All-solid-state lithium-ion secondary battery and method for manufacturing the same

Abstract

The present invention is an all-solid-state lithium ion secondary battery comprising at least one layered body formed by arranging a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in that order. At least one current collector layer that is included in the positive electrode layer and / or the negative electrode layer is a layer that comprises a specific metal in a constituent material or a coating layer. The solid electrolyte layer includes a lithium-containing oxide that includes lithium, boron and oxygen, water included at a specific molar ratio with respect to this lithium-containing oxide, and a lithium salt.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state lithium-ion secondary battery and a method for manufacturing an all-solid-state lithium-ion secondary battery. [Background technology]

[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 concerns. Furthermore, because they are liquid, compacting them is difficult, and capacity limitations arise when batteries are enlarged. On the other hand, all-solid-state lithium-ion secondary batteries are one of the next-generation batteries that can solve these problems. The basic structure of an all-solid-state lithium-ion secondary battery is shown in Figure 1. Viewed from the negative electrode side, an all-solid-state lithium-ion secondary battery 10 has 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 and has 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, in all-solid-state lithium-ion secondary batteries, the solid electrolyte layer is required to have excellent lithium ion conductivity in order to obtain desired charge-discharge characteristics. As the solid electrolyte constituting the solid electrolyte layer, a sulfide-based solid electrolyte or an oxide-based solid electrolyte is mainly used. Because sulfide-based solid electrolytes are soft and plastically deformable, the particles bond together simply by being pressed. 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 produce 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. In order to increase the interparticle adhesion of oxide-based solid electrolytes, a high-temperature sintering process is required, which is constrained by factors such as 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, in order to use the lithium-containing oxide described in Patent Document 1 as a solid electrolyte sheet, a high-temperature sintering process is required. 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 describes a composite containing a lithium compound having a specific profile of the reduced pair distribution function G(r) obtained from X-ray total scattering measurement and lithium tetraborate. 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 them, and therefore, this composite can be formed into a lithium ion conductor exhibiting good lithium ion conductivity by pressure treatment without being subjected to high-temperature sintering treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-052755 [Patent Document 2] International Publication No. 2021 / 193204 Summary of the Invention [Problem to be solved by the invention]

[0005] The composite described in Patent Document 2 is composed of a lithium-containing oxide, yet is soft, and can ensure interparticle bonding without being subjected to a sintering treatment or without incorporating a binder such as an organic polymer, thereby possessing properties that have not been achieved by previous oxide-based solid electrolytes. However, as the inventors continued their studies, they found that the lithium ion conductivity is currently insufficient for practical use as a solid electrolyte layer in all-solid-state lithium ion secondary batteries, and that there is room for improvement for practical use.

[0006] The present invention provides an all-solid-state lithium ion secondary battery that uses a lithium-containing oxide in a solid electrolyte layer, and the solid electrolyte layer has excellent interparticle binding properties, high lithium ion conductivity, and excellent safety even without being subjected to high-temperature sintering treatment or even without blending a binder such as an organic polymer, and the all-solid-state lithium ion secondary battery has a current collector layer that uses a metal that has been difficult to use under high-temperature sintering conditions. Another object of the present invention is to provide a method for producing an all-solid-state lithium ion secondary battery using a lithium-containing oxide in a solid electrolyte layer, in which the solid electrolyte layer has excellent interparticle binding properties, higher lithium ion conductivity, and excellent safety even without being subjected to high-temperature sintering treatment or even without blending a binder such as an organic polymer, and the method for producing an all-solid-state lithium ion secondary battery has a current collector layer using a metal that has been difficult to use under conditions of high-temperature sintering in an atmosphere containing oxygen gas. [Means for solving the problem]

[0007] The object of the present invention has been achieved by the following means.

[0008] [1] An all-solid-state lithium ion secondary battery having at least one laminate formed by arranging a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order, at least one of the positive electrode layer and the negative electrode layer includes a current collector layer; at least one of the current collector layers is a layer containing, as a constituent material, a metal that melts at 670°C under normal pressure or a layer containing this metal in a coating layer; the solid electrolyte layer includes an amorphous solid electrolyte including a lithium-containing oxide containing Li, B, and O, water, and a lithium salt, and in this amorphous solid electrolyte, a ratio of the content of the lithium salt to the content of the lithium-containing oxide is 0.001 to 1.5 in terms of molar ratio, and a ratio of the content of the water to the content of the lithium-containing oxide is 1 to 12 in terms of molar ratio. [2] [1] The all-solid-state lithium-ion secondary battery according to [1], wherein the metal that melts at 670°C under normal pressure is Al or an Al alloy. [3] The lithium-containing oxide is Li 2+x B 4+y O 7+z The all-solid-state lithium-ion secondary battery according to [1] or [2], comprising: However, -0.3 <x<0.3、-0.3<y<0.3、-0.3<z<0.3である。 [4] A method for manufacturing an all-solid-state lithium ion secondary battery having at least one laminate formed by arranging a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order, comprising: at least one of the positive electrode layer and the negative electrode layer includes a current collector layer; at least one of the current collector layers is a layer containing Cu as a constituent material or a layer containing Cu in a coating layer, the solid electrolyte layer includes an amorphous solid electrolyte including a lithium-containing oxide containing Li, B, and O, water, and a lithium salt, and in this amorphous solid electrolyte, a ratio of the content of the lithium salt to the content of the lithium-containing oxide is 0.001 to 1.5 in terms of molar ratio, and a ratio of the content of the water to the content of the lithium-containing oxide is 1 to 12 in terms of molar ratio; a laminate of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer in an atmosphere containing oxygen gas at 300°C or less.

[0009] When describing a numerical range in the present invention or specification, if the upper and lower limits of the numerical range are described separately, any of the upper and lower limits can be appropriately combined to form a specific numerical range. On the other hand, when describing multiple numerical ranges expressed using "~", the upper and lower limits forming the numerical range are not limited to the specific combinations written before and after "~" as a specific numerical range, and can be a numerical range obtained by appropriately combining the upper and lower limits of each numerical range. Note that in the present invention or specification, a numerical range expressed using "~" means a range that includes the numerical values ​​written before and after "~" as the upper and lower limits. [Effects of the Invention]

[0010] The all-solid-state lithium ion secondary battery of the present invention uses a lithium-containing oxide in a solid electrolyte layer, and the solid electrolyte layer has excellent interparticle binding properties, high lithium ion conductivity, and excellent safety even without being subjected to high-temperature sintering treatment or even without blending a binder such as an organic polymer, and is an all-solid-state lithium ion secondary battery having a current collector layer using a metal that has been difficult to use under conditions of high-temperature sintering. Furthermore, the method for producing an all-solid-state lithium ion secondary battery of the present invention uses a lithium-containing oxide for the solid electrolyte layer, and the solid electrolyte layer has excellent inter-particle binding properties, higher lithium ion conductivity, and excellent safety even without being subjected to high-temperature sintering treatment or even without blending a binder such as an organic polymer, and it is possible to produce an all-solid-state lithium ion secondary battery having a current collector layer using a metal that has been difficult to use under conditions of high-temperature sintering in an atmosphere containing oxygen gas. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of the configuration of an all-solid-state lithium ion secondary battery. [Figure 2]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 (I) used in the present invention. [Figure 3] FIG. 3 is a diagram showing an example of the reduced pair distribution function G(r) obtained from the X-ray total scattering measurement of the solid electrolyte (I) used in the present invention. [Figure 4] FIG. 4 shows an example of a spectrum obtained when solid-state 7Li-NMR measurement of the solid electrolyte (I) used in the present invention is carried out at 20° C. or 120° C. [Figure 5] FIG. 5 shows an example of a spectrum obtained when solid-state 7Li-NMR measurement of lithium tetraborate crystal is carried out at 20° C. or 120° C. [Figure 6] FIG. 6 is a diagram showing an example of a spectrum obtained when solid-state 7Li-NMR measurement of the solid electrolyte (I) used in the present invention is carried out at 20°C. [Figure 7] FIG. 7 is a diagram in which the peaks shown in FIG. 6 are separated into waveforms. [Figure 8] FIG. 8 is a diagram showing an example of the Raman spectrum of the solid electrolyte (I) used in the present invention. [Figure 9] FIG. 9 is a diagram showing the Raman spectrum of lithium tetraborate crystal. [Figure 10] FIG. 10 shows the reduced pair distribution function G(r) obtained by X-ray total scattering measurement of powdered Li2B4O7 crystal. [Figure 11] FIG. 11 shows the X-ray diffraction pattern of powdered Li2B4O7 crystals. DETAILED DESCRIPTION OF THE INVENTION

[0012] [All-solid-state lithium-ion secondary battery] The all-solid-state lithium ion secondary battery of the present invention (hereinafter also referred to as "secondary battery of the present invention") is an all-solid-state lithium ion secondary battery having at least one laminate formed by arranging a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order, at least one of the positive electrode layer and the negative electrode layer includes a current collector layer, and at least one of the current collector layers is a layer having as a constituent material a metal that melts at 670°C under normal pressure or a layer having this metal in a coating layer. The solid electrolyte layer contains a solid electrolyte (I) of a specific composition in an amorphous state, which will be described later. In the secondary battery of the present invention, the solid electrolyte (I) having a specific composition described later has excellent particle binding properties. Therefore, the particles are bound by processing and molding (non-sintering) without the high-temperature sintering process that has been essential in the production of secondary batteries using conventional oxide-based solid electrolytes, and high ionic conductivity (10 -3 Therefore, it is possible to provide a secondary battery having a configuration in which a metal that melts at 670°C under normal pressure is contained in the constituent material of the current collector layer or in the coating layer, which metal previously melted under high-temperature sintering conditions and was therefore difficult to use.

[0013] The configuration of the secondary battery of the present invention is not particularly limited as long as it has at least one laminate formed by arranging a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order, and includes a configuration (configuration of a small laminated battery) in which a plurality of these layers are laminated such that a solid electrolyte layer is disposed between adjacent positive electrode layers and negative electrode layers. Each of the constituent layers (including the current collector layer, etc.) that constitute the secondary battery of the present invention may have a single-layer structure or a multi-layer structure. Of the configurations of the above-mentioned small laminated battery, with the exception of a configuration in which the solid electrolyte layer is a solid electrolyte (I) of a specific composition, at least one of the positive electrode layer and the negative electrode layer includes a current collector layer, and at least one of the current collector layers is a layer having, as a constituent material, a metal that melts at 670°C under normal pressure or a layer having this metal in a coating layer, reference can be made to the configuration of a solid battery described in, for example, paragraphs

[0021] to

[0046] of JP 2016-001602 A and the configuration can be applied to the present invention. Each layer of the secondary battery of the present invention will be described below.

[0014] <Solid electrolyte layer> The solid electrolyte layer constituting the secondary battery of the present invention is a layer formed by forming an amorphous solid electrolyte of a specific composition or a mixture of this solid electrolyte and other components into a layer shape. This amorphous solid electrolyte of a specific composition contains a lithium-containing oxide containing Li, B, and O (hereinafter also referred to as "lithium-containing oxide"), water, and a lithium salt. In this amorphous solid electrolyte having a specific composition, the ratio of the content of the lithium salt to the content of the lithium-containing oxide (lithium salt / lithium-containing oxide) is 0.001 to 1.5 in molar ratio. Also, in this amorphous solid electrolyte having a specific composition, the ratio of the content of the water to the content of the lithium-containing oxide (water / lithium-containing oxide) is 1 to 12 in molar ratio. Hereinafter, the amorphous solid electrolyte having a specific composition, in which the ratios of the lithium salt content and the water content to the lithium-containing oxide content satisfy the specific molar ratios described above, will also be referred to as "solid electrolyte (I)." The solid electrolyte (I) is usually an inorganic solid electrolyte.

[0015] The solid electrolyte (I) is in an amorphous state (synonymous with a non-crystalline state or an amorphous state) and exhibits elastic properties that allow for easy plastic deformation. As a result, in a constituent layer, such as a solid electrolyte layer containing the solid electrolyte (I), formed by pressure treatment or the like, the adhesion between the solid electrolytes (I) and / or the adhesion between the solid electrolyte (I) and other components present in the constituent layer is improved, thereby reducing interfacial resistance and achieving better ion conductivity. By using this solid electrolyte (I), a constituent layer, such as a solid electrolyte layer, that exhibits excellent lithium ion conductivity 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.

[0016] The water contained in the solid electrolyte (I) includes at least bound water. Although the reason why the solid electrolyte (I) exhibits high lithium ion conductivity is not clear, it is thought that in the solid electrolyte (I), a soft hydration layer is likely to be formed on the surface of the lithium-containing oxide, and this hydration layer contains a large amount of lithium derived from the lithium salt, resulting in higher ion conductivity. Here, in the present invention and the specification, "bound water" refers to water other than water present as free water or OH groups bound to a lithium-containing oxide. Even if the solid electrolyte (I) contains water at the above-mentioned content ratio, 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 lithium-ion secondary battery. That is, the solid electrolyte (I) contains bound water that is not removed or is difficult to remove under normal drying conditions. Note that the solid electrolyte (I) may contain free water as long as it is in the form of solid particles (a state that can be handled as a powder) and functions as a solid electrolyte for an all-solid-state lithium-ion secondary battery. That is, in the present invention, the "all-solid-state lithium-ion secondary battery" also includes a form in which the solid electrolyte contains water, as long as it can be handled as solid particles (solid powder). The solid electrolyte (I) used in the present invention, in which the ratio of the water content to the lithium-containing oxide content is 12 or less in molar ratio, is neither in a paste-like nor gel-like state, but in a solid particle (solid powder) state.

