Electrode composition for all-solid-state secondary batteries, electrode sheet for all-solid-state secondary batteries, all-solid-state secondary battery, and methods for producing electrode sheet for all-solid-state secondary batteries and for producing all-solid-state secondary battery

Abstract

An electrode composition for all-solid-state secondary batteries which comprises an amorphous solid electrolyte and an active material, wherein the solid electrolyte comprises a metal-containing oxide comprising an oxygen element and at least one element selected from among alkali metal elements and alkaline-earth metal elements, at least one metal salt selected from among alkali metal salts and alkaline-earth metal salts, and water and the ratio of the median diameter M of the active material to the median diameter N of the solid electrolyte is 1.2≤M / N≤5.0; an electrode sheet for all-solid-state secondary batteries and an all-solid-state secondary battery which are obtained from or using the electrode composition for all-solid-state secondary batteries; and methods for producing the electrode sheet and the all-solid-state secondary battery.

Description

Electrode composition for all-solid-state secondary battery, electrode sheet for all-solid-state secondary battery, all-solid-state secondary battery, and method for manufacturing electrode sheet for all-solid-state secondary battery and all-solid-state secondary battery

[0001] The present invention relates to an electrode composition for an all-solid-state secondary battery, an electrode sheet for an all-solid-state secondary battery, an all-solid-state secondary battery, and a method for manufacturing an electrode sheet for an all-solid-state secondary battery and an all-solid-state secondary battery.

[0002] Conventionally, organic solvents with high ionic conductivity have been used as electrolytes in lithium-ion secondary batteries. However, organic solvents are flammable, posing safety issues. Furthermore, because they are liquid, they are difficult to compact, and capacity limitations become an issue when batteries are enlarged. In contrast, all-solid-state secondary batteries such as all-solid-state lithium-ion secondary batteries are one of the next-generation batteries that can solve these issues. The basic structure of an all-solid-state lithium-ion secondary battery, which is one embodiment of an all-solid-state secondary battery, is shown in Figure 1. An all-solid-state lithium-ion secondary battery 10 has, from the negative electrode side, a negative electrode current collector layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode current collector layer 5, in this order. Each layer is in contact with each other, forming an adjacent structure. By adopting such a structure, electrons (e － ) is supplied to the solid electrolyte layer 3, and lithium ions (Li ＋ On the other hand, during discharge, the lithium ions (Li ＋ ) is returned to the positive electrode side through the solid electrolyte layer 3, and electrons are supplied to the operating part 6. In the illustrated example, a light bulb is used as a model for the operating part 6, and it is lit by discharge.

[0003] As described above, all-solid-state lithium-ion secondary batteries require excellent lithium-ion conductivity in the solid electrolyte layer to achieve the desired charge / discharge characteristics. Sulfide-based solid electrolytes or oxide-based solid electrolytes are typically used as the solid electrolytes constituting the solid electrolyte layer. Because sulfide-based solid electrolytes are soft and plastically deformable, particles bond together simply by pressure molding. Therefore, sulfide-based solid electrolytes have low interfacial resistance between particles and excellent ionic conductivity. However, sulfide-based solid electrolytes have the problem of reacting with water to generate toxic hydrogen sulfide. In contrast, oxide-based solid electrolytes have the advantage of being highly safe. However, oxide-based solid electrolytes are hard and resistant to plastic deformation. Increasing the interparticle bonding strength of oxide-based solid electrolytes requires a high-temperature sintering process, which is limiting in terms of battery production efficiency and energy costs. For example, Patent Document 1 discloses a solid electrolyte formed from a lithium-containing oxide with a specific elemental composition and describes that this solid electrolyte exhibits high ionic conductivity. However, using this lithium-containing oxide as a solid electrolyte sheet requires a high-temperature sintering process. As a technique for addressing this problem, for example, Patent Document 2 discloses a technique for reducing the lithium ion conductivity at 25° C. to 1.0×10 －６ Patent Document 2 discloses a composite containing a lithium compound having a densitometric value of 0.5 S / cm or more and lithium tetraborate, whose reduced pair distribution function G(r) obtained from X-ray total scattering measurement shows a specific profile. According to the technology described in Patent Document 2, although this composite is composed of a lithium-containing oxide, the lithium tetraborate plastically deforms between the lithium compounds to connect the lithium compounds, and therefore, this composite can be formed into a lithium ion conductor showing good lithium ion conductivity by pressure treatment without being subjected to high-temperature sintering treatment.

[0004] In all-solid-state secondary batteries, the positive electrode active material layer and the negative electrode active material layer (collectively referred to as "active material layer") are generally formed from a composition containing a powdered solid electrolyte and an active material. Because the active material layer contains different types of powders, controlling the particle sizes of these powders has been studied to improve the performance of the active material layer or the battery. For example, Patent Document 3 discloses a mixed powder for lithium-ion batteries, which is a mixed powder of a positive electrode active material for lithium-ion batteries and a solid electrolyte, in which the positive electrode active material for lithium-ion batteries is composed of particles containing a specific lithium metal composite oxide, and the positive electrode active material for lithium-ion batteries and the solid electrolyte each have a specific particle size distribution. The use of this mixed powder for lithium-ion batteries is said to improve initial charge / discharge efficiency. Patent Document 4 discloses an active material layer containing specific amounts of an active material, a fibrous conductive material, a granular conductive material, and a solid electrolyte, and in which the areas of direct contact between these active materials, the granular conductive agent, and the solid electrolyte are in a specific relationship. This active material layer is said to have high density and low electrical resistance. In the active material layer, the solid electrolyte and the active material are tightly adhered to each other, reducing voids, thereby enabling the battery to have low resistance. However, reducing voids reduces the flexibility of the active material layer, making it prone to cracking, peeling, and other problems, resulting in poor handling (reduced yield). This problem becomes even more pronounced in wound-type all-solid-state secondary batteries, in which the active material layer is stacked on top of other layers and wound.

[0005] JP 2018-052755 A International Publication No. 2021 / 193204 JP 2021-114407 A International Publication No. 2020 / 130069

[0006] An object of the present invention is to provide an electrode composition for an all-solid-state secondary battery that can form an active material layer that has low porosity and excellent flexibility. Another object of the present invention is to provide an electrode sheet for an all-solid-state secondary battery and an all-solid-state secondary battery that have an active material layer that has low porosity and excellent flexibility. A further object of the present invention is to provide a method for manufacturing the electrode sheet for an all-solid-state secondary battery and the all-solid-state secondary battery.

[0007] The above-mentioned problems of the present invention have been solved by the following means.

[0008] [1] An electrode composition for an all-solid-state secondary battery, comprising an amorphous solid electrolyte and an active material, wherein the solid electrolyte comprises a metal-containing oxide containing at least one of an alkali metal element and an alkaline earth metal element and oxygen, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water, wherein a ratio of a median diameter M of the active material to a median diameter N of the solid electrolyte is 1.2≦M / N≦5.0. [2] The electrode composition for an all-solid-state secondary battery according to [1], wherein the metal-containing oxide is a lithium-containing oxide containing Li, B, and O, and the metal salt is a lithium salt. [3] The electrode composition for an all-solid-state secondary battery according to [1] or [2], wherein the median diameter N of the solid electrolyte is 0.1 to 10 μm. [4] The electrode composition for an all-solid-state secondary battery according to any one of [1] to [3], wherein the ratio of the content of the solid electrolyte to the content of the active material in the electrode composition for an all-solid-state secondary battery, in mass ratio, is solid electrolyte:active material=20:80 to 80:20. [5] The electrode composition for an all-solid-state secondary battery according to any one of [1] to [4], wherein the ratio of the content of the water to the content of the metal-containing oxide in the solid electrolyte, in molar ratio, is 1 to 12. [6] The electrode composition for an all-solid-state secondary battery according to any one of [1] to [5], wherein the ratio of the content of the metal salt to the content of the metal-containing oxide in the solid electrolyte, in molar ratio, is 0.001 to 1.5. [7] An electrode sheet for an all-solid-state secondary battery having an active material layer containing an amorphous solid electrolyte and an active material, wherein the solid electrolyte contains a metal-containing oxide containing at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water, and the active material layer has a porosity of 0.1 to 15%. [8] The electrode sheet for an all-solid-state secondary battery according to [7], wherein the metal-containing oxide is a lithium-containing oxide containing Li, B, and O, and the metal salt is a lithium salt.[9] An all-solid-state secondary battery comprising a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer arranged in this order, wherein at least one of the positive electrode active material layer and the negative electrode active material layer is an active material layer containing an amorphous solid electrolyte and an active material, wherein the amorphous solid electrolyte contains a metal-containing oxide containing at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water, and wherein the active material layer has a porosity of 0.1 to 15%.

[10] The all-solid-state secondary battery according to [9], wherein the metal-containing oxide is a lithium-containing oxide containing Li, B, and O, and the metal salt is a lithium salt.

[11] A method for producing an electrode sheet for an all-solid-state secondary battery, comprising pressurizing a layer formed using the electrode composition for an all-solid-state secondary battery according to any one of [1] to [6] to form an active material layer.

[12] A method for producing an all-solid-state secondary battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer arranged in this order, the method comprising: forming at least one of the positive electrode active material layer and the negative electrode active material layer by pressure treating a layer formed using the electrode composition for an all-solid-state secondary battery according to any one of [1] to [6].

[0009] In the present invention and the specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0010] The electrode composition for an all-solid-state secondary battery of the present invention can form an active material layer that has low porosity yet excellent flexibility and is resistant to cracking or peeling. The electrode sheet for an all-solid-state secondary battery of the present invention has low porosity yet excellent flexibility. The active material layer of the all-solid-state secondary battery of the present invention has low porosity yet excellent flexibility, resulting in an increased yield in its production and an extended battery life. The method for producing an electrode for an all-solid-state secondary battery of the present invention can obtain the electrode sheet for a secondary battery of the present invention that exhibits the above-mentioned properties. The method for producing an all-solid-state secondary battery of the present invention can obtain the above-mentioned secondary battery of the present invention.

[0011] Fig. 1 is a cross-sectional view showing a schematic example of the configuration of an all-solid-state lithium ion secondary battery. Fig. 2 is a diagram showing an example of an X-ray diffraction pattern for explaining the X-ray diffraction characteristics of the solid electrolyte (II) used in the present invention. Fig. 3 is a diagram showing an example of the reduced pair distribution function G(r) obtained from X-ray total scattering measurement of the solid electrolyte (II) used in the present invention. Fig. 4 is a diagram showing the solid of the solid electrolyte (II) used in the present invention. ７ 5 shows an example of a spectrum obtained when Li-NMR measurement is performed at 20° C. or 120° C. FIG. ７ 6 shows an example of a spectrum obtained when Li-NMR measurement is performed at 20° C. or 120° C. FIG. ７ FIG. 7 is a diagram showing an example of a spectrum obtained when Li-NMR measurement is performed at 20° C. FIG. 7 is a diagram showing waveform separation of the peaks shown in FIG. 6. FIG. 8 is a diagram showing an example of a Raman spectrum of the solid electrolyte (II) used in the present invention. FIG. 9 is a diagram showing a Raman spectrum of lithium tetraborate crystal. FIG. 10 is a diagram showing the Raman spectrum of powdered Li ２ B ４ O ７ 11 shows the reduced pair distribution function G(r) obtained by X-ray total scattering measurement of the crystal. ２ B ４ O ７ FIG. 1 shows the X-ray diffraction pattern of the crystal.

[0012] [Electrode Composition for All-Solid-State Secondary Battery] The electrode composition for an all-solid-state secondary battery of the present invention (hereinafter also referred to as the "electrode composition of the present invention") comprises an amorphous solid electrolyte and an active material. The solid electrolyte is a solid particulate electrolyte comprising a metal-containing oxide containing at least one of an alkali metal element and an alkaline earth metal element and oxygen, at least one of an alkali metal salt and an alkaline earth metal salt, and water. In the electrode composition of the present invention, the ratio (M / N) of the median diameter M of the active material to the median diameter N of the solid electrolyte is controlled to be 1.2≦M / N≦5.0. The electrode composition of the present invention can be suitably used to form an active material layer in an all-solid-state secondary battery. In the electrode composition of the present invention, the solid electrolyte has a specific composition and is amorphous, and exhibits high flexibility and relatively easy plastic deformation. Furthermore, by controlling the relationship between the median diameters of the solid electrolyte and the active material so that it satisfies the above ratio, the active material layer obtained using the electrode composition of the present invention can have a reduced porosity, the solid electrolyte acts as a binder to enhance adhesion between the solid particles, and excellent flexibility. Thus, by using the electrode composition of the present invention, it is possible to form a highly flexible active material layer even without using a sulfide-based solid electrolyte as the solid electrolyte or without using a binder such as an organic polymer.

[0013] The ratio M / N is preferably 1.5≦M / N≦4.0, and more preferably 1.8≦M / N≦3.0.

[0014] In the electrode composition of the present invention, the ratio of the content of the solid electrolyte to the content of the active material, in mass ratio, solid electrolyte:active material is preferably 20:80 to 80:20, more preferably 20:80 to 50:50, and even more preferably 25:75 to 40:60.

[0015] <Solid Electrolyte> The solid electrolyte constituting the electrode composition of the present invention is in an amorphous state (synonymous with a non-crystalline state or an amorphous state) and contains a metal-containing oxide containing at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one of an alkali metal salt and an alkaline earth metal salt, and water. (Hereinafter, this solid electrolyte will also be referred to as "solid electrolyte (I).") The solid electrolyte (I) is usually an inorganic solid electrolyte.

[0016] The solid electrolyte (I) is in an amorphous state and exhibits elastic properties that facilitate plastic deformation. As a result, in a layer containing the solid electrolyte (I) formed by pressure treatment or the like, adhesion between the solid electrolytes (I) and / or adhesion between the solid electrolyte (I) and components (e.g., active materials) present in other constituent layers is improved, reducing interfacial resistance and achieving better ionic conductivity. By using this solid electrolyte (I), an ion conductor exhibiting excellent ionic conductivity, or a constituent layer for an all-solid-state secondary battery, can be formed by pressure treatment or the like, even though it is a highly safe oxide-based solid electrolyte, without being subjected to high-temperature sintering treatment. In the present invention, the solid electrolyte (I) being "amorphous" means that it has a broad scattering band with a peak in the 2θ value range of 20° to 40° in X-ray diffraction using CuKα radiation, and may also have crystalline diffraction lines. The median diameter N of the solid electrolyte (I) is not particularly limited as long as it satisfies the above M / N ratio, and is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm, and even more preferably 0.1 to 2.0 μm. The median diameter (D50) is measured by acquiring particle images using a flow particle image analysis method, calculating the particle size distribution, and analyzing the obtained distribution. The particle diameter corresponds to the circle-equivalent diameter. The method for controlling the median diameter is not particularly limited, and it can be controlled, for example, by micronizing the particles using a mechanical milling process described below and classifying them using a sieve.

[0017] -Water- The water contained in the solid electrolyte (I) includes at least bound water. While the reason why the solid electrolyte (I) exhibits high lithium ion conductivity is unclear, it is believed that in the amorphous solid electrolyte (I), a soft hydration layer is likely to form on the surface of the metal-containing oxide, and this hydration layer contains a large amount of metal derived from the metal salt, resulting in enhanced ion conductivity. Here, in the present invention and specification, "bound water" refers to water other than water present as free water or OH groups bound to the metal-containing oxide. Even if the solid electrolyte (I) contains water, it is in the form of solid particles (including a state in which solid particles are bound together) and functions as a solid electrolyte for an all-solid-state secondary battery. In other words, the solid electrolyte (I) contains bound water that is not or is difficult to remove under normal drying conditions. Note that the solid electrolyte (I) may contain free water as long as it functions as a solid electrolyte for an all-solid-state secondary battery in the form of solid particles (a state that can be handled as a powder). In other words, in the present invention, the term "electrode composition" also encompasses a form in which the solid electrolyte contains water, as long as the solid electrolyte can be treated as solid particles (solid powder). For example, a solid electrolyte (I) described below, in which the molar ratio of the water content to the metal-containing oxide content is 12 or less, is neither a paste nor a gel, but is in the form of solid particles (solid powder). In the solid electrolyte (I), the ratio of the water content to the metal-containing oxide content (water / metal-containing oxide) is preferably controlled to a molar ratio of 1 to 12, more preferably 2 to 12, and even more preferably 3 to 11, from the viewpoint of further enhancing ionic conductivity. Furthermore, this molar ratio is preferably 2 to 10, also preferably 2 to 8, also preferably 2 to 7, and even preferably 3 to 7.

[0018] -Metal-Containing Oxide- Examples of the alkali metal element or alkaline earth metal element contained in the metal-containing oxide include Li, Na, K, Rb, Cs, Fr, Ca, Sr, Ba, and Ra, with Li or Na being preferred, and Li being more preferred. The metal-containing oxide preferably further contains, in addition to at least one of an alkali metal element and an alkaline earth metal element and oxygen, a typical element other than these. Examples of typical elements include B, C, N, F, Si, P, S, Cl, As, Se, Br, Te, and I, with B being preferred. A preferred form of the metal-containing oxide is a lithium-containing oxide containing Li, B, and O (hereinafter also simply referred to as a "lithium-containing oxide").

