Solid-state battery

Abstract

Provided is a solid-state battery provided with a positive electrode layer containing a positive electrode active material containing lithium and a solid electrolyte. In an XRD analysis measured while heating the positive electrode layer in a state in which the lithium desorption amount of the positive electrode active material is 40%, the value of the maximum surface spacing is 1, the self-decomposition temperature at which the relative change with respect to the maximum surface spacing is less than 0.995 is 215 DEG C or more, and the solid electrolyte contains lithium borosilicate glass.

Description

Technical Field

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

[0002] Conventionally, secondary batteries that can be repeatedly charged and discharged have been used in various applications. For example, secondary batteries are sometimes used as power sources for electronic devices such as smartphones and laptop computers.

[0003] Secondary batteries generally use a liquid electrolyte as a medium for ion movement during charge and discharge. This is known as an electrolyte solution. However, in general, such secondary batteries require safety to prevent leakage of the electrolyte solution. Furthermore, organic solvents used in electrolyte solutions are flammable, so safety is also a concern.

[0004] Therefore, solid batteries using solid electrolytes instead of electrolyte solutions have been studied.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 5211721

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2021-525449 Summary of the Invention

[0009] Technical problem to be solved by the invention

[0010] The inventors of the present application have noted that existing solid-state batteries have technical problems that need to be overcome and have newly discovered the need to take countermeasures. Specifically, they have discovered the following technical problems.

[0011] As positive electrode materials in solid-state batteries, lithium transition metal oxides and lithium composite transition metal oxides having a crystalline structure can be used (see Patent Documents 1 and 2). Regarding this, solid-state batteries are sometimes used under high-temperature conditions. However, under these high-temperature conditions, the crystalline structure of the positive electrode active material becomes unstable as lithium is released, potentially degrading the battery characteristics of solid-state batteries under high-temperature conditions.

[0012] The present disclosure has been made in view of such technical problems. Specifically, the main object of the present disclosure is to provide a solid battery that can have more appropriate battery characteristics even under high temperature conditions.

[0013] Technical solutions to technical problems

[0014] To achieve the above-mentioned object, in one embodiment of the present disclosure, there is provided a solid battery comprising a positive electrode layer, the positive electrode layer comprising a positive electrode active material containing lithium and a solid electrolyte.

[0015] In a state where the lithium desorption amount of the positive electrode active material is 40%, in an XRD analysis measured while heating the positive electrode layer, the value of the maximum surface spacing is set to 1, and the self-decomposition temperature at which the relative change relative to the maximum surface spacing is less than 0.995 is above 215°C, and the solid electrolyte contains lithium borosilicate glass.

[0016] Effects of the Invention

[0017] A solid battery according to an embodiment of the present disclosure can have more appropriate battery characteristics even under high-temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a perspective view schematically showing the appearance of a solid state battery according to one embodiment of the present disclosure.

[0019] Figure 2 Observe in the direction of the arrow Figure 1 Schematic cross-sectional view of an AA cross-section of a solid-state battery.

[0020] Figure 3 This is a graph showing relative values of the interplanar spacing of the positive electrode active material with respect to the heating temperature in the solid battery according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0021] The solid-state battery of the present disclosure is described in detail below. While the description will be made with reference to the accompanying drawings as needed, the drawings are merely schematic and exemplary for understanding the present disclosure, and their appearance and dimensional ratios may differ from the actual ones.

[0022] As used herein, "cross-sectional view" refers to the shape of a solid battery when viewed from a direction substantially perpendicular to the stacking direction of the stacked structure (simply, the shape when cut along a plane parallel to the thickness direction of the layer). Furthermore, "top view" or "top view shape" as used herein refers to a schematic diagram of an object when viewed from above or below along the thickness direction of the layer (i.e., the stacking direction described above).

[0023] The terms "upward and downward directions" and "leftward and rightward directions" used directly or indirectly in this specification correspond to the vertical and leftward directions in the drawings, respectively. Unless otherwise specified, identical reference numerals or symbols denote identical components or locations or have identical meanings. In a preferred embodiment, it can be understood that the vertically downward direction (i.e., the direction in which gravity acts) corresponds to the "downward direction," and the opposite direction corresponds to the "upward direction."

[0024] The term "solid-state battery" as used in this disclosure broadly refers to a battery whose constituent elements are composed of solids, and narrowly refers to an all-solid-state battery whose constituent elements (particularly preferably all constituent elements) are composed of solids. In a preferred embodiment, the solid-state battery in this disclosure is a laminated solid-state battery in which the layers constituting the battery structural unit are stacked on top of each other, preferably each of these layers is composed of a sintered body. A "solid-state battery" is a so-called "secondary battery" that can be repeatedly charged and discharged. The term "secondary battery" is not overly restrictive in its name and may also include, for example, storage devices.

[0025] The features of the present disclosure relate to the positive electrode layer included in a solid-state battery. First, the basic structure of the solid-state battery disclosed herein is described below to help understand the overall structure of the solid-state battery. However, the solid-state battery structure described here is merely an example for understanding the invention and does not limit the invention.

[0026] [Basic structure of solid-state batteries]

[0027] Figure 1 This is a perspective view schematically showing the appearance of a solid state battery according to one embodiment of the present disclosure. Figure 2 Observe in the direction of the arrow Figure 1 A schematic cross-sectional view of an AA cross-section of a solid battery. A solid battery has at least a positive electrode and a negative electrode layer and a solid electrolyte. Specifically, Figure 1 as well as Figure 2 As shown, the solid battery 200 includes a solid battery laminate 100 , which includes a battery structural unit composed of a positive electrode layer 10A, a negative electrode layer 10B, and at least a solid electrolyte layer 20 interposed therebetween.

[0028] The solid state battery 200 involved in the present disclosure generally includes:

[0029] The solid battery stack 100 includes at least one battery structural unit along the stacking direction L, which is composed of a positive electrode layer 10A, a negative electrode layer 10B, and a solid electrolyte layer 20 interposed therebetween; and

[0030] The positive electrode terminal 40A and the negative electrode terminal 40B are provided on opposing side surfaces of the solid battery stack 100 .

[0031] In the solid battery stack 100 , positive electrode layers 10A and negative electrode layers 10B are alternately stacked with solid electrolyte layers 20 interposed therebetween.

[0032] Each layer constituting a solid battery can be formed by firing, and the positive electrode layer, negative electrode layer, and solid electrolyte layer can also form a fired layer. Preferably, the positive electrode layer, negative electrode layer, and solid electrolyte layer are fired integrally with each other, so it is preferred that the solid battery stack form an integrally fired body.

[0033] The positive electrode layer is an electrode layer that contains at least a positive electrode active material. The positive electrode layer may further contain a solid electrolyte. In a preferred embodiment, the positive electrode layer is composed of a sintered body that contains at least positive electrode active material particles and solid electrolyte particles. On the other hand, the negative electrode layer is an electrode layer that contains at least a negative electrode active material. The negative electrode layer may further contain a solid electrolyte. In a preferred embodiment, the negative electrode layer is composed of a sintered body that contains at least negative electrode active material particles and solid electrolyte particles. The positive electrode layer and the negative electrode layer having such a structure may also be referred to as a "composite positive electrode body" and a "composite negative electrode body", respectively.