[0017] In the present invention, the solid electrolyte (I) being in an "amorphous state" means that it satisfies the following X-ray diffraction characteristics.

[0018] (X-ray diffraction characteristics) In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (I) using CuKα radiation, none of the following peaks is present: a first peak having a peak top in the diffraction angle 2θ range 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 diffraction angle 2θ range 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 diffraction angle 2θ range 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 diffraction angle 2θ range 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.

[0019] -Strength measurement method- An average intensity (Av1) is calculated over a range of +0.45° to +0.55° from the diffraction angle 2θ at the peak top of Peak X, and an average intensity (Av2) is calculated over a range of −0.55° to −0.45° from the diffraction angle 2θ at the peak top of Peak X, and an 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.

[0020] The X-ray diffraction characteristics will be explained in more detail. When none of the first, second, third, and fourth peaks is present in an X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (I) using CuKα radiation, the solid electrolyte (I) satisfies the above X-ray diffraction characteristics and is in an amorphous state. Furthermore, when the above-mentioned peak X is present in an X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (I) using CuKα radiation, if at least one peak of the peak X has an intensity ratio of 5.0 or less obtained by the above-mentioned intensity measurement method, the above-mentioned X-ray diffraction characteristics are also satisfied, and the solid electrolyte (I) is in an amorphous state. Here, the full width at half maximum (FWHM) of the peak means the peak width (°) at the point where the peak intensity is half the peak intensity at the peak top.

[0021] The above intensity measurement method will be explained in more detail with reference to FIG. 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 (I) using CuKα radiation. The X-ray diffraction pattern shown in FIG. 2 shows a specific peak whose peak top intensity is intensity 1. In the intensity measurement method, as shown in FIG. 2, the average intensity (Av1) of peak X in the range of +0.45° to +0.55° from the diffraction angle 2θ of the peak top is calculated, and the 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 calculated. Next, the arithmetic mean values ​​of Av1 and Av2 are calculated, and the ratio of intensity 1 to the arithmetic mean value is determined as the intensity ratio. When the above X-ray diffraction characteristics are satisfied, this means that the solid electrolyte (I) has no or almost no crystalline structure and 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 (I) is substantially free of a crystalline structure that would impair 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. 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 to produce a large peak, the presence of at least one peak X with an intensity ratio of a predetermined value or less indicates that the solid electrolyte (I) is in an amorphous state.

[0022] The X-ray diffraction measurement is carried out using CuKα radiation under measurement conditions of 0.01° / step and 3° / min.

[0023] In an X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (I) using CuKα radiation, it is preferable that none of the first peak, second peak, third peak, and fourth peak is present, or even if at least one peak X among the first peak, second peak, third peak, and fourth peak is present, the intensity ratio of at least one peak X among the first peak, second peak, third peak, and fourth peak is 3.0 or less. Among these, it is more preferable that none of the first peak, second peak, third peak, and fourth peak is present, or that even if at least one peak X among the 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.

[0024] In the above X-ray diffraction pattern, if the peak top is located in the range of 21.6 to 22.0° and there are two or more peaks with a full width at half maximum of 0.65° or less, the peak with the greatest diffracted X-ray intensity is selected as the first peak, and the above X-ray diffraction characteristics are determined. Furthermore, in the above X-ray diffraction pattern, if there are two or more peaks with a peak top in the range of 25.4 to 25.8° and a full width at half maximum of 0.65° or less, the peak with the greatest diffracted X-ray intensity is selected as the second peak, and the above X-ray diffraction characteristics are evaluated. Furthermore, in the above X-ray diffraction pattern, if there are two or more peaks with a peak top in the range of 33.4 to 33.8° and a full width at half maximum of 0.65° or less, the peak with the greatest diffracted X-ray intensity is selected as the third peak, and the above X-ray diffraction characteristics are evaluated. Furthermore, in the above X-ray diffraction pattern, if there are two or more peaks with a peak top in the range of 34.4 to 34.8° and a full width at half maximum of 0.65° or less, the peak with the greatest diffracted X-ray intensity is selected as the fourth peak, and the above X-ray diffraction characteristics are evaluated.

[0025] (X-ray total scattering characteristics) The solid electrolyte (I) preferably satisfies the following requirement A-1 in terms of X-ray total scattering characteristics. When the solid electrolyte (I) satisfies the above X-ray diffraction characteristics, the solid electrolyte (I) usually satisfies the following requirement A-2.

[0026] -Requirement A-1- In the reduced pair distribution function G(r) obtained from X-ray total scattering measurement of the solid electrolyte (I), there is 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 exceeds 1.0, and the G(r) at the peak top of the second peak is 0.8 or more.

[0027] -Requirement A-2- In the reduced pair distribution function G(r) obtained from X-ray total scattering measurement of the solid electrolyte (I), the absolute value of G(r) is less than 1.0 when r is in the range of more than 5 Å and 10 Å or less.

[0028] When the solid electrolyte (I) satisfies requirements A-1 and A-2, it has a short-range ordered structure related to the interatomic distances of BO and BB, 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 (I) formed by pressure treatment or the like, it is presumed that the adhesion between the solid electrolytes (I) themselves and / or the adhesion between the solid electrolyte (I) and other components present in the constituent layers such as the solid electrolyte layer is improved, thereby reducing interfacial resistance and achieving better ionic conductivity. Requirements A-1 and A-2 will be explained in more detail with reference to the drawings.

[0029] Figure 3 shows an example of the reduced pair distribution function G(r) obtained by X-ray total scattering measurement of a solid electrolyte (I). The vertical axis of Figure 3 is the reduced pair distribution function obtained by Fourier transform of X-ray scattering, and indicates the probability that an atom exists at a position of distance r. X-ray total scattering measurement can be performed at SPring-8 BL04B2 (accelerating voltage 61.4 keV, wavelength 0.2019 Å). The scattering intensity I obtained by the experiment obs is transformed using the following procedure to obtain the reduced pair distribution function G(r). First, the scattering intensity I obs is expressed by the following formula (1). The structure factor S(Q) is calculated by 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. I obs =I coh +I incoh +I 蛍光 (1)

[0030]

number

[0031] The structure factor S(Q) is used for PDF (Pair Distribution Function) analysis. In the above equation (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 the detector discriminator. obs can be deducted from Coherent Scattering I coh is expressed by Debye's scattering formula (Equation (3) below) (N: total number of atoms, f: atomic scattering factor, r ij :ij interatomic distance).

[0032]

number

[0033] If we focus on an arbitrary atom and the atomic density at a distance r is ρ(r), the number of atoms present within a sphere with a radius of r-r+d(r) is 4πr 2 Since the above equation (3) is expressed as the following equation (4), the above equation (3) is ρ(r)dr.

[0034]

number

[0035] If the average density of atoms is ρ0 and the above formula (4) is transformed, the following formula (5) is obtained.

[0036]

number

[0037] From the above formula (5) and formula (2), the following formula (6) is obtained.

[0038]

number

[0039] The pair distribution function g(r) is expressed by the following equation (7).

[0040]

number

[0041] From the above formulas (6) and (7), the following formula (8) is obtained.

[0042]

number

[0043] As described above, the pair distribution function can be calculated by the Fourier transform of the structure factor S(Q). To facilitate observation of medium- and long-range order, the pair distribution function g(r) is transformed into the equation G(r) = 4πr(g(r)-1) to obtain 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 correlation at a specific interatomic distance, the average density will be higher than 1. Therefore, it reflects the element distance and coordination number corresponding to the local to medium distance. As order disappears, ρ(r) approaches the average density, and g(r) approaches 1. Therefore, in amorphous structures, as r increases, order decreases, and g(r) becomes 1, i.e., G(r) becomes 0.

[0044] 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 (I), there is a first peak P1 whose peak top is located in an r range of 1.43±0.2 Å and a second peak P2 whose peak top is located in an 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 0.8 or greater (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 a position of 1.43 Å, there is a peak attributed to the B (boron)-O (oxygen) interatomic distance. Also, at a position of 2.40 Å, there is a peak attributed to the B (boron)-B (boron) interatomic distance. In other words, the observation of the above two peaks (first peak and second peak) means that a periodic structure corresponding to the above two interatomic distances exists in the solid electrolyte (I).

[0045] Furthermore, 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. The fact that 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 described above means that there is almost no long-range ordered structure in the solid electrolyte (I).

[0046] In the reduced pair distribution function G(r), there may be a peak other than the first peak and the second peak in the range of r being 5 Å or less.

[0047] There is no particular limitation on the method for making the solid electrolyte (I) amorphous. For example, in preparing the solid electrolyte (I), a method is available in which a lithium-containing oxide used as a raw material is subjected to mechanical milling. This mechanical milling may be carried out in the presence of a lithium salt.

[0048] -Mechanical milling process- Mechanical milling is a process of pulverizing a sample while applying mechanical energy. Examples of mechanical milling include milling using a ball mill, a vibration mill, a turbo mill, or a disk mill. From the viewpoint of obtaining an amorphous solid electrolyte (I) with good productivity, milling using a ball mill is preferred. Examples of ball mills include a vibration ball mill, a rotary ball mill, and a planetary ball mill, and a planetary ball mill is more preferred.

[0049] The conditions for the milling treatment using a ball mill (hereinafter referred to as ball milling 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 efficient production of the solid electrolyte (I). The average particle size is determined by measuring the diameters of 50 randomly selected milling balls and calculating the arithmetic mean. When the milling balls are not spherical, the major axis is taken as the diameter. The number of milling balls is not particularly limited.

[0050] The material of the grinding pot in the ball milling process is not particularly limited, and examples thereof include agate, silicon nitride, zirconia, alumina, and iron-based alloys, with stabilized zirconia (YSZ) being preferred.

[0051] The rotation speed of the ball milling 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 milling treatment is not particularly limited and can be, for example, 10 to 200 hours, preferably 20 to 140 hours. The atmosphere for the ball milling treatment may be air or an inert gas atmosphere (e.g., argon gas, helium gas, nitrogen gas, etc.).

[0052] The method for producing the solid electrolyte (I) using the lithium-containing oxide that has been subjected to mechanical milling treatment preferably involves the following steps 1A to 3A. Step 1A: A step of subjecting a lithium-containing oxide to mechanical milling in the presence of a lithium salt Step 2A: 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 a solid electrolyte (I).

[0053] 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 (I) defined in the present invention.

[0054] In the above 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 ultrasonic treatment time is not particularly limited, and may be, for example, 10 minutes to 5 hours.

[0055] Step 3A is a step of removing water from the dispersion obtained in Step 2A to obtain a solid electrolyte (I). The method for removing water from the dispersion obtained in Step 2A is not particularly limited, and water may be removed by a heat treatment or a vacuum drying treatment. The drying conditions are not particularly limited, and for example, normal drying conditions applied to general drying processes can be appropriately applied, such as the drying conditions applied in the Examples. Normal drying conditions include air drying (<30% RH), desiccator drying (<5% RH), and heating to 100°C for 30 minutes to 2 hours.

[0056] Before the above step 1A, step 0 may be carried out in which the lithium-containing oxide is subjected to mechanical milling treatment in an environment in which no lithium salt is present.

[0057] In the method for producing the solid electrolyte (I), 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: Mixing the product obtained in Step 1B with water and a lithium salt. Step 3B: A step of removing water from the dispersion obtained in Step 2B to obtain a solid electrolyte (I).

[0058] The method of carrying out steps 1B to 3B differs from the method of carrying out steps 1A to 3A in that a lithium salt is mixed with a lithium-containing oxide that has been subjected to mechanical milling in the presence of water. Therefore, the difference between step 1B and step 1A is that in step 1A, mechanical milling is carried out in the presence of a lithium salt, whereas in step 1B, mechanical milling is carried out 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 (Method 1) in which the product obtained in step 1B, water, and a lithium salt are mixed all at once, a method (Method 2) in which the product obtained in step 1B is mixed with water to prepare a dispersion, and then the obtained dispersion is mixed with a lithium salt, or a method (Method 3) in which the product obtained in step 1B is mixed with water to prepare dispersion 1, a lithium salt is mixed with water to prepare solution 2, and dispersion 1 is mixed with solution 2. 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 the dispersion liquid obtained by mixing the product obtained in Step 1B with water and a lithium salt is mixed, 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 liquid is unlikely to occur, and a larger amount of lithium salt can be mixed. From this perspective, Method 3 is preferred. The procedure of step 3B is the same as that of step 3A.

