrode portion 10 / negative electrode portion 20) is too thick, the compressive stress between it and the adjacent material (solid electrolyte portion and first insulating portion 50) tends to become uneven. On the other hand, if the film thickness of the electrode portion is too thin, the amount of electrode active material is limited, which may reduce the battery capacity. Also, if the film thickness of the electrolyte portion is too thick, the movement of lithium ions may be hindered, which may reduce the battery characteristics. For this reason, the film thickness of each layer of the solid battery element 100 is preferably between 1 μm and 15 μm, taking into consideration the balance of compressive stress, interfacial stability, and energy density.

[0071] The first insulating portion 50 described above is provided adjacent to at least one end of the positive electrode portion 10 and the negative electrode portion 20. Therefore, the first insulating portion 50 provided around the electrode portion acts as a compressive stress in a one-to-one relationship with the electrode portion, thereby limiting the expansion of the electrode portion. As a result, damage to the electrode portion and adjacent solid electrolyte portion 30, etc., can be suitably reduced.

[0072] Next, as shown in Figure 2, the solid-state battery 200A of this disclosure may be provided with an outer casing 60 on the main surface of the solid-state battery element 100 in order to protect the solid-state battery element 100. Specifically, cracks in the solid electrolyte 30 in the solid-state battery element 100 occur due to the amount of expansion of a single layer of the electrode portion, as described above, but damage to the outer casing 60 in the solid-state battery 200A may occur due to the cumulative amount of expansion of the entire solid-state battery element 100. Therefore, the first insulating portion 50 alone may not be sufficient to reduce damage to the outer casing 60.

[0073] Therefore, in the solid-state battery 200A of the present disclosure, a second insulating portion 51 having compressive stress can be further provided between the solid-state battery element 100 and the outer casing 60. In this case, it is preferable that the second insulating portion 51 has a different coefficient of thermal expansion from the adjacent solid-state battery element 100 (for example, the electrode portion and / or the solid electrolyte portion 30), and that its coefficient of thermal expansion is smaller than that of the adjacent electrode portion and / or the solid electrolyte portion 30.

[0074] The second insulating portion 51 can be positioned opposite the main surface of the solid battery element 100 at a distance from it. With this arrangement, the stress of the second insulating portion 51 can be applied inward to the solid battery element 100, rather than outward, which would cause the solid battery element 100 to expand. As a result, the amount of expansion of the solid battery element 100, i.e., the entire solid battery 200A, is effectively suppressed, and the occurrence of damage to the outer casing 60 can be reduced.

[0075] Furthermore, the second insulating portion 51 can suppress internal stress caused by expansion occurring within the solid battery element 100 (i.e., the electrode portion and the solid electrolyte portion 30), thereby reducing the progression of cracks in the outer casing 60. This improves the durability of the solid battery 200A and enhances safety. Moreover, since it is possible to reduce the occurrence of damage to the outer casing 60 while maintaining the performance of the solid battery element 100, it can also contribute to achieving stable operation over the long term.

[0076] As described in relation to the first insulating portion 50, when compressive stress is applied to the second insulating portion 51, tensile stress (or residual stress) is generated in the outer casing 60. In one embodiment of the present disclosure (specifically, when only the second insulating portion 51 is provided), if the compressive stress of the second insulating portion 51 of the chip-type solid battery 200A is 400 MPa or more, it may exceed the tensile stress that the outer casing 60 can withstand. In this case, the tensile stress of the outer casing 60 may reach 800 MPa. Therefore, it is preferable that the compressive stress of the second insulating portion 51 be less than 400 MPa, and particularly 230 MPa or less.

[0077] Specifically, if the compressive stress of the second insulating part 51 is 230 MPa or less (i.e., the tensile stress of the adjacent outer casing part 60 is 100 MPa), the occurrence of cracks in the outer casing part 60 can be reduced, and if it is 225 MPa or less (i.e., the compressive stress of the adjacent outer casing part 60 is 20 MPa or more), the occurrence of cracks in the outer casing part 60 can be suppressed. Furthermore, in order to suppress the accumulation of the expansion amount of the entire solid battery element 100 (i.e., solid battery 200A), if the tensile stress (or residual stress) of the second insulating part 51 has a compressive stress greater than 0 MPa, more specifically 0.13 MPa or more, the occurrence of cracks can be suppressed. In this case, the compressive stress of the adjacent outer casing part 60 can be 330 MPa. In this way, similar to the first insulating part 50, by setting the magnitude of each force within an appropriate range, the expansion of the solid battery element 100 can be suppressed while maintaining the structure of the outer casing part 60.

