Solid-state battery

Abstract

Provided is a solid-state battery which is provided with a positive electrode active material containing Li and a positive electrode layer containing a solid electrolyte, and which is characterized in that the thermogravimetric reduction initiation temperature at which the weight of the positive electrode active material is reduced by 0.67% or more in a state where the lithium desorption amount of the positive electrode active material is 40% is 220 DEG C or more and less than 485 DEG C, and in that the solid electrolyte contains lithium borosilicate glass.

Description

Technical Field

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

[0002] Hitherto, secondary batteries capable of repeated charge and discharge have been used for various purposes. For example, secondary 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 facilitating the movement of ions for charge and discharge. That is, a so-called electrolytic solution is used for secondary batteries. However, in such secondary batteries, safety is generally required in terms of preventing leakage of the electrolytic solution. In addition, organic solvents and the like used for the electrolytic solution are flammable substances, and thus safety is also required in this regard.

[0004] Therefore, research has been conducted on solid batteries using a solid electrolyte instead of an electrolytic solution.

[0005] Prior Art Documents

[0006] Patent Documents

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

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2021-516424 Summary of the Invention

[0009] Technical Problem to be Solved by the Invention

[0010] The inventors of the present application newly found that there are aspects that can be improved in conventional solid batteries, and countermeasures need to be taken therefor.

[0011] Specifically, as the positive electrode active material in a solid battery, a lithium transition metal oxide or a lithium composite transition metal oxide having a crystalline structure can be used (refer to Patent Documents 1 and 2). In this regard, a solid battery is sometimes used under high-temperature conditions. Under the above high-temperature conditions, the crystalline structure of the above positive electrode active material becomes unstable due to the detachment of lithium, and thus the battery characteristics of the solid battery under high-temperature conditions may deteriorate.

[0012] The present invention has been completed in view of the above technical problems. That is, an object of the present invention is to provide a solid battery that can have more appropriate battery characteristics even under high-temperature conditions.

[0013] Technical Solution for Solving the Technical Problem

[0014] To achieve the above object, in one embodiment of the present invention, there is provided a solid battery,

[0015] It has a positive electrode active material containing Li and a positive electrode layer including a solid electrolyte.

[0016] In a state where the amount of lithium released from the positive electrode active material is 40%, the thermal weight reduction start temperature at which the weight of the positive electrode active material is reduced by 0.67% or more is 220°C or higher and less than 485°C, and the solid electrolyte contains lithium borosilicate glass.

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

[0018] Figure 1 It is a perspective view schematically showing the appearance of a solid battery according to an embodiment of the present invention.

[0019] Figure 2 It is when observing in the arrow direction Figure 1 A schematic cross-sectional view when taking the A-A cross-section of the solid battery.

[0020] Figure 3 It is a graph showing the relationship between the heating temperature and the thermal weight change (reduction) rate of the positive electrode active material in a solid battery according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, the solid battery of the present invention will be described in detail. Explanation will be made with reference to the drawings as needed, but the illustrated content is only schematically and exemplarily shown for understanding the present invention, and the appearance, dimensional ratio, etc. may be different from the actual object.

[0022] As used in this specification, "cross-sectional observation" means a form captured from a direction substantially perpendicular to the stacking direction in the stacking structure of the solid battery (simply put, the form when cutting with a plane parallel to the thickness direction of the layer). In addition, "top view observation" or "top view shape" used in this specification means a schematic view based on observing an object from above or below along the thickness direction of the above layer (i.e., the above stacking direction).

[0023] The "vertical direction" and "left - right direction" directly or indirectly used in this specification correspond to the vertical direction and left - right direction in the drawing, respectively. Unless otherwise specified, the same reference numerals or symbols represent the same components, parts, or the same meaning content. In a preferred mode, it can be considered that the vertically downward direction (i.e., the direction of gravity) corresponds to the "lower direction", and the opposite direction corresponds to the "upper direction".

[0024] In the present invention, the "solid-state battery" generally refers to a battery whose constituent elements are composed of solids, and more specifically, to an all-solid-state battery whose constituent elements (especially all constituent elements) are composed of solids. In a preferred embodiment, the solid-state battery in the present invention is a stacked solid-state battery formed by laminating each layer constituting the battery structural unit, and preferably each such layer is composed of a fired body. The "solid-state battery" is a so-called "secondary battery" that can be repeatedly charged and discharged. The "secondary battery" is not overly restricted by its name and may include, for example, energy storage devices.

[0025] The features of the present invention relate to the positive electrode layer included in the solid-state battery. Hereinafter, in order to understand the overall structure of the solid-state battery, the basic structure of the solid-state battery of the present invention will be described first. However, the structure of the solid-state battery described here is merely an example for understanding the invention and does not limit the invention.

[0026] [Basic Structure of Solid-State Battery]

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

[0028] The solid-state battery 200 according to the present invention has: a solid-state battery laminate 100 having at least one battery structural unit composed of a positive electrode layer 10A, a negative electrode layer 10B, and a solid electrolyte layer 20 interposed therebetween along the lamination direction L; and

[0029] a positive electrode terminal 40A and a negative electrode terminal 40B, which are respectively provided on opposite side surfaces of the solid-state battery laminate 100.

[0030] In the solid-state battery laminate 100, the positive electrode layer 10A and the negative electrode layer 10B are alternately laminated with the solid electrolyte layer 20 interposed therebetween.

[0031] In the solid-state battery, each layer formed can be formed by firing, and the positive electrode layer, the negative electrode layer, and the solid electrolyte layer can also form fired layers. Preferably, the positive electrode layer, the negative electrode layer, and the solid electrolyte layer are integrally fired with each other, and the solid-state battery laminate preferably forms an integrally fired body.

[0032] The positive electrode layer is an electrode layer containing at least a positive electrode active material. The positive electrode layer may also contain a solid electrolyte. In a preferred embodiment, the positive electrode layer is composed of a fired body containing at least positive electrode active material particles and solid electrolyte particles. On the other hand, the negative electrode layer is an electrode layer containing at least a negative electrode active material. The negative electrode layer may also contain a solid electrolyte. In a preferred embodiment, the negative electrode layer is composed of a sintered body containing at least negative electrode active material particles and solid electrolyte particles. The positive electrode layer having such a structure is called a "composite positive electrode body", and similarly, the negative electrode layer can be called a "composite negative electrode body".

[0033] The positive electrode active material and the negative electrode active material are substances that participate in the transfer of electrons in a solid-state battery. Ions move (conduct) between the positive electrode layer and the negative electrode layer via the solid electrolyte to transfer electrons, thereby performing charge and discharge. Each electrode layer of the positive electrode layer and the negative electrode layer is particularly preferably a layer capable of intercalating and deintercalating lithium ions or sodium ions. That is, the solid-state 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 charge and discharge of the battery.

