All solid state battery

Abstract

Provided is an all solid state battery in which the moldability of an electrode laminate is improved and which has good properties.　An all solid state battery according to the present invention comprises an electrode laminate in which a positive electrode that includes a molded body of an positive electrode mixture containing an positive electrode active material and a negative electrode that includes a molded body of a negative electrode mixture containing a negative electrode active material are laminated with a solid electrolyte layer therebetween. The electrode laminate is an integral molded body of the molded body of the positive electrode mixture, the solid electrolyte layer, and the molded body of the negative electrode mixture. When LC is defined as the length, in a plan view of the molded body of the positive electrode mixture, of a part thereof where there is the greatest distance from a point on the outer peripheral edge to another point on the outer peripheral edge, LA is defined as the length, in a plan view of the molded body of the negative electrode mixture, of a part thereof where there is the greatest distance from a point on the outer peripheral edge another point on the outer peripheral edge, and LS is defined as the length, in a plan view of the solid electrolyte layer, of a part thereof where there is the greatest distance between a point on the outer peripheral edge and another point on the outer peripheral edge, relational expression (1) is satisfied.　(1): 0≤(|LS / LC-LA / LC|+|LS / LC-1|)×100≤0.7

Description

[Supplement based on Rule 26 08.10.2025] All-solid-state batteries

[0001] This invention relates to an all-solid-state battery having excellent properties.

[0002] While non-aqueous electrolyte batteries, such as lithium-ion batteries using organic electrolytes, are widely used, in recent years, with the expansion of their application fields, there has been a demand for higher capacity and use in high-temperature environments, and consequently, there has been a growing need for improved safety, for example.

[0003] For these reasons, all-solid-state batteries, which use molded solid electrolytes instead of organic electrolytes that use flammable organic solvents, are attracting increasing attention because they can ensure excellent heat resistance.

[0004] As an example of an all-solid-state battery, there is a known type that has an electrode stack obtained by integrally molding a positive electrode, a solid electrolyte layer, and a negative electrode, which are made of powdered positive electrode mixture and pressurized, within a single mold (die) (Patent Document 1, etc.).

[0005] Japanese Patent Publication No. 2022-124944 (paragraph

[0083] , Examples)

[0006] However, our research has revealed that when an electrode stack is manufactured by integrally molding it under pressure within a single mold, as described above, structural damage such as cracking may occur in the solid electrolyte layer of the electrode stack when it is removed from the mold. If structural damage occurs in the solid electrolyte layer of the electrode stack, the movement of ions between the positive and negative electrodes is inhibited, thereby impairing the characteristics of the all-solid-state battery.

[0007] The present invention has been made in view of the above circumstances, and its purpose is to improve the moldability of electrode stacks and provide an all-solid-state battery having good characteristics.

[0008] The all-solid-state battery of the present invention has an electrode laminate in which a positive electrode containing a molded body of a positive electrode mixture containing a positive electrode active material and a negative electrode containing a molded body of a negative electrode mixture containing a negative electrode active material are laminated via a solid electrolyte layer. The electrode laminate is an integrally molded body of the molded body of the positive electrode mixture, the solid electrolyte layer, and the molded body of the negative electrode mixture. In a plan view of the molded body of the positive electrode mixture, the length of the portion having the longest distance among the points from one outer peripheral end point to another outer peripheral end point is L Ｃ is defined as such, and in a plan view of the molded body of the negative electrode mixture, the length of the portion having the longest distance among the points from one outer peripheral end point to another outer peripheral end point is L Ａ is defined as such, and in a plan view of the solid electrolyte layer, the length of the portion having the longest distance among the points from one outer peripheral end point to another outer peripheral end point is L Ｓ When defined as such, it is characterized by satisfying the following relational expression (1).

[0009] 0 ≦ (|L Ｓ / L Ｃ −L Ａ / L Ｃ | + |L Ｓ / L Ｃ −1|) × 100 ≦ 0.7 (1)

[0010] According to the present invention, an all-solid-state battery having good characteristics can be provided.

[0011] It is an explanatory diagram of the length L of the portion having the longest distance among the points from one outer peripheral end point to another outer peripheral end point in a plan view of the positive electrode. It is a cross-sectional view schematically showing an example of the all-solid-state battery of the present invention. Ｃ When forming an electrode laminate by integrally molding a positive electrode having a molded body of a positive electrode mixture and a negative electrode having a molded body of a negative electrode mixture via a solid electrolyte layer, when the pressure is applied in the state where each layer is laminated and then removed from the molding die, the electrode laminate expands and becomes larger than the size of the hole of the molding die. However, since the expansion rates of the molded body of the positive electrode mixture, the molded body of the negative electrode mixture, and the solid electrolyte layer are different from each other, stress is applied to the portion of the solid electrolyte layer and structural failure occurs, which increases the resistance value of the electrode laminate and, consequently, the resistance value of the all-solid-state battery using this.

[0012]

[0013] ​As will be described later, the molded bodies of the positive electrode mixture and negative electrode mixture that constitute the electrode stack used in all-solid-state batteries usually contain a solid electrolyte along with the active material. In principle, the smaller the expansion rate of the molded bodies of the positive electrode mixture and negative electrode mixture after pressure molding, the better the contact between the solid electrolyte particles inside them should be, and therefore the lower the resistance value of the electrode stack. However, the expansion rate of the solid electrolyte layer after pressure molding is relatively large, and the smaller the expansion rate of the molded bodies of the positive electrode mixture and negative electrode mixture after pressure molding, the larger the difference in expansion rate with that of the solid electrolyte layer after pressure molding, making structural damage to the solid electrolyte layer more likely. For this reason, in reality, the smaller the expansion rate of the molded bodies of the positive electrode mixture and negative electrode mixture after pressure molding, the more likely the resistance value of the electrode stack, and consequently the resistance value of the all-solid-state battery using it, is to increase.

[0014] As a result of diligent research to solve the aforementioned problems, the inventors have found that by standardizing the sizes of the positive electrode mixture molded body, the negative electrode mixture molded body, and the solid electrolyte layer constituting the electrode stack integrally molded by pressure, and keeping them within a specific range based on the size of the positive electrode mixture molded body, structural damage to the solid electrolyte layer in the electrode stack can be suppressed, and by using this, the degradation of the characteristics of all-solid-state batteries can be suppressed, thus completing the present invention.

[0015] The all-solid-state battery of the present invention has an electrode laminate in which a positive electrode having a molded body of a positive electrode mixture and a negative electrode having a molded body of a negative electrode mixture are laminated via a solid electrolyte layer, the electrode laminate is an integrally molded body of the positive electrode, the solid electrolyte layer and the negative electrode, and in a plan view of the molded body of the positive electrode mixture, the length of the longest distance from one point on the outer circumference to another point on the outer circumference is L Ｃ Let L be the length of the point with the longest distance between two points on the outer circumference in a plan view of the molded body of the negative electrode mixture. Ａ Let L be the length of the point where the distance is longest from one point on the outer edge to another point on the outer edge in a plan view of the solid electrolyte layer. Ｓ When this is the case, the following relation (1) is satisfied.