[0034] The positive electrode active material and the negative electrode active material are substances that participate in the exchange of electrons in the solid battery. Ions move (conduct) between the positive electrode layer and the negative electrode layer via the solid electrolyte, and the exchange of electrons is carried out, thereby performing charging and discharging. Each electrode layer of the positive electrode layer and the negative electrode layer is particularly preferably a layer that can insert and extract lithium ions or sodium ions. That is, the solid battery is preferably an all-solid-state secondary battery in which lithium ions or sodium ions move between the positive electrode layer and the negative electrode layer via the solid electrolyte to perform charging and discharging of the battery.

[0035] (positive electrode layer)

[0036] The content of the solid electrolyte in the positive electrode layer 10A is not particularly limited, but is generally 10 to 50% by mass, particularly preferably 20 to 40% by mass, relative to the total amount of the positive electrode layer. The positive electrode layer may contain two or more solid electrolytes, in which case the total content of these electrolytes may be within the above range.

[0037] (Negative electrode layer)

[0038] Examples of the negative electrode active material contained in the negative electrode layer include at least one selected from the group consisting of oxides, carbon materials such as graphite, graphite-lithium compounds, lithium alloys, lithium-containing phosphate compounds having a NASICON structure, lithium-containing phosphate compounds having an olivine structure, and lithium-containing oxides having a spinel structure, wherein the oxide contains 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). Examples of lithium alloys include Li-Al. Examples of lithium-containing phosphate compounds having a NASICON structure include Li3V2(PO4)3 and / or LiTi2(PO4)3. Examples of lithium-containing phosphate compounds having an olivine structure include Li3Fe2(PO4)3 and / or LiCuPO4. Examples of lithium-containing oxides having a spinel structure include Li4Ti5O 12 wait.

[0039] Examples of the negative electrode active material capable of intercalating and deintercalating 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, and sodium-containing oxides having a spinel structure.

[0040] The positive electrode layer and / or the negative electrode layer may contain a conductive material. Examples of the conductive material contained in the positive electrode layer and the negative electrode layer include at least one of metal materials such as silver, palladium, gold, platinum, aluminum, copper, and nickel, and carbon.

[0041] Furthermore, the positive electrode layer and / or the negative electrode layer may contain a sintering aid. Examples of the sintering aid 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.

[0042] The thickness of the positive electrode layer and the negative electrode layer is not particularly limited, and for example, each independently can be 2 μm or more and 50 μm or less, and particularly 5 μm or more and 30 μm or less.

[0043] (Positive electrode current collecting layer / negative electrode current collecting layer)

[0044] Although not essential elements of the electrode layer, the positive electrode layer and the negative electrode layer may each include a positive electrode collector layer and a negative electrode collector layer. The positive electrode collector layer and the negative electrode collector layer may each be in the form of a foil. However, if greater emphasis is placed on improving electron conductivity through integrated sintering, reducing solid battery manufacturing costs, and / or reducing the internal resistance of the solid battery, the positive electrode collector layer and the negative electrode collector layer may each be in the form of a sintered body.

[0045] As the positive electrode current collector constituting the positive electrode current collector layer and the negative electrode current collector constituting the negative electrode current collector layer, a material with high electrical conductivity is preferably used, for example, silver, palladium, gold, platinum, aluminum, copper and / or nickel can be used. The positive electrode current collector and the negative electrode current collector can each have an electrical connection portion for electrical connection to the outside, or can be configured to be electrically connected to a terminal.

[0046] It should be noted that when the positive electrode current collecting layer and the negative electrode current collecting layer are in the form of a sintered body, they may also be composed of a sintered body containing a conductive material and a sintering aid. The conductive material contained in the positive electrode current collecting layer and the negative electrode current collecting layer can be selected from the same materials as the conductive materials that can be contained in the positive electrode layer and the negative electrode layer. The sintering aid contained in the positive electrode current collecting layer and the negative electrode current collecting layer can be selected from the same materials as the sintering aids that can be contained in the positive electrode layer and the negative electrode layer.

[0047] As described above, the positive electrode current collecting layer and the negative electrode current collecting layer are not essential to the solid battery, and a solid battery without such a positive electrode current collecting layer and a negative electrode current collecting layer is also conceivable.

[0048] (Solid Electrolyte)

[0049] Solid electrolytes are materials that can conduct lithium or sodium ions. In particular, the solid electrolyte layer that forms the battery's structural unit in solid-state batteries can form a layer between the positive and negative electrode layers that can conduct lithium ions.

[0050] The solid electrolyte layer may also contain a sintering aid. The sintering aid contained in the solid electrolyte layer can be selected from the same materials as the sintering aids that can be contained in the positive electrode layer and the negative electrode layer.

[0051] The thickness of the solid electrolyte layer is not particularly limited. The thickness of the solid electrolyte layer located between the positive electrode layer and the negative electrode layer can be, for example, 1 μm to 15 μm, and particularly 1 μm to 5 μm.

[0052] (Electrode separation section)

[0053] The solid battery 200 of the present disclosure may further include an electrode separation portion (also referred to as a “blank layer” or a “blank portion”) 30 ( 30A, 30B).

[0054] The electrode separator 30A (positive electrode separator) is disposed around the positive electrode layer 10A, thereby separating the positive electrode layer 10A from the negative electrode terminal 40B. Separately, the electrode separator 30B (negative electrode separator) is disposed around the negative electrode layer 10B, thereby separating the negative electrode layer 10B from the positive electrode terminal 40A. While not particularly limited, the electrode separator 30 may be composed of one or more materials selected from the group consisting of, for example, solid electrolytes, insulating materials, and mixtures thereof.

[0055] The solid electrolyte that can constitute the electrode separator 30 can be made of the same material as the solid electrolyte that can constitute the solid electrolyte layer.

[0056] The insulating material that can constitute the electrode separator 30 can also be a material that does not conduct electricity, that is, a non-conductive material. While not particularly limited, the insulating material can be, for example, a glass material or a ceramic material. For example, a glass material can be selected as the insulating material. While not particularly limited, examples of glass materials include at least one selected from the group consisting of soda-lime glass, potassium glass, borate glass, borosilicate glass, barium borosilicate glass, nitrite glass, barium borosilicate glass, bismuth borosilicate glass, bismuth zinc borosilicate glass, bismuth silicate glass, phosphate glass, aluminophosphate glass, and nitrite glass. Furthermore, while not particularly limited, examples of ceramic materials include at least one selected from the group consisting of aluminum oxide (Al2O3), boron nitride (BN), silicon dioxide (SiO2), silicon nitride (Si3N4), zirconium oxide (ZrO2), aluminum nitride (AlN), silicon carbide (SiC), and barium titanate (BaTiO3).