[0059] In the method for producing the solid electrolyte (I), 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: Mixing the product obtained in Step 1C with water Step 3C: A step of removing water from the dispersion obtained in Step 2C and mixing the resulting product with a lithium salt to obtain a solid electrolyte (I).

[0060] The procedure of step 1C is the same as that of step 1B. The procedure of step 2C is the same as that of step 2A. Step 3C differs from Steps 3A and 3B in that the product obtained by removing water from the dispersion obtained in Step 2C is mixed with a lithium salt. In step 3C, the amount of the lithium salt used is not particularly limited, and is appropriately adjusted so as to obtain the solid electrolyte (I) 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 the product is impregnated with a solution in which the lithium salt is dissolved in water and the two are mixed may be used.

[0061] (Composition of solid electrolyte (I)) As described above, the solid electrolyte (I) used in the present invention is an amorphous solid electrolyte, and in this solid electrolyte (I), the ratio of the content of the lithium salt to the content of the lithium-containing oxide is 0.001 to 1.5 in molar ratio, and the ratio of the content of the water is 1 to 12 in molar ratio. The molar ratio of the content of the lithium salt to the content of the lithium-containing oxide in the solid electrolyte (I) is preferably 0.001 to 1.2, more preferably 0.01 to 1.2, further preferably 0.1 to 1.2, and particularly preferably 0.5 to 1.2. The molar ratio of the water content to the lithium-containing oxide content in the solid electrolyte (I) is more preferably 2 to 12, and even more preferably 3 to 11. This molar ratio is also preferably 2 to 10, 2 to 8, 2 to 7, and even more preferably 3 to 7. The molar amounts of the lithium-containing oxide, lithium salt, and water in the solid electrolyte (I) can be determined by elemental analysis. Examples of elemental analysis include the elemental analysis methods described below in the elemental composition of the solid electrolyte (I). The molar amount of water can also be determined by the Karl Fischer method.

[0062] The water content in the solid electrolyte (I) 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 (I) is also preferably 30% by mass or less, and also preferably 25% by mass or less. The water content in the solid electrolyte (I) is usually 5% by mass or more, preferably 10% by mass or more, and preferably 15% by mass or more. Therefore, the water content in the solid electrolyte (I) is preferably 5 to 50% by mass, more preferably 5 to 45% by mass, even more preferably 10 to 40% by mass, particularly preferably 10 to 35% by mass, also preferably 10 to 30% by mass, also preferably 15 to 30% by mass, and also preferably 15 to 25% by mass. The content of the lithium-containing oxide in the solid electrolyte (I) is preferably from 20 to 80 mass %, more preferably from 20 to 75 mass %, and even more preferably from 25 to 70 mass %. The content of the lithium salt in the solid electrolyte (I) is preferably 0.5 to 60 mass %, more preferably 1.0 to 55 mass %, further preferably 2.0 to 50 mass %, and also preferably 5.0 to 50 mass %.

[0063] -Lithium-containing oxide- The lithium-containing oxide constituting the solid electrolyte (I) contains Li, B, and O as described above. The lithium-containing oxide is Li 2+x B 4+y O 7+zCompounds represented by (-0.3 < x < 0.3, -0.3 < y < 0.3, -0.3 < z < 0.3) are preferred. That is, when the molar amount of B is 4.00 and the molar amount of Li is expressed, the molar amount of Li is 1.58 - 2.49 (i.e., 1.7×4 / 4.3 - 2.3×4 / 3.7), and the molar amount of O is preferably 6.23 - 7.89 (i.e., 6.7×4 / 4.3 - 7.3×4 / 3.7). In other words, when the molar amount of B is 4.00, the relative value of the molar amount of Li is 1.58 - 2.49, and the molar amount of O is preferably 6.23 - 7.89. As such a lithium-containing oxide, typically, lithium tetraborate (Li2B4O7) is cited. Also, the above lithium-containing oxide is Li 1+x B 3+y O 5+z Compounds represented by (-0.3 < x < 0.3, -0.3 < y < 0.3, -0.3 < z < 0.3) are also preferred. As such a lithium-containing oxide, typically, lithium triborate (LiB3O5) is cited. Also, the above lithium-containing oxide is 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 a lithium-containing oxide, typically, Li3B 11 O 18 is cited. Also, the above lithium-containing oxide is Li 3+x B[[ID=2 five]] 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 a lithium-containing oxide, typically, Li3B7O 12 is cited. Therefore, the above lithium-containing oxide is the above Li 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+xB 7+y O 12+z It is preferable that the compound is at least one of the above. In addition, instead of the above-mentioned lithium-containing oxide, or together with the above-mentioned lithium-containing oxide, LiBO5, Li2BO 12 , LiB2O3(OH)H2O, and Li4B8O 13 At least one of (OH)2(H2O)3 and the like can also be used. In the solid electrolyte (I), the lithium-containing oxide is preferably in an amorphous state. That is, in order for the solid electrolyte (I) to be in the above-mentioned amorphous state, the lithium-containing oxide is also preferably in a desired amorphous state in the solid electrolyte (I). Among these, the lithium-containing oxide is preferably amorphous lithium tetraborate.

[0064] -Lithium salt- The lithium salt constituting the solid electrolyte (I) used in the present invention is not particularly limited, and Li + and an anion, and Li + and an organic anion are preferred, and Li + and a salt composed of an organic anion having a halogen atom are more preferred. The lithium salt constituting the solid electrolyte (I) used in the present invention preferably contains two or more specific 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 (I) used in the present invention, for example, a compound represented by the following formula (1) is preferred. Equation (1) LiN(R f1 SO2)(R f2 SO2) R f1 and R f2 R each independently represents a halogen atom or a perfluoroalkyl group. f1 and Rf2 may be the same or different from each other. R f1 and R f2 When is a perfluoroalkyl group, the number of carbon atoms in the perfluoroalkyl group is not particularly limited. R 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. f1 and R f2 When is a perfluoroalkyl group, it is preferable that the number of carbon atoms is small.

[0065] The lithium salt that can be contained in the solid electrolyte (I) 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 (I) used in the present invention are shown below.

[0066] (L-1) Inorganic lithium salts: inorganic fluoride salts such as LiPF6, LiBF4, LiAsF6, and LiSbF6; perhalogenates such as LiClO4, LiBrO4, and LiIO4; inorganic chloride salts such as LiAlCl4.

[0067] (L-2) Fluorine-containing organic lithium salt: perfluoroalkanesulfonates such as LiCF3SO3; fluorosulfonylimide salts or perfluoroalkanesulfonylimide salts such as LiN(CF3SO2)2, LiN(CF3CF2SO2)2, LiN(FSO2)2 (also referred to as Li(FSO2)2N in this specification), and LiN(CF3SO2)(C4F9SO2); perfluoroalkanesulfonylmethide salts such as LiC(CF3SO2)3; fluoroalkyl fluorophosphates (preferably perfluoroalkyl fluorophosphates) such as Li[PF5(CF2CF2CF3)], Li[PF4(CF2CF2CF3)2], Li[PF3(CF2CF2CF3)3], Li[PF5(CF2CF2CF2CF3)], Li[PF4(CF2CF2CF2CF3)2], and Li[PF3(CF2CF2CF2CF3)3].

[0068] (L-3) Oxalatoborate salts: lithium bis(oxalato)borate and lithium difluorooxalatoborate.

[0069] Other examples of lithium salts include LiF, LiCl, LiBr, LiI, Li2SO4, LiNO3, Li2CO3, CH3COOLi, LiAsF6, LiSbF6, LiAlCl4, and LiB(C6H5)4. Among them, LiPF6, LiBF4, LiAsF6, LiSbF6, LiClO4, Li(R f11 SO2), LiN(R f11 SO2)2, LiN(FSO2)2, or LiN(R f11 SO2)(R f12 SO2) are preferred, LiPF6, LiBF4, LiN(R f11 SO2)2, LiN(FSO2)2, or LiN(R f11 SO2)(R f12 SO2) is more preferred. In these examples, R f11 and R f12 each independently represents a perfluoroalkyl group, preferably having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and further preferably 1 or 2 carbon atoms. f11 and Rf12 may be the same or different. As the lithium salt, LiNO3 and 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide lithium are also preferred.

[0070] (Elemental composition of solid electrolyte (I)) The component composition of the solid electrolyte (I) has been described based on the compounds constituting the solid electrolyte (I). Next, the solid electrolyte (I) will be described from the viewpoint of a preferred elemental composition. That is, in one embodiment of the secondary battery of the present invention, the solid electrolyte (I) does not have a "lithium-containing oxide" or a "lithium salt" as a matter specifying the invention, and can be specified by the elemental composition, for example, as follows: In the solid electrolyte (I) used in the present invention, when the molar amount of B in the solid electrolyte (I) is 4.00, the molar amount of Li is preferably 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 (I) 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 (I) is 4.00, the molar amounts of elements other than B, Li, and O are preferably each 0.001 to 10.00 (preferably 0.001 to 6.00, more preferably 0.01 to 5.00).

[0071] The content of each element is determined by ordinary elemental analysis. For example, Li and B are analyzed by ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry), N and the like are analyzed by inert gas fusion, and 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 subtracting them from the total powder amount. 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 analytical results of the content of another element, 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 set to 4.00.

[0072] In a preferred embodiment of the solid electrolyte (I), the solid electrolyte (I) further contains, in addition to Li, B, and O, one or more elements (E) selected from the group 4 elements of the periodic table, the group 15 elements of the periodic table, the group 16 elements of the periodic table, the group 17 elements of the periodic table, Si, C, Sc, and Y, more preferably two or more elements (E). Examples of Group 4 elements in the periodic table include Ti, Zr, Hf, and Rf. Examples of Group 15 elements in the periodic table include N, P, As, Sb, Bi, and Mc. Examples of Group 16 elements in the periodic table include S, Se, Te, Po, and Lv. Examples of Group 17 elements in the periodic table 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 it is more preferable to contain two or more elements. The number of types of element (E) contained in the solid electrolyte (I) may be three or more, preferably two to five, and more preferably two to four. A preferred embodiment of the solid electrolyte (I) preferably contains two or more elements (E) selected from F, S, N, P, and C, more preferably two or more elements (E) selected from F, S, C, and N, and even more preferably three elements (E) of F, S, and N.

[0073] In the solid electrolyte (I) containing one or more (preferably two or more) of the above elements (E), when the molar amount of B in the solid electrolyte (I) is taken as 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 taken as 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 (I) is taken as 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.

[0074] In the solid electrolyte (I) containing one or more (preferably two or more) of the above-mentioned elements (E), when the molar amount of B in the solid electrolyte (I) 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 (I) 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.

[0075] In the solid electrolyte (I) containing one or more (preferably two or more) of the above-mentioned elements (E), when the molar amount of B in the solid electrolyte (I) 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 (I) 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.

[0076] One preferred embodiment of the elemental composition of the solid electrolyte (I) containing one or more (preferably two or more) of the above-mentioned elements (E) is 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 23.00). The solid electrolyte may have a molar amount of 0.001 to 10.00 (preferably 0.01 to 10.00), a molar amount of S of 0.001 to 2.00 (preferably 0.01 to 2.00), and a molar amount of N of 0.001 to 1.00 (preferably 0.005 to 1.00).

[0077] The solid electrolyte (I) used in the present invention is in the amorphous state described above, and as a result, the solid electrolyte (I) preferably exhibits the following properties in addition to the above X-ray diffraction properties.

[0078] (solid 7 Li-NMR spectral characteristics) The solid electrolyte (I) is a solid 7Li-NMR measurements are performed 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 the solid electrolyte (I) 7 Li-NMR measurements are performed at 20°C and 120°C, and the full width at half maximum (FWHM 1) of the peak appearing in the chemical shift range of -100 to +100 ppm in the spectrum obtained from the measurement at 20°C and the full width at half maximum (FWHM 2) of the peak appearing in the chemical shift range of -100 to +100 ppm in the spectrum obtained from the measurement at 120°C are determined. The full width at half maximum (FWHM) of the peak is then calculated as a percentage of the full width at half maximum (FWHM 2 / FWHM 1) × 100 (%). The full width at half maximum (FWHM) of the peak refers to the width (ppm) at half the peak height (H) (H / 2). The above characteristics will be explained below with reference to FIG. 4. In FIG. 4, the solid electrolyte (I) 7 The solid line at the bottom of Figure 4 shows an example of the spectrum obtained when Li-NMR measurement was performed at 20°C or 120°C. 7 The spectrum obtained when Li-NMR measurement was performed at 20°C, and 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. Generally, solid 7 In Li-NMR measurements, 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 shows that the mobility of Li is high. Such a solid electrolyte (I) is prone to plastic deformation due to the defect structure described above, and + It is thought that the hopping ability is excellent. For reference, the solid state 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 Figure 5, and the spectrum measured at 120°C, represented by the dashed line in the upper part of Figure 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.

[0079] The above solid 7 The Li-NMR measurement conditions are as follows: Measurements are performed using a 4 mm HX CP-MAS probe with the single pulse method, 90° pulse width: 3.2 μs, observation frequency: 155.546 MHz, observation width: 1397.6 ppm, repetition time: 15 sec, integration: 1 time, and MAS rotation speed: 0 Hz.

