solid-state batteries

Abstract

Provided is a solid-state battery comprising a positive electrode layer including: a positive electrode active material containing Li; and a solid electrolyte. When the lithium desorption amount of the positive electrode active material is 40%, the thermal weight reduction starting temperature, at which the weight of the positive electrode active material is reduced by at least 0.67%, is not less than 220°C but less than 485°C. The solid electrolyte contains lithium borosilicate glass.

Description

Technical Field

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

Background Art

[0002] Conventionally, secondary batteries capable of repeated charge and discharge have been used in various applications. 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 ion movement contributing to charge and discharge. That is, a so-called electrolytic solution is used in secondary batteries. However, in such secondary batteries, safety is generally required in terms of preventing leakage of the electrolytic solution. In addition, since the organic solvents and the like used in the electrolytic solution are flammable substances, safety is also required in that regard.

[0004] Therefore, research has been underway on solid-state batteries using solid electrolytes instead of electrolytic solutions.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The inventor of the present application newly found that there are points that can be improved in conventional solid-state batteries, and that it is necessary to take countermeasures therefor.

[0007] Specifically, lithium transition metal oxides and lithium composite transition metal oxides having a crystalline structure can be used as the positive electrode active material in solid-state batteries (see Patent Documents 1 and 2). In this regard, solid-state batteries may be used under high-temperature conditions, and under such high-temperature conditions, the crystalline structure of the positive electrode active material becomes unstable due to lithium desorption, which may cause the battery characteristics of the solid-state battery to deteriorate under high-temperature conditions.

[0008] This invention has been made in view of the above problems. That is, the object of this invention is to provide a solid-state battery that can have more suitable battery characteristics even under high-temperature conditions. [Means for solving the problem]

[0009] To achieve the above objective, in one embodiment of the present invention, The positive electrode comprises a positive electrode active material containing Li and a positive electrode layer containing a solid electrolyte. A solid-state battery is provided in which, when the lithium desorption amount of the positive electrode active material is 40%, the thermogravimetric reduction start temperature 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. [Effects of the Invention]

[0010] According to one embodiment of the present invention, a solid-state battery can have more favorable battery characteristics even under high-temperature conditions. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic external perspective view of a solid-state battery according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of the AA cross-section of the solid-state battery shown in Figure 1, viewed in the direction of the arrow. [Figure 3] Figure 3 is a graph showing the relationship between the heating temperature of the positive electrode active material and the rate of change (decrease) of the thermogravimetric material in a solid-state battery according to one embodiment of the present invention. [Modes for carrying out the invention]

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

[0013] In this specification, "cross-sectional view" refers to the form of a solid-state battery's stacked structure as viewed from a direction approximately perpendicular to the stacking direction (simply put, the form when cut by a plane parallel to the thickness direction of the layers). Furthermore, in this specification, "plan view" or "plan view shape" refers to a sketch of the object as viewed from above or below along the thickness direction of the layers (i.e., the stacking direction mentioned above).

[0014] In this specification, “up and down” and “left and right” as used directly or indirectly correspond to the up and down and left and right directions in the figures, respectively. Unless otherwise specified, the same reference numeral or symbol indicates the same member, part, or has the same meaning. In a preferred embodiment, the vertical downward direction (i.e., the direction in which gravity acts) can be considered as “downward,” and the opposite direction as “upward.”

[0015] In this invention, the term "solid-state battery" broadly refers to a battery whose constituent elements are solid, and narrowly refers to an all-solid-state battery whose constituent elements (particularly preferably all constituent elements) are solid. In one preferred embodiment, the solid-state battery in this invention is a stacked solid-state battery configured such that each layer constituting the battery constituent unit is stacked on top of each other, and preferably each such layer is made of a fired body. The "solid-state battery" is a so-called "rechargeable battery" that can be repeatedly charged and discharged. The term "rechargeable battery" is not overly restrictive and may also include, for example, energy storage devices.

[0016] The features of this invention relate to the positive electrode layer contained in a solid-state battery. Below, in order to understand the overall structure of the solid-state battery, the basic configuration of the solid-state battery of this invention will be described. However, the configuration of the solid-state battery described here is merely an example for understanding the invention and does not limit the invention.

[0017] [Basic Configuration of Solid-State Batteries] Figure 1 is a schematic external perspective view of a solid-state battery according to one embodiment of the present invention. Figure 2 is a schematic cross-sectional view of the AA cross section of the solid-state battery of Figure 1, viewed in the direction of the arrow. The solid-state battery has at least positive electrode and negative electrode layers and a solid electrolyte. Specifically, as shown in Figures 1 and 2, the solid-state battery 200 includes a solid-state battery stack 100 which includes a battery component unit consisting of a positive electrode layer 10A, a negative electrode layer 10B, and a solid electrolyte 20 interposed at least between them.

[0018] The solid battery 200 according to the present invention is a solid battery stack 100 comprising at least one battery component unit consisting of a positive electrode layer 10A, a negative electrode layer 10B, and a solid electrolyte layer 20 interposed between them, along the stacking direction L; and The solid battery stack 100 has a positive electrode terminal 40A and a negative electrode terminal 40B provided on opposite sides of the stack. In the solid-state battery stack 100, the positive electrode layer 10A and the negative electrode layer 10B are stacked alternately via a solid electrolyte layer 20.

[0019] In solid-state batteries, each constituent layer may be formed by firing, and the positive electrode layer, negative electrode layer, and solid electrolyte layer may form fired layers. Preferably, the positive electrode layer, negative electrode layer, and solid electrolyte layer are each fired integrally with each other, so that the solid-state battery laminate forms an integrally fired body.

[0020] The positive electrode layer is an electrode layer containing at least a positive electrode active material. The positive electrode layer may further contain a solid electrolyte. In one preferred embodiment, the positive electrode layer is composed of a sintered body containing at least positive electrode active material particles and solid electrolyte particles. On the other hand, the negative electrode layer is an electrode layer containing at least a negative electrode active material. The negative electrode layer may further contain a solid electrolyte. In one preferred embodiment, the negative electrode layer is composed of a sintered body containing at least negative electrode active material particles and solid electrolyte particles. A positive electrode layer having such a configuration may be called a "composite positive electrode," and similarly, a negative electrode layer may be called a "composite negative electrode."