[0034] (Positive electrode layer)

[0035] The content of the solid electrolyte in the positive electrode layer 10A is not particularly limited, and is usually 10 to 50% by mass relative to the total amount of the positive electrode layer, and particularly preferably 20 to 40% by mass. The positive electrode layer may also contain two or more solid electrolytes. In this case, their total content only needs to be within the above range.

[0036] (Negative electrode layer)

[0037] 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 phosphoric acid compounds having a NASICON-type structure, lithium-containing phosphoric acid compounds having an olivine-type structure, and lithium-containing oxides having a spinel-type structure. 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). As an example of the lithium alloy, Li-Al etc. can be cited. As an example of the lithium-containing phosphoric acid compound having a NASICON-type structure, Li3V2(PO4)3 and / or LiTi2(PO4)3 etc. can be cited. As an example of the lithium-containing phosphoric acid compound having an olivine-type structure, Li3Fe2(PO4)3 and / or LiCuPO4 etc. can be cited. As an example of the lithium-containing oxide having a spinel-type structure, Li4Ti5O 12 etc.

[0038] In addition, as the negative electrode active material capable of inserting and extracting sodium ions, 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 can be cited.

[0039] The positive electrode layer and / or the negative electrode layer may also contain a conductive material. As the conductive material contained in the positive electrode layer and the negative electrode layer, at least one selected from metal materials such as silver, palladium, gold, platinum, aluminum, copper, and nickel, and carbon can be cited.

[0040] Furthermore, the positive electrode layer and / or the negative electrode layer may also contain a sintering aid. As the 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 can be cited.

[0041] The thicknesses of the positive electrode layer and the negative electrode layer are not particularly limited, and for example, they can be independently 2 μm or more and 50 μm or less, particularly 5 μm or more and 30 μm or less.

[0042] (Positive electrode current collector layer / Negative electrode current collector layer)

[0043] Although not essential elements of the electrode layer, the positive electrode layer and the negative electrode layer may each include a positive electrode current collector layer 11A and a negative electrode current collector layer 11B. The positive electrode current collector layer and the negative electrode current collector layer may each have the form of a foil. However, if more emphasis is placed on viewpoints such as improving the electron conductivity based on integral firing, reducing the manufacturing cost of the solid battery, and / or reducing the internal resistance of the solid battery, the positive electrode current collector layer and the negative electrode current collector layer may each have the form of a fired body.

[0044] 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, materials with high conductivity are 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 may each have an electrical connection portion for electrical connection to the outside, or may be configured to be electrically connected to a terminal.

[0045] In addition, when the positive electrode current collector layer and the negative electrode current collector layer have the form of a fired body, they may also be composed of a fired body containing a conductive material and a sintering aid. The conductive material contained in the positive electrode current collector layer and the negative electrode current collector layer can be selected, for example, from the same materials as those that can be contained in the positive electrode layer and the negative electrode layer. The sintering aid contained in the positive electrode current collector layer and the negative electrode current collector layer is selected, for example, from the same materials as those that can be contained in the positive electrode layer and the negative electrode layer.

[0046] (Solid electrolyte)

[0047] A solid electrolyte is a material capable of conducting lithium ions or sodium ions. This solid electrolyte can form a layer capable of conducting lithium ions between the positive electrode layer and the negative electrode layer. In addition, the solid electrolyte can also be included in the positive electrode layer and the negative electrode layer.

[0048] The solid electrolyte layer can also contain a sintering aid. The sintering aid contained in the solid electrolyte layer can be selected, for example, from the same materials as those that can be contained in the positive electrode layer and the negative electrode layer.

[0049] 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 or more and 15 μm or less, and particularly can be 1 μm or more and 5 μm or less.

[0050] (Electrode separation part)

[0051] The solid battery 200 of the present invention can also have an electrode separation part (also referred to as a "blank layer" or "blank part") 30 (30A, 30B).

[0052] The electrode separation part 30A (positive electrode separation part) separates the above-mentioned positive electrode layer 10A from the negative terminal 40B by being disposed around the positive electrode layer 10A. The electrode separation part 30B (negative electrode separation part) separates the above-mentioned negative electrode layer 10B from the positive terminal 40A by being disposed around the negative electrode layer 10B. Although not particularly limited, the electrode separation part 30 can be composed of, for example, one or more materials selected from the group consisting of a solid electrolyte, an insulating material, and a mixture thereof.

[0053] The solid electrolyte that can form the electrode separation part 30 can use the same material as the solid electrolyte that can form the solid electrolyte layer.

[0054] The insulating material that can form the electrode separation part 30 can also be a non-electrically conductive material, that is, a non-conductive material. Although not particularly limited, the insulating material can be, for example, a glass material, a ceramic material, etc. As this insulating material, for example, a glass material can be selected. Although not particularly limited, the glass material can be at least one selected from the group consisting of soda-lime glass, potash glass, borate glass, borosilicate glass, barium borosilicate glass, zinc borate glass, barium borate glass, bismuth borosilicate salt glass, bismuth zinc borate glass, bismuth silicate glass, phosphate glass, aluminum phosphate glass, and phosphite glass. In addition, although not particularly limited, the ceramic material can be at least one selected from the group consisting of alumina (Al2O3), boron nitride (BN), silicon dioxide (SiO2), silicon nitride (Si3N4), zirconia (ZrO2), aluminum nitride (AlN), silicon carbide (SiC), and barium titanate (BaTiO3).

[0055] (Terminal)

[0056] In the solid-state battery 200 of the present invention, terminals (external terminals) 40 (40A, 40B) are generally provided. In particular, the positive and negative terminals 40A and 40B are provided in pairs on the side surface of the solid-state battery. More specifically, the positive terminal 40A connected to the positive electrode layer 10A and the negative terminal 40B connected to the negative electrode layer 10B are provided in pairs. The terminals 40A and 40B can be provided so as to cover at least one side surface of the solid-state battery, and thus can also be referred to as "end face electrodes". Such terminals 40 (40A, 40B) can be made of a material with high conductivity. As the material of the terminal 40, there is no particular limitation, and at least one conductive material selected from the group consisting of silver, gold, platinum, aluminum, copper, tin, and nickel can be cited.

[0057] The terminals 40 (40A, 40B) may also contain a sintering aid. As the sintering aid, the same materials as those that may be contained in the positive electrode layer 10A can be cited. In a preferred embodiment, the terminals 40 (40A, 40B) are composed of a sintered body containing at least a conductive material and a sintering aid.