[0057] (terminal)

[0058] In the solid battery 200 disclosed herein, terminals (external terminals) 40 (40A, 40B) are generally provided. In particular, positive and negative terminals 40A and 40B are provided in pairs on the side surfaces of the solid battery. More specifically, the positive-side terminal 40A connected to the positive electrode layer 10A and the negative-side terminal 40B connected to the negative electrode layer 10B are provided in pairs. The terminals 40A and 40B can be provided in a manner covering at least one side surface of the solid battery and can also be referred to as "end surface electrodes." Such terminals 40 (40A, 40B) can be made of a material with high electrical conductivity. There is no particular limitation on the material of the terminal 40, and at least one conductive material selected from the group consisting of silver, gold, platinum, aluminum, copper, tin, and nickel can be cited.

[0059] The terminal 40 ( 40A, 40B) may further contain a sintering aid. Examples of the sintering aid include the same materials as those that may be contained in the positive electrode layer 10A.

[0060] In a preferred embodiment, the terminal 40 ( 40A, 40B) is formed of a sintered body containing at least a conductive material and a sintering aid.

[0061] (Outer material)

[0062] The solid-state battery 200 of the present disclosure typically also includes an outer layer material 60. This outer layer material 60 is typically formed on the outermost surface of the solid-state battery and serves to protect the solid-state battery electrically, physically, and / or chemically. The material constituting the outer layer material 60 preferably exhibits excellent insulation, durability, and / or moisture resistance, and is environmentally safe. For example, glass, ceramics, thermosetting resins, photocurable resins, and mixtures thereof can be used.

[0063] As the glass constituting the outer layer material, the same glass material as that constituting the electrode separator can be used. In addition, as the ceramic material constituting the outer layer material, the same ceramic material as that constituting the electrode separator can be used.

[0064] [Features of the solid state battery disclosed herein]

[0065] The inventors of this application conducted in-depth research on solutions for providing solid-state batteries with more suitable battery characteristics even under high-temperature conditions. More specifically, the inventors of this application focused on the positive electrode layer that constitutes the solid-state battery, believing that the positive electrode active material and solid electrolyte contained in the positive electrode layer help suppress the degradation of the battery characteristics of the solid-state battery under high-temperature conditions. Further research has led to the discovery that the self-decomposition temperature, at which the interplanar spacing of the positive electrode active material begins to decrease relatively with heating, is correlated with the battery characteristics of the solid-state battery under high-temperature conditions (i.e., the high-temperature resistance of the solid-state battery).

[0066] Figure 3 This is a graph showing the relative change in the interplanar spacing of the lattice plane (003) of the positive electrode active material in the positive electrode layer of a solid battery according to one embodiment of the present disclosure, based on the heating temperature. As shown in the figure, when the positive electrode layer is heated, the interplanar spacing gradually increases as the temperature rises, and soon reaches a limit point (maximum value). When the heating is further carried out, the interplanar spacing decreases. This reduction in interplanar spacing is based on the self-decomposition (phase separation) of the positive electrode active material accompanying the heating. Therefore, the temperature at which the relative change relative to the maximum interplanar spacing is less than a specified amount can also be referred to as the "self-decomposition temperature" or "phase separation temperature". That is, in this application specification, the self-decomposition temperature refers to the temperature at which the interplanar spacing of the positive electrode active material decreases from the maximum value as the temperature rises, reaching a specified ratio (for example, when the relative change is less than 0.995 when the maximum interplanar spacing is set to 1).

[0067] The inventors of this application have newly discovered that the autolysis temperature can be correlated with the battery characteristics of solid-state batteries under high-temperature conditions. Specifically, they discovered that, under conditions where a solid electrolyte composed of a specific material is present, a positive electrode layer with an autolysis temperature above a predetermined temperature is relatively stable under high-temperature conditions. Furthermore, they discovered that solid-state batteries equipped with such a positive electrode layer can be more appropriately used under high-temperature conditions, leading to the invention described in detail below.

[0068] The solid-state battery disclosed herein includes a positive electrode layer, wherein, under conditions in which the solid electrolyte comprises lithium borosilicate glass, the maximum interplanar spacing measured by XRD analysis while heating the positive electrode layer in a state where the lithium desorption amount of the positive electrode active material is 40% is set to 1, and the temperature at which the relative change from the maximum interplanar spacing falls below 0.995 (the so-called "autodecomposition temperature") is 215°C or higher. In other words, the solid-state battery disclosed herein includes a positive electrode layer, wherein, when the interplanar spacing is measured by X-ray powder diffraction (XRD) analysis performed while heating the positive electrode layer in a state where the lithium desorption amount of the positive electrode active material is 40%, the temperature at which the reduction rate of the interplanar spacing falls below 0.5% relative to the maximum value is 215°C or higher.

[0069] According to the present disclosure, by selecting a positive electrode layer having the above-mentioned characteristics, a solid battery having more appropriate battery characteristics even under high temperature conditions can be provided. That is, according to the present disclosure, a solid battery that can be used more appropriately even under high temperature conditions and is superior in terms of high temperature resistance can be provided. More specifically, in a solid battery having a positive electrode layer having the above-mentioned characteristics, even when exposed to high temperatures (for example, a temperature range of 80°C to 200°C), the degradation of battery characteristics such as resistance value and / or battery capacity can be more appropriately suppressed. Therefore, the solid battery of the present disclosure can more appropriately maintain the battery characteristics of the solid battery even under high temperature conditions.

[0070] "A state in which the amount of lithium removed from the positive electrode active material is 40%" means a state in which the amount of lithium removed is 40%, when the amount of lithium removed relative to the lithium content of the positive electrode active material is expressed as 100%. In other words, "a state in which the amount of lithium removed from the positive electrode active material is 40%" means a state in which the lithium content of the positive electrode active material in the uncharged battery is 60%, with the lithium content of the positive electrode active material in the uncharged battery being 100%. For example, "a state in which the amount of lithium removed from the positive electrode active material is 40%" may be a charged state in which 40% of the lithium content of the positive electrode active material in the fully discharged battery has been removed.

[0071] In the present disclosure, the self-decomposition temperature of the positive electrode active material in a state where 40% of the lithium of the positive electrode active material is separated is evaluated. This is to more appropriately evaluate the behavior of the positive electrode active material under high temperature conditions in a state where the crystalline structure of the positive electrode active material may become unstable. Specifically, lithium is extracted from the positive electrode active material by charging, whereby the crystalline structure of the positive electrode active material may become unstable. The destabilization of the crystalline structure of the positive electrode active material may become more significant under high temperature conditions. That is, under high temperature conditions, solid batteries are prone to deterioration when the amount of lithium separated from the positive electrode active material is about 40% or more. Therefore, by evaluating the self-decomposition temperature of the positive electrode layer in a state where the amount of lithium separated from the positive electrode active material is 40%, the self-decomposition temperature of the positive electrode layer can be more appropriately correlated with the high temperature resistance of the solid battery.

[0072] It should be noted that the amount of lithium desorption can be quantified by XRD analysis of the positive electrode layer of a charged solid-state battery. Alternatively, it can be calculated from the charge capacity of the solid-state battery based on the initial charge and discharge efficiency and unit weight of the positive and negative active materials.