[0078] The first insulating portion 50 reduces the amount of expansion of the single layer of the electrode portion (positive electrode portion 10 / negative electrode portion 20) and the solid electrolyte portion 30, and the second insulating portion 51 reduces the cumulative amount of expansion of the entire solid battery element 100, thereby reducing the occurrence of damage to the outer casing 60. Therefore, these insulating portions 50 and 51 may be provided individually or in combination, taking into account the expansion behavior which changes according to the material properties of the solid battery element 100.

[0079] For example, if the expansion amount of each individual layer is small, but the number of stacked electrode and solid electrolyte sections 30 is large, the overall expansion amount of the solid battery element 100 may increase. In such cases, by providing only the second insulating section 51, it is possible to reduce the occurrence of damage to the outer casing 60 without causing cracks in the solid electrolyte 30. On the other hand, if the expansion amount of each individual layer is large, but the number of stacked electrode and solid electrolyte sections 30 is small, as shown in Figure 3, by providing only the first insulating section 50, it is possible to reduce the occurrence of cracks in the electrode section (positive electrode section 10 / negative electrode section 20) and the solid electrolyte section 30.

[0080] As described above, the arrangement of the first insulating portion 50, which has compressive stress, causes the compressive stress inherent in the first insulating portion 50 to act inward, thereby reducing the outward expansion of the electrode portion during charging. Therefore, the occurrence of damage to the electrode portion (positive electrode portion 10 / negative electrode portion 20) and the solid electrolyte portion 30 can be reduced. Because the expansion of these materials can be suppressed, this can contribute to improving the structural reliability and extending the cycle life of the solid battery 200.

[0081] Furthermore, the arrangement of the second insulating portion 51, which has compressive stress, causes compressive stress to act in the direction of the center (inward direction) of the solid battery element 100, thereby reducing the load on the outer casing 60 caused by the accumulation of internal expansion of the battery. This reduces the occurrence of damage to the outer casing 60 and improves its protection performance from the external environment. As a result, it contributes to improving the safety and operational stability of the solid battery 200A. Moreover, by suppressing damage to the outer casing 60, the deterioration of internal components is suppressed, which can contribute to extending the lifespan of the solid battery 200A.

[0082] Furthermore, the compressive stress during charging and discharging of the 200 / 200A solid-state battery described above can be measured using the following apparatus. In this specification, "residual stress" refers to stress including compressive stress and tensile stress, and in the table of the examples described later, compressive stress is shown as a negative value and tensile stress as a positive value.

[0083] (Confocal X-ray Diffraction Measurement) XRD pattern measurements were performed using an X-ray diffraction analyzer (Bruker D8 Advance). From this XRD pattern, peaks originating from the insulating portion were identified and separated into corresponding peaks. Based on the obtained diffraction pattern, each active material was identified. The step width for the X-ray diffraction measurement was 0.01°, the count time was 0.3 seconds or more, the scanning speed was 10° / min, and the angular range was 15° to 70°.

[0084] For details, the insulating part is exposed by polishing or disassembling the solid battery cell. After confirming with a voltage measurement using a tester, XRD measurement is performed as described above. If there are concerns about material deterioration due to exposure to air, the series of operations and measurements are performed in an inert atmosphere.

[0085] The XRD spectrum peaks originating from the insulating portion obtained above can be separated, and each material can be identified. Subsequently, the stress is calculated using analysis software based on the information from the reflected diffraction lines. Since the lattice plane spacing of the crystal planes in the insulating portion changes with stress, the strain and stress are determined from the change in lattice plane spacing from diffraction nuclei that satisfy Bragg's condition.