[0058] (Outer layer material)

[0059] The solid-state battery 200 of the present invention generally further has an outer layer material 60. The outer layer material 60 can generally be formed on the outermost side of the solid-state battery for electrical, physical, and / or chemical protection. As the material constituting the outer layer material 60, a material having excellent insulation, durability, and / or moisture resistance and being environmentally safe is preferred. For example, glass, ceramics, thermosetting resins, photocurable resins, and mixtures thereof can be used.

[0060] As the glass that can constitute the outer layer material, the same material as the glass material that can constitute the electrode separation portion can be used. In addition, as the ceramic material that can constitute the outer layer material, the same material as the ceramic material that can constitute the electrode separation portion can be used.

[0061] [Features of the solid-state battery of the present invention]

[0062] The inventors of the present application have conducted in-depth research on countermeasures for enabling the solid-state battery to have more appropriate battery characteristics even when used under high-temperature conditions. As a result, the inventors of the present application have achieved this solution based on focusing on the positive electrode layer constituting the solid-state battery. Specifically, the inventors of the present application newly found that, on the premise of a solid electrolyte having a specific material composition in the positive electrode layer, the onset temperature of the thermogravimetric reduction of the positive electrode active material containing Li (lithium) can be related to the battery characteristics (i.e., high-temperature tolerance) under high-temperature conditions.

[0063] Figure 3 It is a graph showing the relationship between the heating temperature of the positive electrode active material in the solid battery according to an embodiment of the present invention and the rate of thermogravimetric change (decrease). As Figure 3 shown, if the heating temperature of the positive electrode active material is increased, the rate of thermogravimetric change (decrease) of the positive electrode active material increases from a specified temperature or higher. In addition, in this figure, two TG (Thermogravimetry) curves (the TG curve related to Example 1 and the TG curve related to Comparative Example 1) with different thermogravimetric reduction start temperatures (i.e., thermogravimetric reduction start temperatures) are shown. As can also be seen from the column of the examples described later, the thermogravimetric reduction start temperature varies depending on the material composition of the positive electrode active material and the solid electrolyte contained in the positive electrode layer, and this different thermogravimetric reduction start temperature may be related to the battery characteristics under high-temperature conditions.

[0064] In the present invention, based on these characteristics, regarding the positive electrode layer, under the condition of containing a solid electrolyte with a specific material composition, a positive electrode active material with a thermogravimetric reduction start temperature within a specific range, particularly a positive electrode active material above a specific lower limit value, is appropriately selected.

[0065] Specifically, in the present invention, regarding the positive electrode layer, as the solid electrolyte, under the condition of containing lithium borosilicate glass, a positive electrode active material with a thermogravimetric reduction start temperature of 220°C or higher and less than 485°C, where the weight reduction is 0.67% or more in a state where the lithium detachment amount of the positive electrode active material is 40% (i.e., a state where 40% of the Li amount of the positive electrode active material has detached), can be selected. In the present invention, by selecting a positive electrode layer having the above characteristics in the solid battery, more appropriate battery characteristics can be obtained under high-temperature conditions. That is, a solid battery with more excellent high-temperature resistance can be provided.

[0066] Specifically, in a solid battery having a positive electrode layer with the above characteristics, even when exposed to high temperatures (for example, in the temperature range of 80°C to 200°C), deterioration of battery characteristics such as the resistance value and / or battery capacity can be more appropriately suppressed. Therefore, the solid battery of the present invention can be appropriately used even under high-temperature conditions.

[0067] In the present invention, the lower limit value (220°C or higher) of the thermogravimetric reduction start temperature of the positive electrode active material helps to maintain the high-temperature resistance of the solid battery, and the upper limit value (less than 485°C) is based on the view of suppressing the decrease in the electronic conductivity of the positive electrode active material. In addition, from the view of appropriately balancing the maintenance of the high-temperature resistance of the solid battery and the suppression of the decrease in the electronic conductivity of the positive electrode active material, the upper limit value of the thermogravimetric reduction start temperature can be 350°C or lower.

[0068] In addition, the thermal weight loss start temperature of the positive electrode active material can be measured using a thermogravimetric differential thermal simultaneous measurement device (manufactured by Rigaku Corporation, device model: TG8120). Specifically, a sample (such as a positive electrode layer) is set in this device, and while nitrogen is introduced at a prescribed speed, heating is performed under the condition of a prescribed heating rate, and the thermal weight loss start temperature of the positive electrode active material with a weight loss of 0.67% or more is measured. In this device, when the sample is heated, a weight change of the positive electrode active material contained in the positive electrode layer occurs starting from a prescribed temperature value. When this weight change occurs, the main beam in the measurement device tilts, and the current flowing through the coil is controlled so that its operation returns to the original state. Since the flowing current corresponds to the weight change, the change behavior of the current is output as the weight change, and thus the thermal weight loss start temperature of the above positive electrode active material can be grasped.

[0069] The "state where the lithium detachment amount of the positive electrode active material is 40%" as mentioned in this specification refers to the state where the lithium detachment amount is 40% when the lithium detachment amount relative to the lithium content of the positive electrode active material is expressed as a percentage. In other words, the "state where the lithium detachment amount of the positive electrode active material is 40%" means that the lithium content of the positive electrode active material in the non-charged state of the battery is set to 100%, and the lithium content of the positive electrode active material is 60%. For example, the "state where the lithium detachment amount of the positive electrode active material is 40%" can be a charged state in which 40% of the lithium contained in the positive electrode active material in the fully discharged battery is extracted. In addition, the extraction state of Li in the positive electrode active material can be measured using XRD.

[0070] In addition, in the present invention, the reason for evaluating the thermal weight loss start temperature of the positive electrode active material in the state where the lithium detachment amount of the positive electrode active material contained in the positive electrode layer is 40% is as follows. During charging of the solid-state battery, by extracting lithium, the crystal structure of the positive electrode active material may become unstable, and this instability may become significant especially under the battery usage conditions at high temperatures when viewed from the charged state where 40% of the Li amount of the positive electrode active material has detached. Along with the instability of the above crystal structure, under high-temperature conditions in the state where 40% of the Li amount of the positive electrode active material has detached, the deterioration of the solid-state battery may easily progress. Based on the above, the thermal weight loss start temperature of the positive electrode active material in the state where 40% of the Li amount of the positive electrode active material has detached is evaluated.

[0071] The above lithium detachment amount can be quantified by XRD analysis. Alternatively, it can also be calculated based on the initial charge-discharge efficiency and the weight per unit area of the positive electrode active material and the negative electrode active material according to the charge amount of the solid-state battery.

[0072] 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. Such a solid electrolyte has relatively high thermal stability. By being contained in the positive electrode layer, it can more appropriately suppress the deterioration of the battery characteristics of the solid battery under high-temperature conditions.