[0073] In the past, efforts to improve the high-temperature resistance of lithium secondary batteries using high-nickel cathode active materials focused on the phase transition temperature of the cathode active material in the fully charged state. Specifically, high-nickel cathode active materials were selected based on the phase transition temperature at which the cathode active material changes from a layered structure to a spinel structure in the fully charged state, and the temperature at which the c-axis length reaches its maximum value when the cathode active material is heated (see Patent Document 2).

[0074] On the other hand, in the present disclosure, as described above, attention is paid to the self-decomposition temperature based on the relative change in the interplanar spacing of the positive electrode active material accompanying the temperature increase. Figure 3 As shown, after the positive electrode active material reaches its maximum interplanar spacing as the temperature increases, it maintains a substantially constant interplanar spacing with continued temperature increases, and exhibits behavior in which the interplanar spacing begins to decrease with further temperature increases. According to the present disclosure, by evaluating the positive electrode active material based on the autodecomposition temperature at which the interplanar spacing begins to decrease, it is possible to more appropriately select a positive electrode active material that can maintain its crystalline structure appropriately under high temperature conditions (e.g., a temperature range of 80°C to 200°C) (i.e., a higher temperature until the transition to a reduced interplanar spacing occurs).

[0075] The upper limit of the self-decomposition temperature of the positive electrode active material is not particularly limited. However, if emphasis is placed on battery characteristics such as the capacity retention rate in the initial stage of the solid battery (i.e., before exposure to high temperature conditions), the self-decomposition temperature can be, for example, 400°C or lower, 350°C or lower, or 330°C or lower. If emphasis is placed on both suppressing degradation of battery characteristics in a high temperature environment and achieving initial battery characteristics of the solid battery, the self-decomposition temperature of the positive electrode active material can be 215°C or higher and 350°C or lower, 215°C or higher and 315°C or lower, 250°C or higher and 315°C or lower, or 280°C or higher and 315°C or lower.

[0076] The lithium borosilicate glass contained in the positive electrode layer is an oxide-based glass material containing at least lithium (Li), silicon (Si), and boron (B) as constituent elements. For example, it can be 50Li4SiO4•50Li3BO3. Because this solid electrolyte has relatively high thermal stability, its inclusion in the positive electrode layer can more effectively suppress degradation of the solid-state battery's battery characteristics under high-temperature conditions.

[0077] In addition to lithium, silicon, boron, and oxygen, lithium borosilicate-based glass may also contain one or more other elements. For example, lithium borosilicate-based glass may further contain at least one element selected from Groups 1 and 2 and Groups 14 to 17 of the periodic table. The content of each element in lithium borosilicate-based glass can be measured, for example, by analyzing the glass-ceramic solid electrolyte using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0078] In addition, the solid electrolyte may further include other solid electrolytes used in known solid batteries in addition to lithium borosilicate glass. Such a solid electrolyte may be, for example, any one or more of a crystalline solid electrolyte, a glass-based solid electrolyte different from lithium borosilicate glass, and a glass-ceramic solid electrolyte. As a crystalline solid electrolyte, for example, oxide-based crystalline materials and sulfide-based crystalline materials may be listed. As an oxide-based crystalline material, for example, a lithium-containing phosphate compound having a NASICON structure, an oxide having a perovskite structure, a garnet-type or garnet-like structure, and an oxide glass-ceramic lithium ion conductor may be listed.

[0079] Examples of lithium-containing phosphate compounds having a NASICON structure include Li x M y (PO4)3 (1≤x≤2, 1≤y≤2, M is at least one selected from the group consisting of titanium (Ti), germanium (Ge), aluminum (Al), gallium (Ga), and zirconium (Zr). As an example of a lithium-containing phosphate compound having a NASICON structure, for example, Li1.2 Al 0.2 Ti 1.8 (PO4)3, etc. As an example of oxides having a perovskite structure, La 0.55 Li 0.35 TiO3, etc. As an example of an oxide having a garnet-type or garnet-like structure, Li7La3Zr2O 12 In addition, sulfide-based crystalline materials include thio-LISICON, such as Li 3.25 Ge 0.25 P 0.75 S4 and Li 10 GeP2S 12 etc. The crystalline solid electrolyte may also contain a polymer material (eg, polyethylene oxide (PEO)).

[0080] Glass-based solid electrolytes include, for example, oxide-based glass materials and sulfide-based glass materials. For example, glass-based solid electrolytes other than lithium borosilicate glass include 30Li2S•26B2S3•44LiI, 63Li2S•36SiS2•1Li3PO4, 57Li2S•38SiS2•5Li4SiO4, 70Li2S•30P2S5, and 50Li2S•50GeS2.

[0081] Glass ceramic solid electrolytes include oxide glass ceramic materials and sulfide glass ceramic materials. As oxide glass ceramic materials, for example, phosphate compounds containing lithium, aluminum, and titanium (LATP) and phosphate compounds containing lithium, aluminum, and germanium (LAGP) can be used. LATP is, for example, Li 1.07 Al 0.69 Ti 1.46 (PO4)3, etc. In addition, LAGP is, for example, Li 1.5 Al 0.5 Ge 1.5 (PO4), etc. In addition, as sulfide-based glass ceramic materials, there are Li7P3S 11 and Li 3.25 P 0.95 S4 et al.

[0082] For example, the solid electrolyte may further include a garnet-type or garnet-like oxide in addition to lithium borosilicate glass. For example, the solid electrolyte in the positive electrode layer of the solid battery disclosed herein may include lithium borosilicate glass and an oxide containing Li, La, and Zr (also known as LLZ or LiLaZr-based oxides) as solid electrolytes. The inventors of this application have discovered that when the positive electrode layer includes at least lithium borosilicate glass as the solid electrolyte, the positive electrode active material can preferentially form an interface with the lithium borosilicate glass, which has relatively high thermal stability. Therefore, even if the positive electrode layer includes a solid electrolyte with relatively low thermal stability, the lithium borosilicate glass can suppress the reaction between the positive electrode active material and the less thermally stable solid electrolyte under high temperature conditions. This allows the inclusion of other solid electrolytes that, while less thermally stable than lithium borosilicate glass, have excellent lithium ion conductivity, resulting in a solid battery that more appropriately balances high-temperature resistance and battery performance (e.g., capacity retention).

[0083] The content of lithium borosilicate glass in the solid electrolyte of the positive electrode layer is not particularly limited, and can be, for example, 10% to 90% by mass, 30% to 80% by mass, or 40% to 60% by mass relative to the total amount of the solid electrolyte in the positive electrode layer. The content of garnet-type oxide-based solid electrolyte in the solid electrolyte of the positive electrode layer is not particularly limited, and can be, for example, 0% to 70% by mass, 5% to 60% by mass, or 10% to 40% by mass relative to the total amount of the solid electrolyte in the positive electrode layer. If the contents of lithium borosilicate glass and garnet-type oxide-based solid electrolyte are respectively within the above-mentioned ranges, a solid battery that can be more suitably used even under high temperature conditions can be provided.

