Solid electrolyte and all-solid-state lithium ion secondary battery

Abstract

Provided is an all-solid-state lithium ion secondary battery in which a solid electrolyte layer contains an amorphous solid electrolyte that contains H2O, a lithium salt, and a lithium-containing oxide that contains Li, B, and O. The value of the ratio in this solid electrolyte of the lithium salt content to the lithium-containing oxide content is 0.001-1.5 as the molar ratio. The amount of H2O in the solid electrolyte constituting the laminate comprising the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is 4.5-12.5 mass%. Also provided is a solid electrolyte that is advantageous as a material for this secondary battery.

Description

Solid electrolyte and all-solid-state lithium-ion secondary battery

[0001] The present invention relates to a solid electrolyte and an all-solid-state lithium-ion secondary battery.

[0002] Conventionally, liquid electrolytes with high ionic conductivity have been used in lithium-ion secondary batteries. However, liquid electrolytes are flammable, which poses safety issues. Furthermore, because they are liquid, they are difficult to make compact, and capacity limitations become an issue when batteries are made larger. In contrast, all-solid-state lithium-ion secondary batteries are expected to be next-generation batteries that can solve these issues. 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 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 5, in this order. Each layer is in contact with each other, forming an adjacent structure. By adopting such a structure, electrons (e － ) is supplied to the solid electrolyte layer 3, and lithium ions (Li ＋ On the other hand, during discharge, the lithium ions (Li ＋ ) passes through the solid electrolyte layer 3 and returns to the positive electrode side, supplying electrons to the operating part 6. In the illustrated example, a light bulb is used as a model for the operating part 6, and is lit by discharge.

[0003] As described above, all-solid-state lithium-ion secondary batteries require excellent lithium-ion conductivity in the solid electrolyte layer to achieve the desired charge / discharge characteristics. Sulfide-based solid electrolytes or oxide-based solid electrolytes are typically used as the solid electrolytes constituting the solid electrolyte layer. Because sulfide-based solid electrolytes are soft and plastically deformable, particles bond together simply by pressure molding. Therefore, sulfide-based solid electrolytes have low interfacial resistance between particles and excellent ionic conductivity. However, sulfide-based solid electrolytes have the problem of generating toxic hydrogen sulfide when reacting with water. In contrast, oxide-based solid electrolytes have the advantage of being highly safe. However, oxide-based solid electrolytes are hard and resistant to plastic deformation. Increasing the interparticle bonding strength of oxide-based solid electrolytes requires a high-temperature sintering process, which is limited 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, using this lithium-containing oxide as a solid electrolyte sheet requires a high-temperature sintering process. As a technique for addressing this problem, for example, Patent Document 2 discloses a method for producing a lithium-containing oxide in an amorphous state, such as amorphous lithium tetraborate, a lithium salt, and water (H ２ Patent Document 2 describes an oxide-based solid electrolyte containing the lithium salt in a molar ratio of 0.001 to 1.5 relative to the lithium-containing oxide. ２ It also describes that the molar ratio of O is 3 to 15. According to the technology described in Patent Document 2, it is possible to provide an oxide-based solid electrolyte with excellent ion conductivity without requiring a sintering treatment.

[0004] JP 2018-052755 A International Publication No. 2022 / 118870

[0005] The solid electrolyte described in Patent Document 2 is H ２The solid electrolyte described in Patent Document 2 is in the form of a solid powder despite containing a relatively large amount of O, is soft despite containing a lithium-containing oxide, and can ensure interparticle bonding without being subjected to a sintering treatment or without incorporating a binder such as an organic polymer, thus possessing properties that have not been achieved by oxide-based solid electrolytes to date. However, as a result of further investigations by the present inventors, it has been found that although the solid electrolyte described in Patent Document 2 has good bonding properties, an all-solid-state lithium-ion secondary battery using this solid electrolyte in a solid electrolyte layer has room for improvement in terms of sufficiently maintaining battery performance during repeated charge and discharge (in terms of cycle characteristics).

[0006] The present invention relates to a method for producing a lithium-containing oxide in an amorphous state, a lithium salt, and H ２ The present invention aims to provide an all-solid-state lithium ion secondary battery that uses an oxide-based solid electrolyte containing O in at least a solid electrolyte layer, and that achieves sufficient discharge capacity while also exhibiting excellent cycle characteristics. ２ The present invention addresses the problem of providing a solid electrolyte made of an oxide-based solid electrolyte containing O, which, when used as a solid electrolyte for an all-solid-state lithium ion secondary battery, enables the resulting battery to achieve sufficient discharge capacity while also having excellent cycle characteristics.

[0007] The object of the present invention has been achieved by the following means: [1] An all-solid-state lithium ion secondary battery comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer arranged in this order, wherein at least the solid electrolyte layer is made of a lithium-containing oxide containing Li, B, and O, a lithium salt, and H ２ and an amorphous solid electrolyte containing O, wherein the ratio of the content of the lithium salt to the content of the lithium-containing oxide in the amorphous solid electrolyte is 0.001 to 1.5 in terms of molar ratio; and wherein the solid electrolyte constituting a laminate including a positive electrode active material layer, the solid electrolyte layer, and a negative electrode active material layer has a H ２ [2] An all-solid-state lithium ion secondary battery, wherein the amount of O is 4.5 to 12.5 mass %. ２＋ｘ B４＋ｙ O ７＋ｚ [3] The all-solid-state lithium-ion secondary battery according to [1] or [2], wherein the lithium salt is represented by the following formula (1): Formula (1): LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ ) In the formula, R ｆ１ and R ｆ２ each independently represents a halogen atom or a perfluoroalkyl group. [4] The all-solid-state lithium ion secondary battery according to any one of [1] to [3], wherein the solid electrolyte contains a polymer having a solubility parameter of 20 or more. [5] A lithium-containing oxide containing Li, B, and O, a lithium salt, and H ２ and O, wherein the solid electrolyte is in an amorphous state, and the ratio of the content of the lithium salt to the content of the lithium-containing oxide in the solid electrolyte is 0.001 to 1.5 in terms of molar ratio, and H ２ [6] A solid electrolyte in which the amount of O is 4.5 to 12.5 mass %. ２＋ｘ B ４＋ｙ O ７＋ｚ [7] The solid electrolyte according to [5], wherein the lithium salt is represented by the following formula (1): Formula (1): LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ ) In the formula, R ｆ１ and R ｆ２ each independently represents a halogen atom or a perfluoroalkyl group. [8] The solid electrolyte according to any one of [5] to [7], wherein the solid electrolyte contains a polymer having a solubility parameter of 20 or more.

[0008] In the present invention and the specification, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits. ２ "H" is determined by Karl Fischer titration at 130°C. ２ That is, in the present invention, "H ２ The term "O" is not limited to those present as water molecules in the solid electrolyte, but may also include, for example, OH groups bonded to lithium-containing oxides.

[0009] The all-solid-state lithium ion secondary battery of the present invention comprises an amorphous lithium-containing oxide, a lithium salt, and H ２ The solid electrolyte of the present invention is formed by using an oxide-based solid electrolyte containing O at least in the solid electrolyte layer, and thus achieves a sufficient discharge capacity and is also excellent in cycle characteristics. ２ When the oxide-based solid electrolyte containing O is used as the solid electrolyte of an all-solid-state lithium ion secondary battery, the resulting battery can have a sufficient discharge capacity and excellent cycle characteristics.

[0010] Fig. 1 is a cross-sectional view showing a schematic example of the configuration of an all-solid-state lithium ion secondary battery. Fig. 2 is a diagram showing an example of an X-ray diffraction pattern for explaining the X-ray diffraction characteristics of the solid electrolyte (I) used in the present invention. Fig. 3 is a diagram showing the X-ray diffraction characteristics of the powdered Li ２ B ４ O ７ FIG. 1 shows the X-ray diffraction pattern of the crystal.

[0011] [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") comprises a positive electrode layer, a solid electrolyte layer, and a negative electrode layer arranged in this order. The solid electrolyte layer is formed using a solid electrolyte of a specific amorphous composition, which will be described later. The positive electrode active material layer constituting the positive electrode layer usually contains the above-mentioned solid electrolyte together with the positive electrode active material, and the negative electrode active material layer constituting the negative electrode layer also usually contains the above-mentioned solid electrolyte together with the negative electrode active material. The secondary battery of the present invention is characterized in that the solid electrolyte (the entire solid electrolyte in the laminate) constituting the laminate (laminate structure excluding the current collector) consisting of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is measured by H titration at 130°C using Karl Fischer titration. ２ The amount of O (determined by Karl Fischer titration at 130°C) ２ The H content (H content) based on Karl Fischer titration at 130°C is 4.5 to 12.5% ​​by mass. ２ The amount of O can be determined by the method described in the Examples below. ２ From the viewpoint of achieving high discharge capacity and improving cycle characteristics, the O amount is preferably 4.5 to 11.5 mass %, more preferably 4.5 to 10.5 mass %, even more preferably 5.0 to 9.5 mass %, and still more preferably 5.0 to 8.5 mass %.

[0012] A preferred embodiment of each layer of the secondary battery of the present invention will be described.

[0013] <Solid Electrolyte Layer> The solid electrolyte layer constituting the secondary battery of the present invention can be formed, for example, as follows: A solid electrolyte of a specific composition in an amorphous state (same as a non-crystalline state or an amorphous state), or a mixture of this solid electrolyte and other components, is subjected to an appropriate drying treatment to form the solid electrolyte into a solid electrolyte having a specific composition in an amorphous state (same as a non-crystalline state or an amorphous state), which is measured by Karl Fischer titration at 130°C. ２ The amount of O is controlled to be 4.5 to 12.5 mass %. ２After reducing the O content to a specific range, the solid electrolyte or the above-mentioned mixture containing the same can be formed into a layer (compression molding, powder compaction, etc.) to form a solid electrolyte layer (pre-drying method). The above-mentioned suitable drying treatment method will be described later. Alternatively, for example, a solid electrolyte of a specific composition in an amorphous state or a mixture of the solid electrolyte and other components can be formed into a layer, or a slurry containing a solid electrolyte of a specific composition in an amorphous state or a mixture of the solid electrolyte and other components can be applied to form a coating, and then, after a suitable drying treatment, the H content can be measured by Karl Fischer titration at 130°C. ２ The amount of O can be controlled to 4.5 to 12.5 mass % to form the solid electrolyte layer constituting the secondary battery of the present invention (post-drying method).

[0014] The above-mentioned amorphous solid electrolyte having a specific composition can be obtained by a method comprising the steps of: a lithium-containing oxide containing Li, B, and O (hereinafter also simply referred to as a "lithium-containing oxide"), a lithium salt, and H ２ The more carefully the drying process is carried out, the more H ２ The amount of O decreases. In this solid electrolyte, 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. The amorphous solid electrolyte having a specific composition may contain, for example, a polymer having a solubility parameter (SP value) of 20 or more. When the solid electrolyte contains a polymer having an SP value of 20 or more, the formed solid electrolyte layer can be imparted with desired high flexibility or adhesion without substantially impairing ionic conductivity.

[0015] In the pre-drying method, by subjecting the solid electrolyte to the appropriate drying treatment, H based on Karl Fischer titration at 130°C can be obtained in the solid electrolyte before being formed into a layer. ２ The O content is more preferably 4.5 to 11.5 mass%, further preferably 4.5 to 10.5 mass%, further preferably 5.0 to 9.5 mass%, and further preferably 5.0 to 8.5 mass%. ２ By adjusting the amount of O, the layer formed by molding (compression molding, powder compaction, etc.) can be formed with the desired small amount of H. ２After the appropriate drying treatment, the solid electrolyte before being formed into a layer is mixed with a positive electrode active material and formed into a layer, thereby forming a positive electrode active material layer, and similarly, the solid electrolyte is mixed with a negative electrode active material and formed into a layer, thereby forming a negative electrode active material layer. In this way, a laminate consisting of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer is formed. If the entire solid electrolyte constituting this laminate has a H content of 0 or less as determined by Karl Fischer titration at 130°C, ２ The amount of O is controlled to be 4.5 to 12.5 mass %.