[0021] The positive electrode active material and the negative electrode active material are materials that are involved in electron transfer in a solid-state battery. Charging and discharging occur when ions move (conduce) between the positive electrode layer and the negative electrode layer via a solid electrolyte, resulting in electron transfer. It is preferable that each electrode layer of the positive and negative electrode layers is capable of intercalating and deintercalating lithium ions or sodium ions. In other words, it is preferable that the solid-state battery is an all-solid-state secondary battery in which charging and discharging occur through the movement of lithium ions or sodium ions between the positive and negative electrode layers via a solid electrolyte.

[0022] (Positive electrode layer) The content of the solid electrolyte in the positive electrode layer 10A is not particularly limited, but is usually 10 to 50% by mass, and 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 types of solid electrolytes, in which case their total content should be within the above range.

[0023] (Negative electrode layer) Examples of negative electrode active materials included in the negative electrode layer include at least one selected from the group consisting of oxides containing at least one element selected from the group consisting of titanium (Ti), silicon (Si), tin (Sn), chromium (Cr), iron (Fe), niobium (Nb), and molybdenum (Mo), carbon materials such as graphite, graphite-lithium compounds, lithium alloys, lithium-containing phosphate compounds having a NASCICON-type structure, lithium-containing phosphate compounds having an olivine-type structure, and lithium-containing oxides having a spinel-type structure. An example of a lithium alloy is Li-Al. An example of a lithium-containing phosphate compound having a NASCICON-type structure is Li3V2(PO4)3 and / or LiTi2(PO4)3. An example of a lithium-containing phosphate compound having an olivine-type structure is Li3Fe2(PO4)3 and / or LiCuPO4. An example of a lithium-containing oxide having a spinel-type structure is Li4Ti5O 12 These are some examples.

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

[0025] The positive electrode layer and / or negative electrode layer may contain a conductive material. Examples of conductive materials included in the positive electrode layer and negative electrode layer include at least one of metallic materials such as silver, palladium, gold, platinum, aluminum, copper, and nickel, as well as carbon.

[0026] Furthermore, the positive electrode layer and / or negative electrode layer may contain a sintering aid. Examples of sintering aids include at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide.

[0027] The thicknesses of the positive electrode layer and the negative electrode layer are not particularly limited, but for example, they may be 2 μm or more and 50 μm or less, and especially 5 μm or more and 30 μm or less, respectively.

[0028] (Positive electrode current collecting layer / Negative electrode current collecting layer) Although not essential elements of the electrode layer, the positive electrode layer and the negative electrode layer may each comprise a positive electrode current collector layer 11A and a negative electrode current collector layer 11B, respectively. The positive electrode current collector layer and the negative electrode current collector layer may each be in the form of foil. However, if greater emphasis is placed on aspects such as improved electronic conductivity through integral firing, reduction of manufacturing costs for solid-state batteries, and / or reduction of internal resistance of solid-state batteries, the positive electrode current collector layer and the negative electrode current collector layer may each be in the form of a fired body.

[0029] It is preferable to use materials with high conductivity for the positive electrode current collector that constitutes the positive electrode current collector layer and the negative electrode current collector that constitutes the negative electrode current collector. For example, silver, palladium, gold, platinum, aluminum, copper, and / or nickel may be used. The positive electrode current collector and the negative electrode current collector may each have an electrical connection part for electrically connecting to the outside, and may be configured to be electrically connectable to terminals.

[0030] Furthermore, if the positive electrode current collector layer and the negative electrode current collector layer are in the form of a fired body, they may be composed of a fired body containing a conductive material and a sintering aid. The conductive material included in the positive electrode current collector layer and the negative electrode current collector layer may be selected from materials similar to those that may be included in the positive electrode layer and the negative electrode layer. The sintering aid included in the positive electrode current collector layer and the negative electrode current collector layer may be selected from materials similar to those that may be included in the positive electrode layer and the negative electrode layer.

[0031] (solid electrolyte) The solid electrolyte is a material that can conduct lithium ions or sodium ions. This solid electrolyte can form a lithium-ion conductive layer between the positive electrode layer and the negative electrode layer. Furthermore, the solid electrolyte can also be contained within the positive electrode layer and the negative electrode layer.

[0032] The solid electrolyte layer may contain a sintering aid. The sintering aid included in the solid electrolyte layer may be selected from materials similar to those that may be included in the positive electrode layer and the negative electrode layer.

[0033] 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 may be, for example, 1 μm to 15 μm, and more particularly 1 μm to 5 μm.

[0034] (electrode separation part) The solid battery 200 of the present invention may further have electrode separation portions (also referred to as "margin layers" or "margin portions") 30 (30A, 30B).

[0035] The electrode separation section 30A (positive electrode separation section) is positioned around the positive electrode layer 10A, thereby separating the positive electrode layer 10A from the negative electrode terminal 40B. The electrode separation section 30B (negative electrode separation section) is positioned around the negative electrode layer 10B, thereby separating the negative electrode layer 10B from the positive electrode terminal 40A. Although not particularly limited, the electrode separation section 30 may be composed of one or more materials selected from the group consisting of, for example, solid electrolytes, insulating materials, and mixtures thereof.

[0036] The solid electrolyte that can constitute the electrode separation section 30 can be made of the same material as the solid electrolyte that can constitute the solid electrolyte layer.

[0037] The insulating material that may constitute the electrode separation section 30 may be a material that does not conduct electricity, i.e., a non-conductive material. Although not particularly limited, the insulating material may be, for example, glass or ceramic material. For example, glass material may be selected as the insulating material. Although not particularly limited, the glass material may be at least one selected from the group consisting of soda-lime glass, potash glass, borate glass, borosilicate glass, barium borosilicate glass, borite glass, barium borate glass, bismuth borosilicate glass, bismuth zinc borate glass, bismuth silicate glass, phosphate glass, aluminophosphate glass, and phosphate glass. Furthermore, although not particularly limited, 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).

[0038] (Terminals) The solid-state battery 200 of the present invention is generally provided with terminals (external terminals) 40 (40A, 40B). In particular, positive and negative terminals 40A and 40B are provided in pairs on the side surface of the solid-state battery. More specifically, a positive terminal 40A connected to the positive electrode layer 10A and a negative terminal 40B connected to the negative electrode layer 10B are provided in pairs. Since terminals 40A and 40B can be provided so as to cover at least one side surface of the solid-state battery, they can also be called "end electrodes". Such terminals 40 (40A, 40B) can be made of a material with high conductivity. The material of the terminals 40 is not particularly limited, but examples include at least one conductive material selected from the group consisting of silver, gold, platinum, aluminum, copper, tin, and nickel.