[0080] The solid electrolyte (I) 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 preferred 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 (I) contains water, the solid electrolyte (I) 7 The Li-NMR spectrum characteristics tend to be as described above. There is no particular upper limit to the percentage of the area intensity, but it is often 50% or less.

[0081] The above characteristics will be explained below with reference to FIGS. In Figure 6, the solid electrolyte (I) 7An 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 (I), and within this first peak, a small peak is observed near the chemical shift of 0 ppm, as enclosed by a dashed line. As mentioned above, Li + When the mobility of the molecule is high, the peak is observed sharply, which is thought to be the influence of the molecule. Next, the waveform separation of the first peak is shown in Figure 7. As shown in Figure 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 the chemical shift range of -3 to +3 ppm and has a full width at half maximum of 5 ppm or less. In the solid electrolyte (I), 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 (peak before waveform separation) represented by the solid line in FIG. 6 {(area intensity of the second peak / area intensity of the first peak)×100(%)} is preferably within the above range. Methods for waveform separation include methods using known software, such as graph processing software Igor Pro from WaveMetrics.

[0082] (Raman spectrum characteristics) The solid electrolyte (I) is characterized by the Raman spectrum of 600-850 cm -1 The coefficient of determination obtained by linear regression analysis by the least squares method in the wavenumber region is preferably 0.9400 or more, more preferably 0.9600 or more, and also preferably 0.9800 or more. There is no particular upper limit, but it is usually 1.0000 or less.

[0083] The above Raman spectrum characteristics will be described with reference to FIG. First, the Raman spectrum of the solid electrolyte (I) is obtained. Raman imaging is used to measure the Raman spectrum. Raman imaging is a microspectroscopic technique that combines Raman spectroscopy with microscopy. Specifically, it is a technique in which excitation light is scanned over the sample to detect measurement light containing Raman scattered light, and the distribution of components is visualized based on the intensity of the measurement light. The Raman imaging measurement conditions were as follows: 27°C, atmospheric air, excitation light 532 nm, objective lens 100x magnification, mapping method point scanning, 1 μm steps, exposure time per point 1 second, number of integrations 1, and measurement range 70 μm x 50 μm. However, the measurement range may be narrower depending on the film thickness of the sample. Furthermore, the Raman spectrum data is subjected to principal component analysis (PCA) to remove noise. Specifically, in the PCA process, spectra are recombined using components with autocorrelation coefficients of 0.6 or higher.

[0084] An example of the Raman spectrum of the solid electrolyte (I) 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 (R) obtained by linear regression analysis using the least squares method in the wavenumber region of 2 ) is calculated from 600 to 850 cm of the Raman spectrum in Figure 8. -1 In the wavenumber region, the regression line (thick line in Figure 8) is calculated by the least squares method, and the coefficient of determination R 2 The coefficient of determination takes a value between 0 (no linear correlation) and 1 (perfect linear correlation of the measurements) depending on the linear correlation of the measurements. In the solid electrolyte (I), as shown in FIG. -1 Almost no peaks are observed in the wavenumber region, resulting in a high coefficient of determination. The coefficient of determination R 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 2is calculated by the following formula: In the formula, x1 and y1 represent the wavenumber in the Raman spectrum and the Raman intensity corresponding to that wavenumber, x2 represents the (arithmetic) average of the wavenumbers, and y2 represents the (arithmetic) average of the Raman intensity.

[0085]

number

[0086] 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 originating from its structure is observed. -1 , and 771~785cm -1 When such a peak is present, a peak is observed in the wavenumber region of 600-850 cm. -1 When linear regression analysis is performed using the least squares method in the wavenumber region of , the coefficient of determination is calculated to be less than 0.9400. In other words, the above coefficient of determination being 0.9400 or more indicates that the solid electrolyte (I) contains almost no crystalline structure. As a result, the solid electrolyte (I) has the property of being easily plastically deformed and the property of Li + It is believed that the compound has excellent hopping properties.

[0087] (Infrared absorption spectrum characteristics) The solid electrolyte (I) has a wavelength of 800 to 1600 cm in the infrared absorption spectrum. -1 3000-3500 cm for the maximum absorption intensity in the wavenumber region -1 The ratio of the maximum absorption intensity in the wavenumber region (3000-3500 cm -1 Maximum absorption intensity in the wavenumber region / 800-1600cm -1 It is preferable that the ratio (maximum absorption intensity in the wave number region of 1 / 5 or more) is 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. Infrared absorption spectrum 3000-3500 cm -1The OH stretching vibration mode is observed in the wavenumber region of 800–1600 cm -1 The B-O stretching vibration mode is observed in the wavenumber region. In the solid electrolyte (I), a strong absorption intensity due to the OH stretching vibration mode is observed, indicating that the solid electrolyte (I) contains many OH groups and / or a large amount of water. In such a solid electrolyte (I), lithium ions tend to move easily, resulting in improved ionic conductivity. In addition, 800~1600cm -1 In the wavenumber region, vibrational modes originating from lithium salts can also be observed.

[0088] The infrared absorption spectrum measurement conditions can be as follows. Objective lens: 32x Cassegrain type (NA 0.65), Detector: MCT-A, Measurement range: 650-4000 cm -1 , resolution: 4cm -1 , Sample cell: Measurement is performed using a diamond cell. The obtained infrared absorption spectrum is corrected to remove signals from atmospheric water and CO2, and then offset correction is applied to the background to set the absorption intensity to 0. In addition, measurements are performed under atmospheric pressure after drying in a vacuum at 40°C for 2 hours.

[0089] The ionic conductivity (27°C) of the solid electrolyte (I) 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 It is often below S / cm.

[0090] Furthermore, it is also preferable that the solid electrolyte (I) exhibits the following characteristics or physical properties.

[0091] (mass reduction rate) The mass loss rate when the solid electrolyte (I) is heated to 800°C is preferably 20 to 40 mass%, more preferably 25 to 35 mass%. The mass loss caused by heating is considered to be due to the removal of water contained in the solid electrolyte (I). When the solid electrolyte (I) contains such water, the lithium ion conductivity can be further improved. In the heat treatment, the sample is heated at a temperature rising rate of 20°C / sec in the range of 25°C to 800°C. A known thermogravimetric differential thermal analyzer (TG-DTA) can be used to measure the mass loss. The mass loss rate is {(mass at 25°C - mass at 800°C) / mass at 25°C} x 100 It is calculated as follows. Before measuring the mass loss rate, the solid electrolyte (I) is vacuum dried at 40° C. for 2 hours. The mass loss rate is measured in the atmosphere.

[0092] The solid electrolyte layer constituting the secondary battery of the present invention may contain other components in addition to the solid electrolyte (I). For example, the solid electrolyte layer may contain 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 solid electrolyte layer or the electrode layer. The solid electrolyte layer may also contain a solid electrolyte other than the solid electrolyte (I). The other solid electrolyte refers to a solid electrolyte capable of moving lithium ions therein. The solid electrolyte is preferably an inorganic solid electrolyte. Examples of the other solid electrolyte include oxide-based solid electrolytes, halide-based solid electrolytes, and hydride-based solid electrolytes, with oxide-based solid electrolytes being preferred.

[0093] The thickness of the solid electrolyte layer constituting the secondary battery of the present invention is not particularly limited and can be, for example, 10 to 1000 μm, preferably 50 to 400 μm, or, for example, 0.1 to 50 μm, in which case, 1 to 20 μm is preferred.

[0094] <Positive electrode layer> Although the positive electrode layer is generally composed of a positive electrode current collector layer and a positive electrode active material layer, it may be composed of a positive electrode active material layer without including a positive electrode current collector layer. In other words, when the positive electrode active material layer also functions as a positive electrode current collector layer, it does not need to be composed of two layers, i.e., a positive electrode current collector layer and a positive electrode active material layer, and may be composed of a single layer. Furthermore, the positive electrode active material layer usually contains a solid electrolyte (preferably an inorganic solid electrolyte) together with the positive electrode active material, but it does not necessarily need to contain a solid electrolyte.

[0095] When the positive electrode active material layer contains a solid electrolyte, the type of the solid electrolyte is not particularly limited. From the viewpoint of achieving both flexibility and safety at a high level, it is preferable to use the above-mentioned solid electrolyte (I). In this way, the solid electrolyte (I) also acts as a binder for the solid particles contained in the positive electrode layer, and the positive electrode layer can be made more flexible. The positive electrode active material layer may contain one or more solid electrolytes. The content of the solid electrolyte in the positive electrode active material layer is not particularly limited, and the total content together with the positive 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 %.

[0096] The positive electrode active material itself used in the positive electrode layer can be any positive electrode active material that can be used in ordinary lithium ion secondary batteries. Preferred forms of the positive electrode active material are described below.

[0097] (Cathode 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, but 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. Furthermore, 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%). A material synthesized by mixing so that the Li / Ma molar ratio is 0.3 to 2.2 is more preferred. Specific examples of transition metal oxides 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.

[0098] (MA) Examples of transition metal oxides with a layered rock salt structure include LiCoO2 (lithium cobalt oxide [LCO]), LiNi2O2 (lithium nickel oxide), and LiNi 0.85 Co 0.10 Al 0.05 O2 (nickel cobalt lithium aluminate [NCA]), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (lithium nickel manganese cobalt oxide [NMC]) and LiNi 0.5 Mn 0.5 O2 (lithium manganese nickel oxide).

[0099] (MB) Transition metal oxides with spinel structure include, for example, LiMn2O4 (LMO), LiNi 0.5 Mn 1.5 O4([LNMO]), LiCoMnO4, Li2FeMn3O8, Li2CuMn3O8, Li2CrMn3O8, and Li2NiMn3O8.

[0100] (MC) Examples of lithium-containing transition metal phosphate compounds include olivine-type iron phosphates such as LiFePO4 ([LFP]) and Li3Fe2(PO4)3, iron pyrophosphates such as LiFeP2O7, cobalt phosphates such as LiCoPO4, cobalt pyrophosphates such as Li2CoP2O7, and monoclinic NASICON-type vanadium phosphates such as Li3V2(PO4)3 (lithium vanadium phosphate).

[0101] (MD) Examples of lithium-containing transition metal halophosphate compounds include iron fluorophosphates such as Li2FePO4F, manganese fluorophosphates such as Li2MnPO4F, and cobalt fluorophosphates such as Li2CoPO4F.

[0102] (ME) Examples of lithium-containing transition metal silicate compounds include Li2FeSiO4, Li2MnSiO4, and Li2CoSiO4.

[0103] The shape of the positive electrode active material is not particularly limited, and is usually particulate. The volume average particle diameter of the positive electrode active material is not particularly limited, and is preferably, for example, 0.1 to 50 μm. The volume average particle diameter of the positive electrode active material can be determined in the same manner as the volume average particle diameter of the negative electrode active material described below. 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.

[0104] The positive electrode active material may be surface-coated with a surface coating agent, sulfur, or phosphorus, as described below, or further with actinic rays, in the same manner as the negative electrode active material described below.

[0105] The positive electrode active material may be used alone or in combination of two or more kinds. The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is preferably 10 to 97 mass %, more preferably 30 to 95 mass %, further preferably 40 to 93 mass %, and particularly preferably 50 to 90 mass %.

[0106] Among these, the positive electrode active material is LiCoO2 (LCO), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM), LiFePO4(LFP), LiMn2O4(LMO), LiNi 0.5 Mn 1.5 O4(LNMO) or Li2CoP2O7, or a material coated with an interface resistance stabilizing layer such as an oxide or carbonaceous material described below, is preferred.

[0107] (Positive electrode current collector layer) The current collector layer constituting the positive electrode layer is an electron conductor, and is usually in the form of a film sheet. Examples of materials for the positive electrode current collector layer include aluminum (Al), aluminum alloys (Al alloys), copper (Cu), stainless steel, nickel, and titanium, with aluminum, aluminum alloys, copper (Cu) and titanium being preferred, and aluminum, aluminum alloys and copper (Cu) being more preferred. The positive electrode current collector layer may also be one having a coating layer (thin film) of carbon, nickel, titanium, aluminum, or silver on the surface of aluminum or stainless steel. Examples of the Al alloy include Al-Cu alloys (approximately 500 to 640°C), Al-Mn alloys (approximately 640°C), Al-Si alloys (approximately 530 to 570°C), Al-Mg alloys (approximately 570 to 650°C), Al-Mg-Si alloys (approximately 580 to 650°C), and Al-Zn-Mg alloys (approximately 480 to 640°C). Note that the temperatures in parentheses all refer to melting points at normal pressure.

[0108] The thickness of the positive electrode active material layer constituting the secondary battery of the present invention is not particularly limited and can be, for example, 5 to 500 μm, preferably 20 to 200 μm, or, for example, 0.1 to 50 μm, in which case, preferably 1 to 20 μm. The thickness of the positive electrode current collector layer constituting the secondary battery of the present invention is not particularly limited and can be, for example, 10 to 100 μm, preferably 10 to 50 μm, or, for example, 0.01 to 20 μm, in which case it is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm.