[0073] In addition, one or more other elements can be added to the lithium borosilicate glass in addition to lithium, silicon, boron, and oxygen. For example, the lithium borosilicate glass can also contain at least one element selected from the group consisting of Group 1 and Group 2 elements and Group 14 to Group 17 elements of the periodic table. The content of each element contained in the lithium borosilicate glass can be measured, for example, by analyzing the glass-ceramic solid electrolyte using inductively coupled plasma atomic emission spectrometry (ICP-AES) or the like.

[0074] In addition to the lithium borosilicate glass as the glass-based solid electrolyte, the above solid electrolyte can further contain other solid electrolytes used in known solid batteries. As such solid electrolytes, for example, any one or two or more of crystalline solid electrolytes, glass-based solid electrolytes different from lithium borosilicate glass, and glass-ceramic solid electrolytes can be used. The crystalline solid electrolyte is, for example, an oxide-based crystalline material or the like. Examples of the oxide-based crystalline material include lithium-containing phosphate compounds having a NASICON structure, oxides having a perovskite structure, oxides having a garnet-type or garnet-like structure, and oxide glass-ceramic-based lithium ion conductors.

[0075] As the lithium-containing phosphate compound having a NASICON structure, 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)) can be cited. As an example of the lithium-containing phosphate compound having a NASICON structure, for example, Li 1.2 Al 0.2 Ti 1.8 (PO4)3 and the like can be cited. As an example of the oxide having a perovskite structure, La 0.55 Li 0.35 TiO3 and the like can be cited. As an example of the oxide having a garnet-type or garnet-like structure, Li7La3Zr2O 12 and the like can be cited. The crystalline solid electrolyte can also contain a polymer material (for example, polyethylene oxide (PEO) or the like).

[0076] Glass-based solid electrolytes include, for example, oxide-based glass materials and the like. For example, as glass-based solid electrolytes other than lithium borosilicate glass, there are 30Li2S·26B2S3·44LiI, 63Li2S·36SiS2·1Li3PO4, 57Li2S·38SiS2·5Li4SiO4, 70Li2S·30P2S5, 50Li2S·50GeS2, and the like.

[0077] Glass-ceramic-based solid electrolytes are, for example, oxide-based glass-ceramic materials and the like. As oxide-based glass-ceramic materials, for example, a phosphate compound (LATP) containing lithium, aluminum, and titanium in its constituent elements and a phosphate compound (LAGP) containing lithium, aluminum, and germanium in its constituent elements can be used. LATP is, for example, Li 1.07 Al 0.69 Ti 1.46 (PO4)3 and the like. In addition, LAGP is, for example, Li 1.5 Al 0.5 Ge 1.5 (PO4) and the like.

[0078] For example, in addition to lithium borosilicate glass, the solid electrolyte can further contain an oxide having a garnet-type or garnet-like structure. For example, in the positive electrode layer of the solid battery of the present invention, lithium borosilicate glass and an oxide containing Li, La, and Zr (corresponding to LiLaZr-based oxide) can be included as the solid electrolyte. The inventors of the present application have found that when at least lithium borosilicate glass is included as the solid electrolyte in the positive electrode layer, the positive electrode active material can preferentially form an interface with lithium borosilicate glass having relatively high thermal stability. Therefore, even when a solid electrolyte having relatively low thermal stability is included in the positive electrode layer, the reaction between the positive electrode active material and the solid electrolyte having low thermal stability under high-temperature conditions can be suppressed by the lithium borosilicate glass. Therefore, other solid electrolytes having poor thermal stability compared to lithium borosilicate glass but excellent lithium ion conductivity can also be included, and a solid battery that can more appropriately balance high-temperature resistance and battery performance (for example, capacity retention rate, etc.) can be obtained.

[0079] The content of lithium borosilicate glass in the solid electrolyte of the positive electrode layer is not particularly limited. For example, it can be 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. Alternatively, the content of the garnet-type oxide-based solid electrolyte in the solid electrolyte of the positive electrode layer is not particularly limited. For example, it can be 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 content of the garnet-type oxide-based solid electrolyte is within the above range, a solid battery that can be more suitably used even under high-temperature conditions can be provided.

[0080] As an example, the above oxide-based solid electrolyte may be a LiLaZr-based oxide (LLZ) with high ionic conductivity. That is, in the present invention, two or more solid electrolytes, namely, a solid electrolyte contributing to thermal stability and a solid electrolyte contributing to high ionic conductivity, can be used. Thereby, the battery characteristics under high-temperature conditions can be maintained, and the ionic conductivity contributing to the charge and discharge of the battery can be ensured.

[0081] In the present invention, as the above positive electrode active material, a positive electrode active material having a layered crystal structure can be used. Specifically, the above positive electrode active material may be a layered rock salt-type metal oxide, for example, a lithium transition metal composite oxide. The "layered rock salt-type metal oxide" refers to a metal oxide, particularly its particles, having a layered rock salt-type crystal structure that can be identified by analyzing the X-ray diffraction pattern.

[0082] In one example, in the present invention, the positive electrode active material may contain an oxide containing Li and Co (equivalent to LCO, corresponding to a LiCo-based oxide), and this LiCo-based oxide contains at least Ti. Thereby, compared with the case where Ti is not contained, the onset temperature of the thermal weight reduction of the positive electrode active material can be increased, and the battery characteristics under high-temperature conditions can be maintained.

[0083] In addition, in addition to Ti, the LiCo-based oxide may further contain 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. When the positive electrode active material is a LiCo-based oxide containing at least Ti, its onset temperature of the thermal weight reduction may be 220 °C or higher and 240 °C or lower.

[0084] Specifically, in the present invention, the positive electrode active material may contain LiCo x Ti y α z O2 (where x + y + z = 1, 0.9 ≤ x < 1, 0.005 ≤ y ≤ 0.01, 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). Additionally, if considering suppressing the increase in the resistance value and capacity deterioration under high-temperature conditions, α is more preferably Al and / or Mg.

[0085] In other examples, in the present invention, the positive electrode active material may contain an oxide containing Li, Ni, Co, and Mn (equivalent to NCM, corresponding to a LiNiCoMn-based oxide). Specifically, the positive electrode active material may be LiNi a Co b Mnc O2 (where a + b + c ≤ 1 and 0.3 ≤ a ≤ 0.8).

[0086] In particular, compared with the case where the positive electrode active material is a Ti-containing LiCo-based oxide, when it is a LiNiCoMn-based oxide, the above-mentioned TG reduction start temperature may be higher. Thus, when the positive electrode active material is a LiNiCoMn-based oxide, the TG reduction start temperature of the positive electrode active material can be further increased, and the battery characteristics under high temperature conditions can be more appropriately exhibited.