[0039] Terminals 40 (40A, 40B) may further contain a sintering aid. Examples of sintering aids include materials similar to those that may be included in the positive electrode layer 10A. In one preferred embodiment, terminals 40 (40A, 40B) are composed of a sintered body containing at least a conductive material and a sintering aid.

[0040] (outer layer material) The solid-state battery 200 of the present invention typically further comprises an outer layer material 60. The outer layer material 60 is generally formed on the outermost surface of the solid-state battery and is intended to provide electrical, physical, and / or chemical protection. The material constituting the outer layer material 60 is preferably excellent in insulating properties, durability, and / or moisture resistance, and is environmentally safe. For example, glass, ceramics, thermosetting resins, photocurable resins, and mixtures thereof can be used.

[0041] The glass material that can constitute the outer layer can be the same material as the glass material that can constitute the electrode separation section. Similarly, the ceramic material that can constitute the outer layer can be the same material as the ceramic material that can constitute the electrode separation section.

[0042] [Features of the Solid-State Battery of the Present Invention] The inventors of this application have diligently studied solutions to enable solid-state batteries to have more favorable battery characteristics even when used under high-temperature conditions. As a result, the inventors have focused on the positive electrode layer that constitutes the solid-state battery and have sought a solution. Specifically, assuming that the positive electrode layer contains a solid electrolyte with a specific material composition, the inventors have newly discovered that the thermogravimetric onset temperature of the positive electrode active material containing lithium (Li) can correlate with the battery characteristics under high-temperature conditions (i.e., high-temperature resistance).

[0043] Figure 3 is a graph showing the relationship between the heating temperature of the positive electrode active material and the rate of thermogravimetric change (decrease) in a solid-state battery according to one embodiment of the present invention. As shown in Figure 3, it can be seen that as the heating temperature of the positive electrode active material is increased, the rate of thermogravimetric change (decrease) of the positive electrode active material increases above a certain temperature. The figure also shows two TG (Thermogravimetry) curves (TG curve for Example 1 and TG curve for Comparative Example 1) with different temperatures at which this thermogravimetric decrease begins (i.e., the thermogravimetric decrease onset temperature). As can be seen from the section on examples described later, this thermogravimetric decrease onset temperature differs depending on the material composition of the positive electrode active material and solid electrolyte contained in the positive electrode layer, and this different thermogravimetric decrease onset temperature may correlate with the battery characteristics under high-temperature conditions.

[0044] In this invention, based on these features, with respect to the positive electrode layer, under the condition that a solid electrolyte of a specific material composition is included, a positive electrode active material having a thermogravimetric reduction onset temperature within a specific range, particularly a positive electrode active material above a specific lower limit, is preferably selected.

[0045] Specifically, in the present invention, with respect to the positive electrode layer, under the condition that lithium borosilicate glass is included as the solid electrolyte, a positive electrode active material can be selected in which, when the lithium desorption amount of the positive electrode active material is 40% (i.e., when 40% of the Li content of the positive electrode active material has been desorbed), the thermogravimetric reduction onset temperature at which the weight decreases by 0.67% or more is 220°C or higher and less than 485°C. In the present invention, by selecting a positive electrode layer having the above characteristics for a solid-state battery, it is possible to have more suitable battery characteristics under high-temperature conditions. In other words, a solid-state battery with superior high-temperature resistance can be provided.

[0046] Specifically, in a solid-state battery equipped with a positive electrode layer having the characteristics described above, the deterioration of battery characteristics such as resistance and / or battery capacity can be more effectively suppressed even when exposed to high-temperature conditions (e.g., a temperature range of 80°C to 200°C). Therefore, the solid-state battery of the present invention can be suitably used even under high-temperature conditions.

[0047] In this invention, the lower limit of the thermogravimetric loss onset temperature of the positive electrode active material (220°C or higher) contributes to maintaining the high-temperature resistance of the solid-state battery, while the upper limit (less than 485°C) is based on the viewpoint of suppressing the decrease in the electronic conductivity of the positive electrode active material. Furthermore, from the viewpoint of suitably achieving both the maintenance of the high-temperature resistance of the solid-state battery and the suppression of the decrease in the electronic conductivity of the positive electrode active material, the upper limit of the thermogravimetric loss onset temperature may be 350°C or lower.

[0048] The thermogravimetric and differential thermal analysis temperature at which the positive electrode active material begins can be measured using a thermogravimetric and differential thermal analysis device (manufactured by Rigaku Corporation, device model number: TG8120). Specifically, a sample (positive electrode layer, etc.) is placed in this device, and it is heated under conditions of a predetermined heating rate while nitrogen is flowing at a predetermined rate, and the temperature at which the thermogravimetric analysis temperature at which the weight of the positive electrode active material decreases by 0.67% or more is measured. In this device, as the sample is heated, a weight change occurs in the positive electrode active material contained in the positive electrode layer from a predetermined temperature value. When this weight change occurs, the main beam in this measuring device tilts, and the current flowing through the coil is controlled to return this movement to its original position. Since the current flowing corresponds to the weight change, the fluctuation behavior of the current is output as a weight change, and the thermogravimetric analysis temperature at which the positive electrode active material begins can be determined.

[0049] In this specification, "a state in which lithium has been removed from the positive electrode active material by 40%" refers to a state in which, when the amount of lithium removed from the lithium content of the positive electrode active material is expressed as a percentage, the amount of lithium removed is 40%. In other words, "a state in which lithium has been removed from the positive electrode active material by 40%" means a state in which the lithium content of the positive electrode active material is 60%, with the lithium content of the positive electrode active material in an uncharged battery being 100%. For example, "a state in which lithium has been removed from the positive electrode active material by 40%" could be a charged state in which 40% of the lithium content of the positive electrode active material in a fully discharged battery has been removed. The state of Li removal from the positive electrode active material can be measured using XRD.

[0050] The reason why the thermogravimetric analysis onset temperature of the positive electrode active material when 40% of the lithium in the positive electrode active material contained in the positive electrode layer is evaluated in this invention is as follows: During charging of a solid-state battery, the crystalline structure of the positive electrode active material may become unstable due to the extraction of lithium. This instability is observed from the charged state when 40% of the Li in the positive electrode active material has been extracted, and can become particularly pronounced under high-temperature battery operating conditions. Due to this instability of the crystalline structure, the degradation of the solid-state battery may progress more easily when 40% of the Li in the positive electrode active material has been extracted under high-temperature conditions. For these reasons, the thermogravimetric analysis onset temperature of the positive electrode active material when 40% of the Li in the positive electrode active material has been extracted is evaluated.