[0019] -Alkali Metal Salt and Alkaline Earth Metal Salt- The alkali metal salt and alkaline earth metal salt (hereinafter also referred to as metal salt) are not particularly limited as long as they are salts of alkali metals or alkaline earth metals. For example, the alkali metal or alkaline earth metal salt can be a salt composed of an alkali metal cation or alkaline earth metal cation and an anion. Examples of the alkali metal in the alkali metal salt and the alkaline earth metal in the alkaline earth metal salt include Li, Na, K, Rb, Cs, Fr, Ca, Sr, Ba, and Ra, with Li or Na being preferred, and Li being more preferred. The alkali metal element or alkaline earth metal element in the metal-containing oxide contained in the electrode composition of the present invention and the alkali metal element or alkaline earth metal element in the metal salt contained in the electrode composition of the present invention may be the same or different. The anion of the alkali metal in the alkali metal salt and the alkaline earth metal salt is preferably an organic anion, more preferably an organic anion having a halogen atom. Specific anions include Cl, － ,Br － , I － , S.O. ４ ２－ , NO ３ － , CO ３ ２－ , C.H. ３ COO － , P.F. ６ － , B.F. ４ －、AsF ６ － 、SbF ６ － 、ClO ４ － 、BrO ４ － 、IO ４ － 、AlCl ４ － 、CF ３ SO ３ － 、(CF ３ SO ２ ) ２ N － 、(CF ３ CF ２ SO ２ ) ２ N － 、(FSO ２ ) ２ N － 、(CF ３ SO ２ )(C ４ F ９ SO ２ )N － 、(CF ３ SO ２ ) ３ C － 、[PF ５ (CF ２ CF ２ CF ３ )] － 、[PF ４ (CF ２ CF ２ CF ３ ) ２ － ]、[PF ３ (CF ２ CF ２ CF ３ ) ３ ] － 、[PF ５ (CF ２ CF ２ CF ２ CF ３ )] － 、[PF ４ (CF ２ CF ２ CF ２ CF ３ ) ２] － , [PF ３ (CF ２ CF ２ CF ２ CF ３ ) ３ ] － , bis(oxalato)borate anion, difluorooxalatoborate anion, etc., and Br － , I － , C.F. ３ SO ３ － , (CF ３ SO ２ ) ２ N － , (CF ３ CF ２ SO ２ ) ２ N － , (FSO ２ ) ２ N － , (CF ３ SO ２ ) (C ４ F ９ SO ２ ) N － , (CF ３ SO ２ ) ３ C － , [PF ５ (CF ２ CF ２ CF ３ )] － , [PF ４ (CF ２ CF ２ CF ３ ) ２ － ], [PF ３ (CF ２ CF ２ CF ３ ) ３ ] － , [PF ５ (CF ２ CF ２ CF ２ CF ３ )] － , [PF ４ (CF ２ CF ２ CF ２ CF ３) ２ ] － , [PF ３ (CF ２ CF ２ CF ２ CF ３ ) ３ ] － is preferred, and (CF ３ SO ２ ) ２ N － , (CF ３ CF ２ SO ２ ) ２ N － , (FSO ２ ) ２ N － , (CF ３ SO ２ ) (C ４ F ９ SO ２ ) N － In the solid electrolyte (I), the ratio of the content of the metal salt to the content of the metal-containing oxide (metal salt / metal-containing oxide) is preferably 0.001 to 1.5, more preferably 0.001 to 1.2, even more preferably 0.01 to 1.2, particularly preferably 0.1 to 1.2, and most preferably 0.5 to 1.2, in terms of molar ratio.

[0020] The solid electrolyte (I) is preferably in a form in which the metal-containing oxide is a lithium-containing oxide containing Li, B, and O, and the metal salt is a lithium salt. This preferred form of the solid electrolyte (I) is also referred to as solid electrolyte (II). Hereinafter, the present invention will be described using an example of a form using the solid electrolyte (II), but the present invention is not limited to the following form except as defined in the present invention.

[0021] In the present invention, when the solid electrolyte (II) is in an "amorphous state", it preferably satisfies the following X-ray diffraction characteristics. That is, when the solid electrolyte (II) satisfies the following X-ray diffraction characteristics, the solid electrolyte (II) is in an "amorphous state".

[0022] (X-ray diffraction characteristics) In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (II) using CuKα rays, none of the following peaks is present: a first peak having a peak top in the range of a diffraction angle 2θ of 21.6 to 22.0° and a full width at half maximum of 0.65° or less; a second peak having a peak top in the range of a diffraction angle 2θ of 25.4 to 25.8° and a full width at half maximum of 0.65° or less; a third peak having a peak top in the range of a diffraction angle 2θ of 33.4 to 33.8° and a full width at half maximum of 0.65° or less; and a fourth peak having a peak top in the range of a diffraction angle 2θ of 34.4 to 34.8° and a full width at half maximum of 0.65° or less; or In the X-ray diffraction pattern, when at least one peak (hereinafter referred to as "peak X") among the first peak, second peak, third peak, and fourth peak is present, at least one peak among peak X has an intensity ratio of 5.0 or less as calculated by the intensity measurement method described below.

[0023] -Intensity measurement method- The average intensity (Av1) in the range of +0.45° to +0.55° from the diffraction angle 2θ at the peak top of Peak X is calculated, and the average intensity (Av2) in the range of -0.55° to -0.45° from the diffraction angle 2θ at the peak top of Peak X is calculated, and the arithmetic average value of Av1 and Av2 is calculated. The ratio of the peak intensity at the peak top of Peak X to this arithmetic average value (peak intensity at the peak top of Peak X / arithmetic average value) is defined as the intensity ratio.

[0024] The X-ray diffraction characteristics will be described in more detail. In the X-ray diffraction pattern obtained from X-ray diffraction measurement of the solid electrolyte (II) using CuKα radiation, if none of the first peak, second peak, third peak, and fourth peak is present, the X-ray diffraction characteristics are satisfied, and the solid electrolyte (II) is in an amorphous state. Furthermore, in the X-ray diffraction pattern obtained from X-ray diffraction measurement of the solid electrolyte (II) using CuKα radiation, if the peak X is present, and if at least one peak of the peak X has an intensity ratio obtained by the intensity measurement method of 5.0 or less, the X-ray diffraction characteristics are also satisfied, and the solid electrolyte (II) is in an amorphous state. Here, the full width at half maximum (FWHM) of the peak means the peak width (°) at 1 / 2 of the peak intensity at the peak top.

[0025] The intensity measurement method will be described in more detail with reference to FIG. 2. FIG. 2 is a diagram showing an example of peak X appearing in a diffraction pattern obtained by X-ray diffraction measurement of solid electrolyte (II) using CuKα radiation. In the diffraction pattern shown in FIG. 2, a specific peak whose peak top intensity exhibits intensity 1 is shown. In the intensity measurement method, as shown in FIG. 2, an average intensity (Av1) in the range of +0.45° to +0.55° from the diffraction angle 2θ of the peak top of peak X is calculated, and an average intensity (Av2) in the range of −0.55° to −0.45° from the diffraction angle 2θ of the peak top of peak X is further calculated. Next, the arithmetic average values ​​of Av1 and Av2 are calculated, and the ratio of intensity 1 to the arithmetic average value is determined as the intensity ratio. When the above X-ray diffraction characteristics are satisfied, this means that there is no or almost no crystalline structure in the solid electrolyte (II), and the solid electrolyte is in an amorphous state. In other words, the first to fourth peaks are mainly peaks derived from the crystalline structure in the solid electrolyte (e.g., the crystalline structure of lithium tetraborate), and the absence of these peaks indicates an amorphous state. Even if at least one of the first to fourth peaks is present, the intensity ratio of at least one of the peaks X present is 5.0 or less, which means that the solid electrolyte (II) is substantially free of a crystalline structure that inhibits the effects of the present invention. For example, a peak derived from a specific component (e.g., a lithium salt) may overlap with any of the first to fourth peaks described above. However, in an amorphous solid electrolyte, all of the first to fourth peaks are usually reduced. Therefore, even if a peak derived from the specific component happens to overlap with any of the first to fourth peaks and a single large peak appears, the presence of at least one peak X with an intensity ratio below a predetermined value indicates that the solid electrolyte (II) is amorphous.

[0026] The X-ray diffraction measurement is carried out using CuKα rays under measurement conditions of 0.01° / step and 3° / min.

[0027] In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (II) using CuKα radiation, it is preferable that none of the above-mentioned first peak, second peak, third peak, and fourth peak is present, or even if at least one peak X among the above-mentioned first peak, second peak, third peak, and fourth peak is present, the intensity ratio of at least one peak among the peaks X is 3.0 or less. Among these, it is more preferable that none of the above-mentioned first peak, second peak, third peak, and fourth peak is present, or even if at least one peak X among the above-mentioned first peak, second peak, third peak, and fourth peak is present, the intensity ratio of at least one peak among the peaks X is 2.0 or less.

[0028] In the X-ray diffraction pattern, if two or more peaks have their peak tops in the range of 21.6 to 22.0° and their full width at half maximum is 0.65° or less, the peak with the highest diffracted X-ray intensity is selected as the first peak, and the X-ray diffraction characteristics are determined. In the X-ray diffraction pattern, if two or more peaks have their peak tops in the range of 25.4 to 25.8° and their full width at half maximum is 0.65° or less, the peak with the highest diffracted X-ray intensity is selected as the second peak, and the X-ray diffraction characteristics are determined. In the X-ray diffraction pattern, if two or more peaks have their peak tops in the range of 33.4 to 33.8° and their full width at half maximum is 0.65° or less, the peak with the highest diffracted X-ray intensity is selected as the third peak, and the X-ray diffraction characteristics are determined. Furthermore, in the X-ray diffraction pattern, if there are two or more peaks whose peak tops are located in the range of 34.4 to 34.8° and whose full width at half maximum is 0.65° or less, the peak with the greatest diffracted X-ray intensity is selected as the fourth peak, and the X-ray diffraction characteristics are determined.

[0029] (X-ray total scattering characteristics) The solid electrolyte (II) preferably satisfies the following requirement A-1 in terms of X-ray total scattering characteristics. Furthermore, when the solid electrolyte (II) satisfies the above X-ray diffraction characteristics, the solid electrolyte (II) usually satisfies the following requirement A-2.

[0030] - Requirement A-1 - In the reduced pair distribution function G(r) obtained from X-ray total scattering measurement of the solid electrolyte (II), there is a first peak whose peak top is located in the range of r 1.43±0.2 Å and a second peak whose peak top is located in the range of r 2.40±0.2 Å, and G(r) at the peak top of the first peak exceeds 1.0, and G(r) at the peak top of the second peak is 0.8 or more.

[0031] - Requirement A-2 - In the reduced pair distribution function G(r) obtained from X-ray total scattering measurement of the solid electrolyte (II), the absolute value of G(r) is less than 1.0 when r is in the range of more than 5 Å and not more than 10 Å.

[0032] When the solid electrolyte (II) satisfies requirements A-1 and A-2, it has a short-range ordered structure related to the interatomic distances of B-O and B-B, but has almost no long-range ordered structure, and therefore the oxide solid electrolyte itself is softer than conventional lithium-containing oxides and exhibits elastic properties that make it more susceptible to plastic deformation. As a result, in a layer containing the solid electrolyte (II) formed by pressure treatment or the like, it is presumed that the adhesion between the solid electrolytes (II) and / or the adhesion between the solid electrolyte (II) and other ion conductors (e.g., active materials) is improved, the interfacial resistance can be reduced, and better ion conductivity can be obtained. Requirements A-1 and A-2 will be described in more detail with reference to the drawings.

[0033] FIG. 3 shows an example of the reduced pair distribution function G(r) obtained by X-ray total scattering measurement of the solid electrolyte (II). The vertical axis of FIG. 3 is the reduced pair distribution function obtained by Fourier transform of the X-ray scattering, and indicates the probability that an atom exists at a position of distance r. The X-ray total scattering measurement can be performed using SPring-8 BL04B2 (accelerating voltage 61.4 keV, wavelength 0.2019 Å). The scattering intensity I obtained by the experiment ｏｂｓ The reduced pair distribution function G(r) is obtained by converting the scattering intensity I ｏｂｓ is expressed by the following formula (1). The structure factor S(Q) (Q: scattering vector) is expressed by the following formula (2), which is the coherent scattering I ｃｏｈ is obtained by dividing by the product of the number of atoms N and the square of the atomic scattering factor f. ｏｂｓ=I ｃｏｈ +I ｉｎｃｏｈ +I 蛍光 (1)

[0034]

[0035] The structure factor S(Q) is used for PDF (Pair Distribution Function) analysis. In the above formula (2), the required intensity is the coherent scattering I ｃｏｈ Incoherent scattering I ｉｎｃｏｈ and X-ray fluorescence I 蛍光 is the scattering intensity I obtained by blank measurement, subtraction using the theoretical formula, and discriminator of the detector. ｏｂｓ Coherent scattering I ｃｏｈ is expressed by Debye's scattering formula (the following formula (3)) (N: total number of atoms, f: atomic scattering factor, r ｉｊ : interatomic distance between i and j).

[0036]

[0037] If we focus on an arbitrary atom and let the atomic density at a distance r be ρ(r), the number of atoms present within a sphere with a radius of r-r+d(r) is 4πr ２ Since ρ(r)dr, the above formula (3) can be expressed as the following formula (4).

[0038]

[0039] The average density of atoms is ρ ０ Then, by transforming the above equation (4), the following equation (5) is obtained.

[0040]

[0041] From the above formula (5) and formula (2), the following formula (6) is obtained.

[0042]

[0043] The pair distribution function g(r) is expressed by the following equation (7).

[0044]

[0045] From the above formulas (6) and (7), the following formula (8) is obtained.

[0046]

[0047] As described above, the pair distribution function can be determined by the Fourier transform of the structure factor S(Q). To make it easier to observe medium- and long-range order, the pair distribution function g(r) is converted to the equation G(r) = 4πr(g(r)-1), which gives the reduced pair distribution function G(r) (Figure 3). g(r), which oscillates around 0, represents the density difference from the average density at each interatomic distance. If there is a correlation at a specific interatomic distance, the average density will be higher than 1. Therefore, it reflects the distance and coordination number of elements corresponding to local to medium distances. As order disappears, ρ(r) approaches the average density, and g(r) approaches 1. Therefore, in an amorphous structure, the larger r becomes, the less order there is, so g(r) becomes 1, i.e., G(r) becomes 0.

[0048] In requirement A-1, as shown in FIG. 3, in the reduced pair distribution function G(r) obtained from X-ray total scattering measurement of the solid electrolyte (II), there is a first peak P1 whose peak top is located in the r range of 1.43±0.2 Å, and a second peak P2 whose peak top is located in the r range of 2.40±0.2 Å, and the G(r) at the peak top of the first peak P1 is greater than 1.0 (preferably 1.2 or greater), and the G(r) at the peak top of the second peak P2 is greater than 0.8 (preferably greater than 1.0). In FIG. 3, the peak top of the first peak P1 is located at 1.43 Å, and the peak top of the second peak P2 is located at 2.40 Å. At the position of 1.43 Å, there is a peak assigned to the interatomic distance of B (boron)-O (oxygen). In addition, at the position of 2.40 Å, there is a peak assigned to the interatomic distance of B (boron)-B (boron). That is, the observation of the two peaks (first peak and second peak) means that a periodic structure corresponding to the two interatomic distances is present in the solid electrolyte (II).

[0049] In requirement A-2, the absolute value of G(r) is less than 1.0 when r is in the range of more than 5 Å and not more than 10 Å, as shown in Figure 3. As described above, the absolute value of G(r) being less than 1.0 when r is in the range of more than 5 Å and not more than 10 Å means that there is almost no long-range ordered structure in the solid electrolyte (II).

[0050] In the reduced pair distribution function G(r), there may be peaks other than the first peak and the second peak in the range of r of 5 Å or less.

[0051] A method for making the solid electrolyte (II) amorphous will be described. The solid electrolyte (I) can also be made amorphous by a similar method. There is no particular limitation on the method for making the solid electrolyte (II) amorphous. For example, in preparing the solid electrolyte (II), there is a method in which a lithium-containing oxide that has been subjected to mechanical milling is used as a raw material. This mechanical milling may be performed in the presence of a lithium salt.

[0052] -Mechanical milling- Mechanical milling is a process in which a sample is pulverized while applying mechanical energy. Examples of mechanical milling include milling using a ball mill, a vibration mill, a turbo mill, or a disk mill. Milling using a ball mill is preferred from the viewpoint of obtaining an amorphous solid electrolyte (II) with good productivity. Examples of ball mills include a vibration ball mill, a rotary ball mill, and a planetary ball mill, with a planetary ball mill being more preferred.

