Evaluation method of all-solid lithium ion battery and manufacturing method of the same

Abstract

To provide an evaluation method which accurately evaluates battery characteristics of an oxide-based all-solid battery, and a manufacturing method of the battery.SOLUTION: An evaluation method of all-solid lithium ion battery comprises: a fired body manufacturing process in which a positive electrode mixture including cathode active material and a solid electrolyte are pressed to manufacture a green compact consisting of a solid electrolyte layer and a positive electrode layer, and the green compact is, while load is applied in a compression direction of the green compact, sintered to manufacture the fired body; a battery manufacturing process in which a laminate manufactured by arranging a negative electrode layer on a surface of the solid electrolyte layer of the green compact is placed into a closed vessel and a specified restraint pressure is applied thereto to manufacture the all-solid lithium ion battery; and a battery evaluation process which evaluates battery characteristics of the all-solid lithium ion battery. In the fired body manufacturing process, the positive electrode mixture is slurry whose solid content is 55-65 mass%, the slurry of the positive electrode mixture is arranged on a flat surface, extended and dried on the flat surface, and then a part of the positive electrode mixture extended on the flat surface and the solid electrolyte are pressed to manufacture the green compact consisting of the solid electrolyte layer and the positive electrode layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, with the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as power sources for these devices has become important. Among these batteries, lithium ion batteries have attracted attention from the viewpoint of their high energy density. In addition, there is a demand for improvements in the energy density and battery characteristics of lithium secondary batteries for large-scale applications such as vehicle-mounted power sources and load leveling.

[0003] LISICON-type oxide-based solid electrolytes are expected to be the next-generation solid electrolyte for all-solid-state batteries as solid materials that conduct Li ions. In addition, it is possible to introduce Li deficiency or excess Li by replacing it with ions of different valence, and it has the advantage that materials can be prepared by combining various elements.

[0004] Non-Patent Document 1 describes a LISICON-type solid electrolyte, Li 3.5 Ge 0.5 V 0.5 O 4 They disclose that they have produced a cell by combining this with NCM111 (a positive electrode active material containing Ni, Co, and Mn in a 1:1:1 composition ratio), a Ni-Co-Mn ternary positive electrode active material, and co-sintering it using spark plasma sintering, resulting in the production of a sintered body for cells that exhibits stable charge and discharge behavior. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Toyoki Okumura, Tomonari Takeuchi, and Hironori Kobayashi, All-Solid-State Batteries with LiCoO2-Type Electrodes: Realization of an Impurity-Free Interface by Utilizing a Cosinterable Li3.5Ge0.5V0.5O4 Electrolyte, ACS Appl. Energy Mater. (2021), 4, 1, 30-34. Summary of the Invention [Problem to be solved by the invention]

[0006] Oxide-based all-solid-state lithium-ion batteries, which use non-flammable oxide-based solid electrolytes, are attracting attention as next-generation batteries that are significantly safer and more reliable than conventional lithium-ion batteries.

[0007] The battery characteristics of oxide-based all-solid-state batteries have been evaluated from various viewpoints. It is necessary to accurately evaluate the battery characteristics of such oxide-based all-solid-state batteries, but there is a problem that the evaluation of the battery characteristics of oxide-based all-solid-state batteries produced using the same cathode active material and solid electrolyte as raw materials varies. If there is a variation in the evaluation of the battery characteristics, it becomes difficult to accurately evaluate the cathode active material and solid electrolyte that are the raw materials.

[0008] Conventionally, in a method for manufacturing an oxide-based all-solid-state battery, a positive electrode composite is provided on a solid electrolyte layer and pressed to produce a green compact having a laminated structure of a positive electrode layer / solid electrolyte layer. Here, the positive electrode composite is prepared by wet mixing a powder of a positive electrode active material and a powder of a solid electrolyte. However, in such a method, the positive electrode active material and the solid electrolyte are not mixed well in the positive electrode composite, resulting in low mixability, which may cause a decrease in performance as a positive electrode layer, and may cause variations in the evaluation of the battery characteristics of the produced oxide-based all-solid-state battery. In addition, since the positive electrode composite is in the form of a powder, when the positive electrode composite is provided on the solid electrolyte layer, the powder of the positive electrode composite is sprinkled on the solid electrolyte layer and then pressed to produce a green compact having a laminated structure of a positive electrode layer / solid electrolyte layer. In such a method, the thickness of the positive electrode composite layer is not uniform, and the surface of the solid electrolyte layer remains exposed, which may cause variations in the evaluation of the battery characteristics of the produced oxide-based all-solid-state battery.

[0009] The present invention has been made to solve the above problems, and aims to provide a method for accurately evaluating the battery characteristics of an oxide-based all-solid-state battery. Another aim of the present invention is to provide a method for producing an all-solid-state lithium ion battery having good battery characteristics. [Means for solving the problem]