[0016] In the post-drying method, the solid electrolyte in the layer or coating film before the appropriate drying treatment is subjected to H based on Karl Fischer titration at 130°C. ２ In this case, by subjecting the formed layer or coating to the above-mentioned appropriate drying treatment, the solid electrolyte layer obtained has a H content of 12.5% ​​by mass based on Karl Fischer titration at 130° C. ２ The amount of O can be controlled to 4.5 to 12.5% ​​by mass. ２ A solid electrolyte having an O content of more than 12.5 mass % is mixed with a positive electrode active material to form a positive electrode active material layer, and similarly, this solid electrolyte is mixed with a negative electrode active material to form a negative electrode active material layer, thereby forming a laminate consisting of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer. By subjecting this laminate to the above-mentioned appropriate drying treatment, the entire solid electrolyte constituting the obtained laminate can be dried by H ２ The amount of O can be controlled to be 4.5 to 12.5 mass %. ２ The O amount is more preferably controlled to 4.5 to 11.5 mass%, even more preferably controlled to 4.5 to 10.5 mass%, even more preferably controlled to 5.0 to 9.5 mass%, and even more preferably controlled to 5.0 to 8.5 mass%.

[0017] Hereinafter, H based on Karl Fischer titration at 130 ° C. ２Regardless of whether the O content is within the range of 4.5 to 12.5 mass %, the solid electrolyte having the above amorphous specific composition is also referred to as "solid electrolyte (I)". ２ The solid electrolyte having an O content of 4.5 to 12.5 mass % is also referred to as "solid electrolyte (Ia)". ２ Although it contains O, it is in the form of solid particles (powder).

[0018] The solid electrolyte (I) is in an amorphous state and exhibits elastic properties that are prone to plastic deformation. As a result, in a solid electrolyte layer containing the solid electrolyte (I) formed through pressure treatment or the like, the adhesion between the solid electrolytes (I) and / or between the solid electrolyte (I) and other ion conductors is improved, reducing interfacial resistance and achieving better ion conductivity. By forming a solid electrolyte layer using this solid electrolyte (I), a lithium ion conductor can be formed that exhibits excellent lithium ion conductivity through pressure treatment or the like, even though it is a highly safe oxide-based solid electrolyte, without being subjected to high-temperature sintering treatment. Furthermore, if the solid electrolyte (I) is in a form containing a polymer with an SP value of 20 or more, the formed solid electrolyte layer can exhibit higher flexibility and further increase adhesion without substantially impairing ion conductivity.

[0019] The above H contained in the solid electrolyte (I) ２ O contains at least bound water. The reason why the solid electrolyte (I) exhibits high lithium ion conductivity is not clear, but it is thought that in the amorphous solid electrolyte (I), a soft hydration layer is 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 a further increase in ion conductivity. In addition, the above H contained in the solid electrolyte (Ia) ２ It is believed that most of the O is bound water. Here, in the present invention and the specification, "bound water" refers to H other than water present as free water. ２ The solid electrolyte (I) is H ２Even if it contains O, it is in the form of solid particles (including a state in which the solid particles are bound together). In other words, the solid electrolyte (I) contains bound water that is not removed or is difficult to remove under normal drying conditions. ２ O may contain free water as a part thereof within a range that does not impair the effects of the present invention.

[0020] In the present invention, the solid electrolyte (I) being in an "amorphous state" means that it satisfies the following X-ray diffraction characteristics.

[0021] (X-ray diffraction characteristics) In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (I) using CuKα rays, none of the following peaks is present: a first peak having a peak top in the range of a diffraction angle 2θ of 21.6 to 22.0° and a full width at half maximum of 0.65° or less; a second peak having a peak top in the range of a diffraction angle 2θ of 25.4 to 25.8° and a full width at half maximum of 0.65° or less; a third peak having a peak top in the range of a diffraction angle 2θ of 33.4 to 33.8° and a full width at half maximum of 0.65° or less; and a fourth peak having a peak top in the range of a diffraction angle 2θ of 34.4 to 34.8° and a full width at half maximum of 0.65° or less; or In the X-ray diffraction pattern, when at least one peak (hereinafter referred to as "peak X") among the first peak, second peak, third peak, and fourth peak is present, at least one peak among peak X has an intensity ratio of 5.0 or less as calculated by the intensity measurement method described below.

[0022] -Intensity measurement method- The average intensity (Av1) in the range of +0.45° to +0.55° from the diffraction angle 2θ at the peak top of Peak X is calculated, and the average intensity (Av2) in the range of -0.55° to -0.45° from the diffraction angle 2θ at the peak top of Peak X is calculated, and the arithmetic average value of Av1 and Av2 is calculated. The ratio of the peak intensity at the peak top of Peak X to this arithmetic average value (peak intensity at the peak top of Peak X / arithmetic average value) is defined as the intensity ratio.

[0023] The X-ray diffraction characteristics will be described in more detail. In the X-ray diffraction pattern obtained from X-ray diffraction measurement of the solid electrolyte (I) using CuKα radiation, if none of the first peak, second peak, third peak, and fourth peak is present, the X-ray diffraction characteristics are satisfied, and the solid electrolyte (I) is in an amorphous state. In addition, in the X-ray diffraction pattern obtained from X-ray diffraction measurement of the solid electrolyte (I) using CuKα radiation, if the peak X is present, and at least one peak of the peak X has an intensity ratio of 5.0 or less obtained by the intensity measurement method, the 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 1 / 2 of the peak intensity at the peak top.

[0024] The intensity measurement method will be described in more detail with reference to FIG. 2. FIG. 2 is a diagram showing an example of peak X appearing in a diffraction pattern obtained by X-ray diffraction measurement of solid electrolyte (I) using CuKα radiation. In the diffraction pattern shown in FIG. 2, a specific peak whose peak top intensity exhibits intensity 1 is shown. In the intensity measurement method, as shown in FIG. 2, an average intensity (Av1) in the range of +0.45° to +0.55° from the diffraction angle 2θ of the peak top of peak X is calculated, and an average intensity (Av2) in the range of −0.55° to −0.45° from the diffraction angle 2θ of the peak top of peak X is further calculated. Next, the arithmetic average values ​​of Av1 and Av2 are calculated, and the ratio of intensity 1 to the arithmetic average value is determined as the intensity ratio. When the above X-ray diffraction characteristics are satisfied, this means that there is no crystalline structure, or almost no crystalline structure, in the solid electrolyte (I), and the solid electrolyte is in an amorphous state. In other words, the first to fourth peaks are mainly peaks derived from the crystalline structure in the solid electrolyte (e.g., the crystalline structure of lithium tetraborate), and the absence of these peaks indicates an amorphous state. Even if at least one of the first to fourth peaks is present, the intensity ratio of at least one of the peaks X present is 5.0 or less, which means that the solid electrolyte (I) is substantially free of a crystalline structure that inhibits the effects of the present invention. For example, a peak derived from a specific component (e.g., a lithium salt) may overlap with any of the first to fourth peaks described above. However, in an amorphous solid electrolyte, all of the first to fourth peaks are usually reduced. Therefore, even if a peak derived from the specific component happens to overlap with any of the first to fourth peaks and a single large peak appears, the presence of at least one peak X with an intensity ratio below a predetermined value indicates that the solid electrolyte (I) is in an amorphous state.

[0025] The X-ray diffraction measurement is carried out using CuKα rays under measurement conditions of 0.01° / step and 3° / min.

[0026] In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte (I) using CuKα radiation, none of the above-mentioned first peak, second peak, third peak, and fourth peak is present, or even if at least one peak X among the above-mentioned first peak, second peak, third peak, and fourth peak is present, it is preferable that the intensity ratio of at least one peak among the peaks X is 3.0 or less. Among these, it is more preferable that none of the above-mentioned first peak, second peak, third peak, and fourth peak is present, or even if at least one peak X among the above-mentioned first peak, second peak, third peak, and fourth peak is present, the intensity ratio of at least one peak among the peaks X is 2.0 or less.

[0027] In the X-ray diffraction pattern, if two or more peaks have their peak tops in the range of 21.6 to 22.0° and their full width at half maximum is 0.65° or less, the peak with the highest diffracted X-ray intensity is selected as the first peak, and the X-ray diffraction characteristics are determined. In the X-ray diffraction pattern, if two or more peaks have their peak tops in the range of 25.4 to 25.8° and their full width at half maximum is 0.65° or less, the peak with the highest diffracted X-ray intensity is selected as the second peak, and the X-ray diffraction characteristics are determined. In the X-ray diffraction pattern, if two or more peaks have their peak tops in the range of 33.4 to 33.8° and their full width at half maximum is 0.65° or less, the peak with the highest diffracted X-ray intensity is selected as the third peak, and the X-ray diffraction characteristics are determined. Furthermore, in the X-ray diffraction pattern, if there are two or more peaks whose peak tops are located in the range of 34.4 to 34.8° and whose full width at half maximum is 0.65° or less, the peak with the greatest diffracted X-ray intensity is selected as the fourth peak, and the X-ray diffraction characteristics are determined.

[0028] 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 used in which a lithium-containing oxide that has been subjected to mechanical milling is used as a raw material. This mechanical milling may be performed in the presence of a lithium salt.

[0029] -Mechanical milling treatment- Mechanical milling treatment is a treatment in which a sample is pulverized while applying mechanical energy. Examples of mechanical milling treatment include a ball mill, a vibration mill, a turbo mill, and a disk mill. From the viewpoint of obtaining an amorphous solid electrolyte (I) with good productivity, a ball mill is preferred. Examples of ball mills include a vibration ball mill, a rotary ball mill, and a planetary ball mill. A planetary ball mill is more preferred.

[0030] The conditions for the ball mill treatment are adjusted appropriately depending on the object to be treated. The material of the milling balls (media) is not particularly limited, and examples thereof include agate, silicon nitride, zirconia, alumina, and iron-based alloys, with stabilized zirconia (YSZ) being preferred. The average particle size of the milling balls is not particularly limited, and is preferably 1 to 10 mm, more preferably 3 to 7 mm, from the viewpoint of enabling the solid electrolyte (I) to be produced with good productivity. The average particle size is determined by measuring the diameters of 50 randomly selected milling balls and calculating the arithmetic mean. When the milling balls are not spherical, the major axis is taken as the diameter. The number of milling balls is not particularly limited.

[0031] The material of the grinding pot in the ball mill treatment is not particularly limited, and examples thereof include agate, silicon nitride, zirconia, alumina, and iron-based alloys, with stabilized zirconia (YSZ) being preferred.

[0032] The rotation speed of the ball mill treatment is not particularly limited and can be, for example, 200 to 700 rpm, more preferably 250 to 550 rpm. The treatment time of the ball mill is not particularly limited and can be, for example, 10 to 200 hours, more preferably 20 to 140 hours. The atmosphere for the ball mill treatment may be air or an inert gas (e.g., argon, helium, nitrogen, etc.) atmosphere.

[0033] In the production of the solid electrolyte (I), it is preferable to carry out the following steps 1A to 3A. Step 1A: A step of subjecting a lithium-containing oxide to mechanical milling treatment in the presence of a lithium salt. Step 2A: A step of mixing the product obtained in step 1A with water. Step 3A: A step of removing water from the dispersion obtained in step 2A to obtain the solid electrolyte (I).

[0034] 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.

[0035] In the above-mentioned step 2A, the amount of water used is not particularly limited. For example, the amount of water used can be 10 to 200 parts by mass, and more preferably 50 to 150 parts by mass, per 100 parts by mass of the product obtained in step 1A. The method for mixing the product obtained in step 1A with water is not particularly limited, and they may be mixed all at once, or water may be added stepwise to the product obtained in step 1A and mixed. When mixing, ultrasonic treatment may be performed as necessary. The time for ultrasonic treatment is not particularly limited, and may be, for example, 10 minutes to 5 hours.