[0053] The conditions for the ball mill treatment are adjusted appropriately depending on the object to be treated. The material of the milling balls (media) is not particularly limited, and examples thereof include agate, silicon nitride, zirconia, alumina, and iron-based alloys, with stabilized zirconia (YSZ) being preferred. The average particle size of the milling balls is not particularly limited, and is preferably 1 to 10 mm, more preferably 3 to 7 mm, from the viewpoint of enabling the solid electrolyte (II) to be produced with good productivity. The average particle size is determined by measuring the diameters of 50 randomly selected milling balls and calculating the arithmetic mean thereof. When the milling balls are not spherical, the major axis is taken as the diameter. The number of milling balls is not particularly limited, and ball mill treatment is generally performed using 10 to 100 balls, preferably 40 to 60 balls.

[0054] The material of the grinding pot in the ball mill treatment is not particularly limited, and examples thereof include agate, silicon nitride, zirconia, alumina, and iron-based alloys, with stabilized zirconia (YSZ) being preferred.

[0055] The rotation speed of the ball mill treatment is not particularly limited and can be, for example, 200 to 700 rpm, preferably 350 to 550 rpm. The treatment time of the ball mill is not particularly limited and can be, for example, 10 to 200 hours, preferably 20 to 140 hours. The ball mill treatment may be performed in air or in an inert gas (e.g., argon, helium, nitrogen, etc.) atmosphere.

[0056] In the production of the solid electrolyte (II), it is preferable to carry out the following steps 1A to 3A. Step 1A: A step of subjecting a lithium-containing oxide to mechanical milling treatment in the presence of a lithium salt. Step 2A: A step of mixing the product obtained in step 1A with water. Step 3A: A step of removing water from the dispersion obtained in step 2A to obtain the solid electrolyte (II).

[0057] In Step 1A, the amount of the lithium salt used is not particularly limited, and is appropriately adjusted so as to obtain the solid electrolyte (II) defined in the present invention.

[0058] In the above-mentioned step 2A, the amount of water used is not particularly limited. For example, the amount of water used can be 10 to 200 parts by mass, and preferably 50 to 150 parts by mass, per 100 parts by mass of the product obtained in step 1A. The method for mixing the product obtained in step 1A with water is not particularly limited, and they may be mixed all at once, or water may be added stepwise to the product obtained in step 1A and mixed. When mixing, ultrasonic treatment may be performed as necessary. The time for ultrasonic treatment is not particularly limited, and may be, for example, 10 minutes to 5 hours.

[0059] Step 3A is a step of removing water from the dispersion obtained in Step 2A to obtain a solid electrolyte (II). The method for removing water from the dispersion obtained in Step 2A is not particularly limited, and water may be removed by heat treatment or vacuum drying treatment. The drying conditions are not particularly limited, and examples thereof include the drying conditions used in the examples.

[0060] Before the step 1A, a step 0 may be carried out in which the lithium-containing oxide is subjected to mechanical milling in an environment in which no lithium salt is present.

[0061] In the production of the solid electrolyte (II), it is also preferable to carry out the following steps 1B to 3B instead of the above steps 1A to 3A. Step 1B: A step of subjecting the lithium-containing oxide to mechanical milling treatment; Step 2B: A step of mixing the product obtained in step 1B with water and a lithium salt; and Step 3B: A step of removing water from the dispersion obtained in step 2B to obtain the solid electrolyte (II).

[0062] The difference between step 1B and step 1A is that in step 1A, mechanical milling is performed in the presence of a lithium salt, whereas in step 1B, mechanical milling is performed without using a lithium salt. Therefore, in step 2B, the product obtained in step 1B is mixed with water and a lithium salt. The procedure of step 2B is not particularly limited, and may be a method of mixing the product obtained in step 1B, water, and a lithium salt all at once (method 1), a method of mixing the product obtained in step 1B with water to prepare a dispersion, and then mixing the resulting dispersion with a lithium salt (method 2), or a method of mixing the product obtained in step 1B with water to prepare dispersion 1, mixing a lithium salt with water to prepare solution 2, and then mixing dispersion 1 with solution 2 (method 3). When mixing the product obtained in step 1B with water, a dispersion treatment such as ultrasonic treatment may be appropriately performed. In Method 2, when mixing a dispersion obtained by mixing the product obtained in Step 1B with water and a lithium salt, if the amount of lithium salt is too large, the resulting liquid is likely to gel, and the amount of lithium salt to be mixed is limited. In contrast, in Method 3, even when the product obtained in Step 1B and a lithium salt are mixed in approximately equimolar amounts, gelation of the dispersion is unlikely to occur, and a larger amount of lithium salt can be mixed. From this perspective, Method 3 is preferred. The procedures of Step 3B and Step 3A are the same.

[0063] In the production of the solid electrolyte (II), it is also preferable to carry out the following steps 1C to 3C instead of the above steps 1A to 3A. Step 1C: A step of subjecting the lithium-containing oxide to mechanical milling treatment. Step 2C: A step of mixing the product obtained in step 1C with water. Step 3C: A step of mixing the product obtained by removing water from the dispersion obtained in step 2C with a lithium salt to obtain the solid electrolyte (II).

[0064] The procedures of Step 1C and Step 1B are the same. The procedures of Step 2C and Step 2A are the same. Step 3C differs from Steps 3A and 3B in that a product obtained by removing water from the dispersion obtained in Step 2C is mixed with a lithium salt. In Step 3C, the amount of lithium salt used is not particularly limited and is appropriately adjusted so as to obtain the solid electrolyte (II) defined in the present invention. The method for mixing the product obtained by removing water from the dispersion obtained in Step 2C with the lithium salt is not particularly limited, and a method in which a solution obtained by dissolving the lithium salt in water is impregnated into the product and the two are mixed may be used.

[0065] (Component Composition of Solid Electrolyte (II)) As described above, the solid electrolyte (II) used in the present invention is an amorphous solid electrolyte, and contains a lithium-containing oxide, a lithium salt, and water. The ratio of the water content to the lithium-containing oxide content in the solid electrolyte (II) is preferably 1 to 12, more preferably 2 to 12, and even more preferably 3 to 11, in molar ratio. This molar ratio is also preferably 2 to 10, also preferably 2 to 8, also preferably 2 to 7, and also preferably 3 to 7. The ratio of the lithium salt content to the lithium-containing oxide content in the solid electrolyte (II) is preferably 0.001 to 1.5, more preferably 0.001 to 1.2, still more preferably 0.01 to 1.2, particularly preferably 0.1 to 1.2, and most preferably 0.5 to 1.2. In the solid electrolyte (II), the ratio of the content of the lithium salt to the content of the lithium-containing oxide is more preferably 0.001 to 1.5 in molar ratio, and the ratio of the content of the water is more preferably 1 to 12 in molar ratio. The molar amounts of the lithium-containing oxide, lithium salt, and water in the solid electrolyte (II) can be determined based on elemental analysis. Examples of elemental analysis include the elemental analysis techniques described below in the elemental composition of the solid electrolyte (II). The molar amount of water can also be determined by the Karl Fischer method or the like.

[0066] The water content in the solid electrolyte (II) is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. The water content in the solid electrolyte (II) is also preferably 30% by mass or less, and even more preferably 25% by mass or less. The water content in the solid electrolyte (II) is usually 5% by mass or more, preferably 10% by mass or more, and even preferably 15% by mass or more. Therefore, the water content in the solid electrolyte (II) is preferably 5 to 50% by mass, more preferably 5 to 45% by mass, even more preferably 10 to 40% by mass, even more preferably 10 to 35% by mass, even preferably 10 to 30% by mass, even preferably 15 to 30% by mass, even preferably 15 to 25% by mass. The lithium-containing oxide content in the solid electrolyte (II) is preferably 20 to 80% by mass, more preferably 20 to 75% by mass, and even more preferably 25 to 70% by mass. The content of the lithium salt in the solid electrolyte (II) is preferably 0.5 to 60 mass%, more preferably 1.0 to 55 mass%, even more preferably 2.0 to 50 mass%, and also preferably 5.0 to 50 mass%.

[0067] - Lithium-containing oxide - As described above, the lithium-containing oxide constituting the solid electrolyte (II) contains Li, B, and O. The lithium-containing oxide is Li ２＋ｘ B ４＋ｙ O ７＋ｚ (-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) is preferred. That is, when the molar amount of B is 4.00 and the molar amount of Li is expressed, it is preferred that the molar amount of Li is 1.58 to 2.49 (i.e., 1.7×4 / 4.3 to 2.3×4 / 3.7) and the molar amount of O is 6.23 to 7.89 (i.e., 6.7×4 / 4.3 to 7.3×4 / 3.7). In other words, when the molar amount of B contained is 4.00, it is preferred that the relative value of the molar amount of Li contained is 1.58 to 2.49 and the molar amount of O is 6.23 to 7.89. Typical examples of such lithium-containing oxides include lithium tetraborate (Li ２ B ４ O ７The lithium-containing oxide may be Li １＋ｘ B ３＋ｙ O ５＋ｚ A compound represented by (-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) is also preferred. As such a lithium-containing oxide, lithium triborate (LiB ３ O ５ The lithium-containing oxide may be Li ３＋ｘ B １１＋ｙ O １８＋ｚ Compounds represented by (-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) are also preferred. As such lithium-containing oxides, typically Li ３ B １１ O １８ The lithium-containing oxide may be Li ３＋ｘ B ７＋ｙ O １２＋ｚ Compounds represented by (-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) are also preferred. As such lithium-containing oxides, typically Li ３ B ７ O １２ Therefore, the lithium-containing oxide can be ２＋ｘ B ４＋ｙ O ７＋ｚ , the above Li １＋ｘ B ３＋ｙ O ５＋ｚ , Li ３＋ｘ B １１＋ｙ O １８＋ｚ , and Li ３＋ｘ B ７＋ｙ O １２＋ｚ In place of the lithium-containing oxide, or together with the lithium-containing oxide, LiBO may be used as the lithium-containing oxide. ５ , Li ２ B ７ O １２ , LiB ２ O ３ (OH)H ２ O and Li ４ B ８ O １３ (OH) ２(H ２ O) ３ At least one of the following may also be used. In the solid electrolyte (II), the lithium-containing oxide is preferably in an amorphous state. That is, in order for the solid electrolyte (II) to be in the above-mentioned amorphous state, the lithium-containing oxide is also preferably in a desired amorphous state in the solid electrolyte (II). Among these, the lithium-containing oxide is preferably lithium tetraborate in an amorphous state.

[0068] - Lithium Salt - The lithium salt constituting the solid electrolyte (II) used in the present invention is not particularly limited, and Li ＋ and an anion, and Li ＋ and an organic anion, and Li ＋ and a salt composed of an organic anion having a halogen atom is more preferred. The lithium salt constituting the solid electrolyte (II) used in the present invention preferably contains two or more elements selected from the group consisting of elements of Group 3 of the periodic table, elements of Group 4 of the periodic table, elements of Group 13 of the periodic table, elements of Group 14 of the periodic table, elements of Group 15 of the periodic table, elements of Group 16 of the periodic table, elements of Group 17 of the periodic table, and H. As the lithium salt constituting the solid electrolyte (II) used in the present invention, for example, a compound represented by the following formula (1) is preferred. Formula (1) LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ ) R ｆ１ and R ｆ２ R each independently represents a halogen atom or a perfluoroalkyl group. ｆ１ and R ｆ２ When R is a perfluoroalkyl group, the number of carbon atoms in the perfluoroalkyl group is not particularly limited. ｆ１ and R ｆ２ is preferably a halogen atom or a perfluoroalkyl group having 1 to 6 carbon atoms, more preferably a halogen atom or a perfluoroalkyl group having 1 to 2 carbon atoms, and even more preferably a halogen atom. When the volume of the terminal group increases, steric hindrance increases, which becomes a factor that inhibits ion conduction. ｆ１and R ｆ２ When is a perfluoroalkyl group, it is preferable that the number of carbon atoms is small.

[0069] The lithium salt that can be contained in the solid electrolyte (II) used in the present invention is not limited to the compound represented by the above formula (1). Examples of the lithium salt that can be contained in the solid electrolyte (II) used in the present invention are shown below.

[0070] (L-1) Inorganic lithium salt: LiPF ６ , LiBF ４ , LiAsF ６ , and LiSbF ６ Inorganic fluoride salts such as LiClO ４ , LiBrO ４ , and LiIO ４ perhalogenates such as LiAlCl ４ Inorganic chloride salts such as

[0071] (L-2) Fluorine-containing organic lithium salt: LiCF ３ SO ３ perfluoroalkanesulfonates such as LiN(CF ３ SO ２ ) ２ , LiN(CF ３ CF ２ SO ２ ) ２ , LiN(FSO ２ ) ２ (In this specification, Li(FSO ２ ) ２ N), and LiN(CF ３ SO ２ ) (C ４ F ９ SO ２ Fluorosulfonylimide salts or perfluoroalkanesulfonylimide salts such as LiC(CF ３ SO ２ ) ３ perfluoroalkanesulfonylmethide salts such as Li[PF ５ (CF ２ CF ２ CF ３ ) )], Li[PF ４ (CF ２ CF ２ CF３ ) ２ ], Li[PF ３ (CF ２ CF ２ CF ３ ) ３ ], Li[PF ５ (CF ２ CF ２ CF ２ CF ３ ) )], Li[PF ４ (CF ２ CF ２ CF ２ CF ３ ) ２ ] and Li[PF ３ (CF ２ CF ２ CF ２ CF ３ ) ３ Fluoroalkyl fluorophosphates (preferably perfluoroalkyl fluorophosphates) such as:

[0072] (L-3) Oxalatoborate salts: lithium bis(oxalato)borate and lithium difluorooxalatoborate.

[0073] In addition to the above, examples of lithium salts include LiF, LiCl, LiBr, LiI, and Li ２ SO ４ , LiNO ３ , Li ２ CO ３ , C.H. ３ COOLi, LiAsF ６ , LiSbF ６ , LiAlCl ４ , and LiB(C ６ H ５ ) ４ Among them, LiPF ６ , LiBF ４ , LiAsF ６ , LiSbF ６ , LiClO ４ , Li(R ｆ１１ SO ２ ), LiN(R ｆ１１ SO ２ ) ２ , LiN(FSO ２ )２ , or LiN(R ｆ１１ SO ２ ) (R ｆ１２ SO ２ ) is preferred, and LiPF ６ , LiBF ４ , LiN(R ｆ１１ SO ２ ) ２ , LiN(FSO ２ ) ２ , or LiN(R ｆ１１ SO ２ ) (R ｆ１２ SO ２ In these examples, R ｆ１１ and R ｆ１２ each independently represents a perfluoroalkyl group, and the number of carbon atoms is preferably 1 to 6, more preferably 1 to 2. In addition, as the lithium salt, LiNO ３ and 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide lithium are also preferred.

[0074] (Elemental Composition of Solid Electrolyte (II)) The component composition of the solid electrolyte (II) has been described based on the compounds constituting the solid electrolyte (II). Next, the solid electrolyte (II) will be described from the perspective of a preferred elemental composition. That is, in one embodiment of the electrode composition of the present invention, the solid electrolyte (II) does not have a "lithium-containing oxide" or a "lithium salt" as an invention-specifying matter, and can be specified by its elemental composition, for example, as follows: The solid electrolyte (II) used in the present invention preferably has a molar amount of Li of 1.58 to 3.49 (preferably 1.58 to 3.00, more preferably 1.90 to 3.00, and even more preferably 2.00 to 3.00) when the molar amount of B in the solid electrolyte (II) is 4.00. When the molar amount of B in the solid electrolyte (II) is 4.00, the molar amount of O is preferably 6.23 to 25.00 (preferably 6.50 to 23.00, more preferably 8.00 to 23.00, even more preferably 10.00 to 23.00, and particularly preferably 10.00 to 18.00). When the molar amount of B in the solid electrolyte (II) is 4.00, the molar amounts of elements other than B, Li, and O are each preferably 0.001 to 10.00 (preferably 0.001 to 6.00, more preferably 0.01 to 5.00).

[0075] The content of each element is determined by ordinary elemental analysis. As an elemental analysis method, for example, Li and B are analyzed by ICP-OES (inductively coupled plasma optical emission spectrometry), N and the like are analyzed by an inert gas fusion method, and, for example, F and S are analyzed by combustion ion chromatography. O can be calculated by adding up the analyzed masses of elements other than O and calculating the difference from the total amount of powder. Note that the method for calculating the content of each element is not limited to the above, and the content of one element may be estimated from the analysis results of the content of other elements, taking into account the structure of the compound used. From the content of each element calculated by elemental analysis, the molar amounts of Li, O, and other elements are calculated when the molar amount of B is 4.00.