[0086] [Method for Manufacturing a Solid Battery] The following describes a method for manufacturing a solid battery according to one embodiment of the present disclosure. The solid battery 200 of the present disclosure can be manufactured by a printing method such as screen printing, a green sheet method using a green sheet, or a combination of the above. The following describes in detail the cases in which the printing method and the green sheet method are adopted for the purpose of understanding the present disclosure, but the present disclosure is not limited to these methods. In other words, the solid battery may be manufactured in accordance with the conventional method for manufacturing solid batteries. Furthermore, the order of description and other chronological matters described below are merely for the convenience of explanation and are not necessarily binding. It should be noted in advance that this manufacturing method is merely an example and does not exclude the use of other methods (production of green sheets corresponding to each component of the solid battery → production of a laminate by stacking each of the green sheets → production of a fired body by firing the laminate).

[0087] (Process for forming an unfired laminate) First, several types of pastes, such as paste for the positive electrode, paste for the negative electrode, paste for the positive electrode current collector, paste for the negative electrode current collector, paste for the solid electrolyte, paste for the insulating part, paste for the outer casing, and paste for the end electrode, are used as inks to form an unfired laminate of a predetermined structure on a substrate by printing.

[0088] Each paste can be prepared by wet mixing predetermined constituent materials for each layer, appropriately selected from the group consisting of positive electrode active material, negative electrode active material, conductive material, solid electrolyte material, insulating material, and sintering aid, with an organic vehicle in which an organic material is dissolved in a solvent. For example, the paste for the positive electrode part includes a positive electrode active material, conductive material, solid electrolyte material, organic material, and solvent. The paste for the negative electrode part includes a negative electrode active material, conductive material, solid electrolyte material, organic material, and solvent. The paste for the solid electrolyte part includes a solid electrolyte material, sintering aid, organic material, and solvent. The paste for the insulating part includes an insulating material, sintering aid, organic material, and solvent. The paste for the outer casing part includes a glassy material, a crystalline material, an organic material, and a solvent.

[0089] In wet mixing, media can be used, specifically the ball mill method or the visco mill method. On the other hand, wet mixing methods that do not use media may be used, such as the sand mill method, high-pressure homogenizer method or kneader dispersion method.

[0090] The supporting substrate is not particularly limited as long as it can support the unfired laminate, and for example, a substrate made of a polymer material such as polyethylene terephthalate can be used. When the unfired laminate is subjected to the firing process while being held on the substrate, the substrate may be one that exhibits heat resistance to the firing temperature.

[0091] During printing, printed layers are sequentially laminated with predetermined thickness and pattern shape to form an unfired laminate on a substrate corresponding to a predetermined solid-state battery structure. Specifically, when manufacturing the solid-state battery shown in Figure 1, for example, multiple printed layers are sequentially laminated with predetermined thickness and pattern shape, starting from the bottom layer. During the formation of each printed layer, a drying process (i.e., solvent evaporation) is performed. In particular, when forming the thick edges of the insulating portion, the thickness can be gradually or stepwise increased by reducing the thickness of each printed layer during lamination.

[0092] As the solid electrolyte material included in the paste for the solid electrolyte portion, powders consisting of lithium-containing phosphate compounds having a nasicone structure, oxides having a perovskite structure, and / or oxides having a garnet-type or garnet-type similar structure may be used, as described above.

[0093] As the positive electrode active material included in the paste for the positive electrode, at least one material from the group consisting of, for example, lithium-containing phosphate compounds having a nasicone-type structure, lithium-containing phosphate compounds having an olivine-type structure, lithium-containing layered oxides, and lithium-containing oxides having a spinel-type structure may be used.

[0094] As the negative electrode active material included in the negative electrode paste, for example, a negative electrode active material selected from at least one of the following groups: an oxide containing at least one element selected from the group consisting of Ti, Si, Sn, Cr, Fe, Nb, and Mo; a lithium-containing phosphate compound having a NASCICON-type structure; a lithium-containing phosphate compound having an olivine-type structure; and a lithium-containing oxide having a spinel-type structure; a material included in the above-mentioned solid electrolyte paste; and a conductive material.