[0036] 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.

[0037] Before the step 1A, a step 0 may be carried out in which the lithium-containing oxide is subjected to mechanical milling in an environment in which no lithium salt is present.

[0038] When the solid electrolyte (I) is in a form containing a polymer having an SP value of 20 or more, for example, a polymer having an SP value of 20 or more can be mixed in the above step 2A.

[0039] In the production of 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: A step of mixing the product obtained in step 1B with water and a lithium salt; and Step 3B: A step of removing water from the dispersion obtained in step 2B to obtain the solid electrolyte (I).

[0040] The difference between step 1B and step 1A is that in step 1A, mechanical milling is performed in the presence of a lithium salt, whereas in step 1B, mechanical milling is performed without using a lithium salt. Therefore, in step 2B, the product obtained in step 1B is mixed with water and a lithium salt. The procedure of step 2B is not particularly limited, and may be a method of mixing the product obtained in step 1B, water, and a lithium salt all at once (method 1), a method of mixing the product obtained in step 1B with water to prepare a dispersion, and then mixing the resulting dispersion with a lithium salt (method 2), or a method of mixing the product obtained in step 1B with water to prepare dispersion 1, mixing a lithium salt with water to prepare solution 2, and then mixing dispersion 1 with solution 2 (method 3). When mixing the product obtained in step 1B with water, a dispersion treatment such as ultrasonic treatment may be appropriately performed. In Method 2, when mixing the dispersion liquid obtained by mixing the product obtained in Step 1B with water and a lithium salt, if the amount of lithium salt is too large, the resulting liquid is likely to gel, and the amount of lithium salt to be mixed is limited. In contrast, in Method 3, even when the product obtained in Step 1B and the 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 procedures of Step 3B and Step 3A are the same.

[0041] When the solid electrolyte (I) is in a form containing a polymer having an SP value of 20 or more, for example, a polymer having an SP value of 20 or more can be mixed in the above step 2B.

[0042] In the production of 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: A step of mixing the product obtained in step 1C with water. Step 3C: A step of mixing the product obtained by removing water from the dispersion obtained in step 2C with a lithium salt to obtain the solid electrolyte (I).

[0043] The procedures of Step 1C and Step 1B are the same. The procedures of Step 2C and Step 2A are the same. Step 3C differs from Steps 3A and 3B in that a product obtained by removing water from the dispersion obtained in Step 2C is mixed with a lithium salt. In Step 3C, the amount of lithium salt used is not particularly limited and is appropriately adjusted so as to obtain the solid electrolyte (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 a solution obtained by dissolving the lithium salt in water is impregnated into the product and the two are mixed may be used.

[0044] When the solid electrolyte (I) is in a form containing a polymer having an SP value of 20 or more, for example, a polymer having an SP value of 20 or more can be mixed in the above step 2C and / or 3C.

[0045] The solid electrolyte (I) obtained as described above has water removed until it becomes a solid particle. ２ The amount of O is considerably higher than 12.5 mass%. Therefore, the solid electrolyte (I) obtained as described above can be further subjected to an appropriate drying treatment to obtain a solid electrolyte (Ia). Such a drying treatment can include a more thorough vacuum drying treatment. In addition, for example, the solid electrolyte (Ia) can be dried at a specific low H ２ In the production of the solid electrolyte (I), the slurry before removing water is applied to a substrate, and the coating is subjected to the above-mentioned appropriate drying treatment, whereby a film of the solid electrolyte (Ia) can be obtained on the substrate.

[0046] (Component Composition of Solid Electrolyte (I)) As described above, the solid electrolyte (I) used in the present invention is an amorphous solid electrolyte, and the ratio of the content of the lithium salt to the content of the lithium-containing oxide in this solid electrolyte (I) is 0.001 to 1.5 in molar ratio. The 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 in molar ratio, more preferably 0.01 to 1.2, still more preferably 0.1 to 1.2, and particularly preferably 0.5 to 1.2. The molar amounts of the lithium-containing oxide and lithium salt in the solid electrolyte (I) can be determined based on elemental analysis.

[0047] In the production of the above solid electrolyte (I), the solid electrolyte (I) obtained by removing water was not subjected to the above-mentioned appropriate drying treatment, and the H ２ The O content is preferably 30% by mass or less, and more preferably 25% by mass or less. ２ If the amount of O is less than 1000 ppm, the solid electrolyte (I) can be handled as a solid particle. In addition, if the solid electrolyte (I) obtained by removing water is not subjected to the above-mentioned appropriate drying treatment, H ２ The O content is, for example, 20 mass % or more.

[0048] - Lithium-containing oxide - As described above, the lithium-containing oxide constituting the solid electrolyte (I) contains Li, B, and O. The lithium-containing oxide is Li ２＋ｘ B ４＋ｙ O ７＋ｚ(-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) is preferred. That is, when the molar amount of B is 4.00 and the molar amount of Li is expressed, it is preferred that the molar amount of Li is 1.58 to 2.49 (i.e., 1.7×4 / 4.3 to 2.3×4 / 3.7) and the molar amount of O is 6.23 to 7.89 (i.e., 6.7×4 / 4.3 to 7.3×4 / 3.7). In other words, when the molar amount of B contained is 4.00, it is preferred that the relative value of the molar amount of Li contained is 1.58 to 2.49 and the molar amount of O is 6.23 to 7.89. Typical examples of such lithium-containing oxides include lithium tetraborate (Li ２ B ４ O ７ The lithium-containing oxide may be Li １＋ｘ B ３＋ｙ O ５＋ｚ A compound represented by (-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) is also preferred. As such a lithium-containing oxide, lithium triborate (LiB ３ O ５ The lithium-containing oxide may be Li ３＋ｘ B １１＋ｙ O １８＋ｚ Compounds represented by (-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) are also preferred. As such lithium-containing oxides, typically Li ３ B １１ O １８ The lithium-containing oxide may be Li ３＋ｘ B ７＋ｙ O １２＋ｚ Compounds represented by (-0.3<x<0.3, -0.3<y<0.3, -0.3<z<0.3) are also preferred. As such lithium-containing oxides, typically Li ３ B ７ O １２ Therefore, the lithium-containing oxide can be ２＋ｘ B ４＋ｙ O ７＋ｚ , the above Li １＋ｘ B ３＋ｙ O ５＋ｚ , Li３＋ｘ B １１＋ｙ O １８＋ｚ , and Li ３＋ｘ B ７＋ｙ O １２＋ｚ In place of the lithium-containing oxide, or together with the lithium-containing oxide, LiBO may be used as the lithium-containing oxide. ５ , Li ２ B ７ O １２ , LiB ２ O ３ (OH)H ２ O and Li ４ B ８ O １３ (OH) ２ (H ２ O) ３ At least one of the following may also be used. In the solid electrolyte (I), the lithium-containing oxide is in an amorphous state. That is, so that the solid electrolyte (I) is in the above-mentioned amorphous state, the lithium-containing oxide is also in a desired amorphous state in the solid electrolyte (I). Among them, the lithium-containing oxide is preferably lithium tetraborate in an amorphous state.

[0049] - 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 is 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 formula (1) is preferred. Formula (1) LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ ) R ｆ１and R ｆ２ R each independently represents a halogen atom or a perfluoroalkyl group. ｆ１ and R ｆ２ When R is a perfluoroalkyl group, the number of carbon atoms in the perfluoroalkyl group is not particularly limited. ｆ１ and R ｆ２ is preferably a halogen atom or a perfluoroalkyl group having 1 to 6 carbon atoms, more preferably a halogen atom or a perfluoroalkyl group having 1 to 2 carbon atoms, and even more preferably a halogen atom. When the volume of the terminal group increases, steric hindrance increases, which becomes a factor that inhibits ion conduction. ｆ１ and R ｆ２ When is a perfluoroalkyl group, it is preferable that the number of carbon atoms is small.

[0050] 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.

[0051] (L-1) Inorganic lithium salt: LiPF ６ , LiBF ４ , LiAsF ６ , and LiSbF ６ Inorganic fluoride salts such as LiClO ４ , LiBrO ４ , and LiIO ４ perhalogenates such as LiAlCl ４ Inorganic chloride salts such as

[0052] (L-2) Fluorine-containing organic lithium salt: LiCF ３ SO ３ perfluoroalkanesulfonates such as LiN(CF ３ SO ２ ) ２ , LiN(CF ３ CF ２ SO ２ ) ２ , LiN(FSO ２ ) ２ (In this specification, Li(FSO ２ ) ２N), and LiN(CF ３ SO ２ ) (C ４ F ９ SO ２ Fluorosulfonylimide salts or perfluoroalkanesulfonylimide salts such as LiC(CF ３ SO ２ ) ３ perfluoroalkanesulfonylmethide salts such as Li[PF ５ (CF ２ CF ２ CF ３ ) )], Li[PF ４ (CF ２ CF ２ CF ３ ) ２ ], Li[PF ３ (CF ２ CF ２ CF ３ ) ３ ], Li[PF ５ (CF ２ CF ２ CF ２ CF ３ ) )], Li[PF ４ (CF ２ CF ２ CF ２ CF ３ ) ２ ] and Li[PF ３ (CF ２ CF ２ CF ２ CF ３ ) ３ Fluoroalkyl fluorophosphates (preferably perfluoroalkyl fluorophosphates) such as:

[0053] (L-3) Oxalatoborate salts: lithium bis(oxalato)borate and lithium difluorooxalatoborate.

[0054] In addition to the above, LiF, LiCl, LiBr, LiI, Li ２ SO ４ , LiNO ３ , Li ２ CO ３ , C.H. ３ COOLi, LiAsF ６, LiSbF ６ , LiAlCl ４ , and LiB(C ６ H ５ ) ４ Among them, LiPF ６ , LiBF ４ , LiAsF ６ , LiSbF ６ , LiClO ４ , Li(R ｆ１ SO ２ ), LiN(R ｆ１ SO ２ ) ２ , LiN(FSO ２ ) ２ , or LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ ) is preferred, and LiPF ６ , LiBF ４ , LiN(R ｆ１ SO ２ ) ２ , LiN(FSO ２ ) ２ , or LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ In these examples, R ｆ１ and R ｆ２ each independently represents a perfluoroalkyl group, preferably having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2. In addition, as the lithium salt, LiNO ３ and 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide lithium are also preferred.

[0055] The content of each element in the solid electrolyte (I) is determined by ordinary elemental analysis. As an elemental analysis method, for example, Li and B are analyzed by ICP-OES (inductively coupled plasma optical emission spectrometry), N and the like are analyzed by an inert gas fusion method, and, for example, F and S are analyzed by combustion ion chromatography. O can be calculated by adding up the analyzed masses of elements other than O and calculating the difference from the total amount of powder. The method for calculating the content of each element is not limited to the above, and the content of one element may be estimated from the analysis results of the content of other elements, taking into account the structure of the compound used. From the content of each element calculated by elemental analysis, the molar amounts of Li, O, and other elements can be calculated when the molar amount of B is 4.00.

[0056] 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 In many cases, it is less than 1000 kJ / cm.

[0057] As described above, the solid electrolyte (I) or (Ia) can contain a polymer having an SP value of 20 or more. By containing such a highly hydrophilic (water-soluble) polymer, the formed layer can be imparted with the desired high flexibility or adhesion without substantially impairing the ionic conductivity of the formed layer. The polymer having an SP value of 20 or more preferably has an SP value of 20 or more and 50 or less, more preferably an SP value of 20 or more and 40 or less, and even more preferably an SP value of 20 or more and 35 or less. The SP value can be determined as follows.