[0016] 0 ≤ (| L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L Ｃ -1 |) × 100 ≤ 0.7 (1)

[0017] In this specification, "integrated molded body" in the context of electrode laminates means a molded electrode laminate in which a single mold is used to form the positive electrode, solid electrolyte layer, and negative electrode, and each layer is formed continuously without being removed from the mold, and the electrode laminate is removed from the mold only after all the layers are assembled. It is presumed that an electrode laminate obtained by this procedure has a different structure at the interface between the positive electrode (molded body of positive electrode mixture) and the solid electrolyte layer, and between the negative electrode (molded body of negative electrode mixture) and the solid electrolyte layer, compared to an electrode laminate obtained by individually molding the positive electrode, solid electrolyte layer, and negative electrode and then laminating them and pressing the whole. For example, it is expected that the adhesion between the positive electrode and the solid electrolyte layer, and between the negative electrode and the solid electrolyte layer will be higher, ensuring superior properties.

[0018] Of the above relational equation (1), |L Ｓ / L Ｃ -L Ａ / L Ｃ The | symbol represents the difference between the size of the solid electrolyte layer and the size of the negative electrode mixture molded body, normalized by the size of the positive electrode mixture molded body. It represents the difference in the degree of expansion between the solid electrolyte layer and the negative electrode mixture molded body in the electrode laminate after integral molding. Furthermore, |L in the above relation (1) Ｓ / L Ｃ -1| represents the difference between the size of the solid electrolyte layer and the size of the molded positive electrode mixture, normalized by the size of the molded positive electrode mixture. It represents the difference in the degree of expansion between the solid electrolyte layer and the molded positive electrode mixture in the electrode laminate after integral molding. And, |L Ｓ / L Ｃ -L Ａ / L Ｃ | × 100 value and | L Ｓ / L ＣWhen the sum of -1|×100 is adjusted to a range of 0 to 0.7, the difference between the degree of expansion of the solid electrolyte layer when removed from the mold during integral molding of the positive electrode, negative electrode, and solid electrolyte layer, and the degree of expansion of the molded body of the positive electrode mixture and the molded body of the negative electrode mixture is adjusted to be small. As a result, excessive stress is not applied to the solid electrolyte layer, and structural failure of the solid electrolyte layer is suppressed.

[0019] (|L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L Ｃ The value of (-1|) × 100 is 0.7 or less, but a smaller value is preferable, a value of 0.5 or less is more preferable, and a value of 0 is most preferable (for example, the molded body of the positive electrode mixture, the molded body of the negative electrode mixture, and the solid electrolyte layer have the same shape in plan view). The degree of expansion of the solid electrolyte layer and the molded bodies of the positive electrode mixture and the negative electrode mixture also varies depending on the pressure molding conditions, the materials constituting the solid electrolyte layer, the molded body of the positive electrode mixture, and the molded body of the negative electrode mixture, so (|L Ｓ / L Ｃ ?L Ａ / L Ｃ | + | L Ｓ / L Ｃ The value of (1) × 100 may be 0.01 or greater, 0.1 or greater, or 0.2 or greater.

[0020] In a plan view of the positive electrode, the length L is the longest distance between one point on the outer edge and another point on the outer edge. ＣThis will be explained using drawings. Figure 1 shows schematic plan views of molded bodies of positive electrode mixtures having various plan view shapes. Figure 1(a) is an example of a molded body 111 of positive electrode mixture with a circular plan view, (b) is an example of a molded body 111 of positive electrode mixture with a square plan view, (c) is an example of a molded body 111 of positive electrode mixture with a regular hexagonal plan view, and (d) is an example of a molded body 111 of positive electrode mixture with a regular hexagonal plan view, but with an isosceles hexagonal shape in which the vertical length in the figure is shortened. In all examples, the distance between point A and point B in the figure corresponds to the longest distance from one point on the outer edge to another point on the outer edge of the molded body 111 in a plan view (i.e., the length between point A and point B is L). Ｃ (That is the case.)

[0021] In the case of a molded positive electrode mixture 111 with a circular shape in plan view as shown in Figure 1(a), the length L of the longest distance between points on the outer circumference of the molded positive electrode mixture 111 is... Ｃ This is the length of the diameter of the circular positive electrode mixture molded body 111. Also, in the case of the positive electrode mixture molded body 111 with a square plan view shape as shown in Figure 1(b), L is the length of the longest distance between points on the outer circumference of the positive electrode mixture molded body 111. Ｃ This is the length of the diagonal of the square-shaped positive electrode mixture molded body 111.

[0022] In the case of a molded positive electrode mixture 111 with a regular hexagonal shape in plan view as shown in Figure 1(c), the length L of the longest distance between points on the outer periphery of the molded positive electrode mixture 111 is... Ｃ This is the length of the diagonal of the hexagonal positive electrode mixture molded body 111. Also, in the case of the positive electrode mixture molded body 111 whose plan view shape is an isosceles hexagon as shown in Figure 1(d), L is the length of the longest distance between points on the outer periphery of the positive electrode mixture molded body 111. Ｃ This is the length of the longest diagonal of the isosceles hexagonal positive electrode mixture molded body 111.

[0023] Also, although not shown in Figure 1, for example, in the case of a molded body of a positive electrode mixture with a rectangular shape in plan view, L Ｃ L is the length of the diagonal of the rectangular positive electrode mixture molded body, and in the case of a positive electrode mixture molded body with an elliptical shape in plan view, L ＣThis represents the length of the major axis (longest diameter) in the molded body of the elliptical positive electrode mixture.

[0024] Furthermore, the length L of the molded negative electrode mixture. Ａ Except for replacing the molded body of the positive electrode mixture with the molded body of the negative electrode mixture, L Ｃ It is the same as, and the length L in the solid electrolyte layer Ｓ However, except that the molded body of the positive electrode mixture was replaced with a solid electrolyte layer, L Ｃ It is the same as this.

[0025] L Ｃ , L Ａ and L Ｓ The specific lengths are L Ｃ :1.0~34.4mm, L Ａ :1.0~34.4mm, L Ｓ Preferably, the length is between 1.0 and 34.5 mm.

[0026] L as used in this specification Ｃ , L Ａ and L Ｓ This can be measured by acquiring an X-ray CT (Computed Tomography) image of a sample formed by bonding an object of known dimensions with a battery, and then comparing the dimensions of the object of known dimensions with the dimensions of each layer of the electrode laminate using image analysis software. The values ​​described in the examples below were obtained by this method.

[0027] Next, the details of the all-solid-state battery of the present invention will be described. The all-solid-state battery of the present invention includes both a primary battery and a secondary battery.

[0028] <Electrode Stack> The electrode stack that makes up an all-solid-state battery is formed by integrally molding a positive electrode and a negative electrode with a solid electrolyte layer in between.

[0029] (Positive electrode) The positive electrode is formed by a powdered positive electrode mixture containing, for example, a positive electrode active material. The positive electrode may consist only of a molded body of the positive electrode mixture, or it may have a molded body of the positive electrode mixture and a current collector.