[0076] In a preferred embodiment of the solid electrolyte (II), in addition to Li, B, and O, the solid electrolyte (II) further contains one or more, more preferably two or more, elements (E) selected from Group 4 elements, Group 15 elements, Group 16 elements, Group 17 elements, Si, C, Sc, and Y. Examples of Group 4 elements include Ti, Zr, Hf, and Rf. Examples of Group 15 elements include N, P, As, Sb, Bi, and Mc. Examples of Group 16 elements include S, Se, Te, Po, and Lv. Examples of Group 17 elements include F, Cl, Br, I, At, and Ts. Among these, it is preferable to contain one or more elements (E) selected from F, Cl, Br, I, S, P, Si, Se, Te, C, Sb, As, Sc, Y, Zr, Ti, Hf, and N, and more preferably to contain two or more. The number of types of element (E) contained in the solid electrolyte (II) may be three or more, preferably two to five, and more preferably two to four. A preferred embodiment of the solid electrolyte (II) is preferably containing two or more elements (E) selected from F, S, N, P, and C, more preferably containing two or more elements (E) selected from F, S, C, and N, and even more preferably containing three elements (E) of F, S, and N.

[0077] In the solid electrolyte (II) containing one or more (preferably two or more) of the above element (E), when the molar amount of B in the solid electrolyte (II) is 4.00 and the molar amount of Li is expressed, the molar amount of Li is preferably 1.58 to 3.49. In other words, when the molar amount of B contained is 4.00, the relative value of the molar amount of Li contained is preferably 1.58 to 3.49. In particular, when the molar amount of B contained in the solid electrolyte (II) is 4.00 and the molar amount of Li is expressed, the molar amount of Li is preferably 1.58 to 3.00, more preferably 1.90 to 3.00, and even more preferably 2.00 to 3.00.

[0078] In the solid electrolyte (II) containing one or more (preferably two or more) of the above element (E), when the molar amount of B in the solid electrolyte (II) is 4.00 and the molar amount of O is expressed, the molar amount of O is preferably 6.23 to 25.00. In other words, when the molar amount of B contained is 4.00, the relative value of the molar amount of O contained is preferably 6.23 to 25.00. In particular, when the molar amount of B contained in the solid electrolyte (II) is 4.00 and the molar amount of O is expressed, the molar amount of O is preferably 6.50 to 23.00, more preferably 8.00 to 23.00, more preferably 10.00 to 23.00, and particularly preferably 10.00 to 18.00.

[0079] In the solid electrolyte (II) containing one or more (preferably two or more) of the above-mentioned element (E), when the molar amount of B in the solid electrolyte (II) is 4.00 and the molar amount of the element (E) is expressed, the molar amount of each element (E) is preferably 0.001 to 10.00. In other words, when the molar amount of B contained is 4.00, the relative value of the molar amount of each element (E) contained is preferably 0.001 to 10.00. In particular, when the molar amount of B contained in the solid electrolyte (II) is 4.00 and the molar amount of the element (E) is expressed, the molar amount of each element (E) is preferably 0.001 to 6.00, and more preferably 0.01 to 5.00.

[0080] One preferred embodiment of the elemental composition of the solid electrolyte (II) containing one or more (preferably two or more) of the above element (E) is a solid electrolyte containing Li, B, O, F, S, and N, in which, when the molar amount of B is 4.00, the molar amount of Li is 1.58 to 3.49 (preferably 1.58 to 3.00, more preferably 1.90 to 3.00, and even more preferably 2.00 to 3.00), and the molar amount of O is 6.23 to 25.00 (preferably 6.50 to 2.00). 3.00, more preferably 8.00 to 23.00, even more preferably 10.00 to 23.00, particularly preferably 10.00 to 18.00), the molar amount of F is 0.001 to 10.00 (preferably 0.01 to 10.00), the molar amount of S is 0.001 to 2.00 (preferably 0.01 to 2.00), and the molar amount of N is 0.001 to 1.00 (preferably 0.005 to 1.00).

[0081] The solid electrolyte (II) used in the present invention is in the amorphous state described above, and as a result, the solid electrolyte (II) preferably exhibits the following properties in addition to the above-mentioned X-ray diffraction properties:

[0082] (solid ７ Li-NMR spectral characteristics) The solid electrolyte (II) is a solid ７ Li-NMR measurement is carried out at 20°C and 120°C, and the full width at half maximum ratio calculated from the obtained spectrum by the following method is preferably 50% or less, more preferably 40% or less, and even more preferably 35% or less. There is no particular lower limit, but it is often 10% or more. The above full width at half maximum ratio is determined by the solid electrolyte (II). ７ Li-NMR measurements are performed at 20°C and 120°C, respectively, and the full width at half maximum (FWHM 1) of a peak appearing in the chemical shift range of -100 to +100 ppm in the spectrum obtained by measurement at 20°C and the full width at half maximum (FWHM 2) of a peak appearing in the chemical shift range of -100 to +100 ppm in the spectrum obtained by measurement at 120°C are determined. The full width at half maximum (FWHM) of a peak is then calculated as a percentage {(FWHM 2 / FWHM 1) x 100}. The full width at half maximum (FWHM) of a peak means the width (ppm) at half the height (H) of the peak (H / 2). The above characteristics will be explained below with reference to FIG. 4. In FIG. 4, the solid electrolyte (II) ７ The figure shows an example of the spectrum obtained when Li-NMR measurement was performed at 20°C or 120°C. The solid line spectrum shown at the bottom of Figure 4 is the spectrum of the solid ７ The spectrum obtained when Li-NMR measurement was performed at 20°C, and the spectrum shown by the dashed line at the top of Figure 4 is the spectrum of the solid ７ This is the spectrum obtained when Li-NMR measurement was performed at 120°C. ７ In Li-NMR measurement, Li ＋When the mobility of Li is high, the peak obtained is sharper. In the embodiment shown in FIG. 4, when the spectrum at 20° C. is compared with the spectrum at 120° C., the spectrum at 120° C. is sharper. In other words, in the embodiment shown in FIG. 4, due to the presence of Li defects, etc., ＋ This indicates that the mobility of Li is increased. Such a solid electrolyte (II) is prone to plastic deformation due to the above-mentioned defect structure, and ＋ For reference, the solid state hopping of a typical lithium tetraborate crystal is ７ When Li-NMR measurements are performed at 20°C or 120°C, the spectrum measured at 20°C, represented by the solid line in the lower part of Fig. 5, and the spectrum measured at 120°C, represented by the dashed line in the upper part of Fig. 5, tend to have approximately the same shape. In other words, lithium tetraborate crystals are free of Li defects and, as a result, have a high elastic modulus and are not prone to plastic deformation.

[0083] The above solid ７ The Li-NMR measurement conditions are as follows: a 4 mm HX CP-MAS probe is used, and the measurement is performed using a single pulse method, with a 90° pulse width of 3.2 μs, an observation frequency of 155.546 MHz, an observation width of 1397.6 ppm, a repetition time of 15 sec, integration once, and a MAS rotation speed of 0 Hz.

[0084] The solid electrolyte (II) used in the present invention is a solid ７ When a spectrum obtained by Li-NMR measurement at 20°C is subjected to waveform separation of a first peak appearing in the range of -100 to +100 ppm, it is preferable that a second peak having a chemical shift in the range of -3 to 3 ppm and a full width at half maximum of 5 ppm or less is present, and the ratio of the area intensity of the second peak to the area intensity of the first peak is 0.5% or more. The ratio of the area intensity is more preferably 2% or more, even more preferably 5% or more, particularly preferably 10% or more, and most preferably 15% or more. In an embodiment of the present invention in which the solid electrolyte (II) contains water, the solid of the solid electrolyte (II) ７The Li-NMR spectrum characteristics tend to be as described above. There is no particular upper limit to the ratio of the area intensity, but it is often 50% or less.

[0085] The above characteristics will be explained below with reference to Fig. 6 and Fig. 7. Fig. 6 shows the solid electrolyte (II) ７ An example of a spectrum obtained when Li-NMR measurement was performed at 20°C is shown in Figure 6. As shown in Figure 6, a peak (corresponding to the first peak) is observed in the range of -100 to +100 ppm for the solid electrolyte (II), and a small peak is observed in the first peak, as surrounded by a dashed line, near the chemical shift of 0 ppm. As described above, Li ＋ When the mobility of the first peak is high, the peak is observed sharply, which is thought to be the influence of the second peak. Next, FIG. 7 shows the waveform separation of the first peak. As shown in FIG. 7, the first peak is separated into a small peak (corresponding to the second peak) represented by a solid line and a large peak represented by a dashed line. The second peak appears in a chemical shift range of -3 to 3 ppm and has a full width at half maximum of 5 ppm or less. For the solid electrolyte (II), the ratio of the area intensity of the second peak represented by the solid line in FIG. 7 to the area intensity of the first peak (the peak before waveform separation) represented by FIG. 6 ((area intensity of the second peak / area intensity of the first peak) × 100 (%)) is preferably within the above range. Examples of waveform separation methods include methods using known software, such as WaveMetrics' graph processing software Igor Pro.

[0086] (Raman Spectral Characteristics) The solid electrolyte (II) has a Raman spectrum of 600 to 850 cm －１ The coefficient of determination obtained by linear regression analysis by the least squares method in the wavenumber region of 0.9400 or more is preferably 0.9600 or more, more preferably 0.9800 or more. There is no particular upper limit, but it is usually 1.0000 or less.

[0087] The Raman spectral characteristics are described with reference to FIG. 8 . First, the Raman spectrum of the solid electrolyte (II) is acquired. Raman imaging is used to measure the Raman spectrum. Raman imaging is a microspectroscopic technique that combines Raman spectroscopy with microscopy. Specifically, it involves scanning excitation light over a sample to detect measurement light containing Raman scattered light and visualizing the distribution of components based on the intensity of the measurement light. The Raman imaging measurement conditions are 27°C, atmospheric air, 532 nm excitation light, 100x objective lens, mapping point scanning, 1 μm steps, 1 second exposure time per point, 1 integration, and a 70 μm × 50 μm measurement range. However, depending on the film thickness of the sample, the measurement range may be narrower. Furthermore, principal component analysis (PCA) is performed on the Raman spectral data to remove noise. Specifically, in the PCA process, spectra are recombined using components with an autocorrelation coefficient of 0.6 or higher.

[0088] An example of the Raman spectrum of the solid electrolyte (II) is shown in Fig. 8. In the graph shown in Fig. 8, the vertical axis represents the Raman intensity and the horizontal axis represents the Raman shift. －１ The coefficient of determination (coefficient of determination R ２ ) is calculated from 600 to 850 cm of the Raman spectrum in FIG. －１ In the wavenumber region, a regression line (thick line in FIG. 8) is obtained by the least squares method, and the coefficient of determination R ２ The coefficient of determination is calculated between 0 (no linear correlation) and 1 (perfect linear correlation of the measured values) depending on the linear correlation of the measured values. In the case of the solid electrolyte (II), as shown in FIG. 8, the coefficient of determination is calculated from 600 to 850 cm －１ As a result, a high coefficient of determination is observed. ２ corresponds to the square of the correlation coefficient (Pearson's product-moment correlation coefficient). More specifically, in this specification, the coefficient of determination R ２ is calculated by the following formula: １and y １ represents the wave number in the Raman spectrum and the Raman intensity corresponding to that wave number, and x ２ is the (additive) mean of the wavenumber, and y ２ represents the (additive) average of the Raman intensities.

[0089]

[0090] On the other hand, for reference, the Raman spectrum of a typical lithium tetraborate crystal is shown in Figure 9. As shown in Figure 9, in the case of a typical lithium tetraborate crystal, the peak at 716 to 726 cm －１ , and 771-785 cm －１ When such a peak is present, a peak is observed in the wave number region of 600 to 850 cm －１ When a linear regression analysis by the least squares method is performed in the wave number region, the coefficient of determination is calculated, and the coefficient of determination is less than 0.9400. In other words, the coefficient of determination being 0.9400 or more indicates that the solid electrolyte (II) contains almost no crystalline structure. As a result, the solid electrolyte (II) has the property of being easily plastically deformed and the property of Li ＋ It is believed that the compound has excellent hopping properties.

[0091] (Infrared absorption spectrum characteristics) The solid electrolyte (II) has an infrared absorption spectrum of 800 to 1600 cm －１ 3000 to 3500 cm for the maximum absorption intensity in the wave number region －１ The ratio of the maximum absorption intensity in the wave number region (3000 to 3500 cm －１ Maximum absorption intensity in the wavenumber region / 800 to 1600 cm －１ The ratio of the maximum absorption intensity in the wave number region of 3000 to 3500 cm of the infrared absorption spectrum is preferably 1 / 5 or more (0.2 or more). In particular, the ratio is preferably 3 / 10 or more, and more preferably 2 / 5 or more. There is no particular upper limit, but it is preferably 1 or less. －１ The OH stretching vibration mode is observed in the wavenumber region of 800 to 1600 cm －１In the wavenumber region of 800 to 1600 cm, the B-O stretching vibration mode is observed. In the solid electrolyte (II), a strong absorption intensity due to the OH stretching vibration mode is observed, indicating that a large number of OH groups and / or a large amount of water are contained. In such a solid electrolyte (II), lithium ions tend to move easily, resulting in improved ionic conductivity. －１ In the wavenumber region, vibrational modes originating from lithium salts can also be observed.

[0092] The infrared absorption spectrum measurement conditions can be as follows: Objective lens: 32x Cassegrain type (NA 0.65), Detector: MCT-A, Measurement range: 650 to 4000 cm －１ , resolution: 4cm －１ The infrared absorption spectrum obtained was compared with that of atmospheric water and CO. ２ Correction is performed to remove signals from the sample, and then offset correction is performed on the background to set the absorption intensity to 0. After vacuum drying at 40° C. for 2 hours, measurement is performed under atmospheric pressure.

[0093] The ionic conductivity (27°C) of the solid electrolyte (II) is not particularly limited, and from the viewpoint of application to various uses, it is 1.0 × 10 －５ S / cm or more is preferable, and 1.0 × 10 －４ S / cm or more is more preferable, and 1.0 × 10 －３ S / cm or more is more preferable, and 3.0×10 －３ The upper limit is not particularly limited, but is preferably 1.0 × 10 －２ In many cases, it is less than 1000 S / cm.

[0094] It is also preferable that the solid electrolyte (II) exhibits the following characteristics or physical properties.

[0095] (Mass Loss Rate) When the solid electrolyte (II) is heated to 800°C, the mass loss rate is preferably 20 to 40% by mass, more preferably 25 to 35% by mass. The mass loss caused by the heating is believed to be due to the removal of water contained in the solid electrolyte (II). The inclusion of such water in the solid electrolyte (II) can further improve lithium ion conductivity. In the heat treatment, the solid electrolyte (II) is heated at a temperature increase rate of 20°C / sec from 25°C to 800°C. A known thermogravimetric differential thermal analysis (TG-DTA) device can be used to measure the mass loss. The mass loss rate is calculated by {(mass at 25°C - mass at 800°C) / mass at 25°C} x 100. To measure the mass loss rate, the solid electrolyte (II) is previously subjected to vacuum drying at 40°C for 2 hours. The mass loss rate is measured in the atmosphere.

[0096] The electrode composition of the present invention may also contain a solid electrolyte other than the solid electrolyte (I). The other solid electrolyte refers to a solid electrolyte capable of moving ions therein. The solid electrolyte is preferably an inorganic solid electrolyte. Examples of the other solid electrolyte include oxide-based solid electrolytes other than the solid electrolyte (I), halide-based solid electrolytes, and hydride-based solid electrolytes, with oxide-based solid electrolytes being preferred.

[0097] <Active Material> The active material constituting the electrode composition of the present invention can be any positive electrode active material and negative electrode active material that can be used in conventional all-solid-state secondary batteries, without any particular limitations. The active material is particulate. The median diameter M of the active material is not particularly limited as long as it satisfies the above M / N ratio, and is preferably 0.2 to 30 μm, more preferably 0.5 to 20 μm, and particularly preferably 0.8 to 15 μm. The median diameter M of the active material can be measured using a laser diffraction / scattering particle size distribution analyzer. The method for controlling the median diameter M of the active material is not particularly limited and can be performed using conventional methods. The median diameter of the active material can be controlled using a pulverizer or classifier. For example, a mortar, ball mill, sand mill, vibration ball mill, satellite ball mill, planetary ball mill, swirling airflow jet mill, or sieve is preferably used. Wet pulverization in the presence of water or an organic solvent such as methanol can also be performed during pulverization. Classification is preferred to achieve the desired particle size. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as desired. Classification can be performed by either a dry method or a wet method. Preferably, similar to the solid electrolyte (I), the particle size can be controlled by reducing the particle size by mechanical milling and then classifying the particles with a sieve.

[0098] Preferred embodiments of the positive electrode active material and the negative electrode active material will be described below. In the following description, the case where the solid electrolyte (II) is used (the form of an all-solid-state lithium ion secondary battery) will be described as an example, but even when the solid electrolyte (I) containing an alkali metal or alkaline earth metal other than lithium is used, the description can be used as appropriate.

[0099] A preferred embodiment of the positive electrode active material will be described below.