[0058] Using a calculation program (HSPiP, ver. 4.1.07), the molecular structure of each polymer is input, and the polymer HSP value (Hansen Solubility Parameter) calculation function included in the program is used to calculate the HSP values ​​(δD, δP, δH). Next, the SP value is calculated using the following formula: SP value = (δD ２ +δP ２ +δH ２ ) １／２ In addition, when a polymer contains a plurality of repeating units, the product of the SP value of each repeating unit and the molar ratio of that repeating unit to all repeating units is calculated, and these are summed to obtain the SP value of the polymer. For example, if a polymer is composed of repeating unit A with an SP value of A (SPA) and repeating unit B with an SP value of B (SPB), and the molar amount of repeating unit A is 0.2 and the molar amount of repeating unit B is 0.8 relative to the molar amount of all repeating units of the polymer of 1, the SP value of this polymer is calculated as follows: SP value = (SPA x 0.2) + (SPB x 0.8)

[0059] The molecular weight of the polymer having an SP value of 20 or more is not particularly limited. For example, a polymer having a weight-average molecular weight of 1,000 to 10,000,000 can be used, and a polymer having a weight-average molecular weight of 2,000 to 10,000,000 is preferably used. For example, the weight-average molecular weight can be determined by gel permeation chromatography (GPC) under the following measurement conditions: Column: Tosoh TSK gel G6000 PWXL (13 μm, 7.8 mm ID×300 mm) + TSK gel G4000 PWXL (10 μm, 7.8 mm ID×300 mm) Eluent: 0.1 M NaCl aqueous solution Flow rate: 1.0 mL / min Injection volume: 100 μL Oven temperature: 40° C. Detector: RI (differential refractive index detector) Molecular weight calibration sample: Pullulan

[0060] Specific examples of polymers with an SP value of 20 or more include carboxymethyl cellulose (CMC, SP value 27.2), polyethylene glycol (PEO, SP value 20.7), polyvinylpyrrolidone (PVP, SP value 22.8), polyvinyl alcohol (PVA, SP value 32.6), polyacrylic acid (SP value 25.6), polyacrylamide (SP value 31.3), poly(N-methylacrylamide) (SP value 27.8), polystyrene sulfone (SP value 23.5), and polylysine (SP value 22.3). In the present invention, the term "carboxymethyl cellulose" refers to carboxymethyl cellulose or a salt thereof. The same applies to polymers that can take the form of a salt, such as "polyacrylic acid." The SP value "27.2" of "carboxymethyl cellulose" is the SP value of carboxymethyl cellulose itself (in the form of a non-salt), and the SP value "25.6" of polyacrylic acid is the SP value of polyacrylic acid itself (in the form of a non-salt). In the present invention, the SP value of a "polymer with an SP value of 20 or more" means, when the polymer is in the form of a salt, the SP value in the structure in which the polymer is converted into a non-salt form.

[0061] When the solid electrolyte (I) or (Ia) contains a polymer having an SP value of 20 or more, the content of the polymer having an SP value of 20 or more in the solid electrolyte (I) or (Ia) is preferably 0.1 to 10.0 mass%, more preferably 0.2 to 8.0 mass%, even more preferably 0.4 to 6.0 mass%, and still more preferably 0.6 to 5.0 mass%. Therefore, when the solid electrolyte (I) or (Ia) contains a polymer having an SP value of 20 or more, the content of the polymer having an SP value of 20 or more in the solid electrolyte layer constituting the secondary battery of the present invention is also preferably 0.1 to 10.0 mass%, more preferably 0.2 to 8.0 mass%, even more preferably 0.4 to 6.0 mass%, and still more preferably 0.6 to 5.0 mass%.

[0062] In the present invention, the polymer having an SP value of 20 or more constitutes the solid electrolyte (I) or (Ia). On the other hand, when the solid electrolyte (I) or (Ia) containing the polymer having an SP value of 20 or more is used to form a positive electrode active material layer, the content of the polymer having an SP value of 20 or more in the positive electrode active material layer constituting the secondary battery of the present invention is preferably 0.1 to 10.0 mass%, more preferably 0.2 to 8.0 mass%, even more preferably 0.4 to 6.0 mass%, and still more preferably 0.6 to 5.0 mass%. Similarly, when a solid electrolyte (I) or solid electrolyte (Ia) containing a polymer with an SP value of 20 or more is used to form a negative electrode active material layer, the content of the polymer with an SP value of 20 or more in the negative electrode active material layer constituting the secondary battery of the present invention is preferably 0.1 to 10.0 mass%, more preferably 0.2 to 8.0 mass%, even more preferably 0.2 to 5.0 mass%, and even more preferably 0.2 to 3.0 mass%. Furthermore, when each layer of the laminate (a laminate consisting of a positive electrode active material layer / a solid electrolyte layer / a negative electrode active material layer) constituting the secondary battery of the present invention contains a polymer with an SP value of 20 or more, the content of the polymer with an SP value of 20 or more in this laminate is preferably 0.1 to 10.0 mass%, more preferably 0.2 to 8.0 mass%, even more preferably 0.4 to 6.0 mass%, and even more preferably 0.6 to 5.0 mass%.

[0063] The solid electrolyte (I) contained in the solid electrolyte layer constituting the secondary battery of the present invention is, as described above, H ２The solid electrolyte (Ia) has an O content reduced to a specific range. This solid electrolyte layer may contain other components in addition to the solid electrolyte (Ia). For example, the solid electrolyte layer may 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. In consideration of safety, at least one of oxide-based solid electrolytes, halide-based solid electrolytes, and hydride-based solid electrolytes is preferred, with oxide-based solid electrolytes being more preferred. The content of the solid electrolyte (Ia) in the solid electrolyte layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even preferably 80% by mass or more, and even preferably 90% by mass. It is also preferable that the solid electrolyte layer be composed of the solid electrolyte (Ia).

[0064] The thickness of the solid electrolyte layer constituting the secondary battery of the present invention is not particularly limited and can be, for example, 5 to 1000 μm, preferably 10 to 100 μm. In the present invention, the layer thickness can be measured by analyzing a cross-sectional scanning electron microscope (SEM) image or by using a laser displacement meter.

[0065] <Positive Electrode Layer> The positive electrode layer is generally composed of a positive electrode current collector and a positive electrode active material layer. However, when the positive electrode current collector also functions as the positive electrode active material layer (in other words, when the positive electrode active material layer also functions as the positive electrode current collector), it does not need to be composed of two layers, i.e., a positive electrode current collector and a positive electrode active material layer, and may have a single-layer configuration. 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 contain a solid electrolyte. The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, preferably 80% by mass or more, and even preferably 90% by mass.

[0066] When the positive electrode active material layer contains a solid electrolyte, the type of this solid electrolyte is not particularly limited. From the viewpoint of prioritizing higher safety, an oxide-based solid electrolyte can be used. 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, making it possible to impart greater flexibility to the positive electrode layer. In the obtained secondary battery of the present invention, the solid electrolyte (I) is H ２ It exists as a solid electrolyte (Ia) with a controlled O content.

[0067] 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.

[0068] (Positive Electrode Active Material) The positive electrode active material is preferably one that can reversibly insert and / or release lithium ions. The positive electrode active material is not particularly limited, and a transition metal oxide is preferred, and a transition metal oxide containing a transition metal element Ma (one or more elements selected from Co, Ni, Fe, Mn, Cu, and V) is more preferred. In addition, this transition metal oxide may be mixed with an 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 the mixed element is preferably 0 to 30 mol% relative to the amount of the transition metal element Ma (100 mol%). More preferably, the mixed material is synthesized by mixing so that the molar ratio of Li / Ma is 0.3 to 2.2. Specific examples of the transition metal oxide include (MA) transition metal oxides having a layered rock salt structure, (MB) transition metal oxides having a spinel structure, (MC) lithium-containing transition metal phosphate compounds, (MD) lithium-containing transition metal halide phosphate compounds, and (ME) lithium-containing transition metal silicate compounds. Among these, (MA) transition metal oxides having a layered rock salt structure are preferred, and LiCoO ２ or LiNi １／３ Co １／３ Mn １／３ O ２ is more preferred.

[0069] (MA) Examples of transition metal oxides having a layered rock salt structure include LiCoO ２ (lithium cobalt oxide [LCO]), LiNiO ２ (lithium nickel oxide), LiNi ０．８５ Co ０．１０ Al ０．０５ O ２ (nickel cobalt lithium aluminum oxide [NCA]), LiNi １／３ Co １／３ Mn １／３ O ２ (Lithium nickel manganese cobalt oxide [NMC]) and LiNi ０．５ Mn ０．５ O ２ (lithium manganese nickel oxide).

[0070] (MB) Examples of transition metal oxides having a spinel structure include LiMn ２ O ４ (LMO), LiNi ０．５ Mn １．５ O ４ ([LNMO]), LiCoMnO ４ , Li ２ FeMn ３ O ８ , Li ２ CuMn ３ O ８ , Li ２ CrMn ３ O ８ , and Li ２ NiMn ３ O ８ Examples include:

[0071] (MC) Examples of lithium-containing transition metal phosphate compounds include LiFePO ４ and Li ３ Fe ２ (P.O. ４ ) ３ Olivine-type iron phosphate salts such as Li ２ CoP ２ O ７ (LCP) and LiFeP ２ O ７ Iron pyrophosphate salts such as LiCoPO ４Cobalt phosphate salts such as Li ３ V ２ (P.O. ４ ) ３ Examples of suitable vanadium phosphate salts include monoclinic NASICON type vanadium phosphate salts such as (lithium vanadium phosphate).

[0072] (MD) Examples of lithium-containing transition metal halide phosphate compounds include Li ２ FePO ４ Fluorophosphate iron salts such as F, Li ２ MnPO ４ Fluorophosphate manganese salts such as F, and Li ２ CoPO ４ Examples of suitable phosphates include cobalt fluorides such as F.

[0073] (ME) Examples of lithium-containing transition metal silicate compounds include Li ２ FeSiO ４ , Li ２ MnSiO ４ , and Li ２ CoSiO ４ Examples include:

[0074] 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 particles 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 calcination method may be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.

[0075] The positive electrode active material may be surface-coated with a surface coating agent, sulfur or phosphorus, or further with actinic rays, in the same manner as the negative electrode active material described below.

[0076] The positive electrode active material may be used alone or in combination of two or more kinds.

[0077] (Positive electrode current collector) The current collector constituting the positive electrode layer is an electron conductor. The positive electrode current collector is usually in the form of a film sheet. Examples of materials constituting the positive electrode current collector include aluminum, aluminum alloys, stainless steel, nickel, and titanium, with aluminum or aluminum alloys being preferred. Note that examples of the positive electrode current collector include aluminum or stainless steel surfaces treated with carbon, nickel, titanium, or silver (thin films formed thereon).

[0078] The thickness of the positive electrode active material layer constituting the secondary battery of the present invention is not particularly limited and may be, for example, 5 to 500 μm, preferably 20 to 200 μm. The thickness of the positive electrode current collector constituting the secondary battery of the present invention is also not particularly limited and may be, for example, 10 to 100 μm, preferably 10 to 50 μm.

[0079] <Negative Electrode Layer> The negative electrode layer is generally composed of a negative electrode current collector and a negative electrode active material layer. However, when the negative electrode current collector also functions as the negative electrode active material layer (in other words, when the negative electrode active material layer also functions as the negative electrode current collector), the negative electrode layer does not necessarily have to be composed of two layers, i.e., the negative electrode current collector and the negative electrode active material layer, and may have a single-layer configuration. 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 contain a solid electrolyte. The content of the negative electrode active material in the negative electrode active material layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, preferably 80% by mass or more, and even preferably 90% by mass.

[0080] When the negative electrode active material layer contains a solid electrolyte, the type of this solid electrolyte is not particularly limited. From the viewpoint of prioritizing higher safety, an oxide-based solid electrolyte can be used. 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, making it possible to impart greater flexibility to the negative electrode layer. In the obtained secondary battery of the present invention, the solid electrolyte (I) is H ２ It exists as a solid electrolyte (Ia) with a controlled O content.