[0030] When an all-solid-state battery is a primary battery, the positive electrode active material can be the same as the positive electrode active material used in known non-aqueous electrolyte primary batteries. Specifically, for example, manganese dioxide, lithium-containing manganese oxide [e.g., LiMn ３ O ６ [For example, composite oxides having the same crystal structure as manganese dioxide (such as β-type, γ-type, or a structure in which β-type and γ-type are mixed), and having a Li content of 3.5% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, and particularly preferably 1% by mass or less], Li ａ Ti ５／３ O ４ Lithium-containing composite oxides such as (4 / 3 ≤ a < 7 / 3); vanadium oxide; niobium oxide; titanium oxide; sulfides such as iron disulfide; graphite fluoride; Ag ２ Silver sulfides such as S; NiO ２ Examples of nickel oxides include:

[0031] When an all-solid-state battery is a secondary battery, the positive electrode active material is not particularly limited as long as it is a positive electrode active material used in known non-aqueous electrolyte secondary batteries, that is, an active material capable of intercepting and releasing Li ions. A specific example of a positive electrode active material is LiM ｒ Mn ２－ｒ O ４ (wherein M is at least one element selected from the group consisting of Li, Na, K, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Zr, Fe, Co, Ni, Cu, Zn, Al, Sn, Sb, In, Nb, Ta, Mo, W, Y, Ru, and Rh, and 0 ≤ r ≤ 1) Spinel-type lithium manganese composite oxide, Li ｒ Mn （１－ｓ－ｒ） Ni ｓ M ｔ O （２－ｕ） F ｖ (wherein M is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, and W, and the following conditions apply: 0.8 ≤ r ≤ 1.2, 0 < s < 0.5, 0 ≤ t ≤ 0.5, u + v < 1, -0.1 ≤ u ≤ 0.2, 0 ≤ v ≤ 0.1) A layered compound represented by LiCo １－ｒ M ｒ O ２(However, M is at least one element selected from the group consisting of Al, Mg, Ti, V, Cr, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0 ≦ r ≦ 0.5) lithium cobalt composite oxide represented by, LiNi １－ｒ M ｒ O ２ (However, M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Mn, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0 ≦ r ≦ 0.5) lithium nickel composite oxide represented by, Li １＋ｓ M １－ｒ N ｒ PO ４ F ｓ (However, M is at least one element selected from the group consisting of Fe, Mn, and Co, N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, 0 ≦ r ≦ 0.5, 0 ≦ s ≦ 1) olivine-type composite oxide represented by, Li ２ M １－ｒ N ｒ P ２ O ７ (However, M is at least one element selected from the group consisting of Fe, Mn, and Co, N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, and 0 ≦ r ≦ 0.5) Examples include pyrophosphate compounds represented by, and only one of these may be used, or two or more may be used in combination.

[0032] In particular, when the all-solid-state battery is a secondary battery, from the viewpoint of ensuring better characteristics, among the above-described cathode active materials, Li-containing composite oxides containing Ni [LiM ｒ Mn ２－ｒ O ４ Among the spinel-type lithium manganese composite oxides represented by, those containing Ni as element M; Li ｒ Mn （１－ｓ－ｒ） Ni ｓ M ｔ O （２－ｕ） F ｖLayered compound represented by LiNi １－ｒ M ｒ O ２ Lithium nickel composite oxides, such as those represented by [the formula shown], are preferably used. Molded bodies of positive electrode mixtures using a Ni-containing Li-containing composite oxide as the positive electrode active material have a relatively high energy density, which allows for a reduction in the thickness of the molded body. When the thickness of the molded body is reduced, the internal resistance of the battery tends to decrease, and better characteristics can be obtained. In molded bodies of positive electrode mixtures using a Ni-containing Li-containing composite oxide as the positive electrode active material, structural damage to the solid electrolyte layer, which tends to expand significantly after integral molding, is likely to occur during the first charge of the battery due to the large amount of shrinkage. However, in the all-solid-state battery of the present invention, the amount of expansion of the solid electrolyte layer is controlled relative to the amount of expansion of the molded body of the positive electrode mixture, so such damage to the solid electrolyte layer can be effectively suppressed.

[0033] When an all-solid-state battery is a secondary battery, the average particle size of the positive electrode active material is preferably 0.1 μm or more, more preferably 0.5 μm or more, preferably 25 μm or less, and more preferably 10 μm or less, from the viewpoint of reducing side reactions that cause degradation of battery capacity and increasing electrode density. The positive electrode active material may be primary particles or secondary particles formed by aggregating primary particles. When the molded body of the positive electrode mixture contains a solid electrolyte, using a positive electrode active material with an average particle size within the above range allows for a larger interface with the solid electrolyte, thereby improving the battery's load characteristics.

[0034] In this specification, the average particle diameter of the positive electrode active material and other particles (such as the solid electrolyte described later) is the 50% diameter value in the volume-based integrated fraction when determining the integrated volume from the smallest particles using a particle size distribution analyzer (such as the Microtrac particle size distribution analyzer "HRA9320" manufactured by Nikkiso Co., Ltd.). ５０ This means...

[0035] When the positive electrode contains a solid electrolyte, it is preferable that the positive electrode active material has a reaction-inhibiting layer on its surface to suppress the reaction with the solid electrolyte contained in the positive electrode.

[0036] If the positive electrode active material and the solid electrolyte come into direct contact within the positive electrode (molded body of the positive electrode mixture), the solid electrolyte may oxidize and form a resistive layer, potentially reducing the ionic conductivity within the molded body. By providing a reaction-inhibiting layer on the surface of the positive electrode active material to suppress the reaction with the solid electrolyte, direct contact between the positive electrode active material and the solid electrolyte can be prevented, thereby suppressing the reduction in ionic conductivity within the molded body due to the oxidation of the solid electrolyte.

[0037] The reaction suppression layer should be composed of a material that has ionic conductivity and can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of materials that can constitute the reaction suppression layer include oxides containing Li and at least one element selected from the group consisting of Nb, P, B, Si, Ge, Ti, Zr, Ta, and W; more specifically, LiNbO ３ Nb-containing oxides such as Li ３ PO ４ Li ３ BO ３ Li ４ SiO ４ Li ４ GeO ４ LiTio ３ LiZrO ３ Li ２ WO ４ These are some examples. The reaction suppression layer may contain only one of these oxides, or it may contain two or more, and furthermore, multiple of these oxides may form a composite compound. Among these oxides, it is preferable to use an Nb-containing oxide, such as LiNbO ３ It is more preferable to use [this].

[0038] The reaction-inhibiting layer is preferably present on the surface in an amount of 0.1 to 2.0 parts by mass per 100 parts by mass of the positive electrode active material. Within this range, the reaction between the positive electrode active material and the solid electrolyte can be effectively suppressed.

[0039] Methods for forming a reaction-suppressing layer on the surface of the positive electrode active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0040] The content of the positive electrode active material in the positive electrode mixture is preferably 20 to 95% by mass, and more preferably 50 to 90% by mass.

[0041] The positive electrode may contain a conductive additive. The conductive additive to be contained in the positive electrode can be the same as the various conductive additives previously exemplified for use in the negative electrode. The content of the conductive additive in the positive electrode mixture is preferably 1 to 10% by mass.

[0042] The positive electrode can contain a solid electrolyte. The solid electrolyte is not particularly limited as long as it has Li ion conductivity, and for example, sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, oxide-based solid electrolytes, etc., can be used.

[0043] As a sulfide-based solid electrolyte, Li ２ S-P ２ S ５ Li ２ S-SiS ２ Li ２ S-P ２ S ５ -GeS ２ Li ２ S-B ２ S ３ Examples include glass particles, as well as thio-LiSICON type [Li] which have recently attracted attention for their high Li ion conductivity. １０ GeP ２ S １２ Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ Li12-12a-b+c+6d-eM １ ３＋ａ－ｂ－ｃ－ｄ M ２ ｂ M ３ ｃ M ４ ｄ M ５ １２－ｅ X ｅ (However, M １ is Si, Ge or Sn, M ２ is P or V, M ３is Al, Ga, Y or Sb, M ４ is Zn, Ca, or Ba, M ５ [where is S or S and O, and X is F, Cl, Br or I, 0 ≤ a < 3, 0 ≤ b + c + d ≤ 3, 0 ≤ e ≤ 3] or argyrodite type [Li ６ PS ５ Li such as Cl ７－ｋ PS ６－ｋ X ｋ (where X represents one or more halogen elements, and is expressed as 0.2 < k < 2.0), Li ７－ｆ＋ｇ PS ６－ｆ Cl ｆ＋ｇ (However, those expressed as 0.05 ≤ g ≤ 0.9, -3.0f + 1.8 ≤ g ≤ -3.0f + 5.7), Li ７－ｈ PS ６－ｈ Cl ｉ Br ｊ (However, those expressed as h = i + j, 0 < h ≤ 1.8, 0.1 ≤ i / j ≤ 10.0) can also be used.