[0084] The constituent material of the positive electrode active material is a layered rock salt-type metal oxide, specifically, a lithium transition metal oxide. The term "layered rock salt-type metal oxide" refers to a metal oxide (particularly its particles) having a layered rock salt-type crystal structure. In a broad sense, this refers to a crystal structure that can be identified as a layered rock salt-type crystal structure by those skilled in the battery field. In a narrower sense, the term "layered rock salt-type metal oxide" refers to a metal oxide (particularly its particles) identified as having a layered rock salt-type crystal structure through analysis of X-ray diffraction patterns using, for example, Rietveld analysis.

[0085] In one embodiment, the positive electrode active material comprises an oxide containing Li and Co (also referred to as LCO or LiCo-based oxide), wherein the LiCo-based oxide contains at least Ti. The inclusion of at least Ti in the LiCo-based oxide can increase the autolysis temperature of the positive electrode active material. This allows for a solid-state battery with improved structural stability of the positive electrode active material under high-temperature conditions and superior high-temperature resistance.

[0086] For example, the self-decomposition temperature of the positive electrode active material containing a Ti-containing LiCo-based oxide can be 215° C. to 350° C., 250° C. to 330° C., or 280° C. to less than 295° C. If the self-decomposition temperature is within the above range, a solid battery containing the positive electrode active material in the positive electrode layer can be suitably used even under high temperature conditions.

[0087] The Ti-containing LiCo-based oxide may further contain at least one element selected from the group consisting of Al, Mg, Ni, Mn, Zr, Zn, Cu, B, P, Si, Ge, Nb, Au, and Pt. x Ti y α z A metal composite oxide represented by O2(I) (wherein, x+y+z≤1, 0.9≤x<1, 0.005≤y≤0.01, 0≤z≤0.05, α: at least one element selected from the group consisting of Mg, Al, Ni, Mn, Zr, Zn, Cu, B, P, Si, Ge, Nb, Au and Pt).

[0088] In formula (I), preferably 0.91≤x<1, more preferably 0.93≤x≤1, and further preferably 0.945≤x≤0.995. In addition, in composition formula (I), it can be 0.003≤y≤0.015, and more preferably 0.005≤y≤0.01. In addition, in composition formula (I), it can be 0≤z≤0.08, or 0.005≤z≤0.07, or 0.01≤z≤0.05. In addition, if it is important to suppress the increase in resistance value and capacity degradation under high temperature conditions, α is more preferably Al and / or Mg.

[0089] In another embodiment, the positive electrode active material comprises an oxide containing Li, Ni, Co, and Mn (also referred to as NCM or LiNiCoMn-based oxide). The positive electrode active material may comprise an oxide having the composition formula LiNi a Co b Mn c A metal composite oxide represented by O2(II) (wherein a+b+c≤1, 0.3≤a≤0.8, more preferably 0.3≤a≤0.6, 0.2≤b≤0.3, 0.2≤c≤0.3).

[0090] LiNiCoMn oxides may further contain Ti, Al and / or Mg. a Co b Mn c β dA metal composite oxide represented by O2(II') (wherein a+b+c≤1, 0.3≤a≤0.6, 0.1≤b≤0.3, 0.1≤c≤0.3, 0≤d≤0.05, and β: at least one element selected from Ti, Mg, and Al). If suppressing resistance increases and capacity degradation under high-temperature conditions is important, β more preferably contains at least Ti.

[0091] In formulas (II) and (II'), preferably 0.2≤a≤0.8, more preferably 0.3≤a≤0.75, and even more preferably 0.3≤a≤0.6. In composition formulas (II) and (II'), 0.1≤b≤0.4, more preferably 0.1≤b≤0.3, or 0.2≤b≤0.3. In composition formulas (II) and (II'), 0.1≤c≤0.4, more preferably 0.1≤c≤0.3, or 0.2≤c≤0.3. In composition formula (II'), 0≤d≤0.08, 0.005≤d≤0.07, or 0.01≤d≤0.05 may be sufficient.

[0092] [Method for manufacturing solid-state batteries]

[0093] The solid-state battery disclosed herein can be manufactured by a printing method such as screen printing, a green sheet method using green sheets, or a composite method thereof. Below, in order to understand the present disclosure, the case of using the printing method and the green sheet method is described in detail, but the present disclosure is not limited to this method. That is, the solid-state battery can be manufactured according to a conventional solid-state battery manufacturing method. In addition, the following time-related matters such as the order of recording are only for ease of explanation and are not necessarily limited to this.

[0094] (Solid Battery Stack Precursor Formation Process)

[0095] In this process, various pastes, such as a positive electrode layer paste, a negative electrode layer paste, a solid electrolyte layer paste, a positive current collector layer paste, a negative current collector layer paste, an electrode separator paste, and an outer layer material paste, are used as inks. Specifically, the pastes are applied by printing and dried to form a solid battery stack precursor having a predetermined structure on a supporting substrate.

[0096] During printing, by sequentially stacking printed layers with a predetermined thickness and pattern shape, a solid battery stack precursor corresponding to a predetermined solid battery structure can be formed on a substrate. The patterning method is not particularly limited as long as it can form the predetermined pattern; examples include one or more of screen printing and gravure printing.

[0097] The paste can be prepared by wet mixing the specified constituent materials of each layer appropriately selected from the group consisting of positive electrode active material particles, negative electrode active material particles, conductive material, solid electrolyte material, current collecting layer material, insulating material, sintering aid and other above-mentioned materials with an organic carrier obtained by dissolving an organic material in a solvent.

[0098] The positive electrode layer paste contains, for example, positive electrode active material particles, a solid electrolyte material, an organic material, a solvent, and, if necessary, a sintering aid.

[0099] The negative electrode layer paste contains, for example, negative electrode active material particles, a solid electrolyte material, an organic material, a solvent, and, if necessary, a sintering aid.

[0100] The solid electrolyte layer paste contains, for example, a solid electrolyte material, an organic material, a solvent, and, if necessary, a sintering aid.

[0101] The positive electrode current collecting layer paste contains a conductive material, an organic material, a solvent, and, if necessary, a sintering aid.

[0102] The negative electrode current collecting layer paste contains a conductive material, an organic material, a solvent, and, if necessary, a sintering aid.

[0103] The electrode separator paste contains, for example, a solid electrolyte material, an insulating material, an organic material, a solvent, and, if necessary, a sintering aid.

[0104] The outer layer material paste contains, for example, an insulating material, an organic material, a solvent, and, if necessary, a sintering aid.

[0105] The organic material contained in the paste is not particularly limited, and 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.

[0106] The type of solvent is not particularly limited, and examples thereof include any one or two or more organic solvents such as butyl acetate, N-methyl-pyrrolidone, toluene, terpineol, and N-methyl-pyrrolidone.

[0107] Wet mixing can use a medium, specifically, a ball mill method or a viscosity mill method, etc. On the other hand, a wet mixing method that does not use a medium can also be used, such as a sand mill method, a high-pressure homogenizer method, or a kneading dispersion method.