[0109] <Negative electrode layer> Although the negative electrode layer is generally composed of a negative electrode current collector layer and a negative electrode active material layer, it may be composed of a negative electrode active material layer without including a negative electrode current collector layer. In other words, when the negative electrode active material layer also functions as a negative electrode current collector layer, it does not need to be composed of two layers, i.e., a negative electrode current collector layer and a negative electrode active material layer, and may be composed of a single layer. Furthermore, the negative electrode active material layer usually contains a solid electrolyte (preferably an inorganic solid electrolyte) together with the negative electrode active material, but it does not necessarily need to contain a solid electrolyte.

[0110] When the negative electrode active material layer contains a solid electrolyte, the type of the solid electrolyte is not particularly limited. From the viewpoint of achieving both flexibility and safety at a high level, it is preferable to use the above-mentioned solid electrolyte (I). In this way, the solid electrolyte (I) also acts as a binder for the solid particles contained in the negative electrode layer, and the negative electrode layer can be made more flexible. The negative electrode active material layer may contain one or more solid electrolytes. The content of the solid electrolyte in the negative electrode active material layer 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 %.

[0111] The negative electrode active material itself used in the negative electrode layer can be any negative electrode active material that can be used in ordinary lithium ion secondary batteries. Preferred forms of the negative electrode active material are described below.

[0112] (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.

[0113] The carbonaceous material used as the negative electrode active material is a material substantially composed of carbon, such as petroleum pitch, carbon black such as 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 and 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, mesophase microspheres, graphite whiskers, and plate-like graphite. These carbonaceous materials can be divided into non-graphitizable carbonaceous materials (also called hard carbon) and graphite-based carbonaceous materials depending on the degree of graphitization. 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. The carbonaceous material is preferably hard carbon or graphite, and more preferably graphite.

[0114] 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 capable of absorbing and releasing lithium, and examples thereof include oxides of metal elements (metal oxides) such as Fe3O4, composite oxides of metal elements, composite oxides of metal elements and metalloid elements, and oxides of metalloid elements (metalloid oxides). Note that composite oxides of metal elements and composite oxides of metal elements and metalloid elements are also collectively referred to as metal composite oxides. As 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 elements" refers to elements that exhibit properties intermediate between those of metallic elements and non-metallic elements, and generally includes six elements: boron, silicon, germanium, arsenic, antimony, and tellurium, and further includes three elements: selenium, polonium, and astatine. Furthermore, "amorphous" means a substance that has a broad scattering band with a peak in the 2θ range of 20 to 40° when measured by X-ray diffraction using CuKα radiation, and may have crystalline diffraction lines. The strongest intensity of the crystalline diffraction lines observed in the 2θ range of 40 to 70° is preferably 100 times or less, more preferably 5 times or less, the intensity of the diffraction line at the peak of the broad scattering band observed in the 2θ range of 20 to 40°, and even more preferably no crystalline diffraction lines.

[0115] Among the compound group consisting of the above amorphous oxides and chalcogenides, amorphous oxides or the above 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 elements thereof are even more preferred. As the amorphous oxide and chalcogenide, Ga2O3, GeO, PbO, PbO2, Pb2O3, Pb2O4, Pb3O4, Sb2O3, Sb2O4, Sb2O8Bi2O3, Sb2O8Si2O3, Sb2O5, Bi2O3, Bi2O4, GeS, PbS, PbS2, Sb2S3 or Sb2S5 are preferred. As a negative electrode active material that can be used in combination with the amorphous oxide negative electrode active material mainly composed of 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.

[0116] 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 above metal oxides, metal composite oxides, or chalcogenides. More specifically, Li2SnO2 is exemplified. The negative electrode active material (for example, a metal oxide) preferably contains titanium (titanium oxide). Specifically, Li4Ti5O 12 Lithium titanate (LTO) is preferred because it has excellent rapid charge / discharge characteristics due to its small volumetric fluctuation during absorption and desorption of lithium ions, and because it can suppress electrode deterioration and improve the lifespan of all-solid-state lithium-ion secondary batteries.

[0117] 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.

[0118] The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is one that is 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, and metals such as Al and In. A negative electrode active material containing silicon (silicon-containing active material) that enables higher battery capacity is preferred, and a silicon-containing active material in which the silicon content of all constituent elements is 50 mol % or more is more preferred. Generally, these negative electrodes containing negative electrode active materials (for example, Si negative electrodes containing silicon element-containing active materials, Sn negative electrodes containing active materials containing tin elements) can occlude more Li ions than carbon negative electrodes (such as graphite and acetylene black). That is, the amount of Li ions occluded per unit mass increases. Therefore, the battery capacity can be increased. As a result, there is an advantage that the battery driving time can be lengthened.

[0119] Examples of the silicon element-containing active material include, for example, Si, SiO x (0 < x ≤ 1) and other silicon materials, and further, silicon-containing alloys containing titanium, vanadium, chromium, manganese, nickel, copper, or lanthanum (for example, LaSi2, VSi2, La-Si, Gd-Si, and Ni-Si), or organized active materials (for example, LaSi2 / Si). In addition, active materials containing silicon elements and tin elements such as SnSiO3 and SnSiS3 can be mentioned. Note that SiO x can be used as a negative electrode active material (semimetal oxide) itself, and can also be used as a negative electrode active material (its precursor material) capable of alloying with lithium in order to generate Si by the operation of an all-solid-state lithium ion secondary battery. Examples of the negative electrode active material having a tin element include, for example, Sn, SnO, SnO2, SnS, SnS2, and the active materials containing the above silicon elements and tin elements.

[0120] [[ID=十四]]In terms of battery capacity, a negative electrode active material capable of alloying with lithium is preferable as the negative electrode active material, the above silicon material or silicon-containing alloy (alloy containing silicon element) is more preferable, and silicon (Si) or silicon-containing alloy is even more preferable.

[0121] It is also preferable to use a titanium niobium composite oxide as the negative electrode active material. The titanium niobium composite oxide is expected to have a high theoretical volume capacity density, long life, and rapid charging ability. Examples of the titanium niobium composite oxide include, for example, TiNb2O7 ([TNO]).

[0122] It should be noted that in the translation of item , the Chinese character "十四" in the original text seems to be incorrect. It should be "14". The translation is adjusted accordingly.The shape of the negative electrode active material is not particularly limited, but is preferably particulate. The volume average particle size of the negative electrode active material is not particularly limited, but is preferably 0.1 to 60 μm, more preferably 0.5 to 20 μm, and even more preferably 1.0 to 15 μm. The volume average particle size is measured by the following procedure. The negative electrode active material is diluted with water (or heptane if the material is unstable in water) to prepare a 1% by mass dispersion in a 20 mL sample bottle. The diluted dispersion sample is irradiated with 1 kHz ultrasound for 10 minutes and then used for testing immediately thereafter. Using this dispersion sample, a laser diffraction / scattering particle size distribution analyzer is used to collect data 50 times at 25°C using a quartz measurement cell to obtain the volume average particle size. For other detailed conditions, refer to JIS Z 8828:2013 "Particle size analysis - dynamic light scattering method" as necessary. Five samples are prepared for each level, and the average value is used.

[0123] The negative electrode active material may be used alone or in combination of two or more kinds. The content of the negative electrode active material in the negative electrode active material layer 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 35 to 75 mass %.

[0124] The surface of the negative electrode active material may be coated with an oxide such as another metal oxide, or a carbon-based material, etc. 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 Li4Ti5O 12, Li2Ti2O5, LiTaO3, LiNbO3, LiAlO2, Li2ZrO3, Li2WO4, Li2TiO3, Li2B4O7, Li3PO4, Li2MoO4, Li3BO3, LiBO2, Li2CO3, Li2SiO3, SiO2, TiO2, ZrO2, Al2O3, BO3, and Li3AlF6. Carbon-based materials such as C, SiC, and SiOC (carbon-doped silicon oxide) can also be used as surface coating materials. The surface of the negative electrode active material may be treated with sulfur or phosphorus. Furthermore, the surface of the negative electrode active material may be subjected to a surface treatment with actinic rays or an active gas (for example, plasma) before or after the above surface coating.

[0125] Among these, TiNb2O7 (TNO), Li4Ti5O 12 (LTO) or Fe3O4, or a material coated with an interface resistance stabilizing layer such as an oxide or carbon-based material, is preferred.

[0126] (negative electrode current collector layer) The current collector layer constituting the negative electrode layer is an electron conductor, and is usually in the form of a film sheet. Examples of materials for the negative electrode current collector layer include aluminum, aluminum alloys, copper, copper alloys, stainless steel, nickel, zinc, and titanium, with aluminum, aluminum alloys, and copper being preferred. The negative electrode current collector layer may also be one having a coating layer (thin film) of carbon, nickel, zinc, titanium, aluminum, gold, or silver on the surface of aluminum, copper, a copper alloy, or stainless steel.

[0127] The thickness of the negative electrode active material layer constituting the secondary battery of the present invention is not particularly limited and can be, for example, 5 to 500 μm, preferably 20 to 200 μm, or, for example, 0.1 to 50 μm, in which case, preferably 1 to 20 μm. The thickness of the negative electrode current collector layer constituting the secondary battery of the present invention is not particularly limited and can be, for example, 10 to 100 μm, preferably 10 to 50 μm, or, for example, 0.01 to 20 μm, in which case, it is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm.

[0128] (Current Collector Layer in Secondary Battery of the Present Invention) In the secondary battery of the present invention, at least one of the positive electrode layer and the negative electrode layer includes a current collector layer, and at least one of the current collector layers is a layer having, as a constituent material, a metal that melts at 670°C under normal pressure, or a layer having this metal in a coating layer. In the present invention and the specification, "a metal that melts at 670°C under normal pressure" means a metal that melts at 670°C under a pressure condition of 101.33 kPa, and means a metal whose melting point at normal pressure is 670°C or lower. Specific examples of "metals that melt at 670°C under normal pressure" include Al (melting point at normal pressure: approximately 650 to 660°C) and Al alloys (melting point at normal pressure: approximately 480 to 650°C) described in the above-mentioned positive electrode current collector layer, and Al (melting point at normal pressure: approximately 650 to 660°C) described in the above-mentioned negative electrode current collector layer. In addition, in conventional all-solid-state lithium ion secondary batteries using oxide-based solid electrolytes, aluminum or an aluminum alloy is sometimes cited as a constituent material of the current collector layer or a material used in the coating layer. However, as described above, conventional oxide-based solid electrolytes require a high-temperature sintering treatment, and therefore, in reality, no all-solid-state lithium ion secondary battery using a conventional oxide-based solid electrolyte has existed that has a current collector layer containing aluminum or an aluminum alloy as a constituent material or a current collector layer containing this metal in a coating layer.

[0129] The positive electrode layer and the negative electrode layer may contain components (other components) other than the solid electrolyte and the active material in their active material layers, such as a conductive additive. As the conductive additive, a commonly known conductive additive can be used. Examples of the conductive additive include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, and furnace black, amorphous carbon such as needle coke, fibrous carbon such as vapor-grown carbon fiber and carbon nanotubes, and carbonaceous materials such as graphene and fullerene. In addition, conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives may also be used. In addition to the above-mentioned conductive additives, ordinary conductive additives that do not contain carbon atoms, such as metal powder or metal fibers, may also be used. A conductive additive is one that does not insert or release Li when the battery is charged or discharged, 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 or 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 or discharged is not uniquely determined, but is determined by its combination with the active material. The content of the conductive additive in the positive electrode active material layer is not particularly limited, but is preferably, for example, 0 to 10 mass %, and more preferably 1 to 5 mass %. The content of the conductive additive in the negative electrode active material layer is not particularly limited, but is preferably, for example, 0 to 10 mass %, and more preferably 1 to 5 mass %.

[0130] Other components include the binder and lithium salts described above.

[0131] <Manufacturing all-solid-state lithium-ion secondary batteries> The secondary battery of the present invention can be manufactured by following a conventional method for manufacturing an all-solid-state secondary battery, except that at least the solid electrolyte layer uses a solid electrolyte (I), at least one of the positive electrode layer and the negative electrode layer includes a current collector layer, and at least one of the current collector layers uses a layer containing a specific metal as a constituent material or a layer containing this metal in a coating layer. That is, the manufacturing method for the secondary battery of the present invention can include a step of obtaining a laminate comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer arranged in this order. Here, the amount of water in the solid electrolyte (I) used may or may not satisfy the amount specified in the present invention. In the manufacturing method for the all-solid-state secondary battery, regardless of the amount of water in the solid electrolyte (I) used, the manufacturing method for the secondary battery of the present invention can also include a step of subjecting the formed solid electrolyte layer to a drying treatment, if necessary, in order to set the amount of water in the solid electrolyte (I) contained in the constituent layers, such as the solid electrolyte layer, to the amount specified in the present invention. This drying step for the constituent layers, such as the solid electrolyte layer, may be performed at any stage after the formation of the constituent layers, such as the solid electrolyte layer, as long as the solid electrolyte (I) of the constituent layers, such as the solid electrolyte layer, in the resulting secondary battery can be adjusted to the water content specified in the present invention. To more reliably achieve the water content specified in the present invention, it is preferable to subject the drying treatment to a laminate, in which at least the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are arranged in this order, while the laminate is placed in a battery cell. The drying method is not particularly limited, and the water content of the solid electrolyte (I) of the solid electrolyte layer can be reduced to the range specified in the present invention by, for example, using a desiccator, subjecting the laminate to vacuum drying, subjecting the laminate to vacuum freeze-drying, or subjecting the laminate to heat treatment. The secondary battery of the present invention is preferably formed by sealing a laminate having the above-mentioned cathode layer, solid electrolyte layer, and anode layer arranged in this order. By sealing, it is possible to more reliably prevent moisture from entering the solid electrolyte layer after the drying step, thereby further improving cycle characteristics. The sealing method is not particularly limited as long as it can block or suppress the intrusion of moisture (air). For example, a method of sealing the laminate by closing the lid of a housing (battery cell) containing the laminate having the above-mentioned cathode layer, solid electrolyte layer, and anode layer arranged in this order via a gasket such as an O-ring can be used. Furthermore, the cell resistance can be improved by heating the resulting laminate (e.g., at 80°C for 2 hours).