[0044] Examples of hydride-based solid electrolytes include LiBH ４ LiBH ４ Solid solutions of the following alkali metal compounds (e.g., LiBH) ４ Examples include those with a molar ratio of 1:1 to 20:1 between the solid solution and the alkali metal compound. Examples of alkali metal compounds in the solid solution include at least one selected from the group consisting of lithium halides (LiI, LiBr, LiF, LiCl, etc.), rubidium halides (RbI, RbBr, RbF, RbCl, etc.), cesium halides (CsI, CsBr, CsF, CsCl, etc.), lithium amide, rubidium amide, and cesium amide.

[0045] Examples of halide-based solid electrolytes include monoclinic LiAlCl ４ , defective spinel type or layered structure LiInBr ４ Monoclinic Li ６－３ｍ Y ｍ X ６(However, this includes cases where 0 < m < 2 and X = Cl or Br), and other publicly known examples can also be used, such as those described in International Publication No. 2020 / 070958 and International Publication No. 2020 / 070955.

[0046] Examples of oxide-based solid electrolytes include Li ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ Glass ceramics, Li ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -GeO ２ Glass ceramics, garnet-type Li ７ La ３ Zr ２ O １２ , NASICON type Li １＋Ｏ Al １＋Ｏ Ti ２－Ｏ (PO ４ ) ３ Li １＋ｐ Al １＋ｐ Ge ２－ｐ (PO ４ ) ３ Perovskite-type Li ３ｑ La ２／３－ｑ TiO ３ These are some examples.

[0047] Among these solid electrolytes, sulfide-based solid electrolytes and those containing chlorine atoms in halide-based solid electrolytes (chloride-based solid electrolytes), as well as oxide-based solid electrolytes, are preferred due to their high Li ion conductivity. Sulfide-based solid electrolytes containing Li and P are more preferred, and argyrodite-type sulfide-based solid electrolytes, which have high Li ion conductivity and high chemical stability, are even more preferred.

[0048] The average particle size of the solid electrolyte in the positive electrode is preferably 0.1 μm or larger, and more preferably 0.2 μm or larger, from the viewpoint of reducing grain boundary resistance, similar to the case of the negative electrode. On the other hand, from the viewpoint of forming a sufficient contact interface between the positive electrode active material and the solid electrolyte, it is preferably 10 μm or smaller, and more preferably 5 μm or smaller.

[0049] The solid electrolyte content in the positive electrode mixture is preferably 4 to 80% by mass, and more preferably 6 to 50% by mass.

[0050] A binder can be included in the positive electrode. Specific examples include fluororesins such as PVDF. However, if good moldability can be ensured in forming the molded body of the positive electrode mixture without using a binder, such as when the positive electrode contains a sulfide-based solid electrolyte, then the positive electrode does not need to contain a binder.

[0051] If a binder is required in the positive electrode, the binder content in the positive electrode mixture is preferably 6% by mass or less, and more preferably 0.5% by mass or more. On the other hand, if moldability can be obtained without a binder, the binder content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is included).

[0052] When a current collector is used for the positive electrode, the current collector can be made of metal foil such as aluminum, nickel, or stainless steel, perforated metal, mesh, expanded metal, foamed metal, or carbon sheet.

[0053] A molded positive electrode mixture can be formed, for example, by compressing a positive electrode mixture prepared by mixing a positive electrode active material, a conductive additive, a solid electrolyte, and a binder used as needed, using pressure molding or the like.

[0054] In the case of a positive electrode having a current collector, it can be manufactured by bonding a molded body of the positive electrode mixture formed by the method described above to the current collector by pressing or other means. Note that the molded body of the positive electrode mixture and the current collector may not be integrated, but rather housed independently within the outer casing.

[0055] The thickness of the molded positive electrode mixture (in the case of a positive electrode with a current collector, the average thickness of the molded positive electrode mixture per side of the current collector; the same applies hereinafter) is usually 100 μm or more, but from the viewpoint of increasing the capacity of all-solid-state batteries, it is preferable to have a thickness of 200 μm or more. In addition, the thickness of the molded positive electrode mixture is usually 3000 μm or less.

[0056] Furthermore, in the molded body of the positive electrode mixture, it is desirable that thickness fluctuations due to expansion after integral molding of the electrode laminate be suppressed. Specifically, from the outer edge of the molded body of the positive electrode mixture to L Ｃ It is preferable that the thickness of the thinnest part in the region inside a distance of 10 is 98% or more of the thickness of the thickest part (it is particularly preferable that the thickness of the thinnest part is 100% of the thickness of the thickest part).

[0057] The thickness of the positive electrode composite molded body can be measured by obtaining an X-ray CT image of a sample formed by bonding a battery to an object of known dimensions, using image analysis software to create a perpendicular line at an arbitrary point in the solid electrolyte layer of the electrode laminate in the direction perpendicular to the plane of the solid electrolyte layer, defining the line segment of the portion of the perpendicular line that passes through the positive electrode as the thickness of the positive electrode, and comparing its length with that of the object of known dimensions. The values ​​described in the examples below were obtained by this method.

[0058] (Negative electrode) The negative electrode is formed by pressurizing a powdered negative electrode mixture containing, for example, a negative electrode active material. The negative electrode may consist only of a molded body of the negative electrode mixture, or it may have a molded body of the negative electrode mixture and a current collector.

[0059] When an all-solid-state battery is a primary battery, examples of negative electrode active materials include metallic lithium and lithium alloys (such as lithium-aluminum alloy and lithium-indium alloy).

[0060] Furthermore, in the case of a solid-state battery as a secondary battery, there are no particular restrictions on the negative electrode active material, as long as it is an active material capable of intercalating and releasing lithium ions, as is used in known non-aqueous electrolyte secondary batteries. For example, one or more carbon-based materials capable of intercalating and releasing lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, calcined organic polymer compounds, mesocarbon microbeads (MCMBs), and carbon fibers, can be used as the negative electrode active material. Oxides may also be used as the negative electrode active material, for example, Li ｘ Nb ｙ TiM ６ ａ O ｛５ｙ＋４／２｝＋δ (However, M ６ is at least one selected from the group consisting of V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Al, Cu, and Si, and is a composite oxide having a monoclinic crystal structure represented by 0 ≤ x ≤ 49, 0.5 ≤ y < 24, -5 ≤ δ ≤ 5, 0 ≤ a ≤ 0.3), titanium dioxide having an anatase structure, Li ２ Ti ３ O ７ Lithium titanate having a ramsdellite structure represented by Li ４ Ti ５ O １２ Examples include spinel-type lithium titanium composite oxides represented by , and one or more of these can be used. Elements, compounds and alloys containing elements such as Si, Sn, Ge, Bi, Sb, and In; nitrides or lithium-containing oxides containing lithium and transition metals such as Co, Ni, Mn, Fe, Cr, Ti, and W, and TiNb ２ O ７ Compounds that can be charged and discharged at low voltages similar to lithium metal, such as niobium composite oxides, tungsten oxide, molybdenum oxide, and vanadium oxide; or metallic lithium or lithium alloys (such as lithium-aluminum alloys and lithium-indium alloys) can also be used as negative electrode active materials.