[0051] The amount of lithium desorption mentioned above can be quantified by XRD analysis. Alternatively, it can be calculated from the charge amount of the solid-state battery based on the initial charge-discharge efficiency and basis weight of the positive and negative electrode active materials.

[0052] 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, and can be, for example, 50Li4SiO4·50Li3BO3. Since such a solid electrolyte has relatively high thermal stability, its inclusion in the positive electrode layer can more effectively suppress the degradation of the battery characteristics of a solid-state battery under high-temperature conditions.

[0053] Furthermore, lithium borosilicate glass may contain one or more additional elements in addition to lithium, silicon, boron, and oxygen. For example, lithium borosilicate glass may further contain at least one element selected from the group consisting of elements from groups 1, 2, and 14-17 of the periodic table. The content of each element in lithium borosilicate glass can be measured by analyzing the glass-ceramic solid electrolyte using, for example, inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0054] In addition to lithium borosilicate glass as the above-mentioned solid electrolyte, the solid electrolyte may further contain other known solid electrolytes used in solid-state batteries. Such solid electrolytes may be, 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. The crystalline solid electrolyte is, for example, an oxide-based crystalline material. 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 a garnet type similar structure, and oxide glass-ceramic lithium ion conductors.

[0055] Examples of the lithium-containing phosphate compound 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)). An example of the lithium-containing phosphate compound having a NASICON structure is, for example, Li 1.2 Al 0.2 Ti 1.8 (PO4)3 and the like. An example of the oxide having a perovskite structure is La 0.55 Li 0.35 TiO3 and the like. An example of the oxide having a garnet type or a garnet type similar structure is Li7La3Zr2O 12 and the like. The crystalline solid electrolyte may contain a polymer material (for example, polyethylene oxide (PEO) etc.).

[0056] Examples of the glass-based solid electrolyte include oxide-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.

[0057] Glass-ceramic solid electrolytes include, for example, oxide-based glass-ceramic materials. Examples of oxide-based glass-ceramic materials include phosphate compounds containing lithium, aluminum, and titanium (LATP) and phosphate compounds containing lithium, aluminum, and germanium (LAGP). For example, LATP is Li 1.07 Al 0.69 Ti 1.46 Examples include (PO4)3. Also, LAGP is, for example, Li 1.5 Al 0.5 Ge 1.5 (PO4), etc.

[0058] For example, the solid electrolyte may further contain an oxide having a garnet-type or garnet-type similar structure in addition to lithium borosilicate glass. For example, the positive electrode layer of the solid battery of the present invention may contain lithium borosilicate glass and an oxide containing Li, La, and Zr (corresponding to a LiLaZr-based oxide) as the solid electrolyte. The inventors of the present invention have found that when the positive electrode layer contains at least lithium borosilicate glass as the solid electrolyte, the positive electrode active material can preferentially form an interface with lithium borosilicate glass, which has relatively high thermal stability. Therefore, even if the positive electrode layer contains a solid electrolyte with relatively low thermal stability, the lithium borosilicate glass can suppress the reaction between the positive electrode active material and the solid electrolyte with low thermal stability under high-temperature conditions. Consequently, it becomes possible to further include other solid electrolytes that have lower thermal stability than lithium borosilicate glass but excellent lithium ion conductivity, and a solid battery that more favorably balances high-temperature resistance and battery performance (e.g., capacity retention rate) can be obtained.

[0059] The content of lithium borosilicate glass in the solid electrolyte of the positive electrode layer is not particularly limited, but can be, for example, 10-90% by mass, 30-80% by mass, or 40-60% by mass relative to the total amount of solid electrolyte in the positive electrode layer. Alternatively, the content of garnet-type oxide-based solid electrolyte in the solid electrolyte of the positive electrode layer is not particularly limited, but can be, for example, 0-70% by mass, 5-60% by mass, or 10-40% by mass relative to the total amount of solid electrolyte in the positive electrode layer. When the content of garnet-type oxide-based solid electrolyte is within the above range, a solid-state battery that can be more suitably used even under high-temperature conditions can be provided.

[0060] For example, such an oxide-based solid electrolyte may be a LiLaZr-based oxide (LLZ) with high ionic conductivity. In other words, in the present invention, two or more types of solid electrolytes can be used, including a solid electrolyte that contributes to thermal stability and a solid electrolyte that contributes to high ionic conductivity. This makes it possible to maintain battery characteristics under high-temperature conditions and to ensure ionic conductivity that contributes to the charging and discharging of the battery.

[0061] In the present invention, the positive electrode active material may be one having a layered crystalline structure. Specifically, the positive electrode active material may be a layered rock salt type metal oxide, for example, a lithium transition metal composite oxide. "Layered rock salt type metal oxide" refers to a metal oxide having a layered rock salt type crystalline structure that can be identified by analyzing an X-ray diffraction pattern, and in particular, its particles.

[0062] For example, in the present invention, the positive electrode active material includes an oxide containing Li and Co (corresponding to LCO, or LiCo-based oxide), and this LiCo-based oxide may contain at least Ti. This allows the thermogravimetric loss onset temperature of the positive electrode active material to be higher compared to the case where Ti is not included, making it possible to maintain battery characteristics under high-temperature conditions.

[0063] Furthermore, this 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, in addition to Ti. When the positive electrode active material is a LiCo-based oxide containing at least Ti, its thermogravimetric onset temperature may be between 220°C and 240°C.

[0064] Specifically, in this invention, the positive electrode active material is LiCo x Ti y α z It may contain O2 (wherein 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). Furthermore, considering the suppression of resistance increase and capacitance degradation under high temperature conditions, α is more preferably Al and / or Mg.

[0065] In another example, in the present invention, the positive electrode active material may include an oxide containing Li, Ni, Co, and Mn (corresponding to NCM, corresponding to a LiNiCoMn-based oxide). Specifically, the positive electrode active material is LiNi a Co b Mn c O2 can be O2 (where a+b+c≦1 and 0.3≦a≦0.8).

[0066] In particular, the thermogravimetric onset temperature can be higher when the positive electrode active material is a LiNiCoMn-based oxide than when it is a LiCo-based oxide containing Ti. This allows for a higher thermogravimetric onset temperature of the positive electrode active material when it is a LiNiCoMn-based oxide, resulting in more favorable battery characteristics under high-temperature conditions.