[0132] In one embodiment of the method for producing a secondary battery of the present invention, at least one of the current collector layers included in at least one of the positive electrode layer and the negative electrode layer is a layer having, as a constituent material, a metal that melts at 670°C under normal pressure, or a layer having this metal in a coating layer. As described above, in the secondary battery of the present invention, at least the solid electrolyte layer is composed of the solid electrolyte (I) and does not require high-temperature sintering, so that metals that melt at 670°C under atmospheric pressure, which have been difficult to use in conventional oxide-based solid electrolytes, can be used as constituent materials for the current collector layer or metals contained in the coating layer. Metals that melt at 670°C under atmospheric pressure are as described above.

[0133] In another embodiment of the method for producing a secondary battery of the present invention, at least one of the current collector layers included in at least one of the positive electrode layer and the negative electrode layer is a layer containing Cu as a constituent material or a layer containing Cu in a coating layer, and a laminate of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer is produced at 300°C or lower in an atmosphere containing oxygen gas. As described above, the secondary battery of the present invention has at least a solid electrolyte layer made of the solid electrolyte (I) and does not require high-temperature sintering, so that even in an oxygen-containing atmosphere, Cu can be used as a constituent material of the current collector layer or a metal contained in the coating layer, even though Cu oxidizes under high-temperature conditions containing oxygen gas, which has been difficult to use in conventional oxide-based solid electrolytes. When the secondary battery is manufactured in an oxygen-containing atmosphere at 300°C or less, the oxidation of Cu can be suppressed by adjusting conditions such as heating time and heating temperature. The oxygen gas-containing atmosphere generally refers to the atmosphere. The oxygen gas concentration is not particularly limited, and the upper limit can be 100 vol% or less, and the lower limit can be, for example, 1 vol% or more. "Manufacturing at 300°C or less" essentially means that there is no need for a high-temperature sintering process, which was essential for conventional oxide-based solid electrolytes. In the present invention, the secondary battery of the present invention can be manufactured by a manufacturing process at 300°C or less in an oxygen gas-containing atmosphere, and can be manufactured in an oxygen gas-containing atmosphere at preferably 200°C or less, more preferably 120°C or less, and even more preferably 100°C or less. In particular, it can be manufactured in an oxygen gas-containing atmosphere at preferably 80°C or less, more preferably 60°C or less, even more preferably 40°C, and particularly preferably under conditions without heating (for example, room temperature of 20 to 27°C).

[0134] Furthermore, there are no particular limitations on the method for forming a laminate in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are arranged in this order. As a method for manufacturing an all-solid-state secondary battery, for example, a cathode-forming composition (cathode slurry) containing a cathode active material is applied to a metal foil serving as a cathode current collector layer to form a cathode active material layer, a solid electrolyte layer-forming dispersion (solid electrolyte slurry) containing a solid electrolyte is then applied to the cathode active material layer to form a solid electrolyte layer, and an anode-forming composition (anode slurry) containing a anode active material is applied to the solid electrolyte layer to form a anode active material layer, and an anode current collector layer (metal foil) is then superimposed on the anode active material layer. If necessary, the entire structure is subjected to a pressure treatment to obtain an all-solid-state lithium-ion secondary battery as shown in FIG. Alternatively, an all-solid-state lithium-ion secondary battery can be produced by reversing the method of forming each layer, forming an anode active material layer, a solid electrolyte layer, and a cathode active material layer on an anode current collector layer, overlaying a cathode current collector layer (metal foil) on the cathode active material layer, and subjecting the whole to pressure treatment as necessary.

[0135] As another method, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are each separately prepared, and these are 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 the laminate is pressurized as necessary to produce an all-solid-state lithium ion secondary battery. In this case, when forming each layer, a support such as a nonwoven fabric may be disposed as necessary to form each layer into a free-standing film. Note that, in general, it is preferable to remove the support from the free-standing film when laminating each layer to fabricate an all-solid-state lithium-ion secondary battery.

[0136] As yet another method, a powder constituting the positive electrode active material layer (hereinafter referred to as positive electrode composite powder), a powder constituting the solid electrolyte layer (hereinafter referred to as solid electrolyte powder), and a powder constituting the negative electrode active material layer (hereinafter referred to as negative electrode composite powder) are pressed into a predetermined shape to form pellets for each layer, which are then stacked on a current collector layer for the positive electrode or negative electrode and pressed, thereby also enabling the production of an all-solid-state lithium ion secondary battery. For example, a solid electrolyte powder is filled into a mold and pressed to form a solid electrolyte pellet. A negative electrode composite powder is filled on one side of the resulting solid electrolyte pellet and pressed to form a negative electrode composite pellet. A positive electrode composite powder is filled on the other side of the resulting solid electrolyte pellet and pressed to form a positive electrode composite pellet. A compact is obtained in which the positive electrode composite pellet, the solid electrolyte pellet, and the negative electrode composite pellet are stacked in this order. The resulting compact is then placed on a negative electrode current collector layer (metal foil) with the negative electrode composite pellet facing downward. A positive electrode current collector layer (metal foil) is then placed on top of the positive electrode composite pellet. The entire assembly is then subjected to a pressure treatment to obtain an all-solid-state lithium-ion secondary battery as shown in FIG. There are no particular limitations on the method for preparing the solid electrolyte powder, and it can be prepared, for example, by freeze-drying a solid electrolyte layer-forming dispersion liquid (solid electrolyte slurry) containing the solid electrolyte in a vacuum. There are no particular limitations on the method for preparing the negative electrode composite powder, and it can be prepared, for example, by mixing a previously prepared solid electrolyte powder with components for forming the negative electrode active material layer, including the negative electrode active material. There are no particular limitations on the method for preparing the positive electrode composite powder, and it can be prepared, for example, by mixing a solid electrolyte powder prepared in advance with components for forming a positive electrode active material layer, including a positive electrode active material. There are no particular restrictions on the pressurizing conditions when producing the negative electrode composite pellets, solid electrolyte pellets, and positive electrode composite pellets. For example, the pellets can be produced by applying a pressure of 50 to 300 MPa for about 10 seconds. Furthermore, the negative electrode composite pellet and the negative electrode current collector layer, and the positive electrode composite pellet and the positive electrode current collector layer can also be pressure-bonded together by applying a pressure of about 60 MPa. There is no particular limitation on the order in which the pellets for each layer are formed. For example, the pellets may be formed in the order of the negative electrode composite pellets, the solid electrolyte pellets, and the positive electrode composite pellets. As another method, a negative electrode composite pellet, a solid electrolyte pellet, and a positive electrode composite pellet are each separately prepared, the obtained pellets are stacked, and the stacked pellets are sandwiched between the positive and negative electrode current collector layers, and then pressed, whereby an all-solid-state lithium ion secondary battery can also be produced.

[0137] Furthermore, a small laminated battery in which a plurality of positive electrode layers, solid electrolyte layers, and negative electrode layers are laminated, with a solid electrolyte layer disposed between adjacent positive electrode layers and negative electrode layers, can be manufactured by referring to the lamination method described in paragraphs

[0033] to

[0046] of JP 2016-001602 A. The positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer can be manufactured based on the manufacturing method of the present invention described above.

[0138] 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.

[0139] 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 layers. The solid electrolyte (I) itself is soft and plastically deformable, and acts as a binder, contributing to improved adhesion between solid particles or layers. Therefore, it is possible to form layers without using a binder such as an organic polymer.

[0140] 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 elevated pressure and then releasing the pressure until the pressure falls within the range of the pressure conditions during use of the secondary battery.

[0141] <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, electronic book players, mobile phones, cordless phone handsets, pagers, handheld terminals, portable fax machines, portable copiers, portable printers, headphone stereos, video camcorders, LCD televisions, 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. [Example]

[0142] The present invention will be described in more detail based on examples, but the present invention is not limited thereto. In the present invention, room temperature means 27°C. Furthermore, the production of the solid electrolyte and the production of the secondary battery described below were carried out in the atmosphere containing moisture and oxygen gas.

[0143] [Reference Example 1: Preparation by the above steps 0, 1A to 3A] Powdered Li2B4O7 crystals (LBO powder) (manufactured by Rare Metallic Co., Ltd.) were ball-milled using a ball mill (Fritsch, planetary ball mill P-7) under the following conditions: pot: stabilized zirconia (YSZ) (45 mL), milling balls: YSZ (average particle diameter: 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"). To 1 g of the obtained fine lithium-containing oxide particles, 0.05 g of LiFSI (chemical formula: Li(FSO2)2N) was added as a lithium salt (5 mass % relative to the fine lithium-containing oxide particles), and the mixture was further ball milled for 100 hours. The obtained powder was added to water so that the powder concentration was 42 mass %, and ultrasonically dispersed for 30 minutes. Subsequently, the obtained dispersion was transferred to a glass petri dish and dried in air at 120°C for 2 hours to obtain a solid electrolyte film. Subsequently, the obtained film was peeled off to obtain a powdered solid electrolyte (I)-1.

[0144] <Production and evaluation of solid electrolyte compacts> The powdered solid electrolyte (I)-1 obtained above was compacted at 27°C (room temperature) under an effective pressure of 220 MPa to obtain a compacted body of the solid electrolyte (compacted body 1). The compacted body 1 had a cylindrical shape with a diameter of 10 mm and a thickness of 1 mm. The ionic conductivity of the obtained compacted body 1 was measured, and the ionic conductivity of the compacted body 1 was found to be 1.5 x 10 at 27°C. -4 S / cm and 4.0 × 10 at 60°C. -4 It was S / cm.

[0145] The ionic conductivity of the solid electrolyte (I)-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).

[0146] X-ray diffraction measurements of solid electrolyte (I)-1 were 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 (I)-1 was found to be in an amorphous state.

[0147] Using the solid electrolyte (I)-1 obtained above, X-ray total scattering measurements were performed at SPring-8L04B2 (accelerating voltage: 61.4 keV, wavelength: 0.2019 Å). The sample was sealed in a 2 mm or 1 mm Kapton capillary and the experiment was performed. The obtained data were Fourier transformed as described above to obtain the reduced pair distribution function. As a result of the analysis, the reduced pair distribution function G(r) obtained from the X-ray total scattering measurement showed that, in the range of r from 1 to 5 Å, G(r) at the peak top exceeded 1.0, and a first peak was confirmed with a peak top located at 1.43 Å, and a second peak was confirmed with G(r) at the peak top exceeded 1.0, and a peak top located at 2.40 Å. On the other hand, in solid electrolyte (I)-1, the peaks assigned to the B-O and B-B distances observed in typical lithium tetraborate crystals were maintained. Typical lithium tetraborate crystals have a structure in which BO4 tetrahedra and BO3 triangles exist in a 1:1 ratio (diborate structure), and it was presumed that this structure was maintained in solid electrolyte (I)-1.

[0148] The solid electrolyte (I)-1 obtained above 7 The solid electrolyte (I)-1 is measured at 20°C using Li-NMR, and the chemical shift of the peak appears in the range of -100 to +100 ppm (FWHM 1). 7 The ratio of the full width at half maximum (FWHM2) 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 {(FWHM2 / FWHM1) × 100} was 33%. Also, solid 7 When the spectrum obtained by Li-NMR measurement at 20°C was subjected to waveform separation of the first peak appearing in the range of -100 to +100 ppm, a second peak with a chemical shift in the range of -3 to +3 ppm and a full width at half maximum of 5 ppm or less was found, and the ratio of the area intensity of the second peak to the area intensity of the first peak was 4%.

[0149] The solid electrolyte (I)-1 obtained above was subjected to infrared absorption spectroscopy under the conditions described above. In the obtained infrared absorption spectrum, -1 3000-3500 cm for the maximum absorption intensity in the wavenumber region -1 The ratio of the maximum absorption intensities in the wavenumber region of 0.72 was found to be 0.72.