[0061] The content of the negative electrode active material in the negative electrode mixture is preferably 10 to 99% by mass, and more preferably 20 to 85% by mass.

[0062] The negative electrode may contain a conductive additive. Examples of conductive additives include carbon materials such as carbon black (thermal black, furnace black, channel black, Ketjen black, acetylene black, etc.), graphite (natural graphite, artificial graphite), graphene, and fibrous carbon (vapor-grown carbon fibers, carbon nanofibers, carbon nanotubes, etc.); powders of elements or alloys of Cu, Ni, Al, Au, and Pd, or porous materials thereof; and one or more of these can be used. The content of the conductive additive in the negative electrode mixture is preferably 1 to 10% by mass.

[0063] The negative electrode may contain a solid electrolyte. The solid electrolyte contained in the negative electrode can be one or more of the various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes that were previously exemplified as being usable in the positive electrode. Among these solid electrolytes, sulfide-based solid electrolytes, chloride-based solid electrolytes, and oxide-based solid electrolytes are preferred due to their high Li ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferred, and argyrodite-type sulfide-based solid electrolytes, which have high Li ion conductivity and high chemical stability, are even more preferred.

[0064] The average particle size of the solid electrolyte is preferably 0.1 μm or larger, and more preferably 0.2 μm or larger, from the viewpoint of reducing grain boundary resistance. On the other hand, from the viewpoint of forming a sufficient contact interface between the negative electrode active material and the solid electrolyte, it is preferably 10 μm or smaller, and more preferably 5 μm or smaller.

[0065] The solid electrolyte content in the negative electrode mixture is preferably 4 to 85% by mass, and more preferably 10 to 70% by mass.

[0066] A binder can be included in the negative electrode. Specific examples include fluororesins such as PVDF. However, if good moldability can be ensured in forming the molded body of the negative electrode mixture without using a binder, such as when a sulfide-based solid electrolyte is included in the negative electrode, then the negative electrode does not need to contain a binder.

[0067] If a binder is required at the negative electrode, the binder content in the negative electrode mixture is preferably 6% by mass or less, and more preferably 0.5% by mass or more. On the other hand, if moldability can be obtained without a binder, the binder content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is included).

[0068] The thickness of the molded negative electrode mixture (in the case of a negative electrode with a current collector, the average thickness of the molded negative electrode mixture per side of the current collector; the same applies hereinafter) is usually 100 μm or more, but from the viewpoint of increasing the capacity of all-solid-state batteries, it is preferable to have a thickness of 200 μm or more. In addition, the thickness of the molded negative electrode mixture is usually 3000 μm or less.

[0069] Furthermore, in the negative electrode (molded body of the negative electrode mixture), it is desirable that thickness fluctuations due to expansion after integral molding of the electrode laminate be suppressed. Specifically, from the outer edge of the molded body of the negative electrode mixture to L Ａ It is preferable that the thickness of the thinnest part in the region inside a distance of 10 is 98% or more of the thickness of the thickest part (it is particularly preferable that the thickness of the thinnest part is 100% of the thickness of the thickest part).

[0070] The thickness of the molded negative electrode composite can be measured by obtaining an X-ray CT image of a sample formed by bonding a battery to an object of known dimensions, using image analysis software to create a perpendicular line perpendicular to the plane of the solid electrolyte layer at any point in the solid electrolyte layer of the electrode laminate, defining the line segment of the perpendicular line passing through the negative electrode as the thickness of the negative electrode, and comparing its length with that of the object of known dimensions. The values ​​described in the examples below were obtained by this method.

[0071] (Solid Electrolyte Layer) The solid electrolyte in the solid electrolyte layer interposed between the positive electrode and the negative electrode can be one or more of the various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes exemplified above as suitable for use in the positive electrode. However, in order to improve battery characteristics, it is desirable to include sulfide-based solid electrolytes, chloride-based solid electrolytes, or oxide-based solid electrolytes, and it is even more desirable to include argyrodite-type sulfide-based solid electrolytes. Furthermore, it is even more desirable to include sulfide-based solid electrolytes, chloride-based solid electrolytes, or oxide-based solid electrolytes in the positive electrode, negative electrode, and solid electrolyte layer, and it is even more desirable to include argyrodite-type sulfide-based solid electrolytes.

[0072] The solid electrolyte layer may contain an expansion inhibitor to suppress expansion when the electrode stack is integrally molded and removed from the mold. Examples of expansion inhibitors to be included in the solid electrolyte layer include powders or fibers of low-friction resins (such as fluororesins like polytetrafluoroethylene (PTFE)); powders of insulating layered compounds (such as hexagonal boron nitride and mica); and nanoparticles of oxides (such as barium titanate and alumina).

[0073] From the viewpoint of improving ionic conductivity between the positive and negative electrodes, the solid electrolyte content in the solid electrolyte layer is preferably 70% by mass or more, and more preferably 80% by mass or more. Since the solid electrolyte layer may consist only of solid electrolyte, the upper limit of the solid electrolyte content in the solid electrolyte layer is 100% by mass.

[0074] Furthermore, when a swelling inhibitor is included in the solid electrolyte layer, the amount of swelling inhibitor in the solid electrolyte layer varies because the swelling inhibitory effect of each type of inhibitor differs, but it is preferably, for example, 0.1 to 10% by mass.

[0075] The thickness (average thickness) of the solid electrolyte layer is preferably 10 to 500 μm.

[0076] Furthermore, it is desirable that the thickness variation due to expansion after integral molding of the electrode stack is suppressed in the solid electrolyte layer, specifically, from the outer edge of the solid electrolyte layer to L Ｓ Preferably, the thickness of the thinnest part in the region inside a distance of 10 is 95% or more of the thickness of the thickest part, and more preferably 98% or more (particularly preferably, the thickness of the thinnest part is 100% of the thickness of the thickest part).

[0077] The thickness of the solid electrolyte layer can be measured by obtaining an X-ray CT image of a sample in which a battery is bonded to an object of known dimensions, using image analysis software to create a perpendicular line at an arbitrary point in the solid electrolyte layer of the electrode laminate in the direction perpendicular to the plane of the solid electrolyte layer, defining the line segment of the solid electrolyte layer through which the perpendicular line passes as the thickness of the solid electrolyte layer, and comparing its length with that of the object of known dimensions. The values ​​described in the examples below were obtained by this method.

[0078] (Plan view shape of electrode stack) There are no particular restrictions on the plan view shape of the electrode stack; it can be circular, elliptical, polygonal (e.g., quadrilateral (square, rectangle), pentagon (regular pentagon), hexagon (regular hexagon, isosceles hexagon), etc.)). Therefore, the plan view shapes of the positive electrode, solid electrolyte layer, and negative electrode can also be circular, elliptical, polygonal (e.g., quadrilateral (square, rectangle), pentagon (regular pentagon), hexagon (regular hexagon, isosceles hexagon), etc.) similar to the plan view shape of the electrode stack.

[0079] (Method for manufacturing electrode stacks) Examples of methods for manufacturing electrode stacks include the following manufacturing method having steps (i) to (iii).

[0080] (i) First, a powdery solid electrolyte layer-forming composition, which consists only of a solid electrolyte or contains a solid electrolyte and an expansion inhibitor, is filled into a mold and pressed with low surface pressure (preliminary press) to form a preliminary solid electrolyte body (a preliminary solid electrolyte body for forming a solid electrolyte layer).