[0067] [Manufacturing method for solid-state batteries] The solid-state battery of the present invention can be manufactured by a printing method such as screen printing, a green sheet method using a green sheet, or a combination of these methods. The following details will describe the cases where the printing method and the green sheet method are employed for the purpose of understanding the present invention, but the present invention is not limited to these methods. In other words, the solid-state battery may be manufactured in accordance with conventional solid-state battery manufacturing methods. Furthermore, the chronological order of the following descriptions is merely for explanatory purposes and is not necessarily binding.

[0068] (Formation process of solid-state battery stack precursor) In this process, several types of pastes are used as inks, such as paste for the positive electrode layer, paste for the negative electrode layer, paste for the solid electrolyte layer, paste for the positive electrode current collector layer, paste for the negative electrode current collector layer, paste for the electrode separation section, and paste for the outer layer material. In other words, a solid-state battery stacking precursor with a predetermined structure is formed on a support substrate by applying and drying the paste using a printing method.

[0069] During printing, a solid-state battery stacking precursor corresponding to a predetermined solid-state battery structure can be formed on a substrate by sequentially stacking printed layers with predetermined thickness and pattern shape. The type of pattern formation method is not particularly limited as long as it is a method capable of forming the predetermined pattern, but for example, it may be one or more of the following: screen printing and gravure printing.

[0070] The paste can be prepared by wet mixing predetermined constituent materials for 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 collector layer material, insulating material, and sintering aid, as well as other materials mentioned above, with an organic vehicle in which an organic material is dissolved in a solvent.

[0071] The paste for the positive electrode layer includes, for example, positive electrode active material particles, a solid electrolyte material, an organic material and a solvent, and optionally a sintering aid.

[0072] The paste for the negative electrode layer includes, for example, negative electrode active material particles, a solid electrolyte material, an organic material and a solvent, and optionally a sintering aid.

[0073] The paste for the solid electrolyte layer comprises, for example, a solid electrolyte material, an organic material, and a solvent, and optionally a sintering aid.

[0074] The paste for the positive electrode current collector layer comprises a conductive material, an organic material, and a solvent, and optionally a sintering aid.

[0075] The paste for the negative electrode current collector layer comprises a conductive material, an organic material, and a solvent, and optionally a sintering aid.

[0076] The paste for the electrode separation section includes, for example, a solid electrolyte material, an insulating material, an organic material, and a solvent, and optionally a sintering aid.

[0077] The paste for the outer layer material includes, for example, an insulating material, an organic material, and a solvent, and optionally a sintering aid.

[0078] The organic material contained in the paste is not particularly limited, but at least one polymer material selected from the group consisting of polyvinyl acetal resin, cellulose resin, polyacrylic resin, polyurethane resin, polyvinyl acetate resin, and polyvinyl alcohol resin can be used.

[0079] The type of solvent is not particularly limited, but may be one or more of the following organic solvents: butyl acetate, N-methylpyrrolidone, toluene, terpineol, and N-methylpyrrolidone.

[0080] In wet mixing, media can be used, specifically the ball mill method or the visco mill method. Alternatively, wet mixing methods that do not use media may be used, such as the sand mill method, high-pressure homogenizer method, or kneader dispersion method.

[0081] The support substrate is not particularly limited as long as it is a support capable of supporting each paste layer, but for example, it may be a release film with a release treatment applied to one surface. Specifically, a substrate made of a polymer material such as polyethylene terephthalate can be used. If the paste layers are to be subjected to the firing process while remaining on the substrate, the substrate may be one that exhibits heat resistance to the firing temperature.

[0082] Alternatively, a green sheet can be formed from each paste, and the resulting green sheets can be stacked to create a solid-state battery stacking precursor.

[0083] In detail, the support substrates to which each paste is applied are dried on a hot plate heated to 30°C to 90°C, thereby forming positive electrode layer green sheets, negative electrode layer green sheets, solid electrolyte layer green sheets, positive electrode current collector layer green sheets, negative electrode current collector layer green sheets, electrode separation section green sheets, and / or outer layer material green sheets, each having a predetermined shape and thickness, on each support substrate (e.g., PET film).

[0084] Next, each green sheet is peeled off the substrate. After peeling, the green sheets of each component are stacked sequentially along the stacking direction to form a solid-state battery stacking precursor. After stacking, a solid electrolyte layer, insulating layer, and / or protective layer may be applied to the side regions of the electrode green sheets by screen printing.

[0085] (Firing process) In the firing process, the solid-state battery stacking precursor is subjected to firing. Although this is merely an example, firing is carried out by removing organic materials by heating in a nitrogen gas atmosphere containing oxygen gas or in air at, for example, 200°C or higher, and then heating in a nitrogen gas atmosphere or in air at, for example, 300°C or higher. The firing may be carried out while pressurizing the solid-state battery stacking precursor in the stacking direction (and possibly in the stacking direction and perpendicular to the stacking direction).

[0086] Through such firing processes, a solid-state battery stack is formed, ultimately resulting in the desired solid-state battery.

[0087] (Process for forming positive and negative terminals) For example, the positive electrode terminal is bonded to the solid-state battery stack using a conductive adhesive, and the negative electrode terminal is also bonded to the solid-state battery stack using a conductive adhesive. This attaches both the positive and negative electrode terminals to the solid-state battery stack. As a result, the desired solid-state battery can be obtained.

[0088] The embodiments of the present invention have been described above, but these are merely typical examples. Therefore, the present invention is not limited thereto, and those skilled in the art will easily understand that various embodiments are conceivable without altering the essence of the invention. [Examples]

[0089] The following describes some examples.

[0090] <Example 1> (Process for manufacturing green sheets for solid electrolyte layers) First, lithium borosilicate glass and an acrylic binder were mixed as a solid electrolyte in a mass ratio of lithium borosilicate glass:acrylic binder = 70:30. The lithium borosilicate glass used had a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio). Next, the resulting mixture was mixed with butyl acetate to a solid content of 30% by mass. This mixture was then stirred with 5 mm diameter zirconia balls for 4 hours to obtain a paste for the solid electrolyte layer. Subsequently, this paste was applied to a release film and dried at 80°C for 10 minutes to produce a green sheet for the solid electrolyte layer as a precursor.