[0087] [Manufacturing method of solid battery]

[0088] The solid battery of the present invention can be manufactured by a printing method such as a screen printing method, a green sheet method using green sheets, or a combination method thereof. Hereinafter, for the purpose of understanding the present invention, the cases of using the printing method and the green sheet method will be described in detail, but the present invention is not limited to this method. That is, the solid battery can be manufactured according to a conventional manufacturing method of a solid battery. In addition, the order of the following description and other matters that change over time are only for convenience of explanation and are not necessarily limited thereto.

[0089] [Forming step of solid battery laminate precursor]

[0090] In this step, for example, various pastes such as a paste for the positive electrode layer, a paste for the negative electrode layer, a paste for the solid electrolyte layer, a paste for the positive electrode current collector layer, a paste for the negative electrode current collector layer, a paste for the electrode separation part, and a paste for the outer layer material are used as inks. That is, by applying and drying the paste using a printing method, a solid battery laminate precursor having a specified structure is formed on a support substrate.

[0091] At the time of printing, by sequentially laminating printing layers with a specified thickness and pattern shape, a solid battery laminate precursor corresponding to the structure of a specified solid battery can be formed on the substrate. The type of the pattern forming method is not particularly limited as long as it can form a specified pattern, and for example, it is any one or two or more of a screen printing method and a gravure printing method.

[0092] The paste can be prepared by wet-mixing the specified constituent materials of each layer and an organic carrier in which an organic material is dissolved in a solvent. The specified constituent materials of each layer are appropriately selected from the group consisting of positive electrode active material particles, negative electrode active material particles, a conductive material, a solid electrolyte material, a current collector layer material, an insulating material, a sintering aid, and other above-mentioned materials.

[0093] The paste for the positive electrode layer contains, for example, positive electrode active material particles, a solid electrolyte material, an organic material, a solvent, and a sintering aid as required.

[0094] The paste for the negative electrode layer contains, for example, negative electrode active material particles, a solid electrolyte material, an organic material, a solvent, and a sintering aid as required.

[0095] The paste for the solid electrolyte layer contains, for example, a solid electrolyte material, an organic material, a solvent, and a sintering aid as required.

[0096] The paste for the positive electrode current collector layer contains a conductive material, an organic material, a solvent, and a sintering aid as required.

[0097] The paste for the negative electrode current collector layer contains a conductive material, an organic material, a solvent, and a sintering aid as required.

[0098] The paste for the electrode separation part contains, for example, a solid electrolyte material, an insulating material, an organic material, a solvent, and a sintering aid as required.

[0099] The paste for the outer layer material contains, for example, an insulating material, an organic material, a solvent, and a sintering aid as required.

[0100] 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 resins, cellulose resins, polyacrylic resins, polyurethane resins, polyvinyl acetate resins, and polyvinyl alcohol resins can be used.

[0101] The type of the solvent is not particularly limited, and for example, it is any one or two or more of organic solvents such as butyl acetate, N-methyl-pyrrolidone, toluene, terpineol, and N-methyl-pyrrolidone.

[0102] In wet mixing, a medium can be used. Specifically, a ball milling method or a visco mill method can be used. On the other hand, a wet mixing method without using a medium can also be used, and a sand milling method, a high-pressure homogenizer method, or a kneading and dispersing method can be used.

[0103] The support substrate is not particularly limited as long as it is a support capable of supporting each paste layer. For example, it is a release film having a release treatment on one side. Specifically, a substrate made of a polymer material such as polyethylene terephthalate can be used. In the case of supplying the paste layer to the firing process while being held on the substrate, a substrate having heat resistance to the firing temperature can be used.

[0104] As another method, each green sheet can be formed from each paste, and the obtained green sheets can be laminated to produce a precursor of the solid battery laminate.

[0105] Specifically, by drying the support substrates coated with each paste on a hot plate heated to 30°C or higher and 90°C or lower, a positive electrode layer green sheet, a negative electrode layer green sheet, a solid electrolyte layer green sheet, a positive electrode current collector layer green sheet, a negative electrode current collector layer green sheet, an electrode separation part green sheet, and / or an outer layer material green sheet, etc., each having a specified shape and thickness, are respectively formed on each support substrate (e.g., a PET film).

[0106] Next, each green sheet is peeled off from the substrate. After peeling, the green sheets of each component are sequentially laminated in the lamination direction, thereby forming a precursor of the solid battery laminate. After lamination, a solid electrolyte layer, an insulating layer, and / or a protective layer, etc., may also be provided in the side region of the electrode green sheet by screen printing.

[0107] (Firing process)

[0108] In the firing process, the precursor of the solid battery laminate is fired. Although it is merely an example, firing is carried out by heating to 200°C or higher in a nitrogen atmosphere containing oxygen or in the atmosphere to remove the organic material, and then heating to 300°C or higher in a nitrogen atmosphere or in the atmosphere. The firing can be carried out while applying pressure to the precursor of the solid battery laminate in the lamination direction (and, depending on the situation, in the lamination direction and the direction perpendicular to the lamination direction).

[0109] By undergoing such firing, a solid battery laminate is formed, and finally the desired solid battery is obtained.

[0110] (Formation process of positive terminal and negative terminal)

[0111] For example, a positive terminal is bonded to the solid battery laminate using a conductive adhesive, and a negative terminal is bonded to the solid battery laminate using a conductive adhesive. Thus, the positive terminal and the negative terminal are respectively mounted on the solid battery laminate. As a result, the desired solid battery can finally be obtained.

[0112] The above has described the embodiments of the present invention, but they are merely typical examples. Therefore, the present invention is not limited thereto, and those skilled in the art can easily understand that various modes can be considered within the scope of not changing the gist of the present invention.

[0113] Examples

[0114] Hereinafter, examples will be described.

[0115] <Example 1>

[0116] (Manufacturing process of green sheet for solid electrolyte layer)

[0117] First, lithium borosilicate glass as a solid electrolyte and an acrylic binder are mixed at a mass ratio of lithium borosilicate glass:acrylic binder = 70:30. Additionally, as the lithium borosilicate glass, a lithium borosilicate glass having a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio) is used. Next, the obtained mixture is mixed into butyl acetate to make the solid content 30 mass%, and then it is stirred with zirconia balls having a diameter of 5 mm for 4 hours, thereby obtaining a paste for the solid electrolyte layer. Then, this paste is coated on a release film and dried at 80°C for 10 minutes, thereby fabricating a green sheet for the solid electrolyte layer as a precursor of the solid electrolyte layer.