[0081] 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.

[0082] (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 metals or semimetals, lithium alone, lithium alloys, and negative electrode active materials that can form alloys with lithium.

[0083] The carbonaceous material used as the negative electrode active material is a material essentially composed of carbon. Examples include carbon black such as petroleum pitch and acetylene black (AB), graphite (natural graphite and artificial graphite such as vapor-grown graphite), and carbonaceous materials obtained by calcining various synthetic resins such as PAN (polyacrylonitrile)-based resins or furfuryl alcohol resins. Further examples include various carbon fibers such as PAN-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated PVA (polyvinyl alcohol)-based carbon fibers, lignin carbon fibers, glassy carbon fibers, and activated carbon fibers, as well as mesophase microspheres, graphite whiskers, and flat graphite. These carbonaceous materials can also be divided into difficult-to-graphitize carbonaceous materials (also called hard carbon) and graphite-based carbonaceous materials depending on the degree of graphitization. Furthermore, the carbonaceous material preferably has the interplanar spacing, density, or crystallite size described in JP-A-62-022066, JP-A-2-006856, and JP-A-3-045473. The carbonaceous material does not need to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-090844 and graphite having a coating layer described in JP-A-6-004516 can also be used. As the carbonaceous material, hard carbon or graphite is preferred, and graphite is more preferred.

[0084] 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), composite oxides of metal elements, composite oxides of metal elements and metalloid elements, and oxides of metalloid elements (metalloid oxides). Composite oxides of metal elements and composite oxides of metal elements and metalloid elements are collectively referred to as metal composite oxides. Among these oxides, amorphous oxides are preferred, and chalcogenides, which are reaction products of metal elements and elements of Group 16 of the periodic table, are also preferred. In the present invention, the term "metalloid element" refers to an element that exhibits properties intermediate between metal elements and nonmetallic elements, and typically includes six elements: boron, silicon, germanium, arsenic, antimony, and tellurium, and three elements: selenium, polonium, and astatine. Furthermore, "amorphous" refers to an element that has a broad scattering band with a peak in the 2θ range of 20 to 40° in an X-ray diffraction method using CuKα radiation, and may also have crystalline diffraction lines. The strongest intensity of the crystalline diffraction lines observed at 2θ values ​​of 40 to 70° is preferably 100 times or less, more preferably 5 times or less, the diffraction line intensity at the apex of a broad scattering band observed at 2θ values ​​of 20 to 40°, and even more preferably no crystalline diffraction lines.

[0085] Among the compound group consisting of the amorphous oxides and chalcogenides, amorphous oxides or the chalcogenides of metalloid elements are more preferred, and (composite) oxides or chalcogenides consisting of one element selected from Groups 13 (IIIB) to 15 (VB) of the periodic table (e.g., Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi) or a combination of two or more of these elements are even more preferred. ２ O ３ , GeO, PbO, PbO ２ , Pb ２ O ３ , Pb ２ O ４ , Pb ３ O ４ , Sb ２ O ３ , Sb ２ O ４ , Sb２ O ８ Bi ２ O ３ , Sb ２ O ８ Si ２ O ３ , Sb ２ O ５ , Bi ２ O ３ , Bi ２ O ４ , GeS, PbS, PbS ２ , Sb ２ S ３ or Sb ２ S ５ As a negative electrode active material that can be used in combination with the amorphous oxide negative electrode active material mainly containing Sn, Si, or Ge, a carbonaceous material that can occlude and / or release lithium ions or lithium metal, lithium alone, a lithium alloy, or a negative electrode active material that can be alloyed with lithium is preferred.

[0086] The oxides of metal elements or semimetal elements (particularly metal (composite) oxides) and the chalcogenides preferably contain at least one of titanium and lithium as a constituent component in terms of high current density charge / discharge characteristics. Examples of metal composite oxides containing lithium (lithium composite metal oxides) include composite oxides of lithium oxide and the metal oxides, metal composite oxides, or chalcogenides. More specifically, Li ２ SnO ２ The negative electrode active material (for example, a metal oxide) preferably contains titanium element (titanium oxide). Specifically, Li ４ Ti ５ O １２ Lithium titanate (LTO) is preferred in that it has excellent rapid charge / discharge characteristics due to small volume fluctuations during absorption and desorption of lithium ions, and it can suppress electrode deterioration and improve the life of the all-solid-state lithium ion secondary battery.

[0087] 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.

[0088] The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is one commonly used as a negative electrode active material for all-solid-state lithium-ion secondary batteries. Examples of the negative electrode active material include negative electrode active materials (alloys) containing silicon or tin, as well as metals such as Al and In. A negative electrode active material containing silicon (silicon-containing active material) is preferred, as it enables higher battery capacity. A silicon-containing active material having a silicon content of 50 mol% or more of the total constituent elements is more preferred. Generally, negative electrodes containing these negative electrode active materials (e.g., Si negative electrodes containing silicon-containing active materials, Sn negative electrodes containing tin-containing active materials) can absorb more Li ions than carbon negative electrodes (e.g., graphite and acetylene black). That is, the amount of Li ions absorbed per unit mass increases. This increases the battery capacity. As a result, the battery operating time can be extended.

[0089] Examples of silicon-containing active materials include silicon materials such as Si and SiOx (0<x≦1), and silicon-containing alloys containing titanium, vanadium, chromium, manganese, nickel, copper, or lanthanum (e.g., LaSi ２ , VSi ２ , La—Si, Gd—Si, and Ni—Si), or textured active materials (e.g., LaSi ２ / Si). Other examples include SnSiO ３ , and SnSiS ３ Examples of the active material containing silicon and tin include: SiOx itself can be used as a negative electrode active material (semi-metal oxide); and since SiOx generates Si during operation of an all-solid-state lithium-ion secondary battery, it can be used as a negative electrode active material (precursor material) that can be alloyed with lithium. Examples of the negative electrode active material containing tin include Sn, SnO, and SnO. ２ , SnS, SnS ２ and active materials containing the silicon and tin elements.

[0090] In terms of battery capacity, the negative electrode active material is preferably a negative electrode active material that can be alloyed with lithium, more preferably the above-mentioned silicon material or silicon-containing alloy (alloy containing silicon element), and even more preferably silicon (Si) or a silicon-containing alloy.

[0091] It is also preferable to use titanium-niobium composite oxide as the negative electrode active material. Titanium-niobium composite oxide has a high theoretical volumetric capacity density, and is expected to enable a long life and rapid charging. Examples of titanium-niobium composite oxides include TiNb ２ O ７ etc.

[0092] The shape of the negative electrode active material is not particularly limited, but particulate is preferred. The volume-average particle diameter 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 diameter is measured using the following procedure. The negative electrode active material is diluted with water (or heptane in the case of a water-unstable substance) in a 20 mL sample bottle to prepare a 1 mass % dispersion. The diluted dispersion sample is irradiated with 1 kHz ultrasound for 10 minutes and used for testing immediately thereafter. Using this dispersion sample, data is acquired 50 times using a laser diffraction / scattering particle size distribution analyzer at 25°C using a quartz measurement cell to obtain the volume-average particle diameter. For other detailed conditions, please refer to the description in 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.

[0093] The negative electrode active material may be used alone or in combination of two or more kinds.

[0094] The surface of the negative electrode active material may be coated with another metal oxide. Examples of the surface coating agent include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si, or Li. Specific examples include titanate spinel, tantalum-based oxides, niobium-based oxides, and lithium niobate-based compounds, such as Li ４ Ti ５ O １２ , Li ２ Ti ２ O ５ , LiTaO３ , LiNbO ３ , LiAlO ２ , Li ２ ZrO ３ , Li ２ WO ４ , Li ２ TiO ３ , Li ２ B ４ O ７ , Li ３ P.O. ４ , Li ２ MoO ４ , Li ３ BO ３ , LiBO ２ , Li ２ CO ３ , Li ２ SiO ３ , SiO ２ , TiO ２ , ZrO ２ , Al ２ O ３ , B ２ O ３ , and Li ３ AlF ６ The surface of the electrode containing the negative electrode active material may be surface-treated with sulfur or phosphorus. Furthermore, the particle surface of the negative electrode active material may be surface-treated with actinic rays or an active gas (e.g., plasma) before or after the surface coating.

[0095] (Negative electrode current collector) The current collector constituting the negative electrode layer is an electron conductor. The negative electrode current collector is usually in the form of a film sheet. Examples of materials constituting the negative electrode current collector include aluminum, copper, copper alloys, stainless steel, nickel, zinc, and titanium, with aluminum, copper, copper alloys, or stainless steel being preferred. Note that examples of the negative electrode current collector include those in which the surface of the above-mentioned constituent materials is treated with carbon, nickel, titanium, or silver.

[0096] The thickness of the negative electrode active material layer constituting the secondary battery of the present invention is not particularly limited and may be, for example, 5 to 500 μm, preferably 20 to 200 μm. The thickness of the negative electrode current collector constituting the secondary battery of the present invention is also not particularly limited and may be, for example, 10 to 100 μm, preferably 10 to 50 μm.

[0097] 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. For example, a conductive additive may be included. Examples of conductive additives include electron-conductive materials such as graphites (e.g., natural graphite and artificial graphite), carbon blacks (e.g., acetylene black, ketjen black, and furnace black), amorphous carbon (e.g., needle coke), fibrous carbon (e.g., vapor-grown carbon fiber and carbon nanotubes), and carbonaceous materials (e.g., graphene and fullerene). Conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives may also be used. In addition to the above conductive additives, conventional conductive additives that do not contain carbon atoms, such as metal powder or metal fiber, may also be used. A conductive additive refers to a material that does not intercalate or deintercalate Li during charging and discharging of the battery and does not function as an active material. Therefore, among the conductive additives, those that can function as an active material in the active material layer when the battery is charged and discharged are classified as active materials rather than as conductive additives. Whether or not a conductive additive functions as an active material when the battery is charged and discharged is not uniquely determined, but is determined by the combination with the active material.

[0098] Other components include lithium salts.

[0099] <Production of All-Solid-State Lithium-Ion Secondary Battery> The secondary battery of the present invention uses a solid electrolyte (I) for at least the solid electrolyte layer, and is a battery in which the solid electrolyte (I) constituting the positive electrode active material layer and the laminate consisting of the solid electrolyte layer and the negative electrode active material layer is subjected to H ２ The amount of O is controlled to 4.5 to 12.5 mass % (H of the solid electrolyte (I) ２As described above, in the obtained secondary battery, the H content of the solid electrolyte (I) constituting the laminate consisting of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is controlled. ２ In order to reduce the amount of O to the level specified in the present invention to obtain a solid electrolyte (Ia), in the production of the secondary battery of the present invention, it is preferable to form a laminate including a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer using the solid electrolyte (I), and then subject it to the appropriate drying treatment described above. It is also preferable to appropriately dry each layer individually and then laminate these dried layers together. In addition, by forming a laminate including a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer using the solid electrolyte (Ia) by sequentially compacting each layer, the H of the solid electrolyte constituting this laminate based on Karl Fischer titration at 130 ° C. can be measured. ２ The amount of O can be controlled to 4.5 to 12.5 mass %. A preferred embodiment of the method for producing a secondary battery of the present invention will be described.