[0150] In the Raman spectrum of the solid electrolyte (I)-1 obtained above, -1 The coefficient of determination obtained by linear regression analysis using the least squares method in the wavenumber region was 0.9974. When the solid electrolyte (I)-1 was heated from 25° C. to 800° C. as described above, the mass loss rate was 29.8%.

[0151] Regarding the analysis of each element in the obtained solid electrolyte (I)-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 by adding up the analyzed masses of elements other than O and subtracting it from the total powder mass. The results are shown in the table below.

[0152] [Reference Example 2: Preparation by the above steps 1B to 3B and method 2] 1 g of the fine lithium-containing oxide particles used in Reference Example 1 was added to water so that the concentration of the fine particles was 42 mass %, and ultrasonic dispersion was performed for 30 minutes. 0.05 g of LiFSI (chemical formula: Li(FSO2)2N) was added as a lithium salt to the obtained dispersion (5 mass % relative to the fine lithium-containing oxide particles), and ultrasonic dispersion was performed for another 30 minutes. The obtained dispersion was transferred to a glass petri dish and dried in the atmosphere at 120°C for 2 hours to obtain a solid electrolyte film. The obtained film was then peeled off to obtain a powdered solid electrolyte (I)-2. Various evaluations were performed on the solid electrolyte (I)-2 in the atmosphere in the same manner as in Reference Example 1. The results are summarized in the table below.

[0153] [Reference Example 3: Preparation by the above steps 1B to 3B and method 3] Powdered Li2B4O7 (LBO powder) (Rare Metallic Co., Ltd.) was ball milled using a ball mill (Fritsch Planetary Ball Mill P-7) 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), amount of LBO powder: 4.2 g, atmosphere: air, ball mill treatment time: 100 hours, to obtain fine lithium-containing oxide. The obtained fine particles of lithium-containing oxide were added to water so that the concentration of the fine particles was 42 mass %, and the mixture was subjected to ultrasonic treatment for 60 minutes, whereby dispersion liquid 1 was obtained. Next, 3.25 g of LiFSI (chemical formula: Li(FSO2)2N) as a lithium salt was added to water to a concentration of 87 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 (I)-3. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were carried out in the atmosphere using solid electrolyte (I)-3 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0154] [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(FSO2)2N) as a lithium salt was added to water at a concentration of 87 mass % and subjected to ultrasonic treatment for 60 minutes to obtain solution 4. The obtained dispersion 3 and solution 4 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 (I)-4. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were carried out in the atmosphere using solid electrolyte (I)-4 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0155] [Reference Example 5: Preparation by the above 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(FSO2)2N) as a lithium salt was added to water at a concentration of 87 mass % and subjected to ultrasonic treatment for 60 minutes to obtain Solution 6. The obtained dispersion 5 and solution 6 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 a powdered solid electrolyte (I)-5. The obtained powdered solid electrolyte (I)-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.

[0156] [Reference Example 6: Preparation by the above 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(F3CSO2)2N) as a lithium salt was added to water at a concentration of 87 mass %, and the mixture was subjected to ultrasonic treatment for 60 minutes to obtain a 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 (I)-6. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were carried out in the atmosphere using solid electrolyte (I)-6 in the same manner as in Reference Example 1. The results are summarized in the table below. In Reference Example 6, the carbon amounts shown in Table 1 below were estimated from the analyzed mass of sulfur, taking into account the weight of each atom in the lithium salt.

[0157] [Comparative Reference Example 1] The LBO powder used in Reference Example 1 (powdered Li2B4O7 crystals that were not ball-milled) was subjected to elemental analysis. As a result, the composition of the obtained LBO 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 compact C1 for comparison. The ionic conductivity of the obtained compact C1 was undetectable. Furthermore, X-ray total scattering measurement was performed using LBO powder to obtain the reduced pair distribution function G(r) in the same manner as in Reference Example 1. Figure 10 shows the reduced pair distribution function G(r) obtained from the LBO powder. The analysis revealed that the reduced pair distribution function G(r) obtained from X-ray total scattering measurement of the LBO powder contained a first peak with a top at 1.40 Å (corresponding to the B-O proximity) and a second peak with a top at 2.40 Å (corresponding to the B-B proximity), with G(r) values ​​at the peak tops of both the first and second peaks being 1.0 or greater (see Figure 10). Furthermore, peaks with tops at 3.65 Å, 5.22 Å, 5.51 Å, and 8.54 Å were also present, and the absolute values ​​of G(r) at the peak tops of each of these peaks clearly exceeded 1.0 (see Figure 10).

[0158] X-ray diffraction measurement was carried out using CuKα radiation on the LBO powder of Comparative Reference Example 1. The measurement conditions were 0.01° / step, 3° / min. Figure 11 shows the X-ray diffraction pattern of the LBO powder of Comparative Reference Example 1. As shown in Figure 11, the LBO powder used in Comparative Reference Example 1 exhibited multiple narrow peaks. 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 included a peak at 25.54° corresponding to the (2,0,2) plane, a peak at 33.58° corresponding to the (2,1,3) plane, and a peak at 34.62° corresponding to the (3,1,2) plane, and the intensities of these three peaks were approximately equal. These peaks were derived from crystalline components.

[0159] [Comparative Reference Example 2] As a result of performing elemental analysis on the fine particles of lithium-containing oxide prepared in Reference Example 1 (powdered Li2B4O7 crystals ball-milled), the composition of the fine particles of lithium-containing oxide was 1.94 B 4.00 O6.80 It was. Next, 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 It was S / cm.

[0160] In the table below, if the reduced pair distribution function G(r) obtained from the X-ray total scattering measurement as described above has 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 if 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-range G(r)" is marked with "A," and otherwise it is marked with "B." In Reference Examples 1 to 5 and 9 to 13 shown in the table below, the G(r) value at the peak top of the first peak was 1.2 or more. In addition, in the above-mentioned reduced pair distribution function G(r), when the absolute value of G(r) is less than 1.0 in the range of r greater than 5 Å and not more than 10 Å, the column "Long-distance G(r)" in the table below is marked with "A", and when the absolute value of G(r) is not less than 1.0, it 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.

[0161] In the table below, the "Elemental Analysis" column shows the molar amount of each element contained in the composition of the solid electrolyte (I) obtained in each Reference Example and the lithium-containing oxide in each Comparative Reference Example as a relative value with the content of B set to "4.00". In the table below, blank spaces mean that the corresponding element is not contained.

[0162] 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.

[0163] 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 listed based on the following criteria. <Standards 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%

[0164] 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 800-1600cm -1 The maximum absorption intensity in the wavenumber region of [A] is 0.20 or more and is indicated as "A", and the maximum absorption intensity in the wavenumber region of [B] is less than 0.20. In the table below, "-" means that no measured value is shown.

[0165] [Table 1]

[0166] [Table 2]

[0167] As shown in the table above, the solid electrolytes (I)-1, (I)-2, (I)-3, (I)-4, (I)-5, and (I)-6 of Reference Examples 1 to 6 have desired characteristics or physical properties and are excellent in ionic conductivity. Furthermore, the results of elemental analysis confirmed that the solid electrolytes in Reference Examples 3 to 6 had a higher Li content. 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). This allowed for a larger amount of lithium salt to be mixed, which is presumably responsible for the increased amount of Li incorporated into the solid electrolyte. Furthermore, Reference Examples 3, 4, and 5, which used LiFSI as the lithium salt, were found to have improved ionic conductivity. This is presumably due to the presence of highly mobile Li in the increased Li.

[0168] <Effect of water in solid electrolyte> A compact (pellet) (10 mm diameter, 0.9 mm thickness) of the solid electrolyte (I)-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 replaced with a Ti electrode. The results are shown in Table 3.

[0169] [Table 3]

[0170] The solid electrolyte (I)-3 of Reference Example 3 has a peak in the infrared absorption spectrum of 3000 to 3500 cm -1 Since strong absorption intensity due to the OH stretching peak is observed in the wavenumber region, it is thought that there are many OH groups and water. Furthermore, the presence of free water and bound water is suspected. In the above, the pellet was first dried by vacuum drying under conditions thought to volatilize the free water, and then dried under more severe drying conditions, and the ionic conductivity at each stage was evaluated.

[0171] As shown in the table above, the pressure was 200 Pa after 5 minutes of drying, and the free water was considered to have evaporated. 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 the ionic conductivity.

[0172] [Reference Example 7: Preparation by the above steps 1B to 3B and method 3] Dispersion 9 having a concentration of fine lithium-containing oxide particles of 42 mass % was obtained in the same manner as in the preparation of dispersion 1 in Reference Example 3 above. Next, 7.12 g of LiTFSI (chemical formula: Li(F3CSO2)2N) as a lithium salt was added to water to a concentration of 87 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 (I)-7. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were carried out in the atmosphere using solid electrolyte (I)-7 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0173] [Reference example 8] A solid electrolyte (I)-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 (I) 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.

[0174] [Reference examples 9-13] Solid electrolytes (I)-9 to (I)-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 (I) were changed to the amounts shown in the table below, and 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 used to carry out evaluation in the atmosphere.

[0175] In the table below, the columns "fine particles of lithium-containing oxide", "lithium salt", and "water" indicate relative molar ratios. For example, in Reference Example 7, the molar ratio of lithium salt to fine particles of lithium-containing oxide is 1, and the molar ratio of water to fine particles of lithium-containing oxide is 11. The molar ratios were calculated by the following method. For the analysis of each element, 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 the 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 the fine particles of the lithium-containing oxide to the lithium salt in the solid electrolyte was calculated from the molar ratio of an element (e.g., B) present only in the fine particles of the lithium-containing oxide to the element present only in the lithium salt. The molar ratio of the fine particles of the lithium-containing oxide to water was calculated by subtracting the molar ratio 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 resulting molar amount of O derived from water and the molar amount of the fine particles of the lithium-containing oxide.

[0176] [Table 4]

[0177] The content (mass %) of each component in the solid electrolyte (I) was calculated based on the molar amount and molecular weight shown in Table 4. The results are shown in Table A below.

[0178] [Table A]

[0179] [Table 5]

[0180] As shown in the above table, the solid electrolytes of the respective reference examples satisfied the composition defined in claim 1 of the present application, had the desired characteristics or properties, and exhibited excellent ionic conductivity.

[0181] [Production Example 1] Production of coated secondary battery <Preparation of fine lithium-containing oxide particles> 45 g of powdered Li2B4O7 crystals (LBO powder) (manufactured by Rare Metallic Co., Ltd.), 770 g of zirconia beads, and 3 mL of water were placed in a 500 mL zirconia pot and sealed with a Teflon (registered trademark) ring and a zirconia lid. This was then subjected to ball milling treatment using a planetary ball milling machine (P-7, manufactured by Fritsch) at 300 rpm (revolutions per minute) for 45 hours to pulverize the LBO powder and obtain fine particles of lithium-containing oxide.

[0182] <Preparation of solid electrolyte slurry: Preparation of solid electrolyte (I) by the above steps 1B to 3B and method 1> 10 g of the fine particles of the lithium-containing oxide, 15 g of water, and 11 g of LiFSI were mixed in a beaker and subjected to ultrasonic treatment using an ultrasonic cleaner for 30 minutes to obtain a dispersion liquid, which was further stirred with a magnetic stirrer for 30 minutes to obtain a solid electrolyte slurry 1. This solid electrolyte slurry 1 was vacuum dried at 40°C and 20 Pa for 15 hours to obtain a powder. The obtained powder was stored in a desiccator (humidity 5%) for several days and then analyzed under atmospheric conditions. It was confirmed that the powder had the above-mentioned X-ray diffraction characteristics and was in an amorphous state. In addition, the ionic conductivity was measured by the above-mentioned method and was 4.5 × 10 -3The molar ratio of the LiFSI content to the lithium-containing oxide content was 1, and the molar ratio of the water content was 9. The elemental composition was Li=3, B=4, O=20, F=2, S=2, and N=1.

[0183] <Preparation of positive electrode slurry> To 5.2 g of the above solid electrolyte slurry 1, 5.0 g of the positive electrode active material LiCoO2 (volume average particle diameter 12 μm) and 4.8 g of a 6 mass % aqueous dispersion of carbon nanotubes (CNT) (manufactured by KJ Specialty Paper Co., Ltd.) as a conductive additive were added, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain positive electrode slurry 1.

[0184] <Preparation of negative electrode slurry> To 7.6 g of the above solid electrolyte slurry 1, 5.0 g of the negative electrode active material TiNb2O7 (volume average particle diameter 10 μm) and 9.8 g of a 6 mass % aqueous dispersion of CNT (manufactured by KJ Specialty Paper Co., Ltd.) as a conductive additive were added, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain negative electrode slurry 1.