[0118] (Process for fabricating a green sheet for the positive electrode material layer)

[0119] First, cobalt oxide, lithium carbonate, nickel, and manganese are mixed, and a LiNiCoMn-based oxide (equivalent to NCM) is synthesized by a solid-phase method of firing. Specifically, in Example 1, LiNi 0.6 Co 0.2 Mn 0.2 O2 is synthesized. Next, the LiNiCoMn-based oxide (equivalent to NCM) having the above composition as a positive electrode active material and lithium borosilicate glass as a solid electrolyte are mixed at a mass ratio of LiNiCoMn-based oxide:lithium borosilicate glass = 75:25. Additionally, as the lithium borosilicate glass, a lithium borosilicate glass having a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio) is used. Next, after mixing the obtained mixture and an acrylic binder at a mass ratio of mixture (LiNiCoMn-based oxide + lithium borosilicate glass):acrylic binder = 70:30, it is mixed into butyl acetate to make the solid content 30 mass%. Then, the obtained mixture is stirred with zirconia balls having a diameter of 5 mm for 4 hours, thereby obtaining a paste for the positive electrode material layer. Then, this paste is coated on a release film and dried at 80°C for 10 minutes, thereby fabricating a green sheet for the positive electrode material layer as a precursor of the positive electrode layer.

[0120] (Process for fabricating a green sheet for the negative electrode material layer)

[0121] First, carbon powder (manufactured by TIMCAL, KS6) serving as the negative electrode active material and lithium borosilicate glass serving as the solid electrolyte are mixed at a mass ratio of carbon powder:lithium borosilicate glass = 70:30. Additionally, as the lithium borosilicate glass, lithium borosilicate glass having a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio) is used. Next, after mixing the resulting mixture and an acrylic binder at a mass ratio of mixture (carbon powder + lithium borosilicate glass):acrylic binder = 70:30, it is mixed into butyl acetate to make the solid content 30 mass%. Then, the resulting mixture is stirred together with zirconia balls having a diameter of 5 mm for 4 hours to obtain a paste for the negative electrode material layer. Next, this paste is coated on a release film and dried at 80°C for 10 minutes to fabricate a green sheet for the negative electrode material layer, which is a precursor of the negative electrode material layer.

[0122] (Process for fabricating a green sheet for the positive electrode current collector layer)

[0123] First, carbon powder (manufactured by TIMCAL, KS6) serving as the conductive material and lithium borosilicate glass serving as the solid electrolyte are mixed at a mass ratio of carbon powder:lithium borosilicate glass = 70:30. Additionally, as the lithium borosilicate glass, lithium borosilicate glass having a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio) is used. Next, after mixing the resulting mixture and an acrylic binder at a mass ratio of mixture (carbon powder + lithium borosilicate glass):acrylic binder = 70:30, it is mixed into butyl acetate to make the solid content 30 mass%. Then, the resulting mixture is stirred together with zirconia balls having a diameter of 5 mm for 4 hours to obtain a paste for the positive electrode current collector layer. Next, this paste is coated on a release film and dried at 80°C for 10 minutes to fabricate a green sheet for the positive electrode current collector layer, which is a precursor of the positive electrode current collector layer.

[0124] (Process for fabricating a green sheet for the negative electrode current collector layer)

[0125] A green sheet for the negative electrode current collector layer is fabricated in the same manner as the above process for fabricating a green sheet for the positive electrode current collector layer.

[0126] (Process for fabricating a green sheet for the outer layer material)

[0127] First, alumina particle powder (manufactured by Nippon Light Metal, AHP300) as particle powder and lithium borosilicate glass as solid electrolyte are mixed at a mass ratio of alumina particle powder:lithium borosilicate glass = 50:50. Then, after mixing the obtained mixture and acrylic binder at a mass ratio of mixture (alumina particle powder + lithium borosilicate glass):acrylic binder = 70:30, it is mixed into butyl acetate to make the solid content 30% by mass. Then, the obtained mixture is stirred with zirconia balls with a diameter of 5 mm for 4 hours to obtain a paste for the main surface outer packaging material. Next, this paste is coated on a release film and dried to fabricate a green sheet for the outer layer material as a precursor of the outer layer material.

[0128] (Process for fabricating a green sheet for the electrode separation part)

[0129] A green sheet for the electrode separation part as a precursor of the electrode separation part is fabricated in the same manner as the above process for fabricating the green sheet for the outer layer material.

[0130] (Process for fabricating a laminate)

[0131] Using the respective green sheets obtained in the above manner, a laminate having the Figure 1 and Figure 2 shown configuration is fabricated as follows. Specifically, first, after processing each green sheet into the Figure 1 and Figure 2 shown shapes, they are demolded from the release film. Next, after sequentially laminating the respective green sheets in a manner corresponding to the structure of the battery element shown in Figure 1 and Figure 2 , thermocompression bonding is performed. Thereby, a laminate as a precursor of the battery element is obtained.

[0132] (Sintering process of the laminate)

[0133] By heating the obtained laminate, the acrylic binder contained in each green sheet is removed, and then further heating is performed to sinter the oxide glass contained in each green sheet.

[0134] (Process for fabricating terminals)

[0135] First, Ag powder (manufactured by Dainichi Chemical Industry Co., Ltd.), which is a conductive particle powder, and oxide glass (Bi-B series glass, manufactured by Asahi Glass Co., Ltd., ASF1096) are mixed at a specified mass ratio. Next, after mixing the obtained mixture (Ag powder + oxide glass) and an acrylic binder at a mass ratio of mixture of Ag powder + oxide glass:acrylic binder = 70:30, it is mixed into butyl acetate solvent to make the solid content 50 mass%. Then, the obtained mixture is stirred with zirconia balls having a diameter of 5 mm for 4 hours to obtain a conductive paste. Next, the conductive paste is attached to the first and second end faces (or side faces) of the laminate where the positive electrode current collector layer and the negative electrode current collector layer are respectively exposed, and positive and negative electrode terminals are formed by sintering. In this way, the solid battery in Example 1 is obtained.