[0100] The method for producing a secondary battery of the present invention includes obtaining a laminate comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer arranged in this order. ２In order to achieve the O content specified in the present invention, the production of the secondary battery of the present invention preferably includes a step of subjecting the positive electrode active material layer, solid electrolyte layer, and negative electrode active material layer, individually or in the form of a laminate, to an appropriate drying treatment. This drying method is not particularly limited, and can be performed, for example, by subjecting them to vacuum drying (preferably vacuum freeze drying) or by leaving them in a box with a dew point of, for example, −10°C or lower. Heat treatment or other treatments may also be combined. The secondary battery of the present invention is preferably formed by sealing a laminate in which the above-mentioned positive electrode layer, solid electrolyte layer, and negative electrode layer are arranged in this order. Sealing can more reliably prevent moisture from entering the solid electrolyte layer, thereby further improving cycle characteristics. The sealing method is not particularly limited, and it is sufficient if it completely blocks or suppresses moisture (air) from entering. For example, a method of sealing the laminate in which the above-mentioned positive electrode layer, solid electrolyte layer, and negative electrode layer are arranged in this order is used to close the lid of a housing (battery cell) via a gasket such as an O-ring.

[0101] Furthermore, the method for forming a laminate having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer arranged in this order is not particularly limited. For example, a positive electrode-forming composition (slurry) containing a positive electrode active material and a solid electrolyte is applied to a metal foil serving as a positive electrode current collector to form a positive electrode active material layer, and then a solid electrolyte layer-forming dispersion (slurry) containing a solid electrolyte is applied to the positive electrode active material layer to form a solid electrolyte layer. Similarly to the positive electrode active material layer, a negative electrode-forming composition (slurry) containing a negative electrode active material and a solid electrolyte is applied to a metal foil serving as a negative electrode current collector to form a negative electrode active material layer. The multilayer coating film of the solid electrolyte layer / positive electrode active material layer / positive electrode current collector and the coating film of the negative electrode active material layer / negative electrode current collector are then bonded together to form a structure of positive electrode current collector / positive electrode active material layer / solid electrolyte layer / negative electrode active material layer / negative electrode current collector. The entire structure is then dried to a desired level and subjected to a pressure treatment to obtain an all-solid-state lithium-ion secondary battery as shown in FIG. 1.

[0102] Alternatively, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer may be separately prepared, stacked, dried to a desired level, and then pressed to produce an all-solid-state lithium ion secondary battery. In this case, a support such as a nonwoven fabric may be provided as needed during the formation of each layer, making each layer a self-supporting film. ２ A layer can also be formed by directly compacting or molding a solid electrolyte (Ia) in which the O content is controlled to 4.5 to 12.5 mass % without forming it into a slurry. ２ A positive electrode-forming composition (solid particles) containing a solid electrolyte (Ia) having a controlled O content and a positive electrode active material was prepared. ２ A solid electrolyte (Ia) containing a controlled amount of O is mixed with a negative electrode active material to prepare a negative electrode-forming composition (solid particles). The positive electrode-forming composition is placed on a positive electrode current collector and compacted to form a positive electrode active material layer on the positive electrode current collector. The solid electrolyte (Ia) is then placed on the positive electrode active material layer and compacted to form a solid electrolyte layer on the positive electrode active material layer. The negative electrode-forming composition and a negative electrode current collector are then placed on the solid electrolyte layer and compacted, and the entire structure is subjected to a pressure treatment, if necessary, to produce an all-solid-state lithium-ion secondary battery. As described above, the order of forming the layers may be reversed. The secondary battery of the present invention is not limited to the method described above, as long as the secondary battery defined in the present invention is obtained.

[0103] In the production of the secondary battery of the present invention, even without using a sulfide-based solid electrolyte as the solid electrolyte, the oxide-based solid electrolyte (Ia) that can be easily plastically deformed by pressure enables the formation of layers with reduced interfacial resistance between solid particles or between layers. The solid electrolyte (Ia) itself is soft and plastically deformable, and acts as a binder, contributing to improved adhesion between solid particles or between layers, so it is also possible to form layers without using a binder such as an organic polymer.

[0104] The secondary battery of the present invention is preferably initialized after manufacture or before use. The initialization method is not particularly limited, and can be performed, for example, by performing initial charge / discharge under an increased pressure and then releasing the pressure until the pressure falls within the range of the pressure conditions during use of the secondary battery.

[0105] <Applications of All-Solid-State Lithium-Ion Secondary Battery> 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 electronic devices such as notebook computers, pen-input PCs, mobile PCs, e-book players, mobile phones, cordless phone handsets, pagers, handheld terminals, mobile fax machines, mobile copiers, mobile printers, headphone stereos, video camcorders, LCD TVs, handheld vacuum cleaners, portable CD players, mini-discs, electric shavers, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, and backup power supplies. Other consumer applications include automobiles, electric vehicles, motors, lighting fixtures, toys, game consoles, road conditioners, clocks, flash devices, cameras, and medical devices (pacemakers, hearing aids, shoulder massagers, etc.). Furthermore, the secondary battery can be used for various military and space applications. It can also be combined with solar cells.

[0106] The present invention will be described in more detail based on examples, but the present invention is not to be construed as being limited to these examples.

[0107] [Reference Example 1] Powdered Li was mixed using a ball mill (P-7 manufactured by Fritsch). ２ B ４ O ７Crystals (LBO powder) (manufactured by Rare Metallic Co., Ltd.) were ball milled under the following conditions: pot: stabilized zirconia (YSZ) (45 mL), milling balls: YSZ (average particle size: 5 mm, number: 50), rotation speed: 370 rpm (revolutions per minute), amount of LBO powder: 1 g, atmosphere: air, and ball mill treatment time: 100 hours, to obtain a finely divided lithium-containing oxide (hereinafter also referred to as "fine lithium-containing oxide"). 0.05 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added (5% by mass relative to the fine particles of the lithium-containing oxide), and the mixture was ball milled for another 100 hours. The obtained powder was added to water so that the powder concentration was 42% by mass, and ultrasonically dispersed for 30 minutes. Subsequently, the obtained dispersion was transferred to a glass petri dish and dried at 120°C for 2 hours in the atmosphere to obtain a solid electrolyte film. Subsequently, the obtained film was peeled off to obtain a powdered solid electrolyte (I)-1.

[0108] <Preparation and Evaluation of a Compacted Solid Electrolyte> 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 solid electrolyte (compacted powder 1). The compacted powder 1 had a cylindrical shape with a diameter of 10 mm and a thickness of 0.5 to 1 mm. The ionic conductivity of the compacted powder 1 obtained was measured, and the ionic conductivity of the compacted powder 1 was found to be 1.5 x 10 at 27°C. －４ S / cm and 4.0 × 10 at 60°C －４ The viscosity was S / cm.

[0109] 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).

[0110] X-ray diffraction measurement of solid electrolyte (I)-1 was carried out using CuKα radiation as described above. The measurement conditions were 0.01° / step, 3° / min. As a result, it was found that the X-ray diffraction characteristics described above were satisfied, and solid electrolyte (I)-1 was found to be in an amorphous state.

[0111] 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 as the difference from the total amount of powder by adding up the analyzed masses of elements other than O. The results are shown in the table below.

[0112] [Reference Example 2] 1 g of the fine particles of the lithium-containing oxide used in Reference Example 1 was added to water so that the concentration of the fine particles was 42 mass %, and ultrasonic dispersion was performed for 30 minutes. 0.05 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added (5% by mass relative to the fine particles of the lithium-containing oxide), and ultrasonic dispersion was further carried out for 30 minutes. The obtained dispersion was transferred to a glass petri dish and dried at 120°C for 2 hours in the atmosphere to obtain a solid electrolyte film. Subsequently, the obtained film was peeled off to obtain a powdery solid electrolyte (I)-2. Various evaluations were carried out 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.

[0113] [Reference Example 3] Powdered Li was mixed using a ball mill (P-7 manufactured by Fritsch). ２ B ４ O ７(LBO powder) (manufactured by Rare Metallic) was ball milled under the following conditions: pot: YSZ (45 ml), milling balls: YSZ (average particle size: 5 mm, mass: 70 g), rotation speed: 530 rpm (revolutions per minute), LBO powder amount: 4.2 g, atmosphere: air, ball mill treatment time: 100 hours, to obtain a fine lithium-containing oxide. The obtained fine lithium-containing oxide was added to water so that the concentration of the fine lithium-containing oxide was 42 mass%, and the mixture was ultrasonically treated for 60 minutes to obtain dispersion 1. Next, 3.25 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added to water to a concentration of 87% by mass, and the mixture was subjected to ultrasonic treatment for 60 minutes to obtain Solution 2. The obtained Dispersion 1 and Solution 2 were mixed and stirred with a magnetic stirrer for 60 minutes. The obtained dispersion was then vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered solid electrolyte (I)-3. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were performed in the atmosphere using solid electrolyte (I)-3 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0114] Reference Example 4 Dispersion 3 was obtained in the same manner as in the preparation of Dispersion 1 in Reference Example 3. Next, 2.32 g of LiFSI (chemical formula: Li(FSO ２ ) ２ N) was added to water at a concentration of 87% by mass and subjected to ultrasonic treatment for 60 minutes to obtain Solution 4. The obtained Dispersion 3 and Solution 4 were mixed and stirred and mixed with a magnetic stirrer for 60 minutes. Subsequently, the obtained dispersion was vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered solid electrolyte (I)-4. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were performed in the atmosphere using solid electrolyte (I)-4 in the same manner as in Reference Example 1. The results are summarized in the table below.

[0115] [Reference Example 5] Dispersion 5 was obtained in the same manner as in the preparation of Dispersion 1 in Reference Example 3. Next, 4.65 g of LiFSI (chemical formula: Li(FSO ２ ) ２N) was added to water at a concentration of 87% by mass and subjected to ultrasonic treatment for 60 minutes to obtain Solution 6. The obtained Dispersion 5 and Solution 6 were mixed and stirred and mixed with a magnetic stirrer for 60 minutes. Subsequently, the obtained dispersion was vacuum-dried at 40°C and 10 Pa for 15 hours to obtain a powdered solid electrolyte (I)-5. The obtained powder was immediately subjected to various evaluations in the atmosphere in the same manner as in Reference Example 1. The results are summarized in the table below.

[0116] Reference Example 6 Dispersion 7 was obtained in the same manner as in the preparation of Dispersion 1 in Reference Example 3. Next, 7.13 g of LiTFSI (chemical formula: Li(F ３ CSO ２ ) ２ N) was added to water at a concentration of 87% by mass and ultrasonically treated for 60 minutes to obtain Solution 8. The obtained Dispersion 7 and Solution 8 were mixed and stirred with a magnetic stirrer for 60 minutes. The obtained dispersion was then vacuum-dried at 40°C and 10 Pa for 15 hours to obtain powdered solid electrolyte (I)-6. The obtained powder was allowed to stand in the atmosphere for a certain period of time, and various evaluations were performed in the atmosphere using solid electrolyte (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 content shown in Table 1 below was estimated from the analyzed mass of sulfur, taking into account the atomic weight of each atom in the lithium salt.

[0117] Comparative Example 1 The LBO powder (powdered Li without ball milling) used in Example 1 was ２ B ４ O ７ As a result of elemental analysis of the LBO powder, the composition of the obtained powder was １．９６ B ４．００ O ６．８０The LBO powder was compacted at 27°C (room temperature) under an effective pressure of 220 MPa to obtain a comparative powder compact C1. The ionic conductivity of the obtained powder compact C1 was undetectable. Furthermore, X-ray diffraction measurements were performed on the LBO powder as described above. The measurement conditions were 0.01° / step and 3° / min. Figure 3 shows the X-ray diffraction pattern of the LBO powder of Comparative Reference Example 1. As shown in Figure 3, 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 corresponding to the (2,0,2) plane at 25.54°, a peak corresponding to the (2,1,3) plane at 33.58°, and a peak corresponding to the (3,1,2) plane at 34.62°, and the intensities of these three peaks were approximately equal. These peaks are due to crystalline components.

[0118] Comparative Example 2: The fine particles of the lithium-containing oxide prepared in Example 1 (powdered Li ２ B ４ O ７ As a result of elemental analysis of the fine particles of lithium-containing oxide (crystals ball-milled), the composition of the fine particles of lithium-containing oxide was １．９４ B ４．００ O ６．８０ 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 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 The viscosity was S / cm.