[0010] The present invention, which has been completed based on the above findings, is defined by the following (1) to (14). (1) A method for evaluating an all-solid-state lithium ion battery including a solid electrolyte layer including an oxide-based solid electrolyte, a positive electrode layer including a positive electrode active material, and a negative electrode layer, comprising: a sintered body preparation step of pressing the positive electrode composite material containing the positive electrode active material and the solid electrolyte to prepare a compact of the solid electrolyte layer / positive electrode layer, and sintering the compact while applying a load in the compression direction to prepare a sintered body; a battery production process in which a laminate produced by providing a negative electrode layer on a surface of the solid electrolyte layer of the fired body is placed in a sealed container and a predetermined confining pressure is applied to produce an all-solid-state lithium ion battery; a battery evaluation step of evaluating battery characteristics of the all-solid-state lithium ion battery; Including, The sintered body preparation step includes providing the positive electrode mixture as a slurry having a solid content of 55 to 65 mass %, spreading the slurry on the flat surface, drying the slurry, and then pressing a part of the positive electrode mixture spread on the flat surface and the solid electrolyte to prepare a compact of the solid electrolyte layer / positive electrode layer. (2) In the sintered body preparation step, the positive electrode mixture slurry is applied to a flat surface in an amount of 9.6 to 26.4 mg / cm2 per unit area. 2 The method for evaluating an all-solid-state lithium ion battery according to (1) above, further comprising stretching the battery so that the battery is stretched. (3) The method for evaluating an all-solid-state lithium ion battery according to (1) or (2), wherein a slurry of the positive electrode mixture containing the positive electrode active material is prepared by mechanically mixing raw materials. (4) The method for evaluating an all-solid-state lithium ion battery according to any one of (1) to (3), wherein in the sintered body preparation step, the slurry of the positive electrode mixture is provided on a flat surface, and the slurry on the flat surface is spread using an applicator of a coating machine while maintaining a constant gap between the applicator and the flat surface. (5) The method for evaluating an all-solid-state lithium ion battery according to any one of (1) to (4), wherein the slurry is spread while maintaining a moving speed of an applicator of the coater on the flat surface at 10 to 20 mm / sec. (6) The method for evaluating an all-solid-state lithium ion battery according to any one of (1) to (5), wherein a slurry of a positive electrode mixture containing the positive electrode active material contains isopropyl alcohol. (7) The oxide-based solid electrolyte is represented by the composition formula 1: Li α A x M y O 4 (In the composition formula 1, A is Ge, Si or Ti, M is V, P or As, 3.25≦α≦3.75, 0.30≦x≦0.75, and 0.25≦y≦0.70.) It is expressed as The positive electrode active material is represented by the formula 2: Li a Ni b Coc Mn d O 2 (In the composition formula 2, 1.00≦a≦1.08, 0.33≦b≦0.90, and b+c+d=1.0.) The method for evaluating an all-solid-state lithium ion battery according to any one of (1) to (6) above, (8) A method for producing an all-solid-state lithium ion battery including a solid electrolyte layer including an oxide-based solid electrolyte, a positive electrode layer including a positive electrode active material, and a negative electrode layer, comprising: a sintered body preparation step of pressing the positive electrode composite material containing the positive electrode active material and the solid electrolyte to prepare a compact of the solid electrolyte layer / positive electrode layer, and sintering the compact while applying a load in the compression direction to prepare a sintered body; a battery production process in which a laminate produced by providing a negative electrode layer on a surface of the solid electrolyte layer of the fired body is placed in a sealed container and a predetermined confining pressure is applied to produce an all-solid-state lithium ion battery; Including, The sintered body preparation step includes the steps of: providing the positive electrode mixture as a slurry having a solid content of 55 to 65 mass %, spreading the slurry on the flat surface, drying the slurry, and then pressing a part of the positive electrode mixture spread on the flat surface and the solid electrolyte to prepare a compact of the solid electrolyte layer / positive electrode layer. This is a method for producing an all-solid-state lithium-ion battery. (9) In the sintered body preparation step, the positive electrode mixture slurry is applied to a flat surface in an amount of 9.6 to 26.4 mg / cm per unit area. 2 The method for producing an all-solid-state lithium ion battery according to (8) above, (10) The method for producing an all-solid-state lithium ion battery according to (8) or (9), wherein the slurry of the positive electrode mixture containing the positive electrode active material is produced by mechanically mixing raw materials. (11) The method for producing an all-solid-state lithium ion battery according to any one of (8) to (10), wherein in the sintered body producing step, the slurry of the positive electrode mixture is provided on a flat surface, and the slurry on the flat surface is spread using an applicator of a coating machine while maintaining a constant gap between the applicator and the flat surface. (12) The method for producing an all-solid-state lithium ion battery according to any one of (8) to (11), wherein the slurry is spread while maintaining a moving speed of an applicator of the coater on the flat surface of 10 to 20 mm / sec. (13) The method for producing an all-solid-state lithium ion battery according to any one of (8) to (12), wherein a slurry of the positive electrode mixture containing the positive electrode active material contains isopropyl alcohol. (14) The oxide-based solid electrolyte is represented by the composition formula 1: Li α A x M y O 4 (In the composition formula 1, A is Ge, Si or Ti, M is V, P or As, 3.25≦α≦3.75, 0.30≦x≦0.75, and 0.25≦y≦0.70.) It is expressed as The positive electrode active material is represented by the formula 2: Li a Ni b Co c Mn d O 2 (In the composition formula 2, 1.00≦a≦1.08, 0.33≦b≦0.90, and b+c+d=1.0.) The method for producing the all-solid-state lithium ion battery according to any one of (8) to (13), Effect of the Invention

[0011] According to the present invention, it is possible to provide a method for accurately evaluating the battery characteristics of an oxide-based all-solid-state battery. Also, according to the present invention, it is possible to provide a method for manufacturing an all-solid-state lithium ion battery having good battery characteristics. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram showing a state in which a slurry of a positive electrode mixture on a sheet (flat surface) is spread by an applicator of a coater according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram of an all-solid-state lithium-ion battery according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, the embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that appropriate changes and improvements in the design may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0014] <Method for evaluating all-solid-state lithium-ion batteries and method for manufacturing all-solid-state lithium-ion batteries> The method for evaluating an all-solid-state lithium-ion battery according to an embodiment of the present invention is a method for evaluating an all-solid-state lithium-ion battery including a solid electrolyte layer including an oxide-based solid electrolyte, a cathode layer including a cathode active material, and an anode layer, and includes a fired body preparation step, a battery preparation step, and a battery evaluation step, which will be described later. Also, the method for manufacturing an all-solid-state lithium-ion battery according to an embodiment of the present invention is a method for manufacturing an all-solid-state lithium-ion battery including a solid electrolyte layer including an oxide-based solid electrolyte, a cathode layer including a cathode active material, and an anode layer, and includes a fired body preparation step and a battery preparation step, which will be described later.

[0015] <Sintered body production process> In the sintered body preparation process, a positive electrode composite material containing a positive electrode active material and a solid electrolyte are pressed to prepare a compact of a solid electrolyte layer / positive electrode layer, and the compact is sintered while a load is applied in the compression direction to prepare a sintered body.

[0016] The positive electrode mixture is a slurry with a solid content of 55 to 65% by mass. The positive electrode mixture slurry is obtained by mixing a positive electrode active material, an oxide-based solid electrolyte, and a binder, adding a solvent so that the solid content of the slurry becomes 55 to 65% by mass, and mixing with Mazerustar or the like.

[0017] The positive electrode composite slurry has a solid content of 55 to 65% by mass, which provides good dispersibility of the solid content, and can be spread well on a flat surface in the process described below, and can prevent the slurry from spreading too much to cause uneven thickness. As described below, the positive electrode composite slurry may be provided on a sheet such as a PET (polyethylene terephthalate) sheet, and the slurry on the sheet may be stretched and punched out to produce a laminate of the sheet and the positive electrode composite. At this time, the positive electrode composite side of the laminate is placed on the solid electrolyte and pressed, and the sheet is peeled off, which makes it easy to peel off the sheet when stacking the positive electrode composite on the solid electrolyte. The positive electrode composite slurry preferably has a solid content of 55 to 60% by mass, and more preferably 55 to 58% by mass.

[0018] The solvent for producing the slurry of the positive electrode mixture is not particularly limited, but may be anisole, tetrahydrofuran, or the like. It is preferable to add isopropyl alcohol (IPA) to the solvent. By adding isopropyl alcohol, the raw material can be dispersed well, and the remaining of aggregates in the slurry can be suppressed. When isopropyl alcohol is added, it is preferable to add it so that it is contained in 7 to 10 volume % of the entire slurry.

[0019] As the binder, a known binder can be used, but it is preferable to use polycarbonate, hydrogenated styrene-based thermoplastic elastomer, styrene-based thermoplastic elastomer, etc. Also, various thickeners may be added.

[0020] The slurry of the positive electrode mixture containing the positive electrode active material is preferably prepared by mechanically mixing the raw materials. When mixed manually, the raw materials may not be mixed well, which may result in a decrease in the performance of the prepared positive electrode layer and cause variations in the evaluation of the battery characteristics of the oxide-based all-solid-state battery. The raw materials of the slurry of the positive electrode mixture can be mechanically mixed using a mixer such as Mazerustar manufactured by Kurabo Industries Co., Ltd.

[0021] Next, the slurry of the positive electrode composite material is placed on a flat surface, and the slurry on the flat surface is spread out. The flat surface may be a stage having a predetermined size and flat surface, or may be a sheet. In particular, when a thin plastic sheet is used for the flat surface, a laminate of the sheet and the positive electrode composite material can be produced by punching out a part of the sheet as described later, and the positive electrode composite material of the laminate can be easily placed on the solid electrolyte. As the thin plastic sheet, a commercially available PET film or the like can be used.

[0022] The size of the flat surface on which the positive electrode mixture slurry is provided is not particularly limited and can be appropriately designed. For example, the flat surface may have a length×width of 2 to 10 cm×1 to 5 cm.