[0100] (Positive Electrode Active Material) The positive electrode active material is preferably one that can reversibly insert and / or release lithium ions. The positive electrode active material is not particularly limited, and a transition metal oxide is preferred, and a transition metal oxide containing a transition metal element Ma (one or more elements selected from Co, Ni, Fe, Mn, Cu, and V) is more preferred. In addition, this transition metal oxide may be mixed with element Mb (a metal element in Group 1 (Ia) of the periodic table other than lithium, an element in Group 2 (IIa), an element such as Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, or B). The amount of element Mb mixed is preferably 0 to 30 mol% relative to the amount of transition metal element Ma (100 mol%). More preferably, the mixture is synthesized so that the Li / Ma molar ratio is 0.3 to 2.2. Specific examples of the transition metal oxide include (MA) transition metal oxides having a layered rock salt structure, (MB) transition metal oxides having a spinel structure, (MC) lithium-containing transition metal phosphate compounds, (MD) lithium-containing transition metal halide phosphate compounds, and (ME) lithium-containing transition metal silicate compounds. Among these, (MA) transition metal oxides having a layered rock salt structure are preferred, and LiCoO ２ or LiNi １／３ Co １／３ Mn １／３ O ２ is more preferred.

[0101] (MA) Examples of transition metal oxides having a layered rock salt structure include LiCoO ２ (lithium cobalt oxide [LCO]), LiNiO ２ (Lithium nickel oxide [LNO]), LiNi ０．８５ Co ０．１０ Al ０．０５ O ２ (nickel cobalt lithium aluminum oxide [NCA]), LiNi １／３ Mn １／３ Co １／３ O ２ (Lithium nickel manganese cobalt oxide [NMC]), LiNi ０．５ Mn ０．５ O ２ (lithium manganese nickel oxide), and Li ２ MnO ３-LiNiMnCoO ２ Examples include:

[0102] (MB) Examples of transition metal oxides having a spinel structure include LiMn ２ O ４ (LMO), LiNi ０．５ Mn １．５ O ４ ([LNMO]), LiCoMnO ４ , Li ２ FeMn ３ O ８ , Li ２ CuMn ３ O ８ , Li ２ CrMn ３ O ８ , and Li ２ NiMn ３ O ８ Examples include:

[0103] (MC) Examples of lithium-containing transition metal phosphate compounds include LiFePO ４ ([LFP]) and Li ３ Fe ２ (P.O. ４ ) ３ Olivine-type iron phosphate salts such as LiFeP ２ O ７ Iron pyrophosphate salts such as LiMnPO ４ Olivine-type manganese phosphate salts such as [(LMP)], LiNiPO ４ Olivine-type nickel phosphate salts such as [(LNP)], LiCoPO ４ Olivine-type cobalt phosphate salts such as [(LCP)], Li ２ CoP ２ O ７ Olivine-type cobalt pyrophosphate salts such as Li ３ V ２ (P.O. ４ ) ３ Examples of suitable vanadium phosphate salts include monoclinic NASICON type vanadium phosphate salts such as (lithium vanadium phosphate).

[0104] (MD) Examples of lithium-containing transition metal halide phosphate compounds include Li ２ FePO ４Fluorophosphate iron salts such as F, Li ２ MnPO ４ Fluorophosphate manganese salts such as F, and Li ２ CoPO ４ Fluorophosphate cobalt salts such as F are also included.

[0105] (ME) Examples of lithium-containing transition metal silicate compounds include Li ２ FeSiO ４ , Li ２ MnSiO ４ , and Li ２ CoSiO ４ Examples include:

[0106] The positive electrode active material obtained by the baking method may be used after being washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.

[0107] The positive electrode active material may be surface-coated with a surface coating agent, sulfur or phosphorus, or further with actinic rays, in the same manner as the negative electrode active material described below.

[0108] The positive electrode active material may be used alone or in combination of two or more kinds.

[0109] Among these, LiCoO is used as the positive electrode active material. ２ (LCO), LiMn ２ O ４ (LMO), and LiNi １／３ Mn １／３ Co １／３ O ２ (NMC) is preferred.

[0110] A preferred embodiment of the negative electrode active material will be described below.

[0111] (Negative electrode active material) The negative electrode active material is preferably one that can reversibly insert and release lithium ions. The negative electrode active material is not particularly limited, and examples thereof include carbonaceous materials, oxides of metal elements or semimetal elements, lithium alone, lithium alloys, and negative electrode active materials that can form alloys with lithium.

[0112] The carbonaceous material used as the negative electrode active material is a material essentially composed of carbon. Examples include carbon black such as petroleum pitch and acetylene black (AB), graphite (natural graphite and artificial graphite such as vapor-grown graphite), and carbonaceous materials obtained by calcining various synthetic resins such as PAN (polyacrylonitrile)-based resins or furfuryl alcohol resins. Further examples include various carbon fibers such as PAN-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated PVA (polyvinyl alcohol)-based carbon fibers, lignin carbon fibers, glassy carbon fibers, and activated carbon fibers, as well as mesophase microspheres, graphite whiskers, and flat graphite. These carbonaceous materials can also be divided into difficult-to-graphitize carbonaceous materials (also called hard carbon) and graphite-based carbonaceous materials depending on the degree of graphitization. Furthermore, the carbonaceous material preferably has the interplanar spacing, density, or crystallite size described in JP-A-62-022066, JP-A-2-006856, and JP-A-3-045473. The carbonaceous material does not need to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-090844 and graphite having a coating layer described in JP-A-6-004516 can also be used. As the carbonaceous material, hard carbon or graphite is preferred, and graphite is more preferred.

[0113] The oxide of a metal element or a metalloid element used as the negative electrode active material is not particularly limited as long as it is an oxide that can absorb and release lithium. ３ O ４Examples of suitable oxides include oxides of metal elements (metal oxides), composite oxides of metal elements, composite oxides of metal elements and metalloid elements, and oxides of metalloid elements (metalloid oxides). Composite oxides of metal elements and composite oxides of metal elements and metalloid elements are collectively referred to as metal composite oxides. Among these oxides, amorphous oxides are preferred, and chalcogenides, which are reaction products of metal elements and elements of Group 16 of the periodic table, are also preferred. In the present invention, the term "metalloid element" refers to an element that exhibits properties intermediate between metal elements and nonmetallic elements, and typically includes six elements: boron, silicon, germanium, arsenic, antimony, and tellurium, as well as three elements: selenium, polonium, and astatine. The term "amorphous" in the context of amorphous oxides refers to an oxide that exhibits a broad scattering band with a peak in the 2θ range of 20 to 40° in an X-ray diffraction method using CuKα radiation, and may also have crystalline diffraction lines. The strongest intensity of the crystalline diffraction lines observed at 2θ values ​​of 40 to 70° is preferably 100 times or less, more preferably 5 times or less, the diffraction line intensity at the apex of a broad scattering band observed at 2θ values ​​of 20 to 40°, and even more preferably no crystalline diffraction lines.

[0114] Among the compound group consisting of the amorphous oxides and chalcogenides, amorphous oxides or the chalcogenides of metalloid elements are more preferred, and (composite) oxides or chalcogenides consisting of one element selected from Groups 13 (IIIB) to 15 (VB) of the periodic table (e.g., Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi) or a combination of two or more of these elements are even more preferred. ２ O ３ , GeO, PbO, PbO ２ , Pb ２ O ３ , Pb ２ O ４ , Pb ３ O ４ , Sb ２ O ３ , Sb ２ O ４ , Sb ２ O ８ Bi ２ O ３, Sb ２ O ８ Si ２ O ３ , Sb ２ O ５ , Bi ２ O ３ , Bi ２ O ４ , GeS, PbS, PbS ２ , Sb ２ S ３ or Sb ２ S ５ As a negative electrode active material that can be used in combination with the amorphous oxide negative electrode active material mainly containing Sn, Si, or Ge, a carbonaceous material that can occlude and / or release lithium ions or lithium metal, lithium alone, a lithium alloy, or a negative electrode active material that can be alloyed with lithium is preferred.

[0115] The oxides of metal elements or semimetal elements (particularly metal (composite) oxides) and the chalcogenides preferably contain at least one of titanium and lithium as a constituent component in terms of high current density charge / discharge characteristics. Examples of metal composite oxides containing lithium (lithium composite metal oxides) include composite oxides of lithium oxide and the metal oxides, metal composite oxides, or chalcogenides. More specifically, Li ２ SnO ２ The negative electrode active material (for example, a metal oxide) preferably contains titanium element (titanium oxide). Specifically, Li ４ Ti ５ O １２ Lithium titanate (LTO) is preferred in that it has excellent rapid charge / discharge characteristics due to small volume fluctuations during absorption and desorption of lithium ions, and it can suppress electrode deterioration and improve the life of the all-solid-state lithium ion secondary battery.

[0116] The lithium alloy as the negative electrode active material is not particularly limited as long as it is an alloy that is commonly used as a negative electrode active material for all-solid-state lithium ion secondary batteries, and examples thereof include lithium aluminum alloys.

[0117] The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is one commonly used as a negative electrode active material for all-solid-state lithium-ion secondary batteries. Examples of the negative electrode active material include negative electrode active materials (alloys) containing silicon or tin, as well as metals such as Al and In. A negative electrode active material containing silicon (silicon-containing active material) is preferred, as it enables higher battery capacity. A silicon-containing active material having a silicon content of 50 mol% or more of the total constituent elements is more preferred. Generally, negative electrodes containing these negative electrode active materials (e.g., Si negative electrodes containing silicon-containing active materials, Sn negative electrodes containing tin-containing active materials) can absorb more Li ions than carbon negative electrodes (e.g., graphite and acetylene black). That is, the amount of Li ions absorbed per unit mass increases. This increases the battery capacity. As a result, the battery operating time can be extended.

[0118] Examples of silicon-containing active materials include silicon materials such as Si and SiOx (0<x≦1), and silicon-containing alloys containing titanium, vanadium, chromium, manganese, nickel, copper, or lanthanum (e.g., LaSi ２ , VSi ２ , La—Si, Gd—Si, and Ni—Si), or textured active materials (e.g., LaSi ２ / Si). Other examples include SnSiO ３ , and SnSiS ３ Examples of the active material containing silicon and tin include: SiOx itself can be used as a negative electrode active material (semi-metal oxide); and since SiOx generates Si during operation of an all-solid-state lithium-ion secondary battery, it can be used as a negative electrode active material (precursor material) that can be alloyed with lithium. Examples of the negative electrode active material containing tin include Sn, SnO, and SnO. ２ , SnS, SnS ２ and active materials containing the silicon and tin elements.

[0119] In terms of battery capacity, the negative electrode active material is preferably a negative electrode active material that can be alloyed with lithium, more preferably the above-mentioned silicon material or silicon-containing alloy (alloy containing silicon element), and even more preferably silicon (Si) or a silicon-containing alloy.

[0120] It is also preferable to use titanium-niobium composite oxide as the negative electrode active material. Titanium-niobium composite oxide has a high theoretical volumetric capacity density, and is expected to enable a long life and rapid charging. Examples of titanium-niobium composite oxides include TiNb ２ O ７ ([TNO]) can be mentioned.

[0121] The negative electrode active material may be used alone or in combination of two or more kinds.

[0122] The surface of the negative electrode active material may be coated with an oxide such as another metal oxide, or a carbon-based material. These surface coating layers can function as an interface resistance stabilizing layer. Examples of surface coating agents include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si, or Li. Specific examples include titanate spinel, tantalum-based oxides, niobium-based oxides, and lithium niobate-based compounds, such as Li ４ Ti ５ O １２ , Li ２ Ti ２ O ５ , LiTaO ３ , LiNbO ３ , LiAlO ２ , Li ２ ZrO ３ , Li ２ WO ４ , Li ２ TiO ３ , Li ２ B ４ O ７ , Li ３ P.O. ４ , Li ２ MoO ４ , Li ３ BO ３ , LiBO ２ , Li ２ CO ３ , Li ２ SiO３ , SiO ２ , TiO ２ , ZrO ２ , Al ２ O ３ , B ２ O ３ , and Li ３ AlF ６ Carbon-based materials such as C, SiC, and SiOC (carbon-doped silicon oxide) can also be used as the surface coating material. The surface of the negative electrode active material may be surface-treated with sulfur or phosphorus. Furthermore, the particle surface of the negative electrode active material may be surface-treated with active light or active gas (e.g., plasma) before or after the surface coating.

[0123] Among these, the negative electrode active material is Li ４ Ti ５ O １２ (LTO) is preferred.

[0124] <Other Components> The electrode composition of the present invention may contain components (other components) other than the solid electrolyte and the active material. For example, a conductive additive may be included. Examples of conductive additives include electron-conductive materials such as graphites (e.g., natural graphite and artificial graphite), carbon blacks (e.g., acetylene black, ketjen black, and furnace black), amorphous carbon (e.g., needle coke), fibrous carbon (e.g., vapor-grown carbon fiber and carbon nanotubes), and carbonaceous materials (e.g., graphene and fullerene). Conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives may also be used. In addition to the above conductive additives, conventional conductive additives that do not contain carbon atoms, such as metal powder or metal fiber, may also be used. A conductive additive refers to a material that does not intercalate or deintercalate Li during charging and discharging of a battery and does not function as an active material. Therefore, among conductive additives, those that can function as an active material in the active material layer when the battery is charged and discharged are classified as active materials rather than conductive additives. Whether or not a conductive additive functions as an active material when the battery is charged and discharged is not uniquely determined, but is determined by its combination with the active material. The content of the conductive additive in the solid content of the electrode composition for the positive electrode active material layer is not particularly limited, but is preferably, for example, 0 to 10 mass %, and more preferably 1 to 8 mass %. The content of the conductive additive in the solid content of the electrode composition for the negative electrode active material layer is not particularly limited, but is preferably, for example, 0 to 10 mass %, and more preferably 1 to 8 mass %.

[0125] Other components include binders. The binder may include a binder made of an organic polymer. The organic polymer constituting the binder may be particulate or non-particulate. By including a binder, it is possible to more reliably prevent cracks and the like from occurring in the active material layer. The organic polymer constituting the binder may be a typical organic polymer used in electrode compositions. The organic polymer may be water-soluble or water-insoluble. Examples of water-soluble polymers include sodium polyacrylate (PAA-Na), water-soluble alginic acid derivatives, cellulose-based polymers such as carboxymethyl cellulose, and polyacrylamide. The binder contained in the electrode composition of the present invention may include a copolymer latex. The type of copolymer latex is not particularly limited, and examples include aqueous dispersions of conjugated diene copolymers such as styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, methyl methacrylate-butadiene copolymers, and vinylpyridine-butadiene copolymers, acrylic polymers, vinyl acetate polymers, ethylene-vinyl acetate copolymers, chloroprene polymers, and natural rubber, among which conjugated diene copolymers and acrylic copolymers are preferred. One or more of these can be used. The median diameter of the copolymer latex measured by photon correlation method is preferably 10 to 500 nm, more preferably 50 to 300 nm, and even more preferably 100 to 200 nm.

[0126] As other components, the above-mentioned lithium salt may be contained separately, rather than as a component of the solid electrolyte (I).

[0127] Other components include a liquid medium. The electrode composition of the present invention preferably contains water, but may contain a liquid medium other than water. Examples of liquid media other than water include organic solvents that are miscible with water without phase separation when mixed with water (hereinafter referred to as water-soluble organic solvents), and specific examples include N-methylpyrrolidone, methanol, ethanol, acetone, and tetrahydrofuran.

[0128] When the electrode composition of the present invention contains a liquid medium, the content of the solids (components other than the liquid medium, such as the solid electrolyte (I) and the active material) in the electrode composition of the present invention can be adjusted to, for example, 10 to 90 mass%, preferably 20 to 80 mass%, and more preferably 30 to 70 mass%. The concentration of the solids in the electrode composition of the present invention can also be adjusted to 10 to 54 mass%, preferably 20 to 53 mass%, more preferably 30 to 52 mass%, and even more preferably 40 to 52 mass%.

[0129] When the electrode composition of the present invention is an electrode composition for a positive electrode active material layer, the content of the positive electrode active material in the solid content of the electrode composition is not particularly limited, but is preferably 10 to 97 mass%, more preferably 30 to 95 mass%, even more preferably 40 to 93 mass%, and particularly preferably 50 to 90 mass%. When the electrode composition of the present invention is an electrode composition for a positive electrode active material layer, the content of the solid electrolyte (I) in the solid content of the electrode composition is not particularly limited, but is preferably 50 to 99.9 mass%, more preferably 70 to 99.5 mass%, and even more preferably 90 to 99 mass% as the total content with the positive electrode active material. When the electrode composition of the present invention is an electrode composition for a negative electrode active material layer, the content of the negative electrode active material in the solid content of the electrode composition is not particularly limited, but is preferably 10 to 90 mass%, more preferably 20 to 85 mass%, even more preferably 30 to 80 mass%, and particularly preferably 40 to 75 mass%. When the electrode composition of the present invention is an electrode composition for a negative electrode active material layer, the content of the solid electrolyte (I) in the solid content of the electrode composition is not particularly limited, and the total content together with the negative electrode active material is preferably 50 to 99.9 mass%, more preferably 70 to 99.5 mass%, and even more preferably 90 to 99 mass%. The respective contents in the solid content are substantially the same in an active material layer formed using the electrode composition and in a secondary battery using the same.

[0130] The electrode composition of the present invention can be obtained by mixing the solid electrolyte (I) and the active material, and, if necessary, the above-mentioned other components.