[0081] By applying pressure to the solid electrolyte layer formation composition at a lower surface pressure to form a temporary structure, and then applying pressure at a higher surface pressure to form the solid electrolyte layer, it is possible to better suppress the occurrence of cracks in the solid electrolyte layer, form a solid electrolyte layer with a smaller porosity and higher ion conductivity, and improve the adhesion between the solid electrolyte layer and the positive and negative electrodes.

[0082] The surface pressure used for press molding to form a temporary molded body of a solid electrolyte (surface pressure during temporary pressing) varies somewhat depending on the type of solid electrolyte, but is preferably 500 MPa or less, more preferably 400 MPa or less, and more preferably 10 MPa or more, and more preferably 30 MPa or more, from the viewpoint of maintaining the shape of the temporary molded body well.

[0083] (ii) Next, the powdered negative electrode mixture is placed on one side of the provisional molded solid electrolyte in the mold and pressed with low surface pressure (provisional press) to form a provisional molded negative electrode mixture (a provisional molded body for forming the negative electrode).

[0084] Regarding the negative electrode, by first applying low surface pressure to form a provisional negative electrode mixture, and then applying higher surface pressure to form the negative electrode, it is possible to suppress the occurrence of cracks, form a negative electrode with a smaller porosity and higher ion conductivity, and improve the adhesion between the negative electrode and the solid electrolyte layer.

[0085] The surface pressure used for press molding to form a provisional molded body of the negative electrode mixture (surface pressure during provisional pressing) is preferably 1000 MPa or less, more preferably 700 MPa or less, and more preferably 30 MPa or more, and more preferably 100 MPa or more, from the viewpoint of maintaining the shape of the provisional molded body well.

[0086] (iii) Next, the mold is inverted so that the exposed surface of the temporary solid electrolyte body (the surface opposite to the surface on which the temporary negative electrode mixture was formed) is facing upward, and the powdered positive electrode mixture is placed thereon. The positive electrode (molded positive electrode mixture), solid electrolyte layer, and negative electrode (molded negative electrode mixture) are integrally molded by pressurization (main press) to form an electrode laminate.

[0087] The surface pressure during pressure molding for electrode laminate formation (surface pressure during the main press) is preferably 600 MPa or higher. The upper limit of the surface pressure during pressure molding for electrode laminate formation (surface pressure during the main press) is usually around 2000 MPa.

[0088] Alternatively, prior to the main press, the positive electrode mixture placed on the upper surface of the solid electrolyte preliminary molded body can be pressed with a lower surface pressure to form a preliminary molded body of the positive electrode mixture, and then the preliminary molded body of the positive electrode mixture, the preliminary molded body of the solid electrolyte, and the preliminary molded body of the negative electrode mixture can be pressed (main press) to form the electrode laminate.

[0089] By applying pressure to the positive electrode mixture at a lower surface pressure to form a preliminary molded body of the positive electrode mixture, and then applying pressure at a higher surface pressure to form the positive electrode layer, it is possible to form a positive electrode with a small porosity while suppressing the occurrence of cracks, and to improve the adhesion between the positive electrode and the solid electrolyte layer.

[0090] The surface pressure for press molding to form a provisional body of the positive electrode mixture is preferably 500 MPa or less, more preferably 450 MPa or less, even more preferably 400 MPa or less, and from the viewpoint of maintaining the shape of the provisional body well, it is preferably 30 MPa or more, more preferably 100 MPa or more, and even more preferably 150 MPa or more.

[0091] In the example above, the procedure was shown to first form a preliminary molded body of the solid electrolyte, and then form a preliminary molded body of the negative electrode mixture on one side thereof. However, it is also possible to form an electrode laminate by first forming a preliminary molded body of the positive electrode mixture on one side of the preliminary molded body of the solid electrolyte, then placing the negative electrode mixture on the other side of the preliminary molded body of the solid electrolyte, and then performing the main press, or by forming a preliminary molded body of the negative electrode mixture and then performing the main press. Furthermore, it is also possible to form an electrode laminate by first forming a preliminary molded body of the negative electrode mixture or a preliminary molded body of the positive electrode mixture, then forming a preliminary molded body of the solid electrolyte on one side thereof, then placing the positive electrode mixture or a negative electrode mixture on the exposed surface of the preliminary molded body of the solid electrolyte and then performing the main press, or by forming a preliminary molded body of the positive electrode mixture or a preliminary molded body of the negative electrode mixture and then performing the main press.

[0092] In the case of the positive electrode, when integrating the molded positive electrode mixture with the current collector, the current collector can be attached to the surface of the molded positive electrode mixture after the formation of the electrode stack, or the molded positive electrode mixture with the current collector can be integrated by placing the current collector on the positive electrode mixture (or the pre-molded positive electrode mixture) during the preliminary or final pressing of the positive electrode mixture. Similarly, in the case of the negative electrode, when integrating the molded negative electrode mixture with the current collector, the current collector can be attached to the surface of the molded negative electrode mixture after the formation of the electrode stack, or the molded negative electrode mixture with the current collector can be integrated by placing the current collector on the negative electrode mixture (or the pre-molded negative electrode mixture) during the preliminary or final pressing of the negative electrode mixture.

[0093] The degree of expansion of each layer due to the integral molding of the electrode stack can be adjusted by adjusting the surface pressure during the formation of the preliminary molded body of each layer (surface pressure during preliminary pressing) and by adjusting the surface pressure during the integral molding of the electrode stack (surface pressure during final pressing). Therefore, in order to adjust the electrode stack after integral molding so that it satisfies the above relation (1), or to adjust the variation in the thickness of each layer in the electrode stack to the above values, it is sufficient to adjust the surface pressure during the formation of the preliminary molded body of each layer and the surface pressure during the integral molding of the electrode stack, and these can be appropriately set from the ranges shown above. In addition, as mentioned above, the amount of expansion due to the integral molding of the electrode stack is greater for the solid electrolyte layer than for the positive electrode and negative electrode, but the amount of expansion of the solid electrolyte layer can also be reduced by adding the aforementioned expansion inhibitor to the solid electrolyte layer.

[0094] <Battery Configuration> Figure 2 shows a schematic cross-sectional view illustrating an example of the all-solid-state battery of the present invention. The all-solid-state battery 100 shown in Figure 2 is constructed by enclosing an electrode stack 140, which is an integrally molded body having a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130 interposed between them, within an outer casing formed by an outer container 160 and a lid 170.

[0095] External terminals 180 and 190 are provided on the lower surface of the outer casing 160 in the figure for electrically connecting the all-solid-state battery 100 to the applicable device. External terminal 180 is electrically connected to the positive electrode 110 in the electrode stack 140 via a conductive path 181. Furthermore, external terminal 190 is electrically connected to the negative electrode 120 in the electrode stack 140 via a lead 200 and a conductive path 191.

[0096] The positive electrode 110 has a molded body of positive electrode mixture (positive electrode mixture layer) 111 and a current collector 112. The negative electrode 120 has a molded body of negative electrode mixture (negative electrode mixture layer) 121 and a current collector 122.

[0097] A conductive sheet (such as a metal foil or a foamed porous metal) 150 is placed on the surface of the current collector 112 of the positive electrode 110 (the surface opposite to the molded body 111 of the positive electrode mixture). The positive electrode 110 makes electrical contact with the conductive sheet 150 when the current collector 112 comes into contact with it, and this conductive sheet 150 makes electrical contact with the conductive path 181.

[0098] Furthermore, in the all-solid-state battery 100 shown in Figure 2, a spacer 210 is placed between the lead 200 and the cover 170, which has the effect of pressing the electrode stack 140 toward the conductive sheet 150. Due to the action of this spacer 210, the electrical connection between the lead 200 and the negative electrode 120 and conductive path 191, the electrical connection between the positive electrode 110 and the conductive sheet 150, and the electrical connection between the conductive sheet 150 and the conductive path 181 are improved. The spacer 210 can be made of rubber or a metal spring (such as a leaf spring).