[0095] The organic material contained in the paste is not particularly limited, but at least one polymer material selected from the group consisting of polyvinyl acetal resin, cellulose resin, polyacrylic resin, polyurethane resin, polyvinyl acetate resin, and polyvinyl alcohol resin can be used. The solvent is not particularly limited as long as it can dissolve the above organic material, and for example, toluene and / or ethanol may be used.

[0096] As a sintering aid, at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide may be used.

[0097] The coated paste is dried on a hot plate heated to 30°C to 50°C to form a solid electrolyte sheet having a predetermined thickness on a substrate (e.g., PET film).

[0098] After forming the unfired laminate, the unfired laminate may be peeled off the substrate and subjected to the firing process, or the unfired laminate may be subjected to the firing process while remaining on the substrate.

[0099] (Solid-state battery element lamination process) The solid electrolyte sheet is peeled off from the substrate. A positive electrode portion is formed on the solid electrolyte sheet by screen printing, and an insulating portion is formed around the positive electrode portion by screen printing to produce a solid electrolyte sheet with an integrated positive electrode portion. A negative electrode portion is also formed on the solid electrolyte sheet by screen printing, and an insulating portion is formed around the negative electrode portion by screen printing to produce a solid electrolyte sheet with an integrated negative electrode portion. These solid electrolyte sheets with integrated positive electrode portions and solid electrolyte sheets with integrated negative electrode portions are alternately laminated with solid electrolyte portions interposed between them to obtain a solid-state battery element in which solid electrolyte portions are arranged as connecting layers in the uppermost and lowermost layers. Next, it is preferable to perform thermocompression bonding at a predetermined pressure (for example, about 50 to about 100 MPa) followed by isostatic pressing at a predetermined pressure (for example, about 150 to about 300 MPa). By doing so, a predetermined solid-state battery element 100 can be manufactured. Next, the outer casing is formed by dipping the top and bottom surfaces of the solid battery element 100 into the outer casing paste. Furthermore, the outer casing is also formed on the sides of the solid battery element 100 where the end faces of the positive and negative electrodes are not exposed, by dipping them into the outer casing paste.

[0100] (Firing Process) In the firing process, the unfired laminate is fired. Although this is merely an example, firing is carried out by removing organic materials in a nitrogen gas atmosphere containing oxygen gas or in air at, for example, 500°C, and then heating in a nitrogen gas atmosphere or in air at, for example, 700°C to 1000°C. Firing may be carried out while applying pressure to the unfired laminate in the stacking direction (and possibly in the stacking direction and perpendicular to the stacking direction). Firing may be performed all at once after the casing is attached to the solid battery element (simultaneous firing), or the solid battery element may be fired first, then the casing is attached, and then firing is carried out again (sequential firing). The applied pressure is not particularly limited, for example, 1 kg / cm². ２ More than 1000kg / cm ２ The following is particularly true for 5 kg / cm³ ２ More than 500kg / cm ２ The following is acceptable:

[0101] After the firing process, the material is cooled to room temperature (approximately 20-25°C) in order to attach the end-face electrode portion, which will be described later. Compressive stress can be applied to the insulating portion 50 due to the temperature difference between the firing temperature and room temperature. For example, a firing temperature of 1000°C can generate greater compressive stress than a firing temperature of 700°C.

[0102] Next, end-face electrode portions are attached to the resulting laminate. The end-face electrode portions are provided so as to be electrically connectable to the positive electrode portion and the negative electrode portion, respectively. For example, it is preferable to form the terminals by dipping them in a metal paste or the like. Although not particularly limited, it is preferable that the end-face electrode portions be made of at least one selected from silver, gold, platinum, aluminum, copper, tin, and nickel.

[0103] In accordance with this disclosure, structural analysis was performed using drawings that represent the structure of the disclosure in three dimensions for numerical or visual verification. This structural analysis was calculated using the finite element method (FEM, Murata Software, FEMTET). The solid-state battery 200 / 200A related to this disclosure was fabricated using CAD (Computer-aided design) as a chip-type solid-state battery. Its dimensions are 2 mm in height, 10 mm in length, and 5 mm in width, totaling 0.1 cm. ２ In the embodiment, a solid-state battery having a first insulating part and a solid-state battery having a second insulating part were manufactured. Each solid-state battery was manufactured under the conditions shown in Table 1 below, with each layer stacked to a height of 2 mm, and the number of stacks being 50.