[0023] Although the spreading of the positive electrode composite slurry on the flat surface is not particularly limited, the slurry can be spread to a good uniform thickness by using an applicator of a coating machine. FIG. 1 is a schematic diagram showing the state in which the positive electrode composite slurry on a sheet (flat surface) is spread by an applicator of a coating machine. As shown in FIG. 1, the cylindrical applicator of a coating machine (not shown) moves on the sheet on which the positive electrode composite slurry is provided with a certain gap from the flat surface, so that the positive electrode composite slurry on the sheet can be spread while maintaining a certain thickness. In this way, the slurry on the flat surface can be spread to a uniform thickness more easily and accurately by spreading the slurry on the flat surface while keeping the gap between the applicator and the flat surface at a constant value.

[0024] It is preferable to spread the slurry while keeping the moving speed of the applicator of the coater on the flat surface at 10 to 20 mm / sec. If the moving speed of the applicator of the coater on the flat surface is 10 mm / sec or more, it is preferable in terms of maintaining the viscosity of the solvent. If the moving speed of the applicator of the coater on the flat surface is 20 mm / sec or less, it is preferable in terms of maintaining the homogeneity of the coating film. It is more preferable to spread the slurry while keeping the moving speed of the applicator of the coater on the flat surface at 10 to 16 mm / sec, and even more preferable to spread the slurry while keeping it at 14 to 16 mm / sec.

[0025] The positive electrode mixture slurry is applied to a flat surface with a slurry amount per unit area of ​​9.6 to 26.4 mg / cm. 2 According to this configuration, the positive electrode mixture slurry can be spread to a uniform thickness on the flat surface. This also optimizes the thickness of the positive electrode layer, i.e., the Li migration distance, improving the battery characteristics. The positive electrode mixture slurry is preferably spread on the flat surface so that the amount of slurry per unit area is 9.6 to 13.0 mg / cm. 2 It is more preferable to stretch the material so that the thickness becomes equal to or larger than the thickness of the material.

[0026] Next, it is preferable to dry the solvent contained in the spread positive electrode composite slurry by placing the sheet on which the positive electrode composite slurry is provided in a dryer set at 70 to 100° C. for 30 minutes to 1 hour.

[0027] Next, a part of the positive electrode composite material stretched on the flat surface is collected. At this time, only the positive electrode composite material may be collected, but if the flat surface is composed of a sheet, a laminate of the positive electrode composite material / sheet can be obtained by punching out a predetermined area together with the sheet. Next, a part of the collected positive electrode composite material is laminated on a solid electrolyte that has been separately compressed and prepared. If a part of the positive electrode composite material is collected as a laminate of the positive electrode composite material / sheet as described above, the positive electrode composite material side of the laminate is placed on the solid electrolyte and pressed, and the sheet is peeled off, so that the positive electrode composite material can be easily laminated on the solid electrolyte.

[0028] Next, the laminate of the part of the positive electrode composite material and the solid electrolyte is pressed to produce a green compact of the solid electrolyte layer / positive electrode layer. The pressing of the part of the positive electrode composite material and the solid electrolyte is not particularly limited, but is performed with a known pressing machine at a pressure of 300 to 400 g / cm. 2The pressure can be applied to the powder compact of the solid electrolyte layer / positive electrode layer produced by pressing a part of the positive electrode composite with the solid electrolyte, and each of the powder compacts may be formed in a columnar shape. The powder compact may be a columnar shape with circular end faces (cylindrical), a columnar shape with polygonal end faces (rectangular column), or a columnar shape with an indeterminate end face. From the viewpoints of production efficiency and avoidance of stress concentration, the powder compact is preferably a columnar shape. The area of ​​the end face of the powder compact is not particularly limited, but is preferably 0.5 to 1.0 cm. 2 The height of the powder compact is not particularly limited, but may be 0.03 to 0.06 cm.

[0029] Next, the powder compact is sintered while being loaded in the compression direction to produce a sintered body. Although the powder compact may be sintered while being loaded individually, it is preferable to sinter a plurality of powder compacts by applying a uniform load at once, taking efficiency into consideration. In this case, it is preferable to place a flat plate on the plurality of powder compacts and place a weight on the flat plate. In addition, the flat plate is preferably made of MgO or ZrO, since it is placed in a sintering furnace and heated for sintering, although there is no particular limitation thereon. 2 It is preferable that the setter is made of ceramics such as a setter. The setter may be used as a weight. In this case, in addition to the Au film described later, a single flat setter is placed on the powder compacts, and also serves as a weight.

[0030] By placing a weight on the flat plate, multiple compacts are compressed to 30-92g / cm 2 The mass of the weight is not particularly limited, and can be appropriately designed depending on the number of powder compacts and the surface area of ​​the upper end face of the powder compact. When an Au film and a setter (described later) are placed on the powder compact, the mass of the setter is adjusted assuming that the load is applied by the mass of the setter. Note that the Au film has a mass that is about 1 / 100 of the weight, and therefore can be ignored in the calculation of the load. The load applied to multiple powder compacts is 45 to 65 g / cm. 2 It is more preferable that:

[0031] A precious metal film may be provided between the powder compact and the flat surfaces of the setters, etc., provided above and below the powder compact, in order to prevent the diffusion of components of the setters, etc. The precious metal film is not particularly limited, but it is preferable to use an Au film, a Pt film, an Ir film, etc.

[0032] Sintering can be carried out using a known firing furnace or the like, and is preferably carried out at 700 to 800° C. for 2 to 12 hours.

[0033] <Battery manufacturing process> In the battery preparation process, a laminate prepared by providing an anode layer on the surface of the solid electrolyte layer of the fired body is placed in a sealed container, and a predetermined confining pressure is applied to prepare an all-solid-state lithium ion battery. Here, the sealed container is a container for blocking the air, and is not particularly limited as long as it is one generally used for all-solid-state lithium ion batteries. The configuration of the anode layer will be described later. In addition, the material and shape of the sealed container in which the laminate is placed are not particularly limited, and can be appropriately designed according to the shape and size of the desired all-solid-state lithium ion battery. In this way, the all-solid-state lithium ion battery according to the embodiment of the present invention can be prepared.

[0034] <Battery evaluation process> In the method for evaluating an all-solid-state lithium-ion battery according to the embodiment of the present invention, the all-solid-state lithium-ion battery prepared as described above is further subjected to a battery evaluation step. In the battery evaluation step, the all-solid-state lithium-ion battery is evaluated for predetermined battery characteristics. Examples of the battery characteristics of the all-solid-state lithium-ion battery include discharge capacity and cycle characteristics.

[0035] Conventionally, the positive electrode mixture used in the manufacturing method of an oxide-based all-solid-state battery was prepared by wet mixing a powder of a positive electrode active material and a powder of a solid electrolyte. However, in this method, the positive electrode active material and the solid electrolyte do not mix well in the positive electrode mixture, resulting in low mixability, which reduces the performance of the positive electrode layer, and there is a risk of variation in the evaluation of the battery characteristics of the prepared oxide-based all-solid-state battery. In addition, since the positive electrode mixture is in the form of a powder, it is sprinkled on the solid electrolyte layer and then pressed to prepare a compact having a laminated structure of a positive electrode layer / solid electrolyte layer. For this reason, the thickness of the positive electrode mixture layer is not uniform, and the surface of the solid electrolyte layer remains exposed, which may cause variation in the evaluation of the battery characteristics of the prepared oxide-based all-solid-state battery. In contrast, in the embodiment of the present invention, as described above, in the sintered body preparation step, the positive electrode mixture is a slurry with a solid content of 55 to 65% by mass, the positive electrode mixture slurry is provided on a flat surface, the slurry on the flat surface is spread, the slurry is dried, and then a part of the positive electrode mixture spread on the flat surface and the solid electrolyte are pressed to prepare a compact of the solid electrolyte layer / positive electrode layer. Therefore, the compact can be prepared by providing the positive electrode mixture on the solid electrolyte in a constant thickness state. Therefore, the thickness of the positive electrode mixture layer becomes uniform, and the exposure of the surface of the solid electrolyte layer can be suppressed well. Therefore, the occurrence of variations in the evaluation of the battery characteristics of the all-solid-state lithium ion battery can be efficiently suppressed. As a result, the battery characteristics of the all-solid-state lithium ion battery can be accurately evaluated. In addition, by manufacturing the all-solid-state lithium ion battery as described above, the thickness of the positive electrode mixture layer becomes uniform, and the battery characteristics such as the charge capacity and the charge / discharge efficiency become good.