[0136] <Example 2>

[0137] In Example 2, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiNi 0.3 Co 0.3 Mn 0.3 O2 is synthesized. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0138] <Example 3>

[0139] In Example 3, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiNi having a composition different from that in Example 1 and 2 is synthesized 0.72 Co 0.05 Mn 0.2 O2. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0140] <Example 4>

[0141] In Example 4, in the production process of the green sheet for the positive electrode material layer in Example 1, cobalt oxide, lithium carbonate, and titanium are mixed, and lithium cobalt titanate (LiCoO2) is synthesized by the solid phase method of firing. Specifically, in Example 4, as the positive electrode active material, LiCo 0.995 Ti 0.005 O2 is synthesized. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0142] <Example 5>

[0143] In Example 5, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiCo having a composition different from that in Example 4 is synthesized 0.99 Ti 0.01O2. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0144] <Example 6>

[0145] In Example 6, in the production process of the green sheet for the positive electrode material layer in Example 1, cobalt oxide, lithium carbonate, titanium, and aluminum were mixed, and lithium cobaltate (LiCoO2) containing titanium and aluminum was synthesized by the solid-phase method of firing. Specifically, in Example 6, as the positive electrode active material, LiCo 0.985 Ti 0.005 Al 0.01 O2. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0146] <Example 7>

[0147] In Example 7, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiCo with a composition different from that in Example 6 was synthesized. 0.965 Ti 0.005 Al 0.03 O2. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0148] <Example 8>

[0149] In Example 8, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiCo with a composition different from that in Example 6 and 7 was synthesized. 0.945 Ti 0.005 Al 0.05 O2. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0150] <Example 9>

[0151] In Example 9, in the production process of the green sheet for the positive electrode material layer in Example 1, cobalt oxide, lithium carbonate, titanium, and magnesium were mixed, and lithium cobaltate (LiCoO2) containing titanium and magnesium was synthesized by the solid-phase method of firing. Specifically, in Example 9, as the positive electrode active material, LiCo 0.985 Ti 0.005 Mg 0.01 O2. Except for this point, the solid battery is manufactured by the same method as in Example 1.

[0152] <Example 10>

[0153] In Example 10, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiCo with a composition different from that in Example 9 was synthesized.0.965 Ti 0.005 Mg 0.03 O2. Except for this, a solid battery is manufactured by the same method as in Example 1.

[0154] <Example 11>

[0155] In Example 11, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiCo with a composition different from that of Examples 9 and 10 is synthesized 0.945 Ti 0.005 Mg 0.05 O2. Except for this, a solid battery is manufactured by the same method as in Example 1.

[0156] <Example 12>

[0157] In Example 12, in the production process of the green sheet for the positive electrode material layer in Example 1, as the positive electrode active material, LiCo with the same composition as in Example 4 is synthesized 0.995 Ti 0.005 O2. On the other hand, as the solid electrolyte used in the production process of each green sheet in Example 1, instead of using lithium borosilicate glass alone, a mixture of lithium borosilicate glass and LiLaZr-based oxide (Li7La3Zr2O 12 (LLZ)) is used (mass ratio of lithium borosilicate glass: LLZ = 60:40). Except for these aspects, a solid battery is manufactured by the same method as in Example 1.

[0158] <Comparative Example 1>

[0159] A solid battery is manufactured by the same method as in Example 1, except that lithium cobaltate without titanium is used as the positive electrode active material.

[0160] <Comparative Example 2>

[0161] A solid battery is manufactured by the same method as in Example 4, except that LiLaZr-based oxide is used as the solid electrolyte. As the LiLaZr-based oxide, Li7La3Zr2O 12 .

[0162] <Comparative Example 3>

[0163] A solid battery is manufactured by the same method as in Example 1, except that an oxide containing Li, Mn, and Al (corresponding to LiMnAl-based oxide) is used as the solid electrolyte. As the LiMnAl-based oxide, LiMn 1.92 Al 0.08 O4 (LMO).

[0164] (Measurement of Battery Characteristics)

[0165] Set the rated capacity of the battery to 1C, charge it at a constant current of 0.2C to the specified positive electrode potential. After reaching the positive electrode potential, charge it in a constant voltage mode until the current decreases to 0.01C, perform impedance measurement, and obtain the initial resistance value. Thereafter, store it at a high temperature condition (105 °C) for 1 week. After slow cooling to 25 °C by air cooling, perform impedance measurement at 25 °C, discharge it at a constant current of 0.2C to 2V, and perform capacity measurement. In addition, different potentials are used for the positive electrode potential according to the positive electrode active material. Specifically, when the positive electrode active material is LiCo-based oxide (LCO), charge it to a positive electrode potential of 4.35V; when it is LiNiCoMn-based oxide (NCM), charge it to a positive electrode potential of 4.2V; or when it is LiMnAl-based oxide (LMO), charge it to a positive electrode potential of 4.95V.

[0166] For the solid-state batteries of Examples 1 to 12 and Comparative Examples 1 and 2, the resistance increase rate was calculated by dividing the initial resistance value obtained from the impedance measurement results by the resistance value after storage under high temperature conditions. In addition, similarly based on the capacity measurement results, the deteriorated capacity of the discharge capacity after storage under high temperature conditions was obtained. Furthermore, for the solid-state batteries of Examples 1, 2, 4 to 12 and Comparative Examples 1 to 3, the capacity retention rate was measured. Specifically, set the rated capacity of the battery to 1C, charge it at a constant current of 0.2C to the above positive electrode potential. After reaching this positive electrode potential, charge it in a constant voltage mode until the current decreases to 0.01C. Thereafter, discharge it at a constant current of 0.2C until the positive electrode potential reaches 3V. Set such charging and discharging as 1 cycle, and measure the capacity retention rate relative to the initial discharge capacity when repeated 100 cycles.

[0167] In addition, in each of Examples 1 to 12 and Comparative Examples 1 to 3, use a thermogravimetric differential thermal simultaneous measurement (TG-DTA) device (manufactured by Rigaku Corporation, device model: TG8120). Set the positive electrode layer on the device, heat it under the condition of a heating rate of 3 °C / min while introducing nitrogen at a rate of 200 ml / min, and measure the thermogravimetric reduction start temperature of the positive electrode active material in the positive electrode layer at the start of measurement when the weight reduction of the positive electrode active material contained in the positive electrode layer is more than 0.67%. Specifically, if the temperature is increased, the weight change of the positive electrode active material starts from a specified temperature value. If this weight change occurs, the main beam in the device tilts, and the current flowing through the coil is controlled so that its operation returns to the original state. Since the flowing current corresponds to the weight change, the variation behavior of the current is output as the weight change, thereby grasping the thermogravimetric reduction start temperature of the above positive electrode active material.

[0168] In addition, the weight of the positive electrode active material at the start of measurement can be calculated from the weight of the positive electrode layer and the mixing ratio of the positive electrode active material in the positive electrode layer.

[0169] These measurement results are shown in Table 1. In addition, regarding the resistance increase rate and the deterioration capacity, the relative resistance increase rate and the relative deterioration capacity of Examples 1 to 12, Comparative Example 1, and Comparative Example 2 are shown with the resistance increase rate and the deterioration capacity in Comparative Example 1 set to "100".

[0170] [Table 1]

[0171]

[0172]

[0173] From the above measurement results, it can be seen that in Examples 1 to 12, when the lithium detachment amount of the positive electrode active material in the obtained solid battery is 40%, in the case where the solid electrolyte in the positive electrode layer contains lithium borosilicate glass, if the starting temperature of the thermogravimetric reduction is 220°C or higher when the weight of the positive electrode active material decreases by 0.67% or more, both the relative resistance increase rate and the relative deterioration capacity of the solid battery are lower than those in Comparative Example 1 (starting temperature of thermogravimetric reduction: 203°C + solid electrolyte in the positive electrode layer: containing lithium borosilicate glass).