[0104] Table 1 shows the parameters for structural analysis. Structural Analysis Conditions Note that the values ​​for the insulating parts in Table 1 above include the values ​​for both the first insulating part and the second insulating part.

[0105] Next, the conditions shown in Table 1 were set for the solid-state batteries fabricated using CAD. Then, an analysis was performed in which the batteries were fired at a firing temperature in the range of 700 to 900°C (Examples 1 to 7) for 2 hours, and then cooled to room temperature (25°C). Compressive stress is generated in the insulating portion due to the difference between the firing temperature and room temperature, and different magnitudes of compressive stress can be applied to the insulating portion due to the difference in firing temperature.

[0106] Subsequently, the battery was charged with a constant current of 1.0C to a predetermined positive electrode potential (3.8V). After reaching the positive electrode potential, charging was continued in constant voltage mode until the current could be reduced to 0.05C. During this charging and discharging process, it was checked whether or not cracks occurred in the insulating part, its adjacent parts, and the outer casing.

[0107] The presence or absence of crack formation during charging was confirmed in solid-state batteries prepared under the conditions shown in Table 1 above. By changing the firing temperature to 700-900°C, solid-state batteries with different compressive stresses in the first insulating portion were obtained. Table 2 shows the presence or absence of crack formation in Examples 1-7 (with compressive stress) and Comparative Example 1 (without compressive stress). Note that residual stress is a stress that includes compressive stress and tensile stress, and in Table 2, compressive stress is shown as a negative value and tensile stress as a positive value, and the same applies to Table 3. Table 2 Relationship between residual stress and cracks in the first insulating portion ○: No cracks found, △: Cracks found during the first charge / discharge cycle that allow for verification of the solid battery's performance, ×: Cracks found that prevent the solid battery from performing as intended.

[0108] As shown in Table 2, compared to Comparative Example 1, which has no compressive stress when unused, it was shown that by manufacturing a solid-state battery with a first insulating part having compressive stress, the occurrence of cracks in the first insulating part 50 and its adjacent parts can be reduced. In Example 1, when the compressive stress of the first insulating part was 10 MPa, the expansion of the electrode part was suppressed, and as a result, the occurrence of cracks in the first insulating part and the adjacent solid electrolyte part was reduced. In Example 2, when the compressive stress was 20 MPa, it was shown that no cracks occurred in either the first insulating part or the adjacent solid electrolyte part.

[0109] On the other hand, as mentioned above, tensile stress is generated in proportion to the increase in compressive stress. However, even when the compressive stress of the first insulating portion in Example 6 was 200 MPa or more, no cracks occurred in the first insulating portion, and the occurrence of cracks in the solid electrolyte adjacent to the first insulating portion was reduced. Therefore, it was shown that in the solid battery of this disclosure, which is provided with a first insulating portion having compressive stress when not in use, the occurrence of cracks in the solid electrolyte portion during charging of the solid battery can be suitably reduced. In this analysis, ○ was used to indicate no crack occurrence, △ to indicate cracks that allow confirmation of the solid battery performance, and × to indicate cracks that do not allow confirmation of the solid battery performance, with ○ and △ being within the acceptable range.

[0110] Table 3 Relationship between residual stress and cracks in the second insulating section. ○: No cracks found, △: Cracks present that allow the performance of the solid battery to be confirmed during the first charge / discharge, ×: Cracks present that prevent the performance of the solid battery from being guaranteed.

[0111] In the solid-state batteries prepared under the conditions shown in Table 1 above, the presence or absence of cracks in the second insulating part and the outer casing during charging was confirmed. By changing the firing temperature from 700 to 900°C, solid-state batteries with different compressive stresses in the second insulating part were obtained. Table 3 shows the presence or absence of cracks in Examples 8 to 11 (with compressive stress) and Comparative Examples 2 and 3, and the relationship between their compressive and tensile stresses (Note that in Examples 8 to 11, the first insulating part is not provided, and only the second insulating part is provided; see Figure 3).