[0036] <All-solid-state lithium-ion battery> The all-solid-state lithium-ion battery to be evaluated in the evaluation method of the all-solid-state lithium-ion battery according to the embodiment of the present invention includes a solid electrolyte layer containing an oxide-based solid electrolyte, a positive electrode layer containing a positive electrode active material, and a negative electrode layer. The all-solid-state lithium-ion battery can have a configuration as shown in FIG.

[0037] (solid electrolyte layer) The composition of the solid electrolyte layer of the present embodiment is not particularly limited, but may be, for example, a composition represented by the formula 1: Li α A x M y O 4 (In the composition formula 1, A is Ge, Si or Ti, M is V, P or As, 3.25≦α≦3.75, 0.30≦x≦0.75, and 0.25≦y≦0.70.) The oxide-based solid electrolyte of this embodiment is a LISICON-type solid electrolyte, Li α Ge x V y O 4 or a composition in which the base material is substituted with Si, Ti, P or As. With such a configuration, the number of elements constituting the oxide-based solid electrolyte is increased, and the activation energy is reduced, so that an oxide-based solid electrolyte having good ion conductivity can be obtained. As a result, the capacity of the all-solid-state lithium ion battery is increased. In the present invention, the oxide-based solid electrolyte refers to a solid electrolyte having, in its skeleton, an oxoacid ion in which an oxygen atom is coordinately bonded to a central element, as a counter anion to a lithium ion.

[0038] In the oxide-based solid electrolyte of the present embodiment, if α is less than 3.25 in the above composition formula 1, the carrier concentration is low, so that the ion conductivity may be reduced. If α is more than 3.75, the single-phase synthesis may be difficult. In the oxide-based solid electrolyte of the present embodiment, it is preferable that 3.40≦α≦3.70 in the above composition formula 1.

[0039] In the oxide-based solid electrolyte of the present embodiment, when x is less than 0.30 in the above composition formula 1, Li 4 GeO 4 A phase may occur. In addition, if x exceeds 0.75, the crystal lattice becomes large, so the distance between Li sites becomes long, and the ion conductivity may decrease. In the oxide-based solid electrolyte of the present embodiment, in the above composition formula 1, it is preferable that 0.40≦x≦0.60.

[0040] In the oxide-based solid electrolyte of the present embodiment, when y is less than 0.25 in the above composition formula 1, the effect of reducing the activation energy by element substitution is weak, and the effect of improving the ion conductivity may be small. 4 VO 4 There is a risk that impurity phases such as those mentioned above will be generated, resulting in a decrease in ion conductivity. In the oxide-based solid electrolyte of this embodiment, in the above composition formula 1, it is preferable that 0.30≦y≦0.60.

[0041] The average particle size of the oxide-based solid electrolyte of this embodiment is not particularly limited, but may be 0.01 to 100 μm, 0.1 to 100 μm, or 0.1 to 50 μm.

[0042] The oxide-based solid electrolyte of this embodiment can be produced as follows. First, raw materials are weighed out to obtain a desired composition in a glove box filled with an inert gas such as argon gas or nitrogen gas. Each raw material used here is, for example, LiOH H 2 O, GeO 2 , V 2 O 5 , SiO 2 , TiO 2 , H 3 PO 4 , H 3 AsO 3 etc.

[0043] Next, the mixture is mixed in a mortar or the like for 5 to 30 minutes to prepare a mixed powder. At this time, it is preferable to mix for such a time that the average particle size of the mixed powder becomes 5 to 40 μm.

[0044] Next, the mixed powder is placed in an alumina sagger and sintered at 600 to 1000°C for 1 to 20 hours to obtain a powder of the composition formula 1: Li α A x M y O 4(In composition formula 1, A is Ge, Si or Ti, M is V, P or As, 3.25≦α≦3.75, 0.30≦x≦0.75, and 0.25≦y≦0.70.)

[0045] The average thickness of the solid electrolyte layer of the lithium ion battery formed by the oxide-based solid electrolyte of this embodiment is not particularly limited and can be appropriately designed according to the purpose. The average thickness of the solid electrolyte layer of this embodiment may be, for example, 50 μm to 500 μm, or 50 μm to 100 μm.

[0046] (Positive electrode layer) The composition of the positive electrode active material contained in the positive electrode layer of the present embodiment is not particularly limited. For example, a Ni b Co c Mn d O 2 (In composition formula 2, 1.00≦a≦1.08, 0.33≦b≦0.90, and b+c+d=1.0.) More specifically, the positive electrode layer of this embodiment can be a layer of a positive electrode mixture obtained by mixing the positive electrode active material represented by composition formula 2 with the oxide-based solid electrolyte of this embodiment. The content of the positive electrode active material in the positive electrode layer is, for example, preferably 50% by mass or more and 99% by mass or less, and more preferably 55% by mass or more and 75% by mass or less.

[0047] The positive electrode active material of this embodiment preferably has a Ni ratio of 0.60≦b≦0.90. When a high-nickel NCM positive electrode active material having such a high Ni ratio is used, the capacity of the all-solid-state lithium-ion battery generally becomes high. From this viewpoint, it is more preferable that 0.80≦b≦0.90 in the above composition formula 2. The positive electrode active material of this embodiment is not particularly limited as long as it satisfies the above composition formula 2, and a known positive electrode active material can be used.

[0048] Previously, high-nickel NCM positive electrode active materials with a high Ni ratio of 0.60≦b≦0.90 would react with the solid electrolyte to produce a reactant that does not conduct Li ions, causing the battery to fail, but this type of high-nickel NCM positive electrode active material does not produce a reactant with the oxide-based solid electrolyte represented by the above composition formula 1. For this reason, an all-solid-state lithium-ion battery that has the oxide-based solid electrolyte represented by the above composition formula 1 in the solid electrolyte layer and the high-nickel NCM positive electrode active material represented by the above composition formula 2 in the positive electrode layer can provide an oxide-based all-solid-state battery that achieves high capacity.

[0049] The positive electrode mixture may further include a conductive assistant. As the conductive assistant, a carbon material, a metal material, or a mixture thereof may be used. The conductive assistant may include at least one element selected from the group consisting of, for example, carbon, nickel, copper, aluminum, indium, silver, cobalt, magnesium, lithium, chromium, gold, ruthenium, platinum, beryllium, iridium, molybdenum, niobium, osmium, rhodium, tungsten, and zinc. The conductive assistant is preferably a highly conductive carbon element, a metal element, a mixture, or a compound containing carbon, nickel, copper, silver, cobalt, magnesium, lithium, ruthenium, gold, platinum, niobium, osmium, or rhodium. As the carbon material, for example, carbon black such as Ketjen Black, acetylene black, denka black, thermal black, and channel black, graphite, carbon fiber, activated carbon, and the like may be used.

[0050] The average thickness of the positive electrode layer of the all-solid-state lithium ion battery is not particularly limited and can be appropriately designed according to the purpose. The average thickness of the positive electrode layer of the all-solid-state lithium ion battery may be, for example, 1 μm to 100 μm, or 1 μm to 10 μm.