[0131] [Electrode Sheet for All-Solid-State Secondary Battery] The electrode sheet for an all-solid-state secondary battery of the present invention (hereinafter also referred to as the electrode sheet of the present invention) has an active material layer containing an amorphous solid electrolyte and an active material. This solid electrolyte contains a metal-containing oxide containing at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water. That is, the electrode sheet of the present invention contains the above-mentioned solid electrolyte (I) and an active material in the active material layer. Furthermore, in the electrode sheet of the present invention, the porosity of the active material layer is controlled to 0.1 to 15%. The electrode sheet of the present invention has an active material layer whose porosity is controlled within the above-mentioned low range and yet exhibits excellent flexibility. That is, since the solid electrolyte (I) is an oxide-based solid electrolyte that can easily undergo plastic deformation under pressure, plastic deformation of the solid electrolyte (I) causes adhesion between the solid electrolytes (I) and further between the active material, and it is believed that the electrode sheet exhibits high flexibility in this state despite the reduced porosity. Furthermore, since the solid electrolyte (I) itself is soft and plastically deforms, acting as a binder and contributing to improving the adhesion between particles, it is possible to form a layer without using a binder such as an organic polymer. The active material layer of the electrode sheet of the present invention is preferably formed by pressure treating a layer formed using the electrode composition of the present invention. In this preferred embodiment of the electrode sheet, the active material layer contains the solid electrolyte (I) and an active material, the porosity of the active material layer is controlled within the above range, and the ratio of the median diameter M of the active material to the median diameter N of the solid electrolyte is 1.2≦M / N≦5.0.

[0132] In the electrode sheet of the present invention, from the viewpoint of reducing resistance, the porosity of the active material layer is preferably 0.1 to 10%, more preferably 0.1 to 5%. The porosity of the active material layer can be measured by the method described in the Examples. Specifically, the porosity of the active material layer can be calculated by performing a binarization process using the open-source, public domain image processing software "ImageJ" to color voids black and other areas white, and then dividing the area of ​​the black areas by the total area. Here, the porosity is typically measured in an active material layer formed through pressure treatment.

[0133] Electrode sheets for secondary batteries are generally composed of a current collector and an active material layer. However, the electrode sheet of the present invention may be a single active material layer if the active material layer (e.g., a layer formed using the electrode composition of the present invention) also functions as a current collector. The active material layer of the electrode sheet of the present invention may be a positive electrode active material layer containing a positive electrode active material, or a negative electrode active material layer containing a negative electrode active material. The thickness of the active material layer constituting the electrode sheet of the present invention is not particularly limited and may be, for example, 10 to 200 μm, preferably 15 to 150 μm. The thickness of the current collector constituting the electrode sheet of the present invention is also not particularly limited and may be, for example, 5 to 50 μm, preferably 8 to 30 μm.

[0134] The current collector constituting the electrode sheet of the present invention is an electron carrier and is usually sheet-shaped. The current collector can be appropriately selected depending on the active material. Examples of materials constituting the positive electrode current collector include aluminum (Al), aluminum alloys (Al alloys), stainless steel, nickel, and titanium, with aluminum or aluminum alloys being preferred. Examples of the positive electrode current collector include aluminum or stainless steel surfaces treated with carbon, nickel, titanium, or silver (thin films formed thereon). Examples of materials constituting the negative electrode current collector include aluminum, copper (Cu), copper alloys, stainless steel, nickel, and titanium, with aluminum, copper, copper alloys, or stainless steel being preferred. Examples of the negative electrode current collector include aluminum, copper, copper alloys, or stainless steel surfaces treated with carbon, nickel, titanium, or silver.

[0135] The electrode sheet of the present invention may have other layers, for example, a protective layer such as a release sheet, or a coating layer. The electrode sheet of the present invention can be suitably used as a material for constituting an anode active material layer or a cathode active material layer of a secondary battery, or as a laminate of an anode current collector and an anode active material layer (anode layer) or a laminate of a cathode current collector and a cathode active material layer (cathode layer).

[0136] [All-Solid-State Secondary Battery] The all-solid-state secondary battery of the present invention (hereinafter also referred to as the "secondary battery of the present invention") is an all-solid-state secondary battery comprising a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer arranged in this order, wherein at least one of the positive electrode active material layer and the negative electrode active material layer is an active material layer containing an amorphous solid electrolyte and an active material (a positive electrode active material in the case of the positive electrode active material layer, and a negative electrode active material in the case of the negative electrode active material layer). The amorphous solid electrolyte contains a metal-containing oxide containing at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water. That is, the secondary battery of the present invention has an active material layer (hereinafter also referred to as active material layer J) containing the solid electrolyte (I) and an active material as at least one of the positive electrode active material layer and the negative electrode active material layer. Furthermore, the porosity of the active material layer J is controlled to 0.1 to 15%. The porosity of the active material layer J is the same as the porosity of the active material layer of the electrode sheet of the present invention, and the preferred range thereof is also the same.

[0137] In the secondary battery of the present invention, it is sufficient that either the positive electrode active material layer or the negative electrode active material layer is the active material layer J. The remaining positive electrode active material layer and negative electrode active material layer can be the same as the positive electrode active material layer and negative electrode active material layer in a typical all-solid-state secondary battery. Both the positive electrode active material layer and the negative electrode active material layer can also be the active material layer J. The thicknesses of the positive electrode active material layer and the negative electrode active material layer constituting the secondary battery of the present invention are the same as the thicknesses of the active material layers in the electrode sheet of the present invention, and the preferred ranges are also the same.

[0138] The solid electrolyte layer constituting the secondary battery of the present invention is not particularly limited and can have the same configuration as the solid electrolyte layer in a typical all-solid-state secondary battery. From the viewpoint of improving ionic conductivity and flexibility, it is preferable to use the above-mentioned solid electrolyte (I), and it is more preferable to use the solid electrolyte (II) as the solid electrolyte. In addition to the solid electrolyte (I), the solid electrolyte layer may contain the above-mentioned "binder" and the above-mentioned "other solid electrolytes." The thickness of the solid electrolyte layer constituting the secondary battery of the present invention is not particularly limited and can be, for example, 5 to 1000 μm, and preferably 10 to 100 μm.

[0139] The secondary battery of the present invention is preferably a so-called all-solid-state lithium-ion secondary battery. It is preferable to use a solid electrolyte (II) in any of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer. The materials, members, etc. used in the secondary battery of the present invention are not particularly limited, except that the secondary battery of the present invention has the specific positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer. Materials and members used in ordinary all-solid-state secondary batteries can be used.

[0140] [Method for Manufacturing Electrode Sheet for All-Solid-State Secondary Battery] The method for manufacturing an electrode sheet for a secondary battery of the present invention can be performed by referring to a conventional method for manufacturing an electrode sheet for an all-solid-state secondary battery, except that an active material layer is formed by pressurizing a layer formed using the electrode composition of the present invention. That is, the method for manufacturing an electrode sheet of the present invention includes forming an active material layer by pressurizing a layer formed using the electrode composition of the present invention. The pressurization is performed so that the porosity of the active material layer falls within the above-mentioned range. Specifically, the active material layer can be formed by applying the electrode composition (electrode slurry) of the present invention to form a layer, and then subjecting this layer to a pressurization treatment. When a current collector is used, the active material layer can be formed by applying the electrode composition of the present invention to the current collector to form a coating layer, drying it as necessary, and then subjecting the entire layer to a pressurization treatment. Alternatively, the active material layer can be formed by simply pressurizing the electrode composition of the present invention to form a layer. For example, the active material layer can be formed by filling a powder of the electrode composition of the present invention into a predetermined mold and pressurizing it. The conditions for the pressure treatment are not particularly limited as long as the desired porosity can be achieved when the active material layer described below is formed. However, pressure treatment at 1 to 300 MPa is preferred, and pressure treatment at 3 to 200 MPa is more preferred. The pressure treatment may be performed on the electrode composition layer (active material layer before pressure treatment) alone, or on the electrode composition layer laminated with other layers. For example, pressure treatment may be performed after forming a laminate of an electrode composition layer for forming a positive electrode active material layer, a solid electrolyte layer, and an electrode composition layer for forming a negative electrode active material layer. The pressure treatment method is not particularly limited, and may be performed by pressing or by sealing a container under pressure. When the electrode composition contains a liquid medium, the coating layer may be dried before pressure treatment. The drying method is not particularly limited, and may be performed using a desiccator, vacuum drying, vacuum freeze-drying, or heat treatment.

[0141] [Method for manufacturing all-solid-state secondary battery] The method for manufacturing a secondary battery of the present invention can be performed with reference to a method for manufacturing a conventional all-solid-state secondary battery, except that at least one of a positive electrode active material layer and a negative electrode active material layer is formed by pressurizing a layer formed using the electrode composition of the present invention. That is, the method for manufacturing a secondary battery of the present invention is a method for manufacturing an all-solid-state secondary battery comprising a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer arranged in this order, and includes forming at least one of the positive electrode active material layer and the negative electrode active material layer by pressurizing a layer formed using the battery electrode composition of the present invention.

[0142] The positive electrode active material layer and the negative electrode active material layer can be formed by appropriately referring to the description in the above [Method for manufacturing electrode sheet for all-solid-state secondary battery].

[0143] The method for forming a laminate having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer arranged in this order is not particularly limited. For example, a positive electrode-forming composition (positive electrode slurry) containing a positive electrode active material is applied to a metal foil serving as a positive electrode current collector layer to form a positive electrode active material layer. Next, a solid electrolyte layer-forming dispersion (solid electrolyte slurry) containing a solid electrolyte is applied to the positive electrode active material layer to form a solid electrolyte layer. Further, a negative electrode-forming composition (negative electrode slurry) containing a negative electrode active material is applied to the solid electrolyte layer to form a negative electrode active material layer. An anode current collector layer (metal foil) is then overlaid on the anode active material layer. If necessary, the entire assembly is subjected to a pressure treatment to obtain an all-solid-state secondary battery as shown in FIG. 1 . Alternatively, an all-solid-state secondary battery can be produced by reversing the layer formation method, forming a negative electrode active material layer, a solid electrolyte layer, and a positive electrode active material layer on the anode current collector layer, overlaying a positive electrode current collector layer (metal foil) on the positive electrode active material layer, and subjecting the entire assembly to a pressure treatment if necessary.

[0144] Alternatively, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer may be separately prepared, and then these layers may be laminated between a positive electrode current collector layer and a negative electrode current collector layer in the following order: positive electrode current collector layer (metal foil), positive electrode active material layer, solid electrolyte layer, negative electrode active material layer, negative electrode current collector layer (metal foil), and pressure applied as necessary to produce an all-solid-state lithium-ion secondary battery. In this case, a support such as a nonwoven fabric may be provided as necessary during the formation of each layer, making each layer a free-standing film. Note that the support in the free-standing film is usually preferably removed before use when laminating the layers to produce an all-solid-state lithium-ion secondary battery.

[0145] The conditions for the pressure treatment for forming the active material layer are not particularly limited as long as the desired porosity can be achieved in the resulting active material layer, and the pressure treatment can be performed under the same conditions and by the same method as the pressure treatment in the manufacturing method of the electrode sheet of the present invention. The pressure treatment may be performed on the layer itself formed using the electrode composition, or, when the layers are laminated as described above, on the laminate.

[0146] The method for producing the secondary battery of the present invention is not limited to the method described above, as long as the secondary battery defined by the present invention can be obtained.

[0147] In the production of the secondary battery of the present invention, even if a sulfide-based solid electrolyte is not used as the solid electrolyte, the oxide-based solid electrolyte (I) that can be easily plastically deformed by pressure allows for the formation of layers with reduced interfacial resistance between solid particles or between layers. The solid electrolyte (I) itself is soft and plastically deformable, and acts as a binder, contributing to improved adhesion between solid particles or between layers, so it is possible to form layers without using a binder such as an organic polymer.

[0148] The secondary battery of the present invention is preferably initialized after manufacture or before use. The initialization method is not particularly limited, and can be performed, for example, by performing initial charge / discharge under an increased pressure and then releasing the pressure until the pressure falls within the range of the pressure conditions during use of the secondary battery.

[0149] [Applications of All-Solid-State Lithium-Ion Secondary Batteries] The secondary battery of the present invention can be used in a variety of applications. While there are no particular limitations on the application, examples of applications include notebook computers, pen-input PCs, mobile PCs, e-book players, mobile phones, cordless phone handsets, pagers, handheld terminals, mobile fax machines, mobile copiers, mobile printers, headphone stereos, video camcorders, LCD TVs, handheld vacuum cleaners, portable CD players, mini-discs, electric shavers, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, and backup power supplies. Other consumer applications include automobiles, electric vehicles, motors, lighting fixtures, toys, game consoles, road conditioners, clocks, flash devices, cameras, and medical devices (pacemakers, hearing aids, shoulder massagers, etc.). Furthermore, the battery can be used for various military and space applications. It can also be combined with solar cells.

[0150] The present invention will be described in more detail based on examples, but the present invention is not to be construed as being limited to these examples.

[0151] [Reference Example 1: Preparation by the above steps 0, 1A to 3A] Powdered Li was prepared using a ball mill (Fritsch Planetary Ball Mill P-7). ２ B ４ O ７ Crystals (LBO powder) (manufactured by Rare Metallic Co., Ltd.) were ball milled under the following conditions: pot: stabilized zirconia (YSZ) (45 mL), milling balls: YSZ (average particle size: 5 mm, number: 50), rotation speed: 370 rpm (revolutions per minute), amount of LBO powder: 1 g, atmosphere: air, and ball mill treatment time: 100 hours, to obtain a finely divided lithium-containing oxide (hereinafter also referred to as "fine lithium-containing oxide"). 0.05 g of LiFSI (chemical formula: Li(FSO ２ ) ２N) was added (5% by mass relative to the fine particles of the lithium-containing oxide), and the mixture was ball milled for another 100 hours. The obtained powder was added to water so that the powder concentration was 42% by mass, and ultrasonically dispersed for 30 minutes. Subsequently, the obtained dispersion was transferred to a glass petri dish and dried at 120°C for 2 hours in the atmosphere to obtain a solid electrolyte film. Subsequently, the obtained film was peeled off to obtain a powdered solid electrolyte (II)-1.

[0152] <Preparation and Evaluation of Compacted Solid Electrolyte> The powdered solid electrolyte (II)-1 obtained above was compacted at 27°C (room temperature) under an effective pressure of 220 MPa to obtain a compacted solid electrolyte (compacted powder 1). The compacted powder 1 had a cylindrical shape with a diameter of 10 mm and a thickness of 1 mm. The ionic conductivity of the compacted powder 1 obtained was measured, and the ionic conductivity of the compacted powder 1 was found to be 1.5 x 10 at 27°C. －４ S / cm and 4.0 × 10 at 60°C －４ S / cm.

[0153] The ionic conductivity of the solid electrolyte (II)-1 was calculated by placing two electrodes made of In foil so as to sandwich the powder compact 1, measuring the AC impedance between the two In electrodes in a measurement frequency range of 1 Hz to 1 MHz under conditions of a measurement temperature of 27°C or 60°C and an applied voltage of 50 mV, and analyzing the arc diameter of the obtained Cole-Cole plot (Nyquist plot).

[0154] X-ray diffraction measurement of solid electrolyte (II)-1 was carried out using CuKα radiation as described above. The measurement conditions were 0.01° / step, 3° / min. As a result, it was found that the X-ray diffraction characteristics described above were satisfied, and solid electrolyte (II)-1 was found to be in an amorphous state.

[0155] Using the solid electrolyte (II)-1 obtained above, X-ray total scattering measurements were performed using an SPring-8 L04B2 (accelerating voltage: 61.4 keV, wavelength: 0.2019 Å). The sample was sealed in a 2 mmφ or 1 mmφ Kapton capillary, and the experiment was performed. The obtained data was Fourier transformed as described above to obtain a reduced pair distribution function. As a result of the analysis, in the reduced pair distribution function G(r) obtained from the X-ray total scattering measurements, within the r range of 1 to 5 Å, a first peak with a peak top of G(r) exceeding 1.0 and located at 1.43 Å, and a second peak with a peak top of G(r) exceeding 1.0 and located at 2.40 Å, were confirmed. On the other hand, in solid electrolyte (II)-1, the peaks attributed to the B-O distance and B-B distance observed in general lithium tetraborate crystals were maintained. General lithium tetraborate crystals have a peak top of BO. ４ Tetrahedron and BO ３ It is assumed that the structure is a 1:1 triangle structure (diborate structure), and that this structure is maintained in solid electrolyte (II)-1.

[0156] The solid electrolyte (II)-1 obtained above ７ The solid electrolyte (II)-1 is measured by Li-NMR at 20°C. ... ７ The ratio of the full width at half maximum (full width at half maximum 2) of the peak appearing in the chemical shift range of −100 to +100 ppm in the spectrum obtained by Li-NMR measurement at 120° C. {(full width at half maximum 2 / full width at half maximum 1)×100} was 33%. ７ When a spectrum obtained by Li-NMR measurement at 20°C was subjected to waveform separation of a first peak appearing in the range of -100 to +100 ppm, a second peak having a full width at half maximum of 5 ppm or less in a chemical shift range of -3 to 3 ppm was found, and the ratio of the area intensity of the second peak to the area intensity of the first peak was 4%.