[0112] As shown in Table 3, it was demonstrated that crack formation in the second insulating part and the outer casing can be reduced by manufacturing a solid-state battery that has a second insulating part with pre-existing compressive stress when not in use. When the compressive stress of the second insulating part was 0 MPa (i.e., no compressive stress), the expansion of the entire solid-state battery element could not be suppressed. However, when the compressive stress was between 0.13 MPa and 225 MPa, the expansion could be suppressed, and it was shown that no cracks occurred in either the second insulating part or the outer casing.

[0113] On the other hand, as described above, tensile stress is generated in proportion to the increase in compressive stress, so it was confirmed that crack occurrence is reduced when the compressive stress of the second insulating part is less than 400 MPa (specifically 230 MPa). Thus, it has been shown that in a solid-state battery provided with a second insulating part that has compressive stress when not in use, it is possible to suitably reduce the occurrence of cracks in the outer casing when the solid-state battery is charged. The embodiments of this disclosure have been described above, but these are merely typical examples. Therefore, this disclosure is not limited thereto, and those skilled in the art will easily understand that various embodiments are conceivable without changing the gist of this disclosure.

[0114] Furthermore, the above-described embodiment of the present disclosure encompasses the following preferred embodiments: First embodiment: A solid battery comprising a solid battery element having a positive electrode portion, a negative electrode portion, and a solid electrolyte portion interposed between the positive electrode portion and the negative electrode portion, wherein a first insulating portion is provided adjacent to the end of at least one of the electrode portions of the positive electrode portion and the negative electrode portion, and the first insulating portion has compressive stress when not in use. Second embodiment: The solid battery in the first embodiment, wherein the first insulating portion has a different coefficient of thermal expansion from that of at least one of the adjacent electrode portion and the solid electrolyte portion. Third embodiment: The solid battery in the first embodiment or the second embodiment, wherein the coefficient of thermal expansion of the first insulating portion is smaller than the coefficient of thermal expansion of at least one of the adjacent electrode portion and the solid electrolyte portion. Fourth embodiment: The solid battery in the third embodiment, wherein the film thickness of each of the solid battery elements is 1 μm or more and 15 μm or less. Fifth embodiment: A solid-state battery in which, in any of the first to fourth embodiments, the compressive stress of the first insulating portion is 10 MPa or more and 300 MPa or less. Sixth embodiment: A solid-state battery in which, in the fifth embodiment, the compressive stress of the first insulating portion is 20 MPa or more and 100 MPa or less. Seventh embodiment: A solid-state battery in which, in any of the first to sixth embodiments, the solid-state battery further comprises an outer casing and a second insulating portion provided between the solid-state battery element and the outer casing, wherein the second insulating portion has compressive stress when not in use. Eighth aspect: A solid battery comprising a solid battery element having a positive electrode portion, a negative electrode portion, and a solid electrolyte portion interposed between the positive electrode portion and the negative electrode portion, and an outer casing portion surrounding the solid battery element, further comprising a first insulating portion provided adjacent to the end of at least one of the electrode portions of the positive electrode portion and the negative electrode portion, and a second insulating portion provided between the solid battery element and the outer casing portion, wherein the second insulating portion has compressive stress when not in use. Ninth aspect: A solid battery in the seventh or eighth aspect, wherein the second insulating portion has a different coefficient of thermal expansion from at least one of the adjacent electrode portions, the solid electrolyte portion, or the outer casing portion.10th Embodiment: A solid-state battery in which, according to the 9th embodiment, the thermal expansion coefficient of the second insulating portion is smaller than the thermal expansion coefficient of at least one of the adjacent electrode portion, the solid electrolyte portion, or the outer casing portion. 11th Embodiment: A solid-state battery in which, according to the 8th embodiment, the compressive stress of the second insulating portion is 0.13 MPa or more and 230 MPa or less. 12th Embodiment: A solid-state battery in which, according to the 11th embodiment, the residual stress of the outer casing portion is -330 MPa or more and 100 MPa or less with respect to the compressive stress of the second insulating portion. 13th Embodiment: A solid-state battery in which, according to any of the 1st to 12th embodiments, the insulating portion is an oxide-based ceramic. 14th Embodiment: A solid-state battery in which, according to any of the 1st to 13th embodiments, the solid-state battery is of the chip type.