[0108] The supporting substrate is not particularly limited as long as it can support each paste layer. Examples include a release film with a release treatment applied to one side. Specifically, a substrate composed of a polymer material such as polyethylene terephthalate can be used. When the paste layers are held on the substrate during the firing step, the substrate can be heat-resistant to the firing temperature.

[0109] As another method, green sheets may be formed from the respective pastes, and the obtained green sheets may be stacked to produce a solid battery stack precursor.

[0110] In detail, by drying the supporting substrate coated with each paste on a heating plate heated to above 30°C and below 90°C, positive electrode layer green sheets, negative electrode layer green sheets, solid electrolyte layer green sheets, positive electrode current collecting layer green sheets, negative electrode current collecting layer green sheets, electrode separation portion green sheets and / or outer layer material green sheets having specified shapes and thicknesses are formed on each supporting substrate (e.g., PET film).

[0111] Next, the green sheets are peeled from the substrate. After peeling, the green sheets of the various components are stacked sequentially along the stacking direction to form a solid battery stack precursor. After stacking, solid electrolyte layers, insulating layers, and / or protective layers can also be applied to the side regions of the electrode green sheets by screen printing.

[0112] (Firing process)

[0113] In the firing step, the solid battery stack precursor is fired. Although this is merely an example, firing is performed by heating in a nitrogen atmosphere containing oxygen or in air at, for example, 200°C or higher to remove organic materials, and then heating in a nitrogen atmosphere or in air at, for example, 300°C or higher. Firing can be performed while pressurizing the solid battery stack precursor in the stacking direction (in the stacking direction and perpendicular to the stacking direction, depending on the situation).

[0114] By undergoing such firing, a solid battery stack is formed, and ultimately a desired solid battery is obtained.

[0115] (Positive and negative terminal formation process)

[0116] For example, a positive electrode terminal is bonded to a solid battery stack using a conductive adhesive, and a negative electrode terminal is bonded to a solid battery stack using a conductive adhesive. Thus, the positive and negative electrodes are attached to the solid battery stack, respectively, to complete the solid battery.

[0117] Example

[0118] According to the present disclosure, a verification test was conducted. The structure of the solid battery adopts Figure 2 structure.

[0119] <Example 1>

[0120] (Process for producing green sheets for solid electrolyte layers)

[0121] First, as a solid electrolyte, lithium borosilicate glass and an acrylic binder were mixed at a mass ratio of 70:30. The lithium borosilicate glass used had a composition of Li₂O:SiO₂:B₂O₃ (mol%) of 60:10:30. The resulting mixture was then mixed with butyl acetate to a solids content of 30% by mass. The mixture was then stirred with zirconia balls (5 mm in diameter) for four hours to produce a solid electrolyte layer paste. The paste was then applied to a release film and dried at 80°C for 10 minutes to create a solid electrolyte layer green sheet, serving as a solid electrolyte layer precursor.

[0122] (Process for producing green sheets for positive electrode material layers)

[0123] First, cobalt oxide, lithium carbonate, and titanium are mixed and fired to synthesize titanium-containing lithium cobalt oxide (LiCoO2) through a solid-phase method. By controlling the mixing conditions and firing temperature, titanium-containing lithium cobalt oxide with a 003 plane spacing is obtained.

[0124] Next, titanium-containing lithium cobalt oxide (LiCoO2), the positive electrode active material, and lithium borosilicate glass, the solid electrolyte, were mixed at a mass ratio of 75:25. This mixture was then mixed with an acrylic binder at a mass ratio of 70:30 (mixture (titanium-containing lithium cobalt oxide + lithium borosilicate glass) to acrylic binder). The mixture was then added to butyl acetate to a solids content of 30% by mass. The resulting mixture was then stirred with 5mm-diameter zirconia balls for four hours to produce a positive electrode material layer paste. The paste was then applied to a release film and dried at 80°C for 10 minutes to produce a positive electrode material layer green sheet, which served as a positive electrode layer precursor.

[0125] (Process for producing green sheets for negative electrode material layers)

[0126] First, carbon powder (KS6, manufactured by TIMCAL) as the negative electrode active material and lithium borosilicate glass as the solid electrolyte were mixed at a mass ratio of carbon powder:lithium borosilicate glass = 70:30. This mixture was then mixed with an acrylic binder at a mass ratio of mixture (carbon powder + lithium borosilicate glass):acrylic binder = 70:30. The mixture was then added to butyl acetate to achieve a solids content of 30% by mass. The resulting mixture was then stirred with zirconia balls with a diameter of 5 mm for 4 hours to produce a paste for the negative electrode material layer. The paste was then applied to a release film and dried at 80°C for 10 minutes to produce a green sheet for the negative electrode material layer, serving as a negative electrode material layer precursor.

[0127] (Process for producing green sheets for positive electrode current collecting layers)

[0128] First, carbon powder (KS6, manufactured by TIMCAL) as a conductive material and lithium borosilicate glass as a solid electrolyte were mixed at a mass ratio of carbon powder:lithium borosilicate glass = 70:30. This mixture was then mixed with an acrylic binder at a mass ratio of mixture (carbon powder + lithium borosilicate glass):acrylic binder = 70:30. The mixture was then added to butyl acetate to a solids content of 30% by mass. The resulting mixture was then stirred with zirconia balls with a diameter of 5 mm for 4 hours to produce a paste for the positive electrode current collector layer. The paste was then applied to a release film and dried at 80°C for 10 minutes to produce a green sheet for the positive electrode current collector layer, serving as a positive electrode current collector layer precursor.

[0129] (Process for producing green sheets for negative electrode current collecting layers)

[0130] A negative electrode current collecting layer green sheet was produced in the same manner as in the above-mentioned "step of producing a positive electrode current collecting layer green sheet."

[0131] (Process for producing green sheets for outer layer materials)

[0132] First, alumina particle powder (AHP300, manufactured by Nippon Light Metal) and lithium borosilicate glass, serving as a solid electrolyte, were mixed at a mass ratio of 50:50. This mixture was then mixed with an acrylic binder at a mass ratio of 70:30 (alumina particle powder + lithium borosilicate glass) to acrylic binder. The mixture was then added to butyl acetate to achieve a solids content of 30% by mass. The resulting mixture was then stirred with zirconia balls with a diameter of 5 mm for 4 hours to produce a paste for the main surface outer layer material. This paste was then applied to a release film and dried to produce a green sheet for the outer layer material, which served as a precursor for the main surface outer layer material.

[0133] (Process for producing green sheets for electrode separation)

[0134] In the same manner as in the above-mentioned "step of producing a green sheet for an outer layer material", a green sheet for an electrode separator was produced as an electrode separator precursor.

[0135] (Laminate Production Process)

[0136] Using the green sheets obtained as described above, a Figure 1 as well as Figure 2 First, each green sheet is processed into Figure 1 as well as Figure 2 Then, remove the mold from the release film. Figure 1 as well as Figure 2 The layers were stacked in order according to the structure of the battery element shown, and then thermocompression bonded to obtain a stacked body serving as a battery element precursor.

[0137] (Sintering Step of Laminated Body)

[0138] The obtained laminate is heated to remove the acrylic binder contained in each green sheet, and then further heated to sinter the oxide glass contained in each green sheet.