[0099] As shown in Figure 2, in an all-solid-state battery, the electrode stack is usually housed within an outer casing. The outer casing of an all-solid-state battery can be, for example, a case having an outer container and a sealing body, as shown in Figure 2. The outer container can be made of ceramics or resin. The lid can be made of ceramics, resin, or metal (such as iron-nickel alloy or iron-nickel-cobalt alloy). Furthermore, in the outer casing, the external terminals and the conductive paths connecting the electrodes of the electrode stack to the external terminals can be made of metals such as manganese, cobalt, nickel, copper, molybdenum, silver, palladium, tungsten, platinum, gold, or alloys containing these metals.

[0100] The outer container and the lid can be sealed by bonding them together with adhesive. Alternatively, when using a metal lid, the side wall of the recess in the outer container that faces the lid can be constructed of metal (such as an iron-nickel alloy or an iron-nickel-cobalt alloy) and then welded to the lid, or sealed by brazing with an alloy such as gold-tin (Au-Sn).

[0101] Furthermore, if both the outer container and the lid are made of ceramics, they can also be sealed by welding them with low-melting-point glass.

[0102] Furthermore, the casing of the all-solid-state battery is not limited to the container shown in Figure 2, but can be any container, for example, that has a conductive path from the inside to the outside of the casing, and that allows the porous metal substrate on the surface of the electrodes of the electrode stack to come into contact with the conductive path, thereby enabling electrical conductivity between the electrodes and the conductive path. For example, a container consisting of an outer can and a sealed can can be used. All-solid-state batteries using such a container as the casing will be coin-shaped (button-shaped).

[0103] In cases where the casing of an all-solid-state battery consists of an outer can and a sealing can, examples include cases where the outer can and the sealing can are crimped together with a gasket, as well as cases where the outer can and the sealing can are bonded together with resin.

[0104] Stainless steel can be used for the outer casing and sealing casing. Polypropylene and nylon can be used as gasket materials, and if heat resistance is required due to the application of the all-solid-state battery, heat-resistant resins with a melting point exceeding 240°C can also be used. Examples of such heat-resistant resins include fluororesins (such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA)), polyphenylene ether (PPE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK). Furthermore, when the all-solid-state battery is applied to an application requiring heat resistance, a glass hermetic seal can be used for sealing.

[0105] Furthermore, the casing of the all-solid-state battery can also be a sheet-like container made of a resin film such as a metal laminate film.

[0106] The shape of the casing of the all-solid-state battery in plan view may be circular, or it may be a polygon such as a square or rectangle.

[0107] The present invention will be described in detail below based on examples. However, the following examples are not intended to limit the present invention.

[0108] (Example 1) Lithium titanate (Li) with an average particle size of 2 μm ４ Ti ５ O １２ (negative electrode active material) and a sulfide-based solid electrolyte (Li) with an average particle size of 0.7 μm ６ PS ５ A negative electrode mixture was prepared by mixing Cl) and graphene (a conductive additive) in a mass ratio of 55:35:10.

[0109] Also, LiNbO ３ LiNi particles with an average particle size of 10 μm, on which a coating layer is formed. ０．６ Co ０．２ Mn ０．２ O ２ (Positive electrode active material) and a sulfide-based solid electrolyte (Li) with an average particle size of 0.7 μm ６ PS ５A positive electrode mixture was prepared by mixing Cl) and graphene in a mass ratio of 66:30:4.

[0110] Next, a sulfide-based solid electrolyte (Li) with an average particle size of 0.7 μm ６ PS ５ 8 mg of Cl) powder was placed in a powder molding die (circular cross-section), and press molding was performed using a press machine at a surface pressure of 100 MPa to form a preliminary molded body of the solid electrolyte. Furthermore, 153 mg of the negative electrode mixture was placed on the upper surface of the preliminary molded body of the solid electrolyte and press molding was performed at a surface pressure of 100 MPa to form another preliminary molded body of the negative electrode mixture on top of the preliminary molded body of the solid electrolyte.

[0111] Next, a nickel-based foamed metal porous material [Nickel "Cellmet" (registered trademark)] from Sumitomo Electric Industries, Ltd., cut into a circle with a diameter of 7.25 mm (thickness: 1.2 mm, porosity: 98%), was placed on top of the provisional molded body of the negative electrode mixture formed on the provisional molded body of the solid electrolyte layer. Pressure molding was then performed with a surface pressure of 400 MPa to form an integrated structure of the provisional molded body of the solid electrolyte layer, the provisional molded body of the negative electrode mixture, and the current collector for the negative electrode.

[0112] Furthermore, after inverting the mold, 82 mg of the positive electrode mixture was placed on the upper surface of the solid electrolyte temporary molded body inside the mold (the side opposite to the surface having the negative electrode mixture temporary molded body) and molded with a surface pressure of 100 MPa to form a positive electrode mixture temporary molded body on top of the solid electrolyte temporary molded body.

[0113] Next, a piece of nickel-based foamed metal porous material, the same as that used for the negative electrode, was placed on a provisional positive electrode formed on the solid electrolyte layer. Pressurized molding was then performed at a surface pressure of 1400 MPa to obtain an electrode laminate in which the positive electrode, solid electrolyte layer, and negative electrode were integrally molded.

[0114] In the resulting electrode stack, L Ｃ =7.463mm, L Ａ = 7.466 mm, and L Ｓ = 7.489 mm, and the value in the above relational expression (1) [(|L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L ＣThe result of [-1|) × 100] was 0.67.

[0115] Furthermore, in the resulting electrode laminate, the molded body of the positive electrode mixture extends from the outer edge to L Ｃ The average thickness in the region inward from a distance of 10 / 10 was 660 μm, and the thickness of the thinnest part (656 μm) was 98.2% of the thickness of the thickest part (668 μm). The molded body of the negative electrode mixture was from the outer edge L Ａ The average thickness in the region inward from a distance of 10 / 10 was 1541 μm, the thickness of the thinnest part (1524 μm) was 98.3% of the thickness of the thickest part (1550 μm), and the solid electrolyte layer was L from the outer edge. Ｓ The average thickness in the region inward from a distance of 10 / 10 was 110 μm, and the thickness of the thinnest part (108 μm) was 97.3% of the thickness of the thickest part (111 μm).

[0116] An outer container (ceramic depth 2.5 mm) having a cross-sectional structure similar to that shown in Figure 2, made of ceramics, with a seal ring made of iron-nickel-cobalt alloy placed on the upper part of the side wall, had a nickel-based foamed metal porous material, the same as that used for the positive and negative electrodes, cut to a diameter of 7.25 mm and placed on the inner bottom surface. The electrode stack was then placed on top of the nickel-based foamed metal porous material with the positive electrode facing downwards, and a lead (Ni foil) was placed on top of the negative electrode of the electrode stack, and a rubber sheet (spacer) with a thickness of 400 μm was placed on top of that. Subsequently, a lid made of iron-nickel-cobalt alloy was placed on the side wall of the recess of the outer container, and the outer container was sealed by welding the lid and the outer container together while compressing the rubber sheet in the thickness direction, thereby obtaining an all-solid-state secondary battery. In the obtained all-solid-state secondary battery, the rubber sheet spacer was compressed in the thickness direction, and as a result, the electrode stack pressed against the conductive sheet made of foamed metal porous material. Furthermore, the thickness of the conductive sheet in the all-solid-state secondary battery was 200 μm.