[0174] In addition, it can be seen that in Comparative Example 2 (starting temperature of thermogravimetric reduction: 210°C + solid electrolyte in the positive electrode layer: containing LiLaZr-based oxide / without lithium borosilicate glass), the relative deterioration capacity of the solid battery is lower than that in Comparative Example 1.

[0175] Furthermore, in Comparative Example 3 (starting temperature of thermogravimetric reduction: 485°C + solid electrolyte in the positive electrode layer: lithium borosilicate glass), compared with Examples 1 to 12, the above capacity retention rate is 0%, so it can be seen that when the battery is charged and discharged repeatedly for 100 cycles, there is no capacity retention relative to the initial discharge capacity.

[0176] From the above, as a whole, in the case of using a positive electrode layer having a solid electrolyte containing lithium borosilicate glass and a positive electrode active material having a thermogravimetric reduction starting temperature of 220°C or higher and less than 485°C as the positive electrode layer, appropriate battery characteristics (relative resistance increase rate, etc.) can be obtained even under high-temperature conditions. That is, it can be seen that the solid battery in this example can have appropriate high-temperature resistance.

[0177] In addition, the present invention can be implemented in the following manner.

[0178] <1> A solid battery

[0179] The positive electrode active material contains Li and the positive electrode layer includes a solid electrolyte.

[0180] When the amount of lithium released from the positive electrode active material is 40%, the onset temperature of thermogravimetric reduction at which the weight of the positive electrode active material decreases by 0.67% or more is 220°C or higher and less than 485°C, and the solid electrolyte contains lithium borosilicate glass.

[0181] <2> The solid battery according to <1>, wherein

[0182] The positive electrode active material has a layered rock salt type crystal structure.

[0183] <3> The solid battery according to <1> or <2>, wherein

[0184] The onset temperature of thermogravimetric reduction is 350°C or lower.

[0185] <4> The solid battery according to any one of <1> to <3>, wherein

[0186] The positive electrode active material contains an oxide containing Li and Co, and the oxide contains at least Ti.

[0187] <5> The solid battery according to <4>, wherein

[0188] In the positive electrode active material, when the oxide containing Li and Co contains Ti, the onset temperature of thermogravimetric reduction is 220°C or higher and 240°C or lower.

[0189] <6> The solid battery according to <4> or <5>, wherein

[0190] The positive electrode active material further contains Mg and / or Al.

[0191] <7> The solid battery according to any one of <4> to <6>, wherein

[0192] The positive electrode active material contains LiCo x Ti y α z O2 (where x + y + z = 1, 0.9 ≤ x < 1, 0.005 ≤ y ≤ 0.01, α: Mg and / or Al).

[0193] <8> The solid battery according to any one of <1> to <7>, wherein

[0194] The positive electrode active material contains an oxide containing Li, Ni, Co, and Mn.

[0195] <9>The solid-state battery according to <8>, wherein,

[0196] the positive electrode active material is LiNi a Co b Mn c O2 (wherein, a + b + c ≤ 1, 0.3 ≤ a ≤ 0.8).

[0197] <10>The solid-state battery according to any one of <1> to <9>, wherein,

[0198] compared with the case where the positive electrode active material is an oxide containing Ti, Li, and Co, when it is an oxide containing Li, Ni, Co, and Mn, the onset temperature of the thermogravimetric reduction is higher.

[0199] <11>The solid-state battery according to any one of <1> to <10>, wherein,

[0200] the solid electrolyte further includes an oxide-based solid electrolyte having a garnet-type crystal structure.

[0201] <12>The solid-state battery according to <11>, wherein,

[0202] the oxide-based solid electrolyte is an oxide containing Li, La, and Zr.

[0203] Industrial Applicability

[0204] The solid-state battery of the present invention can be applied to various fields envisioned for electricity storage. Although merely illustrative, the solid-state battery of the present invention can be used in the electrical, information, and communication fields using mobile devices, etc. (for example, the electrical and electronic device fields or mobile device fields including small electronic devices such as mobile phones, smartphones, laptop computers, digital cameras, activity meters, wrist computers, electronic papers, RFID tags, card-type electronic money, smart watches, etc.); home and small industrial uses (for example, the fields of power tools, golf carts, home, nursing, and industrial robots); large industrial uses (for example, the fields of forklifts, elevators, and port cranes); transportation system fields (for example, the fields of hybrid vehicles, electric vehicles, buses, trams, electric assist bicycles, electric motorcycles, etc.); power system uses (for example, the fields of various power generation, load regulators, smart grids, ordinary household installed energy storage systems, etc.); medical uses (the field of medical devices such as earphone hearing aids); medical uses (the field of medication management systems); and the IoT field; space and deep sea uses (for example, the fields of space probes, submersible survey ships, etc.).

[0205] Explanation of Reference Numerals

[0206] 10: Electrode layer; 10A: Positive electrode layer; 10B: Negative electrode layer; 11: Electrode current collector layer; 11A: Positive electrode current collector layer; 11B: Negative electrode current collector layer; 20: Solid electrolyte layer; 30: Electrode separation part; 30A: Positive electrode separation part; 30B: Negative electrode separation part; 40: Terminal; 40A: Positive terminal; 40B: Negative terminal; 60: Outer layer material; 100: Solid battery laminate; 200: Solid battery.

Claims

1. A solid battery, comprising a positive electrode active material containing Li and a positive electrode layer including a solid electrolyte, wherein a thermogravimetric reduction start temperature at which the weight of the positive electrode active material decreases by 0.67% or more when the lithium release amount of the positive electrode active material is 40% is 220°C or higher and less than 485°C, and the solid electrolyte contains lithium borosilicate glass.

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

3. The solid battery according to claim 1 or 2, wherein the thermogravimetric reduction start temperature is 350°C or lower.

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

5. The solid battery according to claim 4, wherein in the positive electrode active material, when the oxide containing Li and Co contains Ti, the thermogravimetric reduction start temperature is 220°C or higher and 240°C or lower.

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

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

8. The solid battery according to any one of claims 1 to 7, wherein the positive electrode active material contains an oxide containing Li, Ni, Co, and Mn.

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

8.

10. The solid battery according to any one of claims 1 to 9, wherein compared with the case where the positive electrode active material is an oxide containing Li and Co containing Ti, when it is an oxide containing Li, Ni, Co, and Mn, the thermogravimetric reduction start temperature is higher.

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

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

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