[0157] The solid electrolyte (II)-1 obtained above was subjected to infrared absorption spectroscopy under the conditions described above. In the obtained infrared absorption spectrum, －１ 3000 to 3500 cm for the maximum absorption intensity in the wave number region －１ The ratio of the maximum absorption intensities in the wave number region of 0.72 was found to be 0.72.

[0158] In the Raman spectrum of the solid electrolyte (II)-1 obtained above, －１ The coefficient of determination obtained by linear regression analysis by the least squares method in the wavenumber region of 0.9974 was 0.9974. The mass loss rate when the solid electrolyte (II)-1 was heated from 25°C to 800°C as described above was 29.8%.

[0159] Regarding the analysis of each element in the obtained solid electrolyte (II)-1, lithium and boron were quantitatively analyzed by ICP-OES, and fluorine and sulfur were quantitatively analyzed by combustion ion chromatography (combustion IC). N was estimated from the analyzed mass of sulfur taking into account the atomic weight of each element in the Li salt, and O was calculated as the difference from the total amount of powder by adding up the analyzed masses of elements other than O. The results are shown in the table below.

[0160] [Reference Example 2: Preparation by the above-described steps 1B to 3B and method 2] 1 g of the fine particles of the lithium-containing oxide used in Reference Example 1 was added to water so that the concentration of the fine particles was 42 mass %, and the mixture was ultrasonically dispersed for 30 minutes. 0.05 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added (5% by mass relative to the fine particles of the lithium-containing oxide), and ultrasonic dispersion was further carried out for 30 minutes. The obtained dispersion was transferred to a glass petri dish and dried at 120°C for 2 hours in the atmosphere to obtain a solid electrolyte film. Subsequently, the obtained film was peeled off to obtain a powdery solid electrolyte (II)-2. Various evaluations were carried out on the solid electrolyte (II)-2 in the atmosphere in the same manner as in Reference Example 1. The results are summarized in the table below.

[0161] [Reference Example 3: Preparation by the above steps 1B to 3B and method 3] Powdered Li was prepared using a ball mill (Fritsch, planetary ball mill P-7). ２ B ４ O ７ (LBO powder) (manufactured by Rare Metallic) was ball milled under the following conditions: pot: YSZ (45 ml), milling balls: YSZ (average particle size: 5 mm, weight: 70 g), rotation speed: 530 rpm (revolutions per minute), LBO powder amount: 4.2 g, atmosphere: air, ball mill treatment time: 100 hours, to obtain a fine lithium-containing oxide. The obtained fine lithium-containing oxide was added to water so that the concentration of the fine lithium-containing oxide was 42 mass%, and the mixture was ultrasonically treated for 60 minutes to obtain dispersion 1. Next, 3.25 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added to water to a concentration of 87% by mass, and the mixture was subjected to ultrasonic treatment for 60 minutes to obtain Solution 2. The obtained Dispersion 1 and Solution 2 were mixed and stirred with a magnetic stirrer for 60 minutes. The obtained dispersion was then vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered Solid Electrolyte (II)-3. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were performed in the atmosphere using Solid Electrolyte (II)-3 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0162] Reference Example 4: Preparation by the above steps 1B to 3B and method 3 Dispersion 3 was obtained in the same manner as in the preparation of dispersion 1 in Reference Example 3. Next, 2.32 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added to water at a concentration of 87% by mass, and the mixture was subjected to ultrasonic treatment for 60 minutes to obtain Solution 4. The obtained Dispersion 3 and Solution 4 were mixed, and the mixture was stirred and mixed with a magnetic stirrer for 60 minutes. Subsequently, the obtained dispersion was vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered Solid Electrolyte (II)-4. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were performed in the atmosphere using Solid Electrolyte (II)-4 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0163] Reference Example 5: Preparation by the above-described steps 1B to 3B and method 3 Dispersion 5 was obtained in the same manner as in the preparation of dispersion 1 in Reference Example 3. Next, 4.65 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added to water at a concentration of 87% by mass and subjected to ultrasonic treatment for 60 minutes to obtain Solution 6. The obtained Dispersion 5 and Solution 6 were mixed and stirred and mixed with a magnetic stirrer for 60 minutes. Subsequently, the obtained dispersion was vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered solid electrolyte (II)-5. The obtained powdered solid electrolyte (II)-5 was immediately used to perform various evaluations in the atmosphere in the same manner as in Reference Example 1. The results are summarized in the table below.

[0164] Reference Example 6: Preparation by the above-described steps 1B to 3B and method 3 Dispersion 7 was obtained in the same manner as in the preparation of Dispersion 1 in Reference Example 3. Next, 7.13 g of LiTFSI (chemical formula: Li(F ３ CSO ２ ) ２ N) was added to water at a concentration of 87% by mass and ultrasonically treated for 60 minutes to obtain Solution 8. The obtained Dispersion 7 and Solution 8 were mixed and stirred with a magnetic stirrer for 60 minutes. The obtained dispersion was then vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered solid electrolyte (II)-6. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were performed in the atmosphere using solid electrolyte (II)-6 in the same manner as in Reference Example 1. The results are summarized in the table below. In Reference Example 6, the carbon content shown in Table 1 below was estimated from the analyzed mass of sulfur, taking into account the atomic weight of each atom in the lithium salt.

[0165] Comparative Example 1 The LBO powder (powdered Li without ball milling) used in Example 1 was ２ B ４ O ７ As a result of elemental analysis of the LBO powder, the composition of the obtained powder was １．９６ B ４．００ O ６．８０The LBO powder was compacted at 27°C (room temperature) under an effective pressure of 220 MPa to obtain a comparative powder compact C1. The ionic conductivity of the obtained powder compact C1 was undetectable. Furthermore, X-ray total scattering measurement was performed using the LBO powder in the same manner as in Reference Example 1 to obtain the reduced pair distribution function G(r). FIG. 10 shows the reduced pair distribution function G(r) obtained from the LBO powder. As a result of analysis, the reduced pair distribution function G(r) obtained from the X-ray total scattering measurement of the LBO powder contained a first peak (corresponding to B-O proximity) with a peak top at 1.40 Å and a second peak (corresponding to B-B proximity) with a peak top at 2.40 Å, and the G(r) values ​​of the first and second peaks were 1.0 or greater (see FIG. 10). In addition, peaks with tops at 3.65 Å, 5.22 Å, 5.51 Å, and 8.54 Å were present, and the absolute value of G(r) at the peak top of each peak clearly exceeded 1.0 (see FIG. 10 ). X-ray diffraction measurement was performed on the LBO powder of Comparative Reference Example 1 using CuKα radiation. The measurement conditions were 0.01° / step and 3° / min. FIG. 11 shows the X-ray diffraction pattern of the LBO powder of Comparative Reference Example 1. As shown in FIG. 11 , multiple narrow peaks were observed in the LBO powder used in Comparative Reference Example 1. More specifically, the strongest peak corresponding to the (1,1,2) plane was observed at a 2θ value of 21.78°. Other major diffraction peaks were observed at 25.54° corresponding to the (2,0,2) plane, 33.58° corresponding to the (2,1,3) plane, and 34.62° corresponding to the (3,1,2) plane, and the intensities of these three peaks were almost equal. These peaks were derived from crystalline components.

[0166] Comparative Reference Example 2: The fine particles of the lithium-containing oxide prepared in Reference Example 1 (powdered Li ２ B ４ O ７ As a result of elemental analysis of the fine particles of lithium-containing oxide (crystals ball-milled), the composition of the fine particles of lithium-containing oxide was １．９４ B ４．００ O ６．８０Next, the fine particles of the lithium-containing oxide were compacted at 27°C (room temperature) under an effective pressure of 220 MPa to obtain a comparative reference compact (compacted powder R1). The ionic conductivity of the obtained compacted powder R1 was 7.5 x 10 at 27°C. －９ S / cm and 7.5 × 10 at 60 °C －８ S / cm.

[0167] In the table below, when the reduced pair distribution function G(r) obtained from X-ray total scattering measurement as described above has a first peak whose peak top is located in the r range of 1.43±0.2 Å and a second peak whose peak top is located in the r range of 2.40±0.2 Å, and the G(r) at the peak top of the first peak and the G(r) at the peak top of the second peak are greater than 1.0, the column for "short-distance G(r)" is marked with "A," and otherwise the column is marked with "B." Note that in Reference Examples 1 to 5 and Reference Examples 9 to 13 shown in the table below, the value of G(r) at the peak top of the first peak was 1.2 or greater. Furthermore, when the absolute value of G(r) in the reduced pair distribution function G(r) is less than 1.0 in the r range of greater than 5 Å and not more than 10 Å, the column for "long-distance G(r)" in the table below is marked with "A," and when the absolute value of G(r) does not satisfy the condition of less than 1.0, the column is marked with "B." Furthermore, as a result of the X-ray diffraction measurement using the above-mentioned CuKα ray, cases where the above-mentioned X-ray diffraction characteristics were satisfied were rated as "A", and cases where the above-mentioned X-ray diffraction characteristics were not satisfied were rated as "B". Note that in Reference Examples 1 to 6 shown in the table below and Reference Examples 7 to 13 described later, none of the first peak, second peak, third peak, and fourth peak was present in the X-ray diffraction pattern, or the intensity ratio of at least one of the first peak, second peak, third peak, and fourth peak was 2.0 or less.

[0168] In the table below, the "Elemental Analysis" column shows the composition of the solid electrolyte (II) obtained in each Reference Example and the lithium-containing oxide in each Comparative Reference Example as a molar amount of each element, as a relative value with the content of B being "4.00". In the table below, a blank column means that the corresponding element is not contained.

[0169] In the table below, the "full width at half maximum ratio (%)", "coefficient of determination" and "mass reduction rate (%)" are as explained in the above description of Reference Example 1.

[0170] In the table below, the "area intensity ratio" is the solid ７ In Li-NMR measurement, this is the ratio of the area intensity of the second peak to the area intensity of the first peak, and the evaluation results are based on the following criteria: <Criteria for area intensity ratio> A: When the area intensity ratio is 15% or more B: When the area intensity ratio is 0.5% or more and less than 15% C: When the area intensity ratio is less than 0.5%

[0171] In the table below, the "maximum absorption intensity ratio" column indicates whether or not the above-mentioned infrared absorption spectrum characteristics are satisfied. －１ Maximum absorption intensity in the wavenumber region of 800 to 1600 cm －１ [maximum absorption intensity in the wave number region of 1000 Hz] is indicated as "A" when it is 0.20 or more, and as "B" when it is less than 0.20. In the table below, "-" means that the measured value is not shown.

[0172]

[0173]

[0174] As shown in the table above, it can be seen that the solid electrolytes (II)-1, (II)-2, (II)-3, (II)-4, (II)-5, and (II)-6 of Reference Examples 1 to 6 have excellent ionic conductivity. Furthermore, the results of elemental analysis confirmed that the Li content in the solid electrolyte was higher in Reference Examples 3 to 6. In Reference Examples 3 to 6, an aqueous dispersion containing a lithium-containing oxide subjected to mechanical milling was mixed with an aqueous solution containing a lithium salt (Method 3 in Step 2B described above), which allowed for the mixing of a larger amount of lithium salt. It is presumed that this resulted in an increase in the amount of Li incorporated into the solid electrolyte. It was also found that Reference Examples 3, 4, and 5, which used LiFSI as the lithium salt, had improved ionic conductivity. It is presumed that this is due to the inclusion of highly mobile Li in the increased Li.

[0175] <Effect of Water in Solid Electrolyte> A compact (pellet) (diameter 10 mm, thickness 0.9 mm) of solid electrolyte (II)-3 obtained in Reference Example 3 was vacuum-dried at 27°C under a restraint of 60 MPa, and the pressure change and ionic conductivity with respect to the vacuum drying time were investigated. The method for producing the compact and the evaluation of ionic conductivity were the same as described above, except that the In electrode was changed to a Ti electrode. The results are shown in Table 3.

[0176]

[0177] The solid electrolyte (II)-3 of Reference Example 3 has a peak intensity of 3000 to 3500 cm in the infrared absorption spectrum. －１ Since the absorption intensity due to the OH stretching peak is strongly observed in the wavenumber region, it is thought that a large number of OH groups and water are present. Furthermore, the presence of free water and bound water is presumed. In the above, the pellets were first dried under vacuum drying conditions that are thought to volatilize the free water, and then further dried under more severe drying conditions, and the ionic conductivity at each stage was evaluated.

[0178] As shown in the table above, the pressure was 200 Pa after 5 minutes of drying, and the free water was considered to be in a vaporized state. However, the ionic conductivity was 3.8 × 10 －３ Even with a drying time of 1080 minutes and a pressure of 15 Pa, the ionic conductivity was 5.7 × 10 －４ This result indicates that bound water exists in addition to free water, and that this contributes to ionic conductivity.

[0179] Reference Example 7: Preparation by the above-described steps 1B to 3B and method 3 A dispersion 9 having a concentration of lithium-containing oxide fine particles of 42 mass % was obtained in the same manner as in the preparation of dispersion 1 in Reference Example 3. Next, 7.12 g of LiTFSI (chemical formula: Li(F ３ CSO ２ ) ２N was added to water to a concentration of 87% by mass, and the mixture was subjected to ultrasonic treatment for 60 minutes to obtain Solution 10. The obtained Dispersion 9 and Solution 10 were mixed and stirred with a magnetic stirrer for 60 minutes. The obtained dispersion was then vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered Solid Electrolyte (II)-7. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were performed in the atmosphere using Solid Electrolyte (II)-7 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0180] [Reference Example 8] A solid electrolyte (II)-8 was obtained in the same manner as in Reference Example 7, except that the contents of water and LiTFSI in the obtained solid electrolyte (II) were changed to the amounts shown in the table below, and various evaluations were carried out under air in the same manner as in Reference Example 1. The results are summarized in the table below.

[0181] [Reference Examples 9 to 13] Solid electrolytes (II)-9 to (II)-13 were obtained in the same manner as in Reference Example 7, except that LiTFSI was changed to LiFSI and the contents of water and LiFSI in the obtained solid electrolyte (II) were changed to the amounts shown in the table below. Various evaluations were carried out in the atmosphere in the same manner as in Reference Example 1. The results are summarized in the table below. However, in Reference Example 13, the powder obtained after vacuum drying was immediately evaluated in the atmosphere.

[0182] In the table below, the "Lithium-containing oxide fine particles" column, the "Lithium salt" column, and the "Water" column represent relative molar ratios. For example, in Reference Example 7, the molar ratio of lithium salt to lithium-containing oxide fine particles is 1, and the molar ratio of water to lithium-containing oxide fine particles is 11. The molar ratios were calculated by the following method. The analysis of each element was performed by quantitatively analyzing lithium and boron using ICP-OES, and fluorine and sulfur using combustion ion chromatography (combustion IC). N was estimated from the analyzed mass of sulfur taking into account the atomic weight of each element in the Li salt, and O was calculated as the difference from the total amount of solid electrolyte by adding up the analyzed masses of elements other than O. In Reference Examples 7 and 8, the carbon amount was estimated from the analyzed mass of sulfur taking into account the atomic weight of each element in the lithium salt. The molar ratio of lithium-containing oxide fine particles to lithium salt in the solid electrolyte was calculated from the molar ratio of an element (e.g., B) that is only present in the lithium-containing oxide fine particles and an element that is only present in the lithium salt. Furthermore, the molar ratio of the fine particles of the lithium-containing oxide to water was calculated by subtracting the molar ratios of O contained in the fine particles of the lithium-containing oxide and the lithium salt from the molar ratio of O in the solid electrolyte to calculate the molar amount of O derived from water, and then using the obtained molar amount of O derived from water and the molar amount of the fine particles of the lithium-containing oxide.

[0183]

[0184] The content (mass %) of each component in the solid electrolyte (II) was calculated based on the molar amount and molecular weight shown in Table 4. The results are shown in Table A below.

[0185]

[0186]

[0187] As shown in the above table, the solid electrolytes of each Reference Example had the desired characteristics or properties and exhibited excellent ionic conductivity.