[0091] (Process for manufacturing green sheets for positive electrode material layer) First, LiNiCoMn-based oxides (corresponding to NCM) were synthesized by a solid-state method involving mixing cobalt oxide, lithium carbonate, nickel, and manganese and then calcining them. Specifically, in Example 1, LiNi 0.6 Co 0.2 Mn 0.2 O2 was synthesized. Next, a LiNiCoMn-based oxide (corresponding to NCM) having the above composition as the positive electrode active material and lithium borosilicate glass as the solid electrolyte were mixed in a mass ratio of LiNiCoMn-based oxide:lithium borosilicate glass = 75:25. The lithium borosilicate glass used had a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio). Next, the obtained mixture and an acrylic binder were mixed in a mass ratio of mixture (LiNiCoMn-based oxide + lithium borosilicate glass):acrylic binder = 70:30, and this was then mixed with butyl acetate so that the solid content was 30% by mass. The obtained mixture was then stirred with 5 mm diameter zirconia balls for 4 hours to obtain a paste for the positive electrode material layer. Subsequently, this paste was applied to a release film and dried at 80°C for 10 minutes to prepare a green sheet for the positive electrode material layer as a precursor for the positive electrode layer.

[0092] (Process for manufacturing the green sheet for the negative electrode material layer) First, carbon powder (TIMCAL, KS6) was mixed as the negative electrode active material, and lithium borosilicate glass was mixed as the solid electrolyte in a mass ratio of carbon powder:lithium borosilicate glass = 70:30. The lithium borosilicate glass used had a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio). Next, the obtained mixture was mixed with an acrylic binder in a mass ratio of (carbon powder + lithium borosilicate glass):acrylic binder = 70:30, and this was then mixed with butyl acetate so that the solid content was 30% by mass. The resulting mixture was then stirred with 5 mm diameter zirconia balls for 4 hours to obtain a paste for the negative electrode material layer. Subsequently, this paste was applied to a release film and dried at 80°C for 10 minutes to prepare a green sheet for the negative electrode material layer as a precursor for the negative electrode material layer.

[0093] (Process for manufacturing the green sheet for the positive electrode current collector) First, carbon powder (TIMCAL, KS6) was mixed as a conductive material with lithium borosilicate glass as a solid electrolyte in a mass ratio of carbon powder:lithium borosilicate glass = 70:30. The lithium borosilicate glass used had a composition of Li2O:SiO2:B2O3 = 60:10:30 (mol% ratio). Next, the resulting mixture was mixed with an acrylic binder in a mass ratio of (carbon powder + lithium borosilicate glass):acrylic binder = 70:30, and then this was mixed with butyl acetate so that the solid content was 30% by mass. The resulting mixture was then stirred with 5 mm diameter zirconia balls for 4 hours to obtain a paste for the positive electrode current collector layer. Subsequently, this paste was 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 as a precursor for the positive electrode current collector layer.

[0094] (Process for manufacturing the green sheet for the negative electrode current collector) A green sheet for the negative electrode current collector was fabricated using the same process as described above for fabricating the green sheet for the positive electrode current collector.

[0095] (Process for manufacturing the green sheet for the outer layer) First, alumina particle powder (Nippon Light Metal Co., Ltd., AHP300) and lithium borosilicate glass as a solid electrolyte were mixed in a mass ratio of alumina particle powder:lithium borosilicate glass = 50:50. Next, the resulting mixture was mixed with an acrylic binder in a mass ratio of (alumina particle powder + lithium borosilicate glass):acrylic binder = 70:30, and then this was mixed with butyl acetate so that the solid content was 30% by mass. The resulting mixture was then stirred with 5 mm diameter zirconia balls for 4 hours to obtain a paste for the main surface exterior material. Subsequently, this paste was applied to a release film and dried to produce a green sheet for the outer layer material as a precursor for the outer layer material.

[0096] (Process for manufacturing the green sheet for the electrode separation section) Similar to the process for producing the outer layer material green sheet described above, a green sheet for the electrode separation section was produced as a precursor for the electrode separation section.

[0097] (Laminate fabrication process) Using the green sheets obtained as described above, a laminate having the configuration shown in Figures 1 and 2 was fabricated as follows. Specifically, first, each green sheet was processed into the shape shown in Figures 1 and 2, and then released from the release film. Next, each green sheet was sequentially laminated in a manner corresponding to the configuration of the battery element shown in Figures 1 and 2, and then thermocompressed. This resulted in a laminate serving as a battery element precursor.

[0098] (Laminate sintering process) The resulting laminate was heated to remove the acrylic binder contained in each green sheet, and then heated further to sinter the oxide glass contained in each green sheet.

[0099] (Terminal manufacturing process) First, Ag powder (Daiken Chemical Industry) and oxide glass (Bi-B glass, Asahi Glass Co., Ltd., ASF1096) were mixed in a predetermined mass ratio as conductive particle powder. Next, the resulting mixture (Ag powder + oxide glass) and an acrylic binder were mixed in a mass ratio of Ag powder + oxide glass mixture:acrylic binder = 70:30. This mixture was then mixed with butyl acetate solvent until the solid content was 50% by mass. The resulting mixture was then stirred with 5 mm diameter zirconia balls for 4 hours to obtain a conductive paste. Next, this conductive paste was applied to the first and second end faces (or sides) of a laminate with the positive electrode current collector layer and negative electrode current collector layer exposed, respectively, and sintered to form the positive electrode and negative electrode terminals. Thus, the solid-state battery of Example 1 was obtained.