[0139] (Terminal production process)

[0140] First, Ag powder (Daken Chemical Industry Co., Ltd.) as a conductive particle powder and oxide glass (Bi-B glass, Asahi Glass Co., Ltd., ASF1096) were mixed at a predetermined mass ratio. The resulting mixture was then mixed with an acrylic binder at a mass ratio of 70:30 (mixture (Ag powder + oxide glass): acrylic binder). The mixture was then added to a butyl acetate solvent to achieve a solids content of 50% by mass. The resulting mixture was then stirred with zirconia balls with a diameter of 5 mm for 4 hours to produce a conductive paste. This paste was then applied to a release film and adhered to the first and second end faces (or side faces) of the laminate, where the positive and negative electrode current collecting layers were exposed, respectively. The paste was then sintered to form the positive and negative electrode terminals. This resulted in the desired battery.

[0141] <Example 2>

[0142] A solid battery was manufactured by the same method as in Example 1 except that the composition ratio of the positive electrode active material was changed.

[0143] <Examples 3 to 5>

[0144] A solid battery was produced by the same method as in Example 1 except that a predetermined amount of Al was further added as a positive electrode active material.

[0145] <Examples 6 to 8>

[0146] A solid battery was produced by the same method as in Example 1 except that a predetermined amount of Mg was further added as a positive electrode active material.

[0147] <Example 9>

[0148] A solid battery was manufactured by the same method as in Example 1 except that a mixture of lithium borosilicate glass and LiLaZr-based oxide (lithium borosilicate glass:LiLaZr-based oxide = 60:40 (mass ratio)) was used as the solid electrolyte. 12 .

[0149] <Examples 10 and 11>

[0150] A solid battery was manufactured by the same method as in Example 1 except that a LiNiCoMn-based oxide was used as the positive electrode active material.

[0151] Comparative Example 1

[0152] A solid battery was manufactured by the same method as in Example 1, except that lithium cobalt oxide containing no titanium was used as the positive electrode active material.

[0153] Comparative Example 2

[0154] A solid battery was manufactured by the same method as in Example 1 except that LiLaZr-based oxide was used as the solid electrolyte. 12 .

[0155] (Measurement of battery characteristics)

[0156] The rated capacity of the battery is set to 1C, and it is charged at a constant current of 0.2C to the specified positive electrode potential. After reaching the positive electrode potential, it is charged in constant voltage mode until the current is reduced to 0.01C, and the impedance is measured to obtain the initial resistance value. Then, it is stored under high temperature conditions (105°C) for 1 week, slowly cooled to 25°C by air cooling, and then the impedance is measured at 25°C. It is discharged at a constant current of 0.2C to 2V, and the capacity is measured. It should be noted that the positive electrode potential uses different potentials depending on the positive electrode active material. Specifically, when the positive electrode active material is a LiCo-based oxide, it is charged to a positive electrode potential of 4.35V, and when it is a LiNiCoMn-based oxide, it is charged to a positive electrode potential of 4.2V.

[0157] The resistance increase rate was calculated by dividing the resistance value after storage under high temperature conditions by the initial resistance value obtained from the impedance measurement results. In addition, the degradation capacity of the discharge capacity after storage under high temperature conditions was determined based on the capacity measurement results.

[0158] (X-ray diffraction measurement)

[0159] The 003 plane spacing of the positive electrode active material was measured using an X-ray diffraction analyzer (Bruker D8 Advance). The battery was charged at a current of 0.2C. After the positive electrode potential reached 4.55V, constant current and constant voltage charging was performed. Charging was continued until the current decreased to 0.01C, reaching a lithium desorption rate of 40% in the positive electrode active material. The positive electrode layer was then removed from the solid-state battery and placed in the sample holder of the X-ray diffraction analyzer. The positive electrode layer was heated within a measurement temperature range of 25°C to 500°C, with target temperatures set in 20°C increments and a heating rate of 10°C / min. After reaching the target temperature, X-ray diffraction measurements were performed after a 3-minute waiting period. The X-ray diffraction measurements were performed with a step width of 0.01°, a counting time of at least 0.3 seconds, a scanning rate of 10° / min, and an angular range of 15° to 70°.

[0160] Specifically, the positive electrode layer is exposed by grinding or disassembling. After confirming that no short circuit occurs due to the operation by voltage measurement using a tester, XRD measurement is performed as described above. In the case where there is concern about material deterioration due to exposure to the atmosphere, a series of operations and measurements are performed under an inert atmosphere.

[0161] The interplanar spacing at the angle showing the maximum intensity in the peak arising from 003 in the XRD spectrum of the positive electrode active material obtained above was calculated and defined as the interplanar spacing. The maximum interplanar spacing within the measurement temperature range (i.e., the maximum interplanar spacing) was set to 1. At temperatures higher than the temperature at which the maximum interplanar spacing was obtained, the temperature at which the relative interplanar spacing relative to the maximum interplanar spacing fell below 0.995 was defined as the autodecomposition temperature.

[0162] Table 1 shows the evaluation results of the solid-state batteries of Examples 1 to 11 and Comparative Examples 1 to 2. The resistance increase rate and degradation capacity are shown as relative values when the resistance increase rate and degradation capacity in Comparative Example 1 are set to "100," respectively. The relative resistance increase rate and relative degradation capacity of Comparative Example 2 and Examples 1 to 11 are shown.

[0163] [Table 1]

[0164]

[0165] According to the above results, the solid batteries of Examples 1 to 11 showed good battery characteristics even after storage under high temperature conditions, compared with the solid batteries of Comparative Example 1 using an existing positive electrode active material with a positive electrode active material temperature lower than 215°C, and Comparative Example 2 using a LiLaZr-based oxide without lithium borosilicate glass as a solid electrolyte. Specifically, the solid batteries of Examples 1 to 11, in which the self-decomposition temperature of the positive electrode active material is above 215°C and the solid electrolyte contains lithium borosilicate glass, obtained results showing lower resistance increase rates and degradation capacities than the values of Comparative Examples 1 and 2 even after storage under high temperature conditions. That is, the solid battery of the present disclosure can appropriately suppress the degradation of battery characteristics even under high temperature conditions. Therefore, according to the present disclosure, a solid battery having more appropriate battery characteristics even under high temperature conditions is provided.

[0166] (Determination of Cycle Characteristics)

[0167] In addition, for the solid batteries of Examples 1 to 11 and Comparative Examples 1 to 2, the capacity retention rate was measured to evaluate the initial battery characteristics before exposure to high temperature conditions. Specifically, the rated capacity of the battery was set to 1C, and it was charged to the above-mentioned positive electrode potential at a constant current of 0.2C. After reaching the positive electrode potential, it was charged in a constant voltage mode until the current was reduced to 0.01C. Then, it was discharged at a constant current of 0.2C until the positive electrode potential reached 3V. Such charging and discharging was regarded as one cycle, and the capacity retention rate relative to the initial discharge capacity when 100 cycles were repeated was measured. The measurement results are shown in Table 2.