[0185] <Preparation of positive electrode laminate [solid electrolyte layer / positive electrode active material layer / Al current collector layer]> The positive electrode slurry 1 was applied to a 50 μm thick A4-size aluminum foil using a desktop coater with an applicator gap of 100 μm and a coating speed of 30 mm / s. After leaving the mixture at room temperature for 1 hour, the solid electrolyte slurry 1 was applied to the positive electrode slurry coating film in a multilayer fashion using a desktop coater with an applicator gap of 200 μm and a coating speed of 90 mm / s. The multilayer coating film was stored in a desiccator at a relative humidity of 5% or less for 12 hours to dry, and then punched out to a diameter of 10 mm using a hand punch to obtain a positive electrode laminate (solid electrolyte layer / positive electrode active material layer / Al current collector layer). The thickness of the solid electrolyte layer was approximately 60 μm.

[0186] <Preparation of negative electrode laminate [solid electrolyte layer / negative electrode active material layer / Al current collector layer]> The negative electrode slurry 1 was applied to a 50 μm thick A4-size aluminum foil using a desktop coater with an applicator gap of 200 μm and a coating speed of 30 mm / s. After leaving the mixture at room temperature for 1 hour, the solid electrolyte slurry 1 was applied to the negative electrode slurry coating in a multilayer fashion using a desktop coater with an applicator gap of 300 μm and a coating speed of 90 mm / s. The multilayer coating was stored in a desiccator at a relative humidity of 5% or less for 12 hours to dry, and then punched out to a diameter of 10 mm using a hand punch to obtain a negative electrode laminate (solid electrolyte layer / negative electrode material layer / Al current collector layer). The solid electrolyte layer had a thickness of approximately 60 μm.

[0187] <Fabrication of coated secondary battery> The negative electrode side laminate obtained above was placed on a 10 mm diameter SUS stand of an all-solid-state battery evaluation cell (product name: KP-SolidCell) manufactured by Hosensha, with the solid electrolyte layer side facing upward, and the positive electrode side laminate obtained above was placed on top of that with the solid electrolyte layer side facing downward. Next, a Teflon (registered trademark) tube (hereinafter referred to as the Teflon tube) with an inner diameter of 10.2 mm was inserted into the upper side (positive electrode laminate side) of Cell A, which was composed of the positive electrode laminate and the negative electrode laminate stacked in that order. A polished Ti plate with a diameter of 10 mm and a thickness of 2 mm was inserted through the hole at the top of the Teflon tube and placed on top of the positive electrode laminate. A Ti rod with a diameter of 10 mm and a height of 2 cm was then inserted and placed on top of the Ti plate. Next, the upper housing of the KP-SolidCell was fitted and sealed using a double O-ring, four bolts, and wing nuts. Cell A was constrained from above and below with a torque of 5 Nm (equivalent to 30 MPa) using a constraining pressure application mechanism installed above the KP-SolidCell. Next, the KP-SolidCell was opened and cell A was removed. Any excess liquid components that had leaked out due to the application of confining pressure were wiped off, and then cell A was placed in the KP-SolidCell again in the same manner as above, and a confining pressure of 5 Nm (equivalent to 30 MPa) was applied. The cell was then subjected to vacuum freeze-drying for two hours with the top lid open to thoroughly remove moisture from inside Cell A. After removing the KP-SolidCell from the vacuum dryer, the top lid was closed with a double O-ring to seal it. This was left at room temperature for 40 hours to produce a coated secondary battery A. A coated secondary battery B was produced in the same manner as the coated secondary battery A, except that in the production of the coated secondary battery A, a 50 μm thick A4 size Ti foil was used as the current collector layer in the positive electrode instead of the 50 μm thick A4 size Al foil, and a 50 μm thick A4 size Cu foil was used as the current collector layer in the negative electrode instead of the 50 μm thick A4 size Al foil. In the coated secondary batteries A and B, the positive electrode active material layer had a thickness of 80 μm, the solid electrolyte layer had a thickness of 120 μm, and the negative electrode active material layer had a thickness of 100 μm.

[0188] [Production Example 2] Production of powder type secondary battery <Preparation of Solid Electrolyte Powder 1: Preparation of Solid Electrolyte (I) by Steps 1B to 3B and Method 1> 10 g of the fine particles of the lithium-containing oxide prepared in Production Example 1 above, 15 g of water, and 11 g of LiFSI were mixed in a beaker and subjected to ultrasonic treatment (dispersion) using an ultrasonic cleaner for 30 minutes, and then further stirred and dispersed using a magnetic stirrer for 30 minutes to obtain a solid electrolyte slurry. The obtained slurry was freeze-dried at 40°C and 10 Pa for 12 hours to obtain a solid electrolyte powder 1.

[0189] <Preparation of Positive Electrode Composite Powder 1> Positive electrode composite powder 1 was obtained by mixing 100 mg of the above solid electrolyte powder 1, 150 mg of the positive electrode active material LiCoO2 (volume average particle diameter 12 μm), and 3 mg of the conductive additive carbon black (manufactured by Denka Corporation) in a mortar.

[0190] <Preparation of negative electrode composite powder 1> 60 mg of the above solid electrolyte powder 1, 120 mg of anode active material cLTO (LTO having a carbon coating layer, volume average particle diameter 10 μm), and 3 mg of conductive additive carbon black (manufactured by Denka Co., Ltd.) were mixed in a mortar to obtain anode composite powder 1.

[0191] <Manufacturing of powder compacts> A 10 mm diameter SUS punch (short length) was inserted into the hole at the bottom of a SUS tube (inner diameter 10 mm) for powder compaction, and the above solid electrolyte powder 1 was placed through the hole at the top of the SUS tube and leveled. A SUS punch (long length) was inserted through the hole at the top and pressurized at 50 MPa for 10 seconds using a hydraulic press, after which the pressure was released and the SUS punch (long length) was removed from the SUS tube. Next, negative electrode composite powder 1 was placed through the hole at the top of the SUS tube and leveled on the compressed powder layer of solid electrolyte powder 1. A SUS punch (long) was inserted through the hole at the top, and a pressure of 50 MPa was applied for 10 seconds using a hydraulic press. After the pressure was released, the tube was turned upside down from the state in which the SUS punch (long) / SUS tube / SUS punch (short) was on top so that the SUS punch (short) was on top, and then the SUS punch (short) was removed from the SUS tube. Positive electrode composite powder 1 was placed through the hole at the top of the SUS tube and leveled on the compacted powder layer of solid electrolyte powder 1. A short SUS punch was inserted through the hole at the top, and a hydraulic press was used to apply pressure at 200 MPa for 10 seconds. The pressure was then released, and a puncher was used to remove a compact stacked in the order of compacted powder layer of negative electrode composite powder 1 / compacted powder layer of solid electrolyte powder 1 / compacted powder layer of positive electrode composite powder 1, and any excess liquid components that had seeped out were wiped off.

[0192] <Fabrication of powder-type secondary batteries> A 50 μm thick Al foil (negative electrode current collector layer) punched to a diameter of 10 mm was placed on a 10 mm diameter SUS base of an all-solid-state battery evaluation cell (product name: KP-SolidCell) manufactured by Hosen Co., Ltd., and the above-obtained powder compact was placed on top of it with the negative electrode side facing down. A Teflon tube with an inner diameter of 10.2 mm was inserted, and a 50 μm thick Al foil (positive electrode current collector layer) punched to a diameter of 10 mm was placed through the hole at the top of the Teflon tube. A 10 mm diameter, 2 mm thick polished Ti plate was placed on top of that, and a 10 mm diameter, 2 cm high Ti rod was then inserted and placed on top of the Ti plate. Next, the upper housing of the KP-SolidCell was fitted and sealed using a double O-ring, four bolts, and wing nuts. Cell B was constrained from above and below with a torque of 9 Nm (equivalent to 60 MPa) using a constraining pressure application mechanism installed on top of the KP-SolidCell. Here, cell B refers to a cell consisting of a negative electrode current collector layer, a powder compact, and a positive electrode current collector layer stacked in this order. Next, the KP-SolidCell was opened and cell B was removed. Any excess liquid components that had leaked out due to the application of confining pressure were wiped off, and then cell B was placed in the KP-SolidCell again in the same manner as above, and confining pressure was applied with a torque of 9 Nm (equivalent to 60 MPa). The cell was then subjected to vacuum freeze-drying for two hours with the top lid open to thoroughly remove moisture from inside Cell B. After removing the KP-SolidCell from the vacuum dryer, the top lid was closed and sealed using a double O-ring. This was left at room temperature for 40 hours to produce a pressed powder secondary battery C. In this pressed powder secondary battery C, the positive electrode active material layer was 100 μm thick, the solid electrolyte layer was 200 μm thick, and the negative electrode active material layer was 100 μm thick. Table 6 summarizes the configuration of the secondary battery and the evaluation results of the charge / discharge test.

[0193] (Charge / discharge test) A confining pressure (30 MPa) was applied to the coated secondary battery obtained above, and charging and discharging were repeatedly carried out under the following conditions at a temperature of 27° C. using a charge / discharge device 580-NOHFR (product name) manufactured by Toyo Corporation. In addition, the powder secondary battery obtained above was also repeatedly charged and discharged under the following conditions in the same manner as the coated secondary battery, except that the confining pressure was changed to 60 MPa. Charging is performed at a constant current I until the desired battery voltage of 2.8V is reached. β After the voltage reached 2.8V, the voltage was kept constant (2.8V) until the current value reached 2.4C. After charging, open the circuit and leave it for 10 minutes, then a constant current value I β The battery was discharged until the voltage reached 1.5V. The charging and discharging up to this point was considered as one cycle. After discharging, the circuit was opened and left for 10 minutes, then the next charge was started, and charging and discharging were repeated under the same conditions. In the above charging and discharging, the current value I β As an initialization of the battery, the charge / discharge current was set to 0.2 C in the first cycle, and then set to 3 C in the subsequent cycles, and a charge / discharge cycle test was performed. The discharge capacity retention rate (%) was calculated using the following formula and evaluated based on the following evaluation criteria. Discharge capacity retention rate (%) = (discharge capacity after 50 cycles of 3C charge / discharge / discharge capacity after 10 cycles of 3C charge / discharge) × 100 - Evaluation Criteria - A: The discharge capacity retention rate is 70% or more. B: The discharge capacity retention rate is 40% or more and less than 70%. C: The discharge capacity retention rate is less than 40%.

[0194] [Table 6]

[0195] From Table 6 above, it was confirmed that the secondary battery of the present invention having a solid electrolyte layer containing the solid electrolyte (I) exhibited excellent charge-discharge cycle characteristics and functioned as a secondary battery. Thus, the secondary battery of the present invention, while using an oxide-based solid electrolyte, has excellent interparticle bonding properties, and can use a current collector layer made of a metal that has been difficult to use under conditions of high-temperature sintering. Furthermore, the method for producing a secondary battery of the present invention can produce a secondary battery using an oxide-based solid electrolyte, while using a current collector layer made of a metal that has excellent interparticle bonding properties, and that has been difficult to use under conditions of high-temperature sintering in an atmosphere containing oxygen gas.

[0196] 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.

[0197] This application claims priority based on Japanese Patent Application No. 2022-089962, filed in Japan on June 1, 2022, the contents of which are incorporated herein by reference as part of the present specification. [Explanation of symbols]

[0198] 1. Negative electrode current collector layer 2 Negative electrode active material layer 3 Solid electrolyte layer 4 Cathode active material layer 5. Positive electrode current collector layer 6. Operating parts 10 All-solid-state lithium-ion secondary battery

Claims

1. An all-solid-state lithium ion secondary battery having at least one laminate formed by arranging a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order, At least one of the positive electrode layer and the negative electrode layer includes a current collector layer, at least one of the current collector layers is a layer containing a metal that melts at 670°C under normal pressure as a constituent material or a layer containing the metal in a coating layer, the solid electrolyte layer includes an amorphous solid electrolyte including a lithium-containing oxide containing Li, B, and O, water, and a lithium salt, and in the amorphous solid electrolyte, a ratio of the content of the lithium salt to the content of the lithium-containing oxide is 0.001 to 1.5 in terms of molar ratio, and a ratio of the content of the water to the content of the lithium-containing oxide is 1 to 12 in terms of molar ratio.

2. 2. The all-solid-state lithium ion secondary battery according to claim 1, wherein the metal that melts at 670°C under normal pressure is Al or an Al alloy.

3. The lithium-containing oxide is Li ２＋ｘ B ４＋ｙ O ７＋ｚ The all-solid-state lithium-ion secondary battery according to claim 1 or 2, comprising: However, −0.3<x<0.3, −0.3<y<0.3, and −0.3<z<0.

3.

4. A method for manufacturing an all-solid-state lithium ion secondary battery having at least one laminate including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer arranged in this order, comprising: At least one of the positive electrode layer and the negative electrode layer includes a current collector layer, at least one of the current collector layers is a layer containing Cu as a constituent material or a layer containing Cu in a coating layer, the solid electrolyte layer includes an amorphous solid electrolyte including a lithium-containing oxide including Li, B, and O, water, and a lithium salt, and in the amorphous solid electrolyte, a ratio of the content of the lithium salt to the content of the lithium-containing oxide is 0.001 to 1.5 in terms of molar ratio, and a ratio of the content of the water to the content of the lithium-containing oxide is 1 to 12 in terms of molar ratio; a laminate of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer in an atmosphere containing oxygen gas at 300° C. or less.

Images