[0051] (Negative electrode layer) The negative electrode layer of the all-solid-state lithium ion battery is not particularly limited, and may be a layer of a known negative electrode active material for all-solid-state lithium ion batteries. The negative electrode layer may be a layer of a negative electrode mixture obtained by mixing a known negative electrode active material for all-solid-state lithium ion batteries with a solid electrolyte. The content of the negative electrode active material in the negative electrode layer is, for example, preferably 10% by mass or more and 99% by mass or less, and more preferably 20% by mass or more and 90% by mass or less.

[0052] The negative electrode layer may contain a conductive assistant, as in the positive electrode layer. The conductive assistant may be the same material as that described in the positive electrode layer. As the negative electrode active material, for example, a carbon material, specifically, artificial graphite, graphite carbon fiber, resin-calcined carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-calcined carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, non-graphitizable carbon, or a mixture thereof may be used. As the negative electrode material, for example, a metal itself, such as metallic lithium, metallic indium, metallic aluminum, or metallic silicon, or an alloy in combination with other elements or compounds may be used.

[0053] The average thickness of the negative electrode layer of the all-solid-state lithium ion battery is not particularly limited and can be appropriately selected depending on the purpose. The average thickness of the negative electrode layer of the all-solid-state lithium ion battery may be, for example, 1 μm to 100 μm, or 1 μm to 10 μm.

[0054] The method for forming the negative electrode layer of the all-solid-state lithium ion battery is not particularly limited and can be appropriately selected depending on the purpose. Examples of the method for forming the negative electrode layer of the all-solid-state lithium ion battery include a method of compressing and molding negative electrode active material particles, and a method of depositing a negative electrode active material.

[0055] Other members constituting the all-solid-state lithium ion battery are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a positive electrode current collector, a negative electrode current collector, and a battery case.

[0056] The size and structure of the positive electrode current collector are not particularly limited and can be appropriately selected depending on the purpose. Examples of the material for the positive electrode current collector include die steel, stainless steel, aluminum, aluminum alloys, titanium alloys, copper, gold, and nickel. The positive electrode current collector may be in the form of, for example, a foil, a plate, or a mesh. The average thickness of the positive electrode current collector may be, for example, 10 μm to 500 μm, or 50 μm to 100 μm.

[0057] The size and structure of the negative electrode current collector are not particularly limited and can be appropriately selected depending on the purpose. Examples of the material for the negative electrode current collector include die steel, gold, indium, nickel, copper, and stainless steel. The negative electrode current collector may be in the form of, for example, a foil, a plate, or a mesh. The average thickness of the negative electrode current collector may be, for example, 10 μm to 500 μm, or 50 μm to 100 μm.

[0058] The battery case is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include known laminate films that can be used in conventional all-solid-state batteries, etc. Examples of the laminate film include a resin laminate film and a film in which a metal is vapor-deposited on a resin laminate film. The shape of the battery is not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the battery include cylindrical, square, button, coin, and flat types. EXAMPLES

[0059] The following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0060] <1. Preparation of oxide-based solid electrolyte and positive electrode active material> (Examples 1 to 6) Li 3.5 Ge 0.5 V 0.5 O 4 and an oxide-based solid electrolyte having the composition LiNi 0.6 Co 0.2 Mn 0.2 O 2 Positive electrode active materials having the following compositions were prepared. The composition of the positive electrode active material was evaluated as follows. That is, 5 g of a sample (powder) of the positive electrode active material was weighed out and decomposed by the alkali fusion method, and then the composition was analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES) "PS7800" manufactured by Hitachi High-Tech Corporation. The oxygen content was obtained by subtracting the analysis values ​​of Li and metal components, as well as the impurity concentration and residual alkali amount, from the total amount of the analyzed sample, and the z value of the oxygen composition (Oz) was calculated from the oxygen content. The composition of the oxide-based solid electrolyte was evaluated as follows: 0.5 g of a sample (powder) of the oxide-based solid electrolyte was weighed out and dissolved in various acids, and then the composition was analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES) "PS7800" manufactured by Hitachi High-Tech Corporation.

[0061] <2. Preparation of powder compact> Example 1 The positive electrode active material, the oxide-based solid electrolyte, and an anisole solution in which 10% by mass of the binder was dissolved were mixed in this order in a mass ratio of 250:250:250, and anisole was added as a solvent so that the solid content of the slurry was 64% by mass. The mixture was mixed for 400 seconds using a Mazerustar manufactured by Kurabo Industries, Ltd. to prepare a positive electrode composite slurry. The mixing settings in the mixer were set to revolution "9" and rotation "7". Tuftec (registered trademark) manufactured by Asahi Kasei Corporation was used as the binder. Tuftec is a polymer (hydrogenated styrene-based thermoplastic elastomer) in which the double bond portion of a block copolymer made of styrene and butadiene is hydrogenated. Next, the entire amount of the positive electrode composite slurry prepared in the above-mentioned procedure was placed on the flat surface of the PET sheet, so that the amount of slurry per unit area of ​​the PET sheet was 21.8 mg / cm 2The slurry was spread on the PET sheet so that the slurry became uniform. The positive electrode composite slurry was spread on the PET sheet using a cylindrical applicator of a coating machine as shown in Figure 1. The applicator was moved at a speed of 15 mm / sec with a gap of 400 μm between it and the PET sheet, so that the positive electrode composite slurry on the PET sheet was spread while maintaining a thickness of approximately 400 μm. Next, in order to dry the solvent contained in the stretched positive electrode mixture, the PET sheet coated with the positive electrode mixture was placed in a dryer set at 70°C for one hour. Next, the positive electrode composite material stretched on the PET sheet was punched out together with the PET sheet to form a circle with a diameter of 9.95 mm, thereby obtaining a cylindrical laminate of the positive electrode composite material / PET sheet. Next, the positive electrode composite material side of the cylindrical laminate was placed on the solid electrolyte that had been temporarily pressed and formed into a cylindrical shape, and this was pressed at 330 MPa to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer / PET sheet. The PET sheet was slowly peeled off from the pressed green compact using tweezers to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer. A total of five green compacts with this structure were produced. Next, an MgO setter having a flat surface was prepared, an Au film was provided on the flat surface, and five powder compacts were provided on the flat surface of the Au film at equal intervals. Next, with the Au film inserted on top of the compact, an MgO setter (60 g) acting as a weight was placed on top, and the compact was placed in an electric furnace and sintered at 800°C for 2 hours to produce a sintered solid electrolyte layer / positive electrode layer body.