[0115] The solid-state battery disclosed herein can be used in a variety of fields where energy storage is envisioned. While these are merely examples, the solid-state battery disclosed herein can be used in the electrical, information, and communication fields where mobile devices are used (e.g., the electrical and electronic equipment field or mobile device field, including small electronic devices such as mobile phones, smartphones, laptops and digital cameras, activity trackers, ARM computers, electronic paper, RFID tags, card-type electronic money, and smartwatches), household and small industrial applications (e.g., power tools, golf carts, household, caregiving, and industrial robots), large industrial applications (e.g., forklifts, elevators, and port cranes), transportation systems (e.g., hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles, etc.), power grid applications (e.g., various power generation, road conditioners, smart grids, and general household energy storage systems), medical applications (medical equipment such as earphones and hearing aids), pharmaceutical applications (medication management systems, etc.), as well as IoT, space, and deep-sea applications (e.g., space probes, submersible research vessels, etc.).

[0116] 100: Solid-state battery element 200: Solid-state battery 200A, 200B: Solid-state battery 10: Positive electrode section (11: Positive electrode active material section, 12: Positive electrode current collector) 20: Negative electrode section (21: Negative electrode current collector, 22: Negative electrode active material section) 30: Solid electrolyte section 40A: Positive electrode end face electrode section 40B: Negative electrode end face electrode section 50A: First insulating section on the positive electrode side 50B: First insulating section on the negative electrode side 51: Second insulating section 60: Outer casing section 70: End of electrode section

Claims

1. A solid battery comprising a solid battery element having a positive electrode portion, a negative electrode portion, and a solid electrolyte portion interposed between the positive electrode portion and the negative electrode portion, wherein a first insulating portion is provided adjacent to the end of at least one of the electrode portions of the positive electrode portion and the negative electrode portion, and the first insulating portion has compressive stress when not in use.

2. The solid battery according to claim 1, wherein the first insulating portion has a different coefficient of thermal expansion from at least one of the adjacent electrode portion and the solid electrolyte portion.

3. The solid battery according to claim 1 or 2, wherein the thermal expansion coefficient of the first insulating portion is smaller than the thermal expansion coefficient of at least one adjacent electrode portion and solid electrolyte portion.

4. The solid battery according to any one of claims 1 to 3, wherein the film thickness of each solid battery element is 1 μm or more and 15 μm or less.

5. The solid battery according to any one of claims 1 to 4, wherein the compressive stress of the first insulating portion is 10 MPa or more and 300 MPa or less.

6. The solid battery according to claim 5, wherein the compressive stress of the first insulating portion is 20 MPa or more and 100 MPa or less.

7. The solid battery according to any one of claims 1 to 6, further comprising an outer casing and a second insulating portion provided between the solid battery element and the outer casing, wherein the second insulating portion has compressive stress when not in use.

8. A solid battery comprising a solid battery element having a positive electrode portion, a negative electrode portion, and a solid electrolyte portion interposed between the positive electrode portion and the negative electrode portion, and an outer casing surrounding the solid battery element, further comprising a first insulating portion provided adjacent to the end of at least one electrode portion of the positive electrode portion and the negative electrode portion, and a second insulating portion provided between the solid battery element and the outer casing, wherein the second insulating portion has compressive stress when not in use.

9. The solid battery according to claim 7 or 8, wherein the second insulating portion has a different coefficient of thermal expansion from at least one of the adjacent electrode portion, the solid electrolyte portion, or the outer casing portion.

10. The solid battery according to claim 9, wherein the thermal expansion coefficient of the second insulating portion is smaller than the thermal expansion coefficient of at least one adjacent electrode portion, solid electrolyte portion, or outer casing portion.

11. The solid battery according to claim 8, wherein the compressive stress of the second insulating portion is 0.13 MPa or more and 230 MPa or less.

12. The solid battery according to claim 11, wherein the residual stress of the outer casing is -330 MPa or more and 100 MPa or less with respect to the compressive stress of the second insulating portion.

13. The solid battery according to any one of claims 1 to 12, wherein the insulating part is an oxide-based ceramic.

14. The solid battery according to any one of claims 1 to 13, wherein the solid battery is of chip type.

Images