[0119] In the table below, 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 marked with "A", and cases where the above-mentioned X-ray diffraction characteristics were not satisfied were marked with "B". Note that in Reference Examples 1 to 6 shown in the table below and Reference Examples 7 to 13 described below, 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.

[0120] In the table below, the column "Elemental Analysis" shows the composition of the solid electrolyte (I) obtained in each Reference Example and the lithium-containing oxide in each Comparative Reference Example as a molar amount of each element, as a relative value with the content of B set to "4.00".

[0121]

[0122]

[0123] 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 were found to have excellent ionic conductivity. Furthermore, the results of elemental analysis confirmed that the Li content in the solid electrolyte was higher in Reference Examples 3 to 6. In Reference Examples 3 to 6, an aqueous solution containing a mechanically milled lithium compound was mixed with an aqueous solution containing a lithium salt (Method 3 in Step 2B described above), allowing for the mixing of a larger amount of lithium salt. It is presumed that this resulted in an increased amount of Li being incorporated into the solid electrolyte. It was also found that Reference Examples 3, 4, and 5, which used LiFSI as the lithium salt, had improved ionic conductivity compared to Reference Example 6, which used LiTFSI. This is presumed to be due to the presence of highly mobile Li in the increased Li.

[0124] <Effect of Water in Solid Electrolyte> A compact (pellet) (10 mmφ, 0.9 mmt) of 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 changed to a Ti electrode. The results are shown in Table 3.

[0125]

[0126] As shown in the table above, the pressure was 200 Pa after 5 minutes of drying, and the free water was considered to be in a vaporized state. However, the ionic conductivity was 3.8 × 10 －３ Even with a drying time of 1080 minutes and a pressure of 15 Pa, the ionic conductivity was 5.7 × 10 －４This result indicates that bound water exists in addition to free water, and that this contributes to ionic conductivity.

[0127] [Reference Example 7] Dispersion 9 having a concentration of lithium-containing oxide fine particles of 42 mass % was obtained in the same manner as in the preparation of Dispersion 1 in Reference Example 3. Next, 7.12 g of LiTFSI (chemical formula: Li(F ３ CSO ２ ) ２ N was added to water to a concentration of 87% by mass, and the mixture was subjected to ultrasonic treatment for 60 minutes to obtain Solution 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 performed 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.

[0128] [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.

[0129] [Reference Examples 9 to 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 resulting solid electrolyte (I) were changed to the amounts shown in the table below. Various evaluations were carried out in the atmosphere in the same manner as in Reference Example 1. The results are summarized in the table below. However, in Reference Example 13, the powder obtained after vacuum drying was immediately evaluated in the atmosphere.

[0130] In the table below, the "Lithium-containing oxide fine particles" column, the "Lithium salt" column, and the "Water" column represent relative molar ratios. For example, in Reference Example 7, the molar ratio of lithium salt to lithium-containing oxide fine particles is 1, and the molar ratio of water to lithium-containing oxide fine particles is 11. The molar ratios were calculated by the following method. The analysis of each element was performed by quantitatively analyzing lithium and boron using ICP-OES, and fluorine and sulfur using combustion ion chromatography (combustion IC). N was estimated from the analyzed mass of sulfur taking into account the atomic weight of each element in the Li salt, and O was calculated as the difference from the total amount of solid electrolyte by adding up the analyzed masses of elements other than O. In Reference Examples 7 and 8, the carbon amount was estimated from the analyzed mass of sulfur taking into account the atomic weight of each element in the lithium salt. The molar ratio of lithium-containing oxide fine particles to lithium salt in the solid electrolyte was calculated from the molar ratio of an element (e.g., B) that is only present in the lithium-containing oxide fine particles and an element that is only present in the lithium salt. Furthermore, the molar ratio of the fine particles of the lithium-containing oxide to water was calculated by subtracting the molar ratios of O contained in the fine particles of the lithium-containing oxide and the lithium salt from the molar ratio of O in the solid electrolyte to calculate the molar amount of O derived from water, and then using the obtained molar amount of O derived from water and the molar amount of the fine particles of the lithium-containing oxide.

[0131]

[0132] 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.

[0133]

[0134]

[0135] As shown in the above table, the solid electrolytes of each Reference Example had the desired characteristics or properties and exhibited excellent ionic conductivity.

[0136] [Production Example 1] Production of all-solid-state lithium-ion secondary battery (without polymer having SP value of 20 or more) <Preparation of fine particles of lithium-containing oxide> Powdered Li ２ B ４ O ７45 g of crystals (LBO powder) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 770 g of zirconia beads, and 3 mL of water were placed in a 500 mL zirconia pot, which was then sealed with a Teflon ring and a zirconia lid. The LBO powder was milled using a planetary ball mill at 300 rpm for 45 hours to obtain fine particles of a lithium-containing oxide.

[0137] <Preparation of Solid Electrolyte Slurry-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. This dispersion was further stirred with a magnetic stirrer for 30 minutes to obtain 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 (solid electrolyte (I)). The obtained powder was stored in a desiccator (relative 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. Furthermore, the ionic conductivity was measured using the method described above to find a value of 4.5 × 10 －３ The ratio of the content of LiFSI to the content of the lithium-containing oxide was 1 in terms of molar ratio.

[0138] <Preparation of Positive Electrode Slurry-1> 5.2 g of the above solid electrolyte slurry 1 was mixed with the positive electrode active material LiCoO ２ 5.0 g of the above 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 a positive electrode slurry 1. When this positive electrode slurry 1 is applied to a positive electrode current collector or a solid electrolyte layer, etc., and dried to form a positive electrode active material layer, the lithium-containing oxide fine particles contained in the solid electrolyte slurry 1, LiFSI, and water (H ２ O) together to form the solid electrolyte (I) or (Ia).

[0139] <Preparation of negative electrode slurry-1> 7.6 g of the above solid electrolyte slurry 1 was mixed with a negative electrode active material Li ４ Ti ５ O １２5.0 g of the above 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 for 30 minutes with a magnetic stirrer to obtain anode slurry 1. When this anode slurry 1 is applied to an anode current collector or a solid electrolyte layer or the like and dried to form a cathode active material layer, the lithium-containing oxide fine particles contained in the solid electrolyte slurry 1, LiFSI, and water (H ２ O) together to form the solid electrolyte (I) or (Ia).

[0140] <Production of All-Solid-State Lithium-Ion Secondary Battery -1> The battery was produced according to the following procedure. Cathode Slurry 1 was applied to a titanium foil (20 μm thick cathode current collector), and anode Slurry 1 was applied to an aluminum foil (50 μm thick anode current collector). The coating of cathode Slurry 1 was naturally dried for 30 minutes in a constant temperature and humidity chamber at 25°C and a relative humidity of 10%, and then solid electrolyte Slurry 1 was applied as a multilayer on the dried coating. Next, in a constant temperature and humidity chamber controlled at room temperature of 25°C and a relative humidity of 15% (dew point -3°C), the multilayer coating and the coating of anode Slurry 1 were punched out to sizes of 10 mm diameter and 8 mm diameter, respectively. After drying, the two coatings were bonded together so that they were in contact with each other, and then placed in a uniaxial pressure jig (manufactured by Hosen Co., Ltd.) and sealed by restraining at 5 Nm (equivalent to 30 MPa). The resulting mixture was then heated at 80°C for 2 hours and returned to room temperature. Thereafter, the battery was left for a certain period of time until the water content reached an equilibrium state. The resulting cell (positive electrode: 80 μm thick / solid electrolyte layer: 60 μm thick / negative electrode: 100 μm thick) was used as the all-solid-state lithium-ion secondary battery of Example 1.

[0141] [Production Example 2] Production of all-solid-state lithium-ion secondary battery (without polymer having SP value of 20 or more) An all-solid-state lithium-ion secondary battery of Example 2 was obtained in the same manner as in [Production Example 1] above, except that the relative humidity in the constant temperature and humidity chamber of <Production of all-solid-state lithium-ion secondary battery-1> was set to 10% (dew point -9°C).

[0142] [Production Example 3] Production of all-solid-state lithium-ion secondary battery (without polymer having SP value of 20 or more) An all-solid-state lithium-ion secondary battery of Example 3 was obtained in the same manner as in [Production Example 1] above, except that the relative humidity in the constant temperature and humidity chamber of <Production of all-solid-state lithium-ion secondary battery-1> was set to 4% (dew point -20°C).

[0143] Comparative Production Example 1 Production of All-Solid-State Lithium-Ion Secondary Battery (without Polymer Having an SP Value of 20 or More) An all-solid-state lithium-ion secondary battery of Comparative Example 1 was obtained in the same manner as in Production Example 1 above, except that the relative humidity in the constant temperature and humidity chamber of <Production of All-Solid-State Lithium-Ion Secondary Battery-1> was set to 19% (dew point: 0°C).

[0144] Comparative Production Example 2 Production of All-Solid-State Lithium-Ion Secondary Battery (without Polymer Having SP Value of 20 or More) An all-solid-state lithium-ion secondary battery of Comparative Example 2 was obtained in the same manner as in Production Example 1 above, except that the relative humidity in the constant temperature and humidity chamber of <Production of All-Solid-State Lithium-Ion Secondary Battery-1> was set to 2.5% (dew point: −25° C.).

[0145] [Production Example 4] Production of all-solid-state lithium-ion secondary battery (with polymer having SP value of 20 or more) <Preparation of solid electrolyte slurry-2> 10 g of the above-mentioned lithium-containing oxide fine particles, 9.3 g of water, 11 g of LiFSI, and 0.4 g of carboxymethyl cellulose (CMC, sodium salt, SP value: 27.2) were mixed and uniformly dispersed using a mixer (ARE-310 manufactured by THINKY Corporation) to obtain solid electrolyte slurry 2 (solid content concentration 70 mass%). The coating film obtained from this solid electrolyte slurry 2 was stored in a desiccator (relative humidity 5%) for several days and then analyzed under atmospheric conditions. It was confirmed that the coating film had the above-mentioned X-ray diffraction characteristics and was in an amorphous state. In addition, when the ionic conductivity was measured using the method described above, it was 4.5 × 10 －３ S / cm. In other words, it was confirmed that the addition of CMC did not affect the ionic conductivity. In addition, the ratio of the content of LiFSI to the content of the lithium-containing oxide was 1 in molar ratio.

[0146] <Preparation of Positive Electrode Slurry-2> A mixture of 0.5 g of the fine particles of the lithium-containing oxide, 1.43 g of a 6 mass % aqueous dispersion of CNT (manufactured by KJ Specialty Paper Co., Ltd.), 3.77 g of water, 0.55 g of LiFSI, and a positive electrode active material, LiCoO ２ 6 g of the above and 0.1 g of carboxymethyl cellulose (CMC, sodium salt, SP value: 27.2) were mixed and uniformly dispersed using a mixer (ARE-310 manufactured by THINKYO CORPORATION) to obtain a positive electrode slurry 2 (solid content concentration: 58.6 mass %). When this positive electrode slurry 2 is applied to a positive electrode current collector or a solid electrolyte layer or the like and dried to form a positive electrode active material layer, the lithium-containing oxide fine particles, LiFSI, CMC, and water (H ２ O) together to form the solid electrolyte (I) or (Ia).

[0147] <Preparation of negative electrode slurry-2> 0.6 g of the fine particles of the lithium-containing oxide, 4.2 g of a 6 mass % aqueous dispersion of CNT (manufactured by KJ Specialty Paper Co., Ltd.), 3.0 g of water, 0.66 g of LiFSI, and a negative electrode active material Li ４ Ti ５ O １２ 4.5 g of the above and 0.035 g of carboxymethyl cellulose (CMC, sodium salt, SP value: 27.2) were mixed and uniformly dispersed using a mixer (ARE-310 manufactured by THINKYO CORPORATION) to obtain anode slurry 2 (solid content concentration: 46.5 mass %). When this anode slurry 2 is applied to anode current collector or solid electrolyte layer or the like and dried to form a cathode active material layer, the lithium-containing oxide fine particles, LiFSI, CMC, and water (H ２ O) together to form the solid electrolyte (I) or (Ia).