[0062] Example 2 The positive electrode active material, the oxide-based solid electrolyte, the anisole solution in which 10% by mass of the binder was dissolved, and the anisole solution in which 5% by mass of the thickener was dissolved were mixed in this order in a mass ratio of 250:250:250:100, and anisole was added as a solvent so that the solid content of the slurry was 64% by mass. The mixture was mixed for 400 seconds using a Mazerustar manufactured by Kurabo Industries, Ltd. to prepare a positive electrode composite slurry. The mixing settings in the mixer were set to revolution "9" and rotation "7". Tuftec was used as the binder, and ETHOCEL (registered trademark) was used as the thickener. The amount of ETHOCEL added was 1 / 5 (by mass) of the amount of Tuftec. ETHOCEL is a thermoplastic cellulose ether of ethyl cellulose. Next, the entire amount of the positive electrode mixture slurry prepared in the above-mentioned procedure was placed on the flat surface of the PET sheet, so that the amount of slurry per unit area of ​​the PET sheet was 26.2 mg / cm 2 The slurry was spread on the PET sheet so that the slurry became uniform. The positive electrode composite slurry was spread on the PET sheet using a cylindrical applicator of a coating machine as shown in Figure 1. The applicator was moved at a speed of 15 mm / sec with a gap of 400 μm between it and the PET sheet, so that the positive electrode composite slurry on the PET sheet was spread while maintaining a thickness of approximately 400 μm. Next, in order to dry the solvent contained in the stretched positive electrode mixture, the PET sheet coated with the positive electrode mixture was placed in a dryer set at 70°C for one hour. Next, the positive electrode composite material stretched on the PET sheet was punched out together with the PET sheet to form a circle with a diameter of 9.95 mm, thereby obtaining a cylindrical laminate of the positive electrode composite material / PET sheet. Next, the positive electrode composite material side of the cylindrical laminate was placed on the solid electrolyte that had been temporarily pressed and formed into a cylindrical shape, and this was pressed at 330 MPa to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer / PET sheet. The PET sheet was slowly peeled off from the pressed green compact using tweezers to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer. A total of five green compacts with this structure were produced. Next, an MgO setter having a flat surface was prepared, an Au film was provided on the flat surface, and five powder compacts were provided on the flat surface of the Au film at equal intervals. Next, with the Au film inserted on top of the compact, an MgO setter (60 g) acting as a weight was placed on top, and the compact was placed in an electric furnace and sintered at 800°C for 2 hours to produce a sintered solid electrolyte layer / positive electrode layer body.

[0063] Example 3 The positive electrode active material, the oxide-based solid electrolyte, the anisole solution in which the binder was dissolved at 10% by mass, and the anisole solution in which the thickener was dissolved at 5% by mass were mixed in this order at a mass ratio of 250:250:250:100, and anisole was added as a solvent so that the solid content of the slurry was 55% by mass. The mixture was mixed for 400 seconds with a Mazerustar manufactured by Kurabo Industries, Ltd. to obtain a positive electrode composite slurry. The mixing settings in the mixer were set to revolution "9" and rotation "7". Tuftec was used as the binder, and Ethocel (registered trademark) was used as the thickener. The amount of Ethocel added was 1 / 5 (by mass) of the amount of Tuftec. Next, the entire amount of the positive electrode composite slurry prepared in the above-mentioned procedure was placed on the flat surface of the PET sheet, so that the amount of slurry per unit area of ​​the PET sheet was 14.7 mg / cm 2 The slurry was spread on the PET sheet so that the slurry became uniform. The positive electrode composite slurry was spread on the PET sheet using a cylindrical applicator of a coating machine as shown in Figure 1. The applicator was moved at a speed of 15 mm / sec with a gap of 300 μm between it and the PET sheet, so that the positive electrode composite slurry on the PET sheet was spread while maintaining a thickness of approximately 300 μm. Next, in order to dry the solvent contained in the stretched positive electrode mixture, the PET sheet coated with the positive electrode mixture was placed in a dryer set at 70°C for one hour. Next, the positive electrode composite material stretched on the PET sheet was punched out together with the PET sheet to form a circle with a diameter of 9.95 mm, thereby obtaining a cylindrical laminate of the positive electrode composite material / PET sheet. Next, the positive electrode composite material side of the cylindrical laminate was placed on the solid electrolyte that had been temporarily pressed and formed into a cylindrical shape, and this was pressed at 330 MPa to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer / PET sheet. The PET sheet was slowly peeled off from the pressed green compact using tweezers to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer. A total of five green compacts with this structure were produced. Next, an MgO setter having a flat surface was prepared, an Au film was provided on the flat surface, and five powder compacts were provided on the flat surface of the Au film at equal intervals. Next, with the Au film inserted on top of the compact, an MgO setter (60 g) acting as a weight was placed on top, and the compact was placed in an electric furnace and sintered at 800°C for 2 hours to produce a sintered solid electrolyte layer / positive electrode layer body.

[0064] Example 4 The positive electrode active material, the oxide-based solid electrolyte, the anisole solution in which the binder was dissolved at 10% by mass, and the anisole solution in which the thickener was dissolved at 5% by mass were mixed in this order at a mass ratio of 250:250:250:100, and anisole was added as a solvent so that the solid content of the slurry was 55% by mass. The mixture was mixed for 400 seconds with a Mazerustar manufactured by Kurabo Industries, Ltd. to obtain a positive electrode composite slurry. The mixing settings in the mixer were set to revolution "9" and rotation "7". Tuftec was used as the binder, and Ethocel (registered trademark) was used as the thickener. The amount of Ethocel added was 1 / 5 (by mass) of the amount of Tuftec. Next, the entire amount of the positive electrode composite slurry prepared in the above-mentioned procedure was placed on the flat surface of the PET sheet, so that the amount of slurry per unit area of ​​the PET sheet was 11.9 mg / cm 2 The slurry was spread on the PET sheet so that the slurry became uniform. The positive electrode composite slurry was spread on the PET sheet using a cylindrical applicator of a coating machine as shown in Figure 1. The applicator was moved at a speed of 15 mm / sec with a gap of 200 μm between it and the PET sheet, so that the positive electrode composite slurry on the PET sheet was spread while maintaining a thickness of approximately 200 μm. Next, in order to dry the solvent contained in the stretched positive electrode mixture, the PET sheet coated with the positive electrode mixture was placed in a dryer set at 70°C for one hour. Next, the positive electrode composite material stretched on the PET sheet was punched out together with the PET sheet to form a circle with a diameter of 9.95 mm, thereby obtaining a cylindrical laminate of the positive electrode composite material / PET sheet. Next, the positive electrode composite material side of the cylindrical laminate was placed on the solid electrolyte that had been temporarily pressed and formed into a cylindrical shape, and this was pressed at 330 MPa to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer / PET sheet. The PET sheet was slowly peeled off from the pressed green compact using tweezers to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer. A total of five green compacts with this structure were produced. Next, an MgO setter having a flat surface was prepared, an Au film was provided on the flat surface, and five powder compacts were provided on the flat surface of the Au film at equal intervals. Next, with the Au film inserted on top of the compact, an MgO setter (60 g) acting as a weight was placed on top, and the compact was placed in an electric furnace and sintered at 800°C for 2 hours to produce a sintered solid electrolyte layer / positive electrode layer body.

[0065] Example 5 The positive electrode active material, the oxide-based solid electrolyte, the anisole solution in which the binder was dissolved at 10% by mass, and the anisole solution in which the thickener was dissolved at 5% by mass were mixed in this order at a mass ratio of 250:250:250:100, and anisole and IPA were added as solvents so that the solid content of the slurry was 55% by mass. The mixture was mixed for 400 seconds with a Mazerustar manufactured by Kurabo Industries, Ltd. to obtain a positive electrode composite slurry. The mixing settings in the mixer were set to revolution "9" and rotation "7". IPA was added so that it was 10% by mass in the slurry. Tuftec was used as the binder, and ETHOCEL (registered trademark) was used as the thickener. The amount of ETHOCEL added was 1 / 5 (by mass) of the amount of Tuftec. Next, the entire amount of the positive electrode composite slurry prepared in the above-mentioned procedure was placed on the flat surface of the PET sheet, so that the amount of slurry per unit area of ​​the PET sheet was 10.1 mg / cm 2 The slurry was spread on the PET sheet so that the slurry became uniform. The positive electrode composite slurry was spread on the PET sheet using a cylindrical applicator of a coating machine as shown in Figure 1. The applicator was moved at a speed of 15 mm / sec with a gap of 200 μm between it and the PET sheet, so that the positive electrode composite slurry on the PET sheet was spread while maintaining a thickness of approximately 200 μm. Next, in order to dry the solvent contained in the stretched positive electrode mixture, the PET sheet coated with the positive electrode mixture was placed in a dryer set at 70°C for one hour. Next, the positive electrode composite material stretched on the PET sheet was punched out together with the PET sheet to form a circle with a diameter of 9.95 mm, thereby obtaining a cylindrical laminate of the positive electrode composite material / PET sheet. Next, the positive electrode composite material side of the cylindrical laminate was placed on the solid electrolyte that had been temporarily pressed and formed into a cylindrical shape, and this was pressed at 330 MPa to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer / PET sheet. The PET sheet was slowly peeled off from the pressed green compact using tweezers to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer. A total of five green compacts with this structure were produced. Next, an MgO setter having a flat surface was prepared, an Au film was provided on the flat surface, and five powder compacts were provided on the flat surface of the Au film at equal intervals. Next, with the Au film inserted on top of the compact, an MgO setter (60 g) acting as a weight was placed on top, and the compact was placed in an electric furnace and sintered at 800°C for 2 hours to produce a sintered solid electrolyte layer / positive electrode layer body.