[0188] <Preparation of electrode composition (slurry)> (Example 1-1) 1. Preparation of solid electrolyte Powdered Li was milled using a ball mill (Fritsch Corporation, planetary ball mill P-7). ２ B ４ O ７Crystals (LBO powder) (manufactured by Rare Metallic Co., Ltd.) were ball milled under the following conditions: pot: stabilized zirconia (YSZ) (45 mL), milling balls: YSZ (average particle size: 5 mm, number: 50), rotation speed: 370 rpm (revolutions per minute), amount of LBO powder: 1 g, atmosphere: air, and ball mill treatment time: 100 hours, to obtain a finely divided lithium-containing oxide. 1 g of the obtained fine lithium-containing oxide was mixed with 0.05 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added (5% by mass relative to the fine particles of the lithium-containing oxide), and the mixture was ball milled for another 100 hours. The obtained powder was added to water so that the powder concentration was 42% by mass, and ultrasonically dispersed for 30 minutes. Subsequently, the obtained dispersion was transferred to a glass petri dish and dried at 120°C for 2 hours in the atmosphere to obtain a solid electrolyte film. Subsequently, the obtained film was peeled off to obtain a powdered solid electrolyte SE1 (solid electrolyte for Example 1-1). The particle size distribution of the solid electrolyte SE1 was approximately several μm to 30 μm, and the median diameter (D50) was 7.8 μm. The particle size distribution of the solid electrolyte was calculated by acquiring particle images using a flow particle image analysis method and creating a histogram (particle size distribution) of the particle size of the solid electrolyte. The above particle diameter corresponds to the circle equivalent diameter. When the powder of this solid electrolyte SE1 was analyzed, it was confirmed that it had the above-mentioned X-ray diffraction characteristics and was in an amorphous state. Furthermore, when the ionic conductivity was measured by the above-mentioned method, it was 1.5 × 10 at 27 °C. －４ The elemental composition was the same as that of Reference Example 1.

[0189] 2. Preparation of active material Powdered LiCoO ２ The crystals (LCO powder) (positive electrode active material) were classified to have the median diameters shown in the table below and used as active material AC. The particle size distribution of active material AC was approximately 3 μm to 25 μm, and the median diameter was 10.5 μm. The particle size distribution of active material AC was measured using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by HORIBA).

[0190] 3. Preparation of Electrode Composition (Slurry) 4.6 g of active material AC, 4.6 g of solid electrolyte SE1, 10.0 g of carbon nanotube (CNT) dispersion (solid content 8.0% by mass) (manufactured by KJ Specialty Paper Co., Ltd.), and 0.8 g of water were placed in a container, and the mixture was stirred using a planetary mixer (manufactured by Thinky Corporation, product name: Awatori Rentaro ARE310) at a rotation speed of 2000 rpm and a revolution speed of 800 rpm for 20 minutes to obtain slurry SL-1 as an electrode composition with a solid content of 50% by mass.

[0191] Examples 1-2 to 1-6, Comparative Examples 1-1 to 1-3 A solid electrolyte and an active material were obtained in the same manner as in Example 1-1, except that the ball mill conditions were changed so that the median diameter of the solid electrolyte would be the median diameter shown in the table below, and an active material having a median diameter shown in the table below was used as the active material. These were then mixed in the same manner as in Example 1-1 to obtain each slurry.

[0192] (Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-3) The active material was converted from LCO powder to Li ４ Ti ５ O1 ２ A solid electrolyte and an active material were obtained in the same manner as in Example 1-1, except that the negative electrode active material was changed to (LTO powder) (negative electrode active material), the ball mill conditions were changed so that the median diameter of the solid electrolyte would be the median diameter shown in the table below, and an active material having the median diameter shown in the table below was used as the active material. These were then mixed in the same manner as in Example 1-1 to obtain each slurry.

[0193] (Examples 3-1 to 3-5, Comparative Examples 3-1 to 3-3) The active material was converted from LCO powder to LiMn ２ O ４ A solid electrolyte and an active material were obtained in the same manner as in Example 1-1, except that the starting material was changed to (LMO powder) (positive electrode active material), the ball mill conditions were changed so that the median diameter of the solid electrolyte would be the median diameter shown in the table below, and an active material having a median diameter shown in the table below was used as the active material, and these were mixed in the same manner as in Example 1-1 to obtain each slurry.

[0194] (Examples 4-1 to 4-5, Comparative Examples 4-1 to 4-3) The active material was converted from LCO powder to LiNi １／３ Mn １／３ Co １／３O ２ A solid electrolyte and an active material were obtained in the same manner as in Example 1-1, except that the solid electrolyte was changed to (NMC powder) (positive electrode active material), the ball mill conditions were changed so that the median diameter of the solid electrolyte would be the median diameter shown in the table below, and an active material having a median diameter shown in the table below was used as the active material. These were then mixed in the same manner as in Example 1-1 to obtain each slurry.

[0195] (Porosity Evaluation) Each of the slurries prepared in the above Examples and Comparative Examples was coated with a tabletop coater so that the mixture (solid content) amount was 3 mg / cm ２ The coating was applied to a current collector foil (20 μm thick, A4-sized Al foil) so that the coating was uniform. This was then stored in a desiccator with a relative humidity of 5% or less for 12 hours to dry, producing an electrode laminate (active material layer / Al current collector layer, before pressing). The resulting electrode laminate was pressed at 5 MPa using a flat press to produce an electrode sheet having an active material layer. A cross-section polisher (product name: IM4000 ion milling device, manufactured by Hitachi Corporation) was used to prepare a sample in which the cross section in the thickness direction of the sheet was exposed. The active material layer in this cross section was photographed using a scanning electron microscope (SEM). The obtained SEM image (magnification: 1000 times) was binarized using the image processing software "ImageJ" to make the void areas black and the other areas white, and the area of ​​the black areas was calculated based on the total area (area 10000 μm ２ The porosity was calculated by dividing the measured length by the average length (length: 50 μm × width: 200 μm) and the obtained porosity was evaluated according to the following evaluation criteria. The SEM used was an SU-8030 model SEM manufactured by Hitachi High-Technologies Corporation. --Evaluation criteria-- A: Less than 5% B: 5% or more and 15% or less C: More than 15% and 30% or less D: More than 30%

[0196] (Electrode bending evaluation) The flexibility of the electrode sheet was evaluated by a bending resistance test using a mandrel tester (in accordance with JIS K 5600-5-1:1999) as follows: Each of the slurries (solid content 50% by mass) prepared in the above Examples and Comparative Examples was applied to a tabletop coater so that the mixture (solid content) was 5 mg / cm.２ The coating was applied to a current collector foil (20 μm thick, A4-sized Al foil) so that the coating was uniform. The coating was then stored in a desiccator with a relative humidity of 5% or less for 12 hours to dry, producing an electrode laminate (active material layer / Al current collector layer, before pressing). The resulting electrode laminate was pressed using a flat press at 5 MPa to obtain an electrode sheet. The porosity of the active material layer of the resulting electrode sheet was approximately the same as the porosity obtained in the above-mentioned porosity evaluation. A rectangular test piece measuring 10 mm wide and 100 mm long was cut from each electrode sheet. The surface of the test piece facing the active material layer was positioned opposite the mandrel (the current collector was on the mandrel side), and the width direction of the test piece was parallel to the axis of the mandrel. The test piece was bent 180° (once) along the outer circumferential surface of the mandrel, and then visually observed for cracks and / or peeling in the active material layer. This test was first performed using a mandrel with a diameter of 32 mm. If neither cracking nor peeling occurred, the mandrel diameter (unit: mm) was gradually decreased to 32, 25, 20, 16, 12, 10, 8, 6, 5, 4, 3, and 2, and the diameter of the mandrel at which cracking and / or peeling first occurred was recorded. The diameter at which cracking and / or peeling first occurred (defect diameter) was used to evaluate flexibility according to the following evaluation criteria. In the present invention, the smaller the defect diameter, the more flexible the electrode sheet. --Evaluation Criteria-- A: 5 mm or less B: 6 mm to 12 mm C: 16 mm to 25 mm D: 32 mm

[0197] (Evaluation of cycle characteristics and resistance) All-solid-state secondary batteries were manufactured using each of the slurries obtained in the above Examples and Comparative Examples (Examples 20-01 to 20-06, Comparative Examples 20-01 and 20-02), and their cycle characteristics and resistance were evaluated as follows. Details are shown below. 1. Manufacture of all-solid-state secondary batteries 1) Preparation of positive electrode laminate For the positive electrode laminate, each of the slurries shown in Table 10 (slurries prepared in Examples 1-1, 1-5, 1-4, Comparative Examples 1-1, and 1-2) was applied to a tabletop coater in a mixture (solid content) amount of 3 mg / cm. ２Each of the slurries was applied to a current collector foil (20 μm thick A4 size Al foil) so that the amount of each slurries was 2 mg / cm 3 and then stored and dried in a desiccator with a relative humidity of 5% or less for 12 hours to prepare a positive electrode laminate (positive electrode active material layer / Al current collector layer, before pressing). 2) Preparation of Negative Electrode Laminate For the negative electrode laminate, each of the slurries (slurries prepared in Examples 2-1, 2-2, 2-3, 2-5, 2-6, Comparative Examples 2-1, and 2-2) shown in Table 10 was applied to a desktop coater in a mixture (solid content) amount of 2 mg / cm 3. ２ Each of the solutions was applied to a current collector foil (20 μm thick, A4-sized Al foil) so that the resultant mixture was uniformly mixed. The mixture was then stored in a desiccator with a relative humidity of 5% or less for 12 hours to dry, and a negative electrode laminate (negative electrode active material layer / Al current collector layer, before pressure application) was prepared. 3) Production of an All-Solid-State Secondary Battery A battery was manufactured using an all-solid-state battery evaluation cell (KP-SolidCell, manufactured by Hosen Co., Ltd.). Specifically, 80 mg of the solid electrolyte SE1 obtained above was placed in a battery protective tube with a diameter of 10 mm and pressurized at 60 MPa to form a solid electrolyte layer. The positive electrode laminate obtained above was placed on one side of the solid electrolyte layer, and the negative electrode laminate obtained above was placed on the other side, with the active material layer facing the solid electrolyte layer. The solid electrolyte layer was then sealed while pressurized at 60 MPa, and an all-solid-state battery evaluation cell (all-solid-state secondary battery) was produced. This all-solid-state secondary battery has, in addition to a solid electrolyte layer, a positive electrode active material layer and a negative electrode active material layer formed by pressure treating each electrode composition layer.

[0198] 2. Cycle Characteristics Test A charge / discharge test was performed on the all-solid-state battery evaluation cell manufactured above using an ABE1024-5V0.1A-4 charge / discharge tester (product name, manufactured by Electrofield) to evaluate cycle characteristics. Details are as follows. The all-solid-state battery evaluation cell was initialized by charging / discharging under the following condition 1A. (Condition 1A) Charge: constant current 0.1C, 2.65V termination Discharge: constant current 0.1C, 1.5V termination This was repeated three times. The initialized all-solid-state battery evaluation cell was charged / discharged under the following conditions 2A-1, 2A-2, and 2A-3 in this order. (Condition 2A-1) Charge: constant current, constant voltage 0.5C, 2.65V-0.1C Termination Discharge: constant current 0.1C, 1.5V Termination (Condition 2A-2) Charge: constant current, constant voltage 0.5C, 2.65V-0.1C Termination Discharge: constant current 0.5C, 1.5V Termination The above charge and discharge constitute one cycle, and 49 charge and discharge cycles were performed. (Condition 2A-3) Charge: constant current, constant voltage 0.5C, 2.65V-0.1C Termination Discharge: constant current 0.1C, 1.5V Termination Discharge capacity retention rate A was evaluated according to the following evaluation criteria: discharge capacity retention rate A (%) = (discharge capacity under condition 2A-3) ÷ (discharge capacity under condition 2A-1) × 100. A higher discharge capacity retention rate A indicates better cycle characteristics (longer cycle life). --Evaluation criteria-- A: 90% or more B: 85% or more and less than 90% C: 80% or more and less than 85% D: 70% or more and less than 80% E: 50% or more and less than 70% F: Less than 50%

[0199] 3. Battery Resistance Test A charge / discharge test was performed on the all-solid-state battery evaluation cell manufactured above using an ABE1024-5V 0.1A-4 charge / discharge tester (product name, manufactured by Electrofield) to evaluate the battery resistance. Details are as follows. The all-solid-state battery evaluation cell was initialized by charging / discharging under the following condition 1B. (Condition 1B) Charge: constant current 0.1C, termination at 2.65V Discharge: constant current 0.1C, termination at 1.5V This was repeated three times. The initialized all-solid-state battery evaluation cell was subjected to charging and discharging under the following conditions 2B and 3B. (Condition 2B) Charge: Constant current, constant voltage 1C, 2.65V-0.1C Termination Discharge: Constant current 1C, 1.5V Termination (Condition 3B) Charge: Constant current, constant voltage 1C, 2.65V-0.1C Termination Discharge: Constant current 3C, 1.5V Termination Discharge capacity retention rate B was evaluated according to the following evaluation criteria, where B (%) = (discharge capacity under condition 3B) / (discharge capacity under condition 2B) x 100. A higher discharge capacity retention rate B indicates lower battery resistance. --Evaluation criteria-- A: 96% or more B: 94% or more and less than 96% C: 92% or more and less than 94% D: 87% or more and less than 92% E: 80% or more and less than 87% F: Less than 80%

[0200]

[0201]

[0202]

[0203]

[0204] In Tables 6 to 9, the unit of the median diameter of each solid electrolyte and each active material is "μm."

[0205]

[0206] As shown in Tables 6 to 9 above, when the median diameter M of the active material in the electrode composition and the median diameter N of the solid electrolyte did not satisfy the 1.2≦M / N≦5.0 specified in the present invention, an electrode sheet having an active material layer with a porosity reduced to the specific range specified in the present invention could not be prepared. Furthermore, despite the high porosity, the electrode sheet also had poor flexibility. In contrast, by controlling the particle size ratio of the active material to the solid electrolyte in the electrode composition within the range specified in the present invention, an electrode sheet with reduced porosity could be prepared, and the electrode sheet exhibited excellent flexibility. Furthermore, as shown in Table 10 above, secondary batteries having active material layers with porosities outside the range specified in the present invention had low discharge capacity ratios at 1C and 3C discharges, relatively high resistance, and poor cycle characteristics. In contrast, secondary batteries having active material layers with porosities within the range specified in the present invention had relatively low resistance and excellent cycle characteristics.

[0207] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0208] This application claims priority based on Japanese Patent Application No. 2022-089967, filed in Japan on June 1, 2022, the contents of which are incorporated herein by reference.

[0209] REFERENCE SIGNS LIST 1 negative electrode current collector 2 negative electrode active material layer 3 solid electrolyte layer 4 positive electrode active material layer 5 positive electrode current collector 6 operating part 10 all-solid-state lithium ion secondary battery

Claims

1. The solid electrolyte in an amorphous state and the active material are included. The solid electrolyte includes a metal-containing oxide including at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water; The electrode composition for an all-solid-state secondary battery, wherein a ratio of a median diameter M of the active material to a median diameter N of the solid electrolyte satisfies 1.2≦M / N≦5.

0.

2. 2. The electrode composition for an all-solid-state secondary battery according to claim 1, wherein the metal-containing oxide is a lithium-containing oxide containing Li, B, and O, and the metal salt is a lithium salt.

3. 3. The electrode composition for an all-solid-state secondary battery according to claim 1, wherein the median diameter N of the solid electrolyte is 0.1 to 10 μm.

4. 3. The electrode composition for an all-solid-state secondary battery according to claim 1, wherein a ratio of a content of the solid electrolyte to a content of the active material in the electrode composition for an all-solid-state secondary battery is, in terms of mass ratio, solid electrolyte:active material=20:80 to 80:

20.

5. 3. The electrode composition for an all-solid-state secondary battery according to claim 1, wherein the ratio of the content of the water to the content of the metal-containing oxide in the solid electrolyte is 1 to 12 in terms of molar ratio.

6. 3. The electrode composition for an all-solid-state secondary battery according to claim 1, wherein a ratio of a content of the metal salt to a content of the metal-containing oxide in the solid electrolyte is 0.001 to 1.5 in terms of a molar ratio.

7. An electrode sheet for an all-solid-state secondary battery having an active material layer containing an amorphous solid electrolyte and an active material, The solid electrolyte includes a metal-containing oxide including at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water; The electrode sheet for an all-solid-state secondary battery, wherein the active material layer has a porosity of 0.1 to 15%.

8. 8. The electrode sheet for an all-solid-state secondary battery according to claim 7, wherein the metal-containing oxide is a lithium-containing oxide containing Li, B, and O, and the metal salt is a lithium salt.

9. An all-solid-state secondary battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer arranged in this order, At least one of the positive electrode active material layer and the negative electrode active material layer is an active material layer containing an amorphous solid electrolyte and an active material, The amorphous solid electrolyte includes a metal-containing oxide including at least one of an alkali metal element and an alkaline earth metal element and an oxygen element, at least one metal salt of an alkali metal salt and an alkaline earth metal salt, and water, The porosity of the active material layer is 0.1 to 15%. All-solid-state secondary battery.

10. The all-solid-state secondary battery according to claim 9 , wherein the metal-containing oxide is a lithium-containing oxide containing Li, B, and O, and the metal salt is a lithium salt.

11. A method for producing an electrode sheet for an all-solid-state secondary battery, comprising: pressurizing a layer formed using the electrode composition for an all-solid-state secondary battery according to claim 1 or 2 to form an active material layer.

12. A method for producing an all-solid-state secondary battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer arranged in this order, comprising the steps of:

3. A method for producing an all-solid-state secondary battery, comprising: forming at least one of the positive electrode active material layer and the negative electrode active material layer by subjecting a layer formed using the electrode composition for an all-solid-state secondary battery according to claim 1 to a pressure treatment.