[0168] [Table 2]

[0169]

[0170] Based on the above results, the solid batteries of Examples 10 and 11, which include a positive electrode active material containing lithium borosilicate glass as a solid electrolyte and having an autodecomposition temperature of 295°C or higher, achieved a lower capacity retention rate than that of Comparative Example 1. Specifically, the positive electrode active material with an autodecomposition temperature of 295°C or higher maintained battery characteristics adequately even under high-temperature conditions, while exhibiting a relatively low capacity retention rate. On the other hand, the solid batteries of Examples 1 to 9, whose positive electrode active material had an autodecomposition temperature of 215°C or higher but less than 295°C, maintained adequate battery characteristics even after storage under high-temperature conditions and also exhibited an adequate capacity retention rate before exposure to high-temperature conditions.

[0171] The embodiments of the present disclosure have been described above, but these are only typical examples. Therefore, the present disclosure is not limited thereto, and those skilled in the art will readily appreciate that various embodiments are conceivable without departing from the spirit of the present disclosure.

[0172] It should be noted that the above-mentioned one embodiment of the present disclosure includes the following preferred aspects.

[0173] Method 1:

[0174] A solid battery comprises a positive electrode layer, the positive electrode layer comprising a positive electrode active material containing lithium and a solid electrolyte,

[0175] In a state where the lithium desorption amount of the positive electrode active material is 40%, in an XRD analysis measured while heating the positive electrode layer, the value of the maximum surface spacing is set to 1, and the self-decomposition temperature at which the relative change relative to the maximum surface spacing is less than 0.995 is above 215°C, and the solid electrolyte contains lithium borosilicate glass.

[0176] Method 2:

[0177] According to the solid battery according to the first aspect, the positive electrode active material has a layered rock salt type crystal structure.

[0178] Method 3:

[0179] According to the solid state battery described in the first or second aspect, the autodecomposition temperature is 215° C. or higher and 315° C. or lower.

[0180] Method 4:

[0181] According to the solid battery according to any one of the first to third aspects, the positive electrode active material includes an oxide containing Li and Co, and the oxide contains at least Ti.

[0182] Method 5:

[0183] According to the solid battery according to the fourth aspect, in the positive electrode active material, when the oxide contains Ti, the autodecomposition temperature is 215°C or higher and lower than 295°C.

[0184] Method 6:

[0185] According to the solid battery of the fourth or fifth aspect, the positive electrode active material further contains Mg and / or Al.

[0186] Method 7:

[0187] According to any one of the fourth to sixth aspects of the solid battery, the positive electrode active material contains LiCo x Ti y α zO2 (wherein, x+y+z≤1, 0.9≤x<1, 0.005≤y≤0.01, 0≤z≤0.05, α: Mg and / or Al).

[0188] Method 8:

[0189] In the solid battery according to any one of the first to third aspects, the positive electrode active material includes an oxide containing Li, Ni, Co, and Mn.

[0190] Method 9:

[0191] According to the solid battery of the eighth aspect, the positive electrode active material is LiNi a Co b Mn c O2 (where a+b+c≤1, 0.3≤a≤0.6).

[0192] Method 10:

[0193] In the solid state battery according to any one of the first to ninth aspects, the solid electrolyte further includes an oxide-based solid electrolyte having a garnet-type crystal structure.

[0194] Method 11:

[0195] According to the solid battery according to the tenth aspect, the oxide-based solid electrolyte is an oxide containing Li, La, and Zr.

[0196] Industrial applicability

[0197] The solid-state battery disclosed in the present invention can be applied to various fields where electricity storage is assumed. Although it is only an example, the solid-state battery disclosed in the present invention can be applied to the electrical, information, and communication fields using mobile devices, etc. (for example, the electrical and electronic equipment fields or mobile equipment fields including small electronic devices such as mobile phones, smart phones, laptops, digital cameras, activity meters, wristband computers, electronic paper, RFID tags, card-type electronic money, and smart watches); household and small industrial uses (for example, the fields of power tools, golf carts, and household, nursing, and industrial robots); large industrial uses (for example, the fields of forklifts, elevators, and port cranes); transportation system fields (for example, hybrid vehicles, electric vehicles, buses, trams, electric-assisted bicycles, electric motorcycles, etc.); power system uses (for example, various power generation, load regulators, smart grids, and general household-installed power storage systems, etc.); and medical uses (medical equipment fields such as headphones and hearing aids); pharmaceutical uses (in the fields of medication management systems); and IoT fields; space and deep-sea uses (for example, space probes, submersible research vessels, etc.).

[0198] Description of Reference Numerals

[0199] 10: Electrode layer; 10A: Positive electrode layer; 10B: Negative electrode layer; 11: Electrode collecting layer; 11A: Positive electrode collecting layer; 11B: Negative electrode collecting layer; 20: Solid electrolyte layer; 30: Electrode separation portion; 30A: Positive electrode separation portion; 30B: Negative electrode separation portion; 40: Terminal; 40A: Positive electrode terminal; 40B: Negative electrode terminal; 60: Outer layer material; 100: Solid battery stack; 200: Solid battery.

Claims

1. A solid battery comprising a positive electrode layer comprising a positive electrode active material containing lithium and a solid electrolyte, In an XRD analysis performed while heating the positive electrode layer in a state where the lithium desorption amount of the positive electrode active material is 40%, the value of the maximum interplanar spacing is set to 1, the self-decomposition temperature at which the relative change with respect to the maximum interplanar spacing is less than 0.995 is above 215°C, and the solid electrolyte contains lithium borosilicate glass.

2. The solid state battery according to claim 1, wherein The positive electrode active material has a layered rock salt type crystal structure.

3. The solid state battery according to claim 1 or 2, wherein The autodecomposition temperature is 215° C. or higher and 315° C. or lower.

4. The solid state battery according to any one of claims 1 to 3, wherein The positive electrode active material includes an oxide containing Li and Co, and the oxide contains at least Ti.

5. The solid state battery according to claim 4, wherein In the positive electrode active material, when the oxide contains Ti, the autodecomposition temperature is 215° C. or higher and lower than 295° C.

6. The solid state battery according to claim 4 or 5, wherein: The positive electrode active material further contains Mg and / or Al.

7. The solid state battery according to any one of claims 4 to 6, wherein The positive electrode active material comprises LiCo x Ti y α z O2, wherein x+y+z≤1, 0.9≤x<1, 0.005≤y≤0.01, 0≤z≤0.05, α: Mg and / or Al.

8. The solid state battery according to any one of claims 1 to 3, wherein The positive electrode active material includes an oxide containing Li, Ni, Co, and Mn.

9. The solid state battery according to claim 8, wherein The positive electrode active material is LiNi a Co b Mn c O2, where a+b+c≤1, 0.3≤a≤0.

6.

10. The solid state battery according to any one of claims 1 to 9, wherein The solid electrolyte further includes an oxide-based solid electrolyte having a garnet-type crystal structure.

11. The solid battery according to claim 10, wherein The oxide-based solid electrolyte is an oxide containing Li, La, and Zr.

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