[0066] Example 6 The positive electrode active material, the oxide-based solid electrolyte, the anisole solution in which 10% by mass of the binder was dissolved, and the anisole solution in which 5% by mass of the thickener was dissolved were mixed in this order in a mass ratio of 250:250:250:100, and anisole and IPA were added as solvents so that the solid content of the slurry was 55% by mass. The mixture was mixed for 400 seconds with a Mazerustar manufactured by Kurabo Industries, Ltd. to obtain a positive electrode composite slurry. The mixing settings in the mixer were set to revolution "9" and rotation "7". IPA was added so that it was 5% by mass in the slurry. Tuftec was used as the binder, and ETHOCEL (registered trademark) was used as the thickener. The amount of ETHOCEL added was 1 / 5 (by mass) of the amount of Tuftec. Next, the entire amount of the positive electrode composite slurry prepared in the above-mentioned procedure was placed on the flat surface of the PET sheet, so that the amount of slurry per unit area of ​​the PET sheet was 11.6 mg / cm 2 The slurry was spread on the PET sheet so that the slurry became uniform. The positive electrode composite slurry was spread on the PET sheet using a cylindrical applicator of a coating machine as shown in Figure 1. The applicator was moved at a speed of 15 mm / sec with a gap of 200 μm between it and the PET sheet, so that the positive electrode composite slurry on the PET sheet was spread while maintaining a thickness of approximately 200 μm. Next, in order to dry the solvent contained in the stretched positive electrode mixture, the PET sheet coated with the positive electrode mixture was placed in a dryer set at 70°C for one hour. Next, the positive electrode composite material stretched on the PET sheet was punched out together with the PET sheet to form a circle with a diameter of 9.95 mm, thereby obtaining a cylindrical laminate of the positive electrode composite material / PET sheet. Next, the positive electrode composite material side of the cylindrical laminate was placed on the solid electrolyte that had been temporarily pressed and formed into a cylindrical shape, and this was pressed at 330 MPa to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer / PET sheet. The PET sheet was slowly peeled off from the pressed green compact using tweezers to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer. A total of five green compacts with this structure were produced. Next, an MgO setter having a flat surface was prepared, an Au film was provided on the flat surface, and five powder compacts were provided on the flat surface of the Au film at equal intervals. Next, with the Au film inserted on top of the compact, an MgO setter (60 g) acting as a weight was placed on top, and the compact was placed in an electric furnace and sintered at 800°C for 2 hours to produce a sintered solid electrolyte layer / positive electrode layer body.

[0067] Comparative Example 1 The positive electrode active material, the oxide-based solid electrolyte, and an anisole solution in which 10% by mass of the binder was dissolved were mixed in this order in a mass ratio of 250:250:250, and anisole was added as a solvent so that the solid content of the slurry was 72% by mass. The mixture was mixed for 400 seconds using a Mazerustar manufactured by Kurabo Industries, Ltd. to prepare a positive electrode composite slurry. The mixing settings in the mixer were set to revolution "9" and rotation "7". Tuftec (registered trademark) manufactured by Asahi Kasei Corporation was used as the binder. Tuftec is a polymer (hydrogenated styrene-based thermoplastic elastomer) in which the double bond portion of a block copolymer made of styrene and butadiene is hydrogenated. Next, the entire amount of the positive electrode composite slurry prepared in the above-mentioned procedure was placed on the flat surface of the PET sheet, so that the amount of slurry per unit area of ​​the PET sheet was 26.1 mg / cm 2 The slurry was spread on the PET sheet so that the slurry became uniform. The positive electrode composite slurry was spread on the PET sheet using a cylindrical applicator of a coating machine as shown in Figure 1. The applicator was moved at a speed of 15 mm / sec with a gap of 400 μm between it and the PET sheet, so that the positive electrode composite slurry on the PET sheet was spread while maintaining a thickness of approximately 400 μm. Next, in order to dry the solvent contained in the stretched positive electrode mixture, the PET sheet coated with the positive electrode mixture was placed in a dryer set at 70°C for one hour. Next, the positive electrode composite material stretched on the PET sheet was punched out together with the PET sheet to form a circle with a diameter of 9.95 mm, thereby obtaining a cylindrical laminate of the positive electrode composite material / PET sheet. Next, the positive electrode composite material side of the cylindrical laminate was placed on the solid electrolyte that had been temporarily pressed and formed into a cylindrical shape, and this was pressed at 330 MPa to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer / PET sheet. The PET sheet was slowly peeled off from the pressed green compact using tweezers to produce a cylindrical green compact of the solid electrolyte layer / positive electrode layer. A total of five green compacts with this structure were produced. Next, an MgO setter having a flat surface was prepared, an Au film was provided on the flat surface, and five powder compacts were provided on the flat surface of the Au film at equal intervals. Next, with the Au film inserted on top of the compact, an MgO setter (60 g) acting as a weight was placed on top, and the compact was placed in an electric furnace and sintered at 800°C for 2 hours to produce a sintered solid electrolyte layer / positive electrode layer body.

[0068] 3. Fabrication of all-solid-state lithium-ion batteries (Examples 1 to 6, Comparative Example 1) Next, a polymer solid electrolyte and metallic Li were pressure-bonded to the negative electrode side of the solid electrolyte layer of the sintered body of the solid electrolyte layer / cathode layer to form the negative electrode layer. The laminate produced in this way was placed in a sealed battery test cell (sealed container) made of SUS304 to block out the atmosphere, and a confining pressure of 0.4 N m was applied to create an all-solid-state secondary battery. In this way, five all-solid-state lithium-ion batteries were produced.

[0069] <4. Charge / discharge test> For each of the fired solid electrolyte layer / cathode layer bodies of Examples 1 to 6 and Comparative Example 1, a polymer solid electrolyte and metallic Li were pressure-bonded to the negative electrode side of the solid electrolyte layer to form a negative electrode layer. The laminate thus produced was placed in a sealed SUS304 battery test cell to block the atmosphere, and a confining pressure of 0.4 N·m was applied to produce an all-solid-state secondary battery. In this way, an all-solid-state lithium-ion battery was produced. These operations were carried out in a purged glove box (Miwa Manufacturing Co., Ltd., DBO-3L) substituted with Ar gas. Moreover, the all-solid-state lithium ion batteries of Examples 1 to 6 and Comparative Example 1 were each initially charged and discharged at 60° C. and 0.05 C to evaluate their initial charge and discharge capacities. The charge / discharge efficiency (%) was calculated by the following formula (1). (Formula 1) {(initial discharge capacity) / (initial charge capacity)}×100

[0070] In this manner, the initial charge capacity, initial discharge capacity, and charge / discharge efficiency of five samples were measured for each of the all-solid-state lithium-ion batteries of Examples 1 to 6 and Comparative Example 1. The standard deviation of the initial charge capacity was divided by the average value of the initial charge capacity to calculate the coefficient of variation in the initial charge capacity. The standard deviation of the initial discharge capacity was divided by the average value of the initial discharge capacity to calculate the coefficient of variation in the initial discharge capacity. The standard deviation of the charge / discharge efficiency was divided by the average value of the charge / discharge efficiency to calculate the coefficient of variation in the charge / discharge efficiency. The above manufacturing conditions and test results are shown in Table 1.