[0100] <Example 2> In Example 2, in the process of manufacturing the green sheet for the positive electrode material layer in Example 1, LiNi was used as the positive electrode active material.0.3 Co 0.3 Mn 0.3 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0101] <Example 3> In Example 3, in the process of preparing the green sheet for the positive electrode material layer in Example 1, LiNi having a different composition from that of Examples 1 and 2 is used as the positive electrode active material. 0.72 Co 0.05 Mn 0.2 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1. <Example 4> In Example 4, titanium-containing lithium cobalt oxide (LiCoO2) was synthesized by a solid-phase method in which cobalt oxide, lithium carbonate, and titanium were mixed and calcined, in the process of manufacturing the green sheet for the positive electrode material layer in Example 1. Specifically, in Example 4, LiCo was used as the positive electrode active material. 0.995 Ti 0.005 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0102] <Example 5> In Example 5, in the process of manufacturing the green sheet for the positive electrode material layer in Example 1, a different composition of LiCo was used as the positive electrode active material compared to Example 4. 0.99 Ti 0.01 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0103] <Example 6> In Example 6, lithium cobalt oxide (LiCoO2) containing titanium and aluminum was synthesized by a solid-state method in which cobalt oxide, lithium carbonate, titanium, and aluminum were mixed and calcined in the process of preparing the green sheet for the positive electrode material layer in Example 1. Specifically, in Example 6, LiCo was used as the positive electrode active material. 0.985 Ti 0.005 Al 0.01O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0104] <Example 7> In Example 7, in the process of preparing the green sheet for the positive electrode material layer in Example 1, a different composition of LiCo was used as the positive electrode active material compared to Example 6. 0.965 Ti 0.005 Al 0.03 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0105] <Example 8> In Example 8, in the process of manufacturing the green sheet for the positive electrode material layer in Example 1, a LiCo with a different composition from that of Examples 6 and 7 was used as the positive electrode active material. 0.945 Ti 0.005 Al 0.05 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0106] <Example 9> In Example 9, lithium cobalt oxide (LiCoO2) containing titanium and magnesium was synthesized by a solid-phase method in which cobalt oxide, lithium carbonate, titanium, and magnesium were mixed and calcined in the process of preparing the green sheet for the positive electrode material layer in Example 1. Specifically, in Example 9, LiCo was used as the positive electrode active material. 0.985 Ti 0.005 Mg 0.01 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0107] <Example 10> In Example 10, in the process of preparing the green sheet for the positive electrode material layer in Example 1, a different composition of LiCo was used as the positive electrode active material compared to Example 9. 0.965 Ti 0.005 Mg 0.03 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0108] <Example 11> In Example 11, in the process of preparing the green sheet for the positive electrode material layer in Example 1, the positive electrode active material is LiCo with a different composition from that of Examples 9 and 10. 0.945 Ti 0.005 Mg 0.05 O2 was synthesized. Apart from this, the solid-state battery was manufactured using the same method as in Example 1.

[0109] <Example 12> In Example 12, in the process of manufacturing the green sheet for the positive electrode material layer in Example 1, the positive electrode active material is LiCo having the same composition as in Example 4. 0.995 Ti 0.005 O2 was synthesized. On the other hand, as the solid electrolyte used in the manufacturing process of each green sheet in Example 1, lithium borosilicate glass was used instead of lithium borosilicate glass alone, and lithium borosilicate glass and LiLaZr-based oxide (Li7La3Zr2O 12 A mixture of (LLZ) (lithium borosilicate glass:LLZ = 60:40 by mass ratio) was used. Apart from these points, the solid-state battery was manufactured in the same manner as in Example 1.

[0110] <Comparative Example 1> A solid-state battery was manufactured in the same manner as in Example 1, except that lithium cobalt oxide without titanium was used as the positive electrode active material.

[0111] <Comparative Example 2> A solid-state battery was manufactured in the same manner as in Example 4, except that a LiLaZr-based oxide was used as the solid electrolyte. The LiLaZr-based oxide used was Li7La3Zr2O 12 I used it.

[0112] <Comparative Example 3> A solid-state battery was manufactured in the same manner as in Example 1, except that an oxide containing Li, Mn, and Al (corresponding to a LiMnAl-based oxide) was used as the solid electrolyte. 1.92 Al 0.08 O4(LMO) was used.

[0113] (Measurement of battery characteristics) The battery's rated capacity was set to 1C. It was charged to a predetermined positive electrode potential with a constant current of 0.2C. After reaching the positive electrode potential, charging was continued in constant voltage mode until the current was reduced to 0.01C. Impedance measurements were then performed to determine the initial resistance. Subsequently, the battery was stored under high-temperature conditions (105°C) for one week, slowly cooled to 25°C by air cooling, and then impedance measurements were performed at 25°C. The battery was then discharged to 2V with a constant current of 0.2C, and capacity measurements were performed. The positive electrode potential used varied depending on the positive electrode active material. Specifically, if the positive electrode active material was LiCo oxide (LCO), charging was performed to a positive electrode potential of 4.35V; if it was LiNiCoMn oxide (NCM), charging was performed to 4.2V; and if it was LiMnAl oxide (LMO), charging was performed to a positive electrode potential of 4.95V.

[0114] For the solid batteries of Examples 1-12 and Comparative Examples 1 and 2, the resistance increase rate was calculated by dividing the initial resistance value obtained from impedance measurement results by the resistance value after storage under high-temperature conditions. Similarly, the degradation capacity of the discharge capacity after storage under high-temperature conditions was determined from the capacity measurement results. Furthermore, the capacity retention rate was measured for the solid batteries of Examples 1, 2, 4-12 and Comparative Examples 1-3. Specifically, the rated capacity of the battery was set to 1C, and it was charged to the positive electrode potential described above with a constant current of 0.2C. After reaching the positive electrode potential, charging was performed in constant voltage mode until the current could be reduced to 0.01C. After that, discharge was performed with a constant current of 0.2C until the positive electrode potential reached 3V. This charging and discharging was considered one cycle, and the capacity retention rate relative to the initial discharge capacity was measured after repeating this 100 cycles.

[0115] Furthermore, in each of Examples 1-12 and Comparative Examples 1-3, a thermogravimetric and differential thermal simultaneous measurement (TG-DTA) device (manufactured by Rigaku Corporation, device model number: TG8120) was used to set the positive electrode layer in the device and heat it under conditions of a heating rate of 3°C while flowing nitrogen at a rate of 200 ml / min. The thermogravimetric at which the weight of the positive electrode active material contained in the positive electrode layer decreased by 0.67% or more from the start of measurement was measured. Specifically, as the temperature is increased, a weight change in the positive electrode active material occurs from a predetermined temperature value. When this weight change occurs, the main beam in the device tilts, and the current flowing through the coil is controlled to return this movement to its original position. Since the current flowing corresponds to the weight change, the fluctuation behavior of the current is output as a weight change, and the thermogravimetric at which the thermogravimetric at which the above-mentioned temperature decrease begins was determined. 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.

[0116] These measurement results are shown in Table 1. The resistance increase rate and degradation capacitance are shown as the relative resistance increase rate and relative degradation capacitance for Examples 1-12 and Comparative Examples 1 and 2, with the resistance increase rate and degradation capacitance in Comparative Example 1 set to "100".

[0117] [Table 1] TIFF0007868701000002.tif121170

[0118] Based on the measurement results above, it was found that in Examples 1 to 12, when the lithium desorption amount of the positive electrode active material of the obtained solid battery was 40%, and the solid electrolyte in the positive electrode layer contained lithium borosilicate glass, if the thermogravimetric reduction onset temperature at which the weight of the positive electrode active material decreased by 0.67% or more was 220°C or higher, both the relative resistance increase rate and the relative degradation capacity of the solid battery were lower than the values ​​in Comparative Example 1 (thermogravimetric reduction onset temperature: 203°C + solid electrolyte in positive electrode layer: containing lithium borosilicate glass).