[0148] <Production of All-Solid-State Lithium-Ion Secondary Battery-2> Cathode slurry 2 was applied to a titanium foil (20 μm thick cathode current collector), and anode slurry 2 was applied to an aluminum foil (50 μm thick anode current collector). The coating of cathode slurry 2 was naturally dried for 30 minutes in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 10%, and then solid electrolyte slurry 2 was applied as a multilayer on the dried coating. Next, in a constant temperature and humidity chamber controlled at room temperature of 25 ° C. and a relative humidity of 15% (dew point -3 ° C.), the multilayer coating and the coating of anode slurry 2 were punched out to sizes of 10 mm diameter and 8 mm diameter, respectively. After drying, the two coatings were bonded together so that they were in contact, and then placed in a uniaxial pressure jig (manufactured by Hosen Co., Ltd.) and sealed by restraining at 5 Nm (equivalent to 30 MPa). Subsequently, the mixture was heated at 80 ° C. for 2 hours and returned to room temperature. After that, the mixture was left for a certain period of time until the moisture content reached an equilibrium state. The obtained cell (positive electrode: 80 μm thick / solid electrolyte layer: 60 μm thick / negative electrode: 100 μm thick) was used as the all-solid-state lithium ion secondary battery of Example 4.

[0149] [Production Example 5] Production of all-solid-state lithium-ion secondary battery (containing polymer with SP value of 20 or more) An all-solid-state lithium-ion secondary battery of Example 5 was obtained in the same manner as in [Production Example 4] above, except that the relative humidity of the constant temperature and humidity chamber in <Production of all-solid-state lithium-ion secondary battery-2> was set to 10% (dew point -9°C).

[0150] [Production Example 6] Production of all-solid-state lithium-ion secondary battery (containing polymer with SP value of 20 or more) An all-solid-state lithium-ion secondary battery of Example 6 was obtained in the same manner as in [Production Example 4] above, except that the relative humidity of the constant temperature and humidity chamber in <Production of all-solid-state lithium-ion secondary battery-2> was set to 4% (dew point -20°C).

[0151] Comparative Production Example 3 Production of All-Solid-State Lithium-Ion Secondary Battery (Containing Polymer with SP Value of 20 or More) An all-solid-state lithium-ion secondary battery of Comparative Example 3 was obtained in the same manner as in Production Example 4 above, except that the relative humidity of the constant temperature and humidity chamber in Production of All-Solid-State Lithium-Ion Secondary Battery-2 was set to 19% (dew point: 0°C).

[0152] Comparative Production Example 4 Production of All-Solid-State Lithium-Ion Secondary Battery (Containing Polymer with SP Value of 20 or More) An all-solid-state lithium-ion secondary battery of Comparative Example 4 was obtained in the same manner as in Production Example 4 above, except that the relative humidity of the constant temperature and humidity chamber in <Production of All-Solid-State Lithium-Ion Secondary Battery-2> was set to 2.5% (dew point -25°C).

[0153] [Production Examples 7 to 13] Production of all-solid-state lithium-ion secondary batteries (with polymer having SP value of 20 or more) All-solid-state lithium-ion secondary batteries of Examples 7 to 13 were obtained in the same manner as [Production Example 5] above, except that the type and content of polymer with an SP value of 20 or more was changed as shown in the table below. In the table below, PEO stands for polyethylene oxide (polyethylene glycol), PVP stands for polyvinylpyrrolidone, and PVA stands for polyvinyl alcohol. Note that all CMCs are sodium salts.

[0154] [Analysis method] <H ２ The all-solid-state lithium ion secondary battery prepared above was disassembled in a temperature and humidity controlled room with a room temperature of 25°C and a dew point of -25°C, and H ２ Immediately after disassembly, a laminate portion (sample) consisting of a positive electrode active material layer / solid electrolyte layer / negative electrode active material layer was placed in a vial and sealed to prevent fluctuations in the amount of O. The mass of the empty vial and the mass of the sealed vial were measured, and the difference was taken as the sample mass. In addition, a blank vial containing only the atmosphere in a constant temperature and humidity chamber was also prepared and sealed. The vial was placed in a moisture vaporizer for Karl Fischer measurement, heated to a temperature of 130°C, and held for 1 minute. While the temperature was held at 130°C and moisture was vaporized, the H of each sample was measured by Karl Fischer titration using a coulometric moisture measuring device. ２ O amount (H ２ The mass of H detected per unit time was measured. ２ The test was continued until the O level was below the baseline (blank). Typical baseline values ​​were 0.1-0.4 μg / sec. H was determined by Karl Fischer titration. ２ From the amount of O to the blank H ２ The amount of O was subtracted, and the obtained value was used as the H contained in the sample. ２The mass of the sample and the amount of H in the sample were ２ From the masses of O, the positive electrode active material, the negative electrode active material, and the conductive additive (CNT), the H in the solid electrolyte constituting the laminate consisting of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is calculated using the following formula: ２ The amount of O (mass%) was calculated. ２ The amount of O is shown in the table below. The positive electrode active material, negative electrode active material, and conductive additive do not contain detectable H. ２ It has been confirmed that the sample does not contain O. ２ O mass] / ([sample mass]-[positive electrode active material mass]-[negative electrode active material mass]-[conductive additive mass])}

[0155] [Test Example] <Battery Initialization> The all-solid-state lithium-ion secondary battery prepared above was charged and discharged under the following conditions at a temperature of 26°C using a Scribner Associates 580-type charge / discharge measurement system. The battery was charged at a constant current value of 3.0 C rate until the battery voltage reached 2.5 V. After reaching 2.5 V, the voltage was kept constant (2.5 V) and the battery was charged until the current value reached 2.4 C rate. After charging, the circuit was opened and the battery was left for 10 minutes, and then discharged at a constant current value of 3.0 C rate until the battery voltage reached 1.8 V. This charge / discharge cycle was counted as one cycle, and the battery was initialized by performing 20 charge / discharge cycles.

[0156] <Charge-Discharge Cycle Characteristics> The initialized all-solid-state lithium-ion secondary battery was repeatedly charged and discharged at a temperature of 26°C using a Scribner Associates 580-type charge-discharge measurement system under the following conditions: Charging was performed at a constant current value of 3.0 C rate until the battery voltage reached 2.6 V. After reaching 2.6 V, the voltage was kept constant (2.6 V) and charging was continued until the current value reached 2.4 C rate. After charging, the circuit was opened and the battery was left for 10 minutes. Then, the battery was discharged at a constant current value of 3.0 C rate until the battery voltage reached 1.5 V. This cycle of charging and discharging was counted as one cycle. After discharging, the circuit was opened and the battery was left for 10 minutes. Then, charging and discharging were repeated in the same manner as above. In this charge-discharge cycle characteristic test, the ratio of the discharge capacity (II) at the 200th cycle to the discharge capacity (I) at the first cycle (discharge capacity retention rate (%) = 100 × discharge capacity (II) / discharge capacity (I)) was calculated. The results are shown in the table below. For reference, the polymer content in each layer of the secondary battery is also shown in a separate table.

[0157]

[0158]

[0159] As shown in the table above, for a laminate consisting of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer that constitute a battery, the H ２ It was found that by controlling the O content within the range of 4.5 to 12.5 mass %, the discharge capacity can be sufficiently increased and maintained at a high level even after repeated charge and discharge.

[0160] Next, the flexibility (suppleness) of the layers was also evaluated, and the results are described below. A laminate (a laminate consisting of a positive electrode current collector, a positive electrode active material layer, and a solid electrolyte layer laminated together, without the incorporation of a polymer with an SP value of 20 or more) consisting of a titanium foil (20 μm thick positive electrode current collector) and a multilayer coating film thereon, as prepared in Production Example 2 above, was prepared with the positive electrode layer thickness changed to 180 μm (the positive electrode active material layer thickness was 160 μm) and the solid electrolyte layer thickness changed to 120 μm. This was dried for one day in a desiccator at 25°C and 3% relative humidity, removed from the desiccator, and then placed in a room at 25°C and 30% relative humidity. The titanium foil side was placed against an 8 mm diameter glass rod and bent at a 360° angle so that the titanium foil side was facing inward. As a result, the positive electrode active material layer peeled off from the titanium foil, and cracks also occurred in the solid electrolyte layer. In contrast, in the laminate (a laminate consisting of a positive electrode current collector, a positive electrode active material layer, and a solid electrolyte layer, containing a polymer with an SP value of 20 or more) prepared in Production Example 5, which consisted of a titanium foil (20 μm thick positive electrode current collector) and a multilayer coating thereon, the thickness of the positive electrode layer was changed to 180 μm (the thickness of the positive electrode active material layer was changed to 160 μm) and the thickness of the solid electrolyte layer was changed to 120 μm, and a bending test was performed in the same manner as above. No peeling occurred between the layers of the laminate, and no cracks occurred in the positive electrode active material layer or the solid electrolyte layer. These results demonstrate that by incorporating a polymer with an SP value of 20 or more in the solid electrolyte, flexibility can be imparted to the formed layers without reducing discharge capacity or cycle characteristics, and therefore bending resistance can be sufficiently improved even when each layer is formed into a thick film.

[0161] 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.

[0162] This application claims priority based on Japanese Patent Application No. 2023-201370, filed on November 29, 2023, the contents of which are incorporated herein by reference as part of the present specification.

[0163] REFERENCE SIGNS LIST 1 negative electrode current collector 2 negative electrode active material layer 3 solid electrolyte layer 4 positive electrode active material layer 5 positive electrode current collector 6 operating part 10 all-solid-state lithium ion secondary battery

Claims

1. An all-solid-state lithium ion secondary battery having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer arranged in this order, wherein at least the solid electrolyte layer is made of a lithium-containing oxide containing Li, B, and O, a lithium salt, and H ２ The present invention relates to a method for producing a laminate comprising: a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, the method comprising the steps of: forming a laminate comprising: a positive electrode active material layer and a negative electrode active material layer; and determining whether the positive electrode active material layer and the solid electrolyte layer are in a state where the lithium salt content is in a range of 0.001 to 1.5 by molar ratio; ２ An all-solid-state lithium ion secondary battery having an O content of 4.5 to 12.5 mass %.

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

3.

3. The all-solid-state lithium ion secondary battery according to claim 2, wherein the lithium salt is represented by the following formula (1): Formula (1) LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ ) In the formula, R ｆ１ and R ｆ２ each independently represents a halogen atom or a perfluoroalkyl group.

4. The all-solid-state lithium ion secondary battery according to claim 3, wherein the solid electrolyte comprises a polymer having a solubility parameter of 20 or more.

5. Lithium-containing oxides containing Li, B, and O, lithium salts, and H ２ A solid electrolyte comprising: O; the solid electrolyte is in an amorphous state; a molar ratio of the content of the lithium salt to the content of the lithium-containing oxide in the solid electrolyte is 0.001 to 1.5; and H ２ A solid electrolyte having an O content of 4.5 to 12.5 mass %.

6. The lithium-containing oxide is Li ２＋ｘ B ４＋ｙ O ７＋ｚ The solid electrolyte of claim 5, comprising: wherein -0.3<x<0.3, -0.3<y<0.3, and -0.3<z<0.

3.

7. The solid electrolyte according to claim 6, wherein the lithium salt is represented by the following formula (1): Formula (1) LiN(R ｆ１ SO ２ ) (R ｆ２ SO ２ ) In the formula, R ｆ１ and R ｆ２ each independently represents a halogen atom or a perfluoroalkyl group.

8. The solid electrolyte of claim 7, wherein the solid electrolyte comprises a polymer having a solubility parameter of 20 or greater.