[0071] [Table 1]

[0072] (Evaluation Results) In all of Examples 1 to 6, the coefficients of variation of the initial charge capacity, initial discharge capacity, and charge / discharge efficiency of the all-solid-state lithium ion batteries were good, at 5.0% or less. Therefore, it was possible to efficiently suppress the occurrence of variations in the evaluation of the battery characteristics of the all-solid-state lithium ion batteries. As a result, it was possible to accurately evaluate the battery characteristics of the all-solid-state lithium ion batteries. On the other hand, the coefficients of variation of the initial charge capacity, the initial discharge capacity, and the charge / discharge efficiency of the all-solid-state lithium ion battery in Comparative Example 1 exceeded 5.0%, which resulted in variations in the evaluation of the battery characteristics of the all-solid-state lithium ion battery, making it difficult to accurately evaluate the battery characteristics of the all-solid-state lithium ion battery.

[0073] From the above, it was found that the evaluation method of the all-solid-state lithium ion battery according to the embodiment of the present invention can suppress the occurrence of variations in the evaluation of the battery characteristics of the oxide-based all-solid-state battery, and the battery characteristics can be accurately evaluated. Also, it was found that the manufacturing method of the all-solid-state lithium ion battery according to the embodiment of the present invention can obtain an all-solid-state lithium ion battery having good battery characteristics.

Claims

1. A method for evaluating an all-solid-state lithium ion battery including a solid electrolyte layer including an oxide-based solid electrolyte, a positive electrode layer including a positive electrode active material, and a negative electrode layer, comprising: a sintered body preparation step of pressing the positive electrode composite material containing the positive electrode active material and the solid electrolyte to prepare a compact of a solid electrolyte layer / positive electrode layer, and sintering the compact while applying a load in a compression direction thereof to prepare a sintered body; a battery production process in which a laminate produced by providing a negative electrode layer on a surface of the solid electrolyte layer of the fired body is placed in a sealed container and a predetermined confining pressure is applied to produce an all-solid-state lithium ion battery; A battery evaluation step of evaluating battery characteristics of the all-solid-state lithium ion battery; Including, The sintered body preparation step includes providing the positive electrode mixture as a slurry having a solid content of 55 to 65 mass %, spreading the slurry on the flat surface, drying the slurry, and then pressing a part of the positive electrode mixture spread on the flat surface and the solid electrolyte to prepare a compressed body of the solid electrolyte layer / positive electrode layer.

2. In the sintered body preparation step, the positive electrode mixture slurry is applied to a flat surface in an amount of 9.6 to 26.4 mg / cm per unit area. 2 The method for evaluating an all-solid-state lithium ion battery according to claim 1, wherein the battery is stretched so that the thickness of the battery is equal to or larger than the thickness of the all-solid-state lithium ion battery.

3. The method for evaluating an all-solid-state lithium ion battery according to claim 1 , wherein the slurry of the positive electrode mixture containing the positive electrode active material is prepared by mechanically mixing raw materials.

4. 2. The method for evaluating an all-solid-state lithium ion battery according to claim 1, wherein, in the sintered body preparation step, the slurry of the positive electrode composite is provided on a flat surface, and the slurry on the flat surface is spread using an applicator of a coating machine while maintaining a gap between the applicator and the flat surface at a constant value.

5. The method for evaluating an all-solid-state lithium ion battery according to claim 4, wherein the slurry is spread while maintaining a moving speed of an applicator of the coater on the flat surface at 10 to 20 mm / sec.

6. The method for evaluating an all-solid-state lithium ion battery according to claim 1 , wherein a slurry of the positive electrode mixture containing the positive electrode active material contains isopropyl alcohol.

7. The oxide-based solid electrolyte has the composition formula 1: Li α A x M y O 4 (In the composition formula 1, A is Ge, Si or Ti, M is V, P or As, 3.25≦α≦3.75, 0.30≦x≦0.75, and 0.25≦y≦0.70.) It is expressed as The positive electrode active material is represented by the composition formula 2: Li a Ni b Co c Mn d O 2 (In the composition formula 2, 1.00≦a≦1.08, 0.33≦b≦0.90, and b+c+d=1.0.) The method for evaluating an all-solid-state lithium ion battery according to any one of claims 1 to 6, wherein

8. A method for producing an all-solid-state lithium ion battery including a solid electrolyte layer including an oxide-based solid electrolyte, a positive electrode layer including a positive electrode active material, and a negative electrode layer, comprising: a sintered body preparation step of pressing the positive electrode composite material containing the positive electrode active material and the solid electrolyte to prepare a compact of a solid electrolyte layer / positive electrode layer, and sintering the compact while applying a load in a compression direction thereof to prepare a sintered body; a battery production process in which a laminate produced by providing a negative electrode layer on a surface of the solid electrolyte layer of the fired body is placed in a sealed container and a predetermined confining pressure is applied to produce an all-solid-state lithium ion battery; Including, The sintered body preparation step includes providing the positive electrode mixture as a slurry having a solid content of 55 to 65 mass %, spreading the slurry on the flat surface, drying the slurry, and then pressing a part of the positive electrode mixture spread on the flat surface and the solid electrolyte to prepare a compact of the solid electrolyte layer / positive electrode layer.

9. In the sintered body preparation step, the positive electrode mixture slurry is applied to a flat surface in an amount of 9.6 to 26.4 mg / cm per unit area. 2 The method for producing an all-solid-state lithium ion battery according to claim 8, wherein the solid-state lithium ion battery is stretched so that ...

10. The method for producing an all-solid-state lithium ion battery according to claim 8, wherein the cathode mixture slurry containing the cathode active material is produced by mechanically mixing raw materials.

11. 9. The method for producing an all-solid-state lithium ion battery according to claim 8, wherein in the sintered body preparation step, the slurry of the positive electrode mixture is provided on a flat surface, and the slurry on the flat surface is spread using an applicator of a coating machine while maintaining a gap between the applicator and the flat surface at a constant value.

12. The method for producing an all-solid-state lithium ion battery according to claim 11, wherein the slurry is spread while maintaining a moving speed of an applicator of the coater on the flat surface of 10 to 20 mm / sec.

13. The method for producing an all-solid-state lithium ion battery according to claim 8, wherein the slurry of the positive electrode mixture containing the positive electrode active material contains isopropyl alcohol.

14. The oxide-based solid electrolyte has the composition formula 1: Li α A x M y O 4 (In the composition formula 1, A is Ge, Si or Ti, M is V, P or As, 3.25≦α≦3.75, 0.30≦x≦0.75, and 0.25≦y≦0.70.) It is expressed as The positive electrode active material is represented by the composition formula 2: Li a Ni b Co c Mn d O 2 (In the composition formula 2, 1.00≦a≦1.08, 0.33≦b≦0.90, and b+c+d=1.0.) The method for producing an all-solid-state lithium ion battery according to any one of claims 8 to 13, wherein

Images