[0119] Furthermore, in Comparative Example 2 (thermogravimetric reduction onset temperature: 210°C + solid electrolyte in positive electrode layer: containing LiLaZr oxide / without lithium borosilicate glass), it was found that the relative degradation capacity of the solid-state battery was even lower than that of Comparative Example 1.

[0120] Furthermore, in Comparative Example 3 (thermogravimetric reduction onset temperature: 485°C + solid electrolyte in the positive electrode layer: lithium borosilicate glass), the capacity retention rate was 0% compared to Examples 1 to 12. This indicates that when the battery is charged and discharged 100 times, the capacity is not maintained relative to the initial discharge capacity.

[0121] From the above, it was found that, overall, when a positive electrode layer is used that comprises a solid electrolyte containing lithium borosilicate glass and a positive electrode active material having a thermogravimetric reduction onset temperature of 220°C to less than 485°C, suitable battery characteristics (such as relative resistance increase rate) can be obtained even under high-temperature conditions. In other words, it was found that the solid-state battery in this embodiment can have suitable high-temperature resistance.

[0122] Furthermore, the present invention may take the following embodiments. <1> The positive electrode comprises a positive electrode active material containing Li and a positive electrode layer containing a solid electrolyte. A solid-state battery in which, when the lithium desorption amount of the positive electrode active material is 40%, the thermogravimetric reduction start temperature 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. <2> The positive electrode active material has a layered rock salt type crystal structure. <1> Solid-state batteries as described above. <3> The temperature at which the thermogravimetric reduction begins is 350°C or lower. <1> or <2> Solid-state batteries as described above. <4> The positive electrode active material comprises an oxide containing Li and Co, and the oxide contains at least Ti. <1> ~ <3> A solid battery as described in any of the following. <5> In the positive electrode active material, when the oxide containing Li and Co contains Ti, the thermogravimetric loss onset temperature is 220°C or higher and 240°C or lower. <4> Solid-state batteries as described above. <6> The positive electrode active material further comprises Mg and / or Al. <4> or <5> Solid-state batteries as described above. <7> The positive electrode active material is LiCo x Ti y α z O2 (wherein the formula x+y+z=1, 0.9≦x<1, 0.005≦y≦0.01, α:Mg and / or Al), <4> ~ <6> A solid battery as described in any of the following. <8> The positive electrode active material includes an oxide containing Li, Ni, Co, and Mn. <1> ~ <7> A solid battery as described in any of the following. <9> The positive electrode active material is LiNi a Co b Mn c O2 (where a+b+c≦1 and 0.3≦a≦0.8) <8> Solid-state batteries as described above. <10> The thermogravimetric analysis onset temperature is higher when the positive electrode active material is an oxide containing Li, Ni, Co, and Mn than when it is an oxide containing Ti, Li, and Co. <1> ~ <9> A solid battery as described in any of the following. <11> The solid electrolyte further comprises an oxide-based solid electrolyte having a garnet-type crystal structure. <1> ~ <10> A solid battery as described in any of the following. <12> The aforementioned oxide-based solid electrolyte is an oxide containing Li, La, and Zr. <11> Solid-state batteries as described above. [Industrial applicability]

[0123] The solid-state battery of the present invention can be used in a variety of fields where energy storage is anticipated. While this is merely an example, the solid-state battery of the present invention can be used in the electrical, information, and communication fields where mobile devices are used (e.g., the electrical and electronic equipment field or mobile device field, including small electronic devices such as mobile phones, smartphones, laptops and digital cameras, activity trackers, arm computers, electronic paper, RFID tags, card-type electronic money, and smartwatches), household and small-scale industrial applications (e.g., power tools, golf carts, household, caregiving, and industrial robots), large-scale industrial applications (e.g., forklifts, elevators, and port cranes), transportation systems (e.g., hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles, etc.), power grid applications (e.g., various power generation, road conditioners, smart grids, and general household energy storage systems), medical applications (medical equipment such as earphones and hearing aids), pharmaceutical applications (medication management systems, etc.), as well as IoT fields and space and deep-sea applications (e.g., space probes, submersible research vessels, etc.). [Explanation of symbols]

[0124] 10: Electrode layer 10A: Positive electrode layer 10B: Negative electrode layer 11: Electrode current collecting layer 11A: Positive electrode current collecting layer 11B: Negative electrode current collecting layer 20: Solid electrolyte layer 30: Electrode separation part 30A: Positive electrode separation section 30B: Negative electrode separation section 40: Terminals 40A: Positive terminal 40B: Negative terminal 60: Outer layer material 100: Solid-state battery stack 200: Solid state battery

Claims

1. The positive electrode comprises a positive electrode active material containing Li, and a positive electrode layer containing a solid electrolyte. In a state where the lithium desorption amount of the positive electrode active material is 40%, the thermogravimetric loss start temperature 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. A solid-state battery in which the positive electrode active material has a layered rock salt crystal structure.

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

3. The solid-state battery according to claim 1, wherein the positive electrode active material comprises an oxide containing Li and Co, and the oxide contains at least Ti.

4. The solid-state battery according to claim 3, wherein in the positive electrode active material, when the oxide containing Li and Co contains Ti, the thermogravimetric reduction onset temperature is 220°C or higher and 240°C or lower.

5. The solid battery according to claim 3, wherein the positive electrode active material further comprises Mg and / or Al.

6. The positive electrode active material is LiCo ｘ Ti ｙ α ｚ O ２ The solid battery according to claim 3, comprising (wherein x + y + z = 1, 0.9 ≤ x < 1, 0.005 ≤ y ≤ 0.01, α: Mg and / or Al).

7. The solid battery according to claim 1, wherein the positive electrode active material comprises an oxide containing Li, Ni, Co, and Mn.

8. The positive electrode active material is LiNi ａ Co ｂ Mn ｃ O ２ The solid battery according to claim 7, wherein a + b + c ≤ 1 and 0.3 ≤ a ≤ 0.8 in the formula.

9. The solid-state battery according to claim 1, wherein the thermogravimetric onset temperature is higher when the positive electrode active material is an oxide containing Li, Ni, Co, and Mn than when the positive electrode active material is an oxide containing Li and Co containing Ti.

10. The solid battery according to claim 1, wherein the solid electrolyte further comprises 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. That's all.

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