[0117] (Example 2) The positive electrode active material is LiNi with an average particle size of 4 μm ０．６ Co ０．２ Mn ０．２ O ２A solid-state secondary battery was fabricated in the same manner as in Example 1, except that the solid electrolyte of the solid electrolyte layer was changed to include 0.1% by mass of PTFE.

[0118] In the electrode stack, L Ｃ =7.456mm, L Ａ = 7.466 mm, and L Ｓ = 7.475 mm, and the value in the above relational expression (1) [(|L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L Ｃ The result of [-1|) × 100] was 0.39.

[0119] Furthermore, in the electrode laminate, the molded body of the positive electrode mixture extends from the outer edge to L Ｃ The average thickness in the region inward from a distance of 10 / 10 was 662 μm, and the thickness of the thinnest part (658 μm) was 99.1% of the thickness of the thickest part (664 μm). The molded body of the negative electrode mixture was from the outer edge L Ａ The average thickness in the region inward from a distance of 10 / 10 was 1544 μm, the thickness of the thinnest part (1535 μm) was 98.9% of the thickness of the thickest part (1552 μm), and the solid electrolyte layer was L from the outer edge. Ｓ The average thickness in the region inward from a distance of 10 / 10 was 110 μm, and the thickness of the thinnest part (109 μm) was 98.2% of the thickness of the thickest part (111 μm).

[0120] (Example 3) Cathode active material is LiNi ０．５ Mn １．５ O ４ Except for the following changes, the electrode stack was formed in the same manner as in Example 1, and an all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the solid electrolyte of the solid electrolyte layer was changed to a mixture of 0.1% by mass of PTFE, the composition ratio of the positive electrode mixture was changed to 74:23:3 in terms of the mass ratio of the positive electrode active material, sulfide-based solid electrolyte, and graphene, and the amount of positive electrode mixture used in battery fabrication was changed to 97 mg and the amount of negative electrode mixture was changed to 147 mg.

[0121] In the electrode stack, L Ｃ=7.459mm, L Ａ = 7.466 mm, and L Ｓ = 7.475 mm, and the value in the above relational expression (1) [(|L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L Ｃ The result of [-1|) × 100] was 0.35.

[0122] Furthermore, in the electrode laminate, the molded body of the positive electrode mixture extends from the outer edge to L Ｃ The average thickness in the region inward from a distance of 10 / 10 is 750 μm, and the thickness of the thinnest part (748 μm) is 98.9% of the thickness of the thickest part (756 μm). The molded body of the negative electrode mixture extends from the outer edge L Ａ The average thickness in the region inward from a distance of 10 / 10 is 1480 μm, the thickness of the thinnest part (1475 μm) is 99.1% of the thickness of the thickest part (1488 μm), and the solid electrolyte layer extends from the outer edge L Ｓ The average thickness in the region inward from a distance of 10 / 10 was 109 μm, and the thickness of the thinnest part (107 μm) was 97.3% of the thickness of the thickest part (110 μm).

[0123] (Example 4) Cathode active material is LiCoO ２ Except for the following changes, the composition ratio of the positive electrode mixture was changed to 66:30:4 in terms of the mass ratio of positive electrode active material, sulfide-based solid electrolyte, and graphene, and the amount of positive electrode mixture used in battery fabrication was changed to 104 mg and the amount of negative electrode mixture to 138 mg, the electrode stack was formed in the same manner as in Example 1, and an all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that this electrode stack was used.

[0124] In the electrode stack, L Ｃ =7.469mm, L Ａ = 7.466 mm, and L Ｓ = 7.489 mm, and the value in the above relational expression (1) [(|L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L ＣThe result of [-1|) × 100] was 0.58.

[0125] Furthermore, in the electrode laminate, the molded body of the positive electrode mixture extends from the outer edge to L Ｃ The average thickness in the region inward from a distance of 10 / 10 is 810 μm, the thickness of the thinnest part (808 μm) is 99.0% of the thickness of the thickest part (816 μm), and the molded body of the negative electrode mixture is L from the outer edge. Ａ The average thickness in the region inward from a distance of 10 / 10 was 1391 μm, and the thickness of the thinnest part (1387 μm) was 99.0% of the thickness of the thickest part (1401 μm). The solid electrolyte layer extends from the outer edge L Ｓ The average thickness in the region inward from a distance of 10 / 10 was 110 μm, and the thickness of the thinnest part (109 μm) was 99.1% of the thickness of the thickest part (110 μm).

[0126] (Example 5) An all-solid-state secondary battery was prepared in the same manner as in Example 4, except that 0.1% by mass of PTFE was mixed into the solid electrolyte of the solid electrolyte layer.

[0127] In the electrode stack, L Ｃ =7.469mm, L Ａ = 7.466 mm, and L Ｓ = 7.475 mm, and the value in the above relational expression (1) [(|L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L Ｃ The result of [-1|) × 100] was 0.21.

[0128] Furthermore, in the electrode laminate, the molded body of the positive electrode mixture extends from the outer edge to L Ｃ The average thickness in the region inward from a distance of 10 / 10 is 810 μm, and the thickness of the thinnest part (809 μm) is 98.9% of the thickness of the thickest part (818 μm). The molded body of the negative electrode mixture extends from the outer edge L ＡThe average thickness in the region inward from a distance of 10 / 10 was 1390 μm, the thinnest part (1386 μm) was 99.2% of the thickest part (1397 μm), and the solid electrolyte layer was L from the outer edge. Ｓ The average thickness in the region inward from a distance of 10 / 10 was 109 μm, and the thickness of the thinnest part (107 μm) was 97.3% of the thickness of the thickest part (110 μm).

[0129] (Comparative Example 1) A solid electrolyte layer containing a sulfide-based solid electrolyte (Li) with an average particle size of 0.7 μm ６ PS ５ An all-solid-state secondary battery was prepared in the same manner as in Example 2, except that Cl was used without the addition of PTFE.

[0130] In the electrode stack, L Ｃ =7.456mm, L Ａ = 7.466 mm, and L Ｓ = 7.489 mm, and the value in the above relational expression (1) [(|L Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L Ｃ The result of [-1|) × 100] was 0.76.

[0131] Furthermore, in the electrode laminate, the molded body of the positive electrode mixture extends from the outer edge to L Ｃ The average thickness in the region inward from a distance of 10 / 10 was 661 μm, and the thickness of the thinnest part (659 μm) was 98.8% of the thickness of the thickest part (667 μm). The molded body of the negative electrode mixture was from the outer edge L Ａ The average thickness in the region inward from a distance of 10 / 10 is 1540 μm, the thickness of the thinnest part (1537 μm) is 99.0% of the thickness of the thickest part (1552 μm), and the solid electrolyte layer extends from the outer edge L Ｓ The average thickness in the region inward from a distance of 10 / 10 was 110 μm, and the thickness of the thinnest part (108 μm) was 98.2% of the thickness of the thickest part (110 μm).

[0132] (Comparative Example 2) A sulfide-based solid electrolyte (Li) with an average particle size of 0.7 μm is used in the solid electrolyte layer. ６ PS ５ An attempt was made to form an electrode laminate in the same manner as in Example 3, except that Cl was used without the addition of PTFE, but cracks occurred and the electrode laminate could not be formed properly.

[0133] The following evaluations were performed on the all-solid-state secondary batteries in the examples and comparative examples.

[0134] (Resistance Measurement) For the all-solid-state secondary batteries of the examples and comparative examples, constant current charging was performed at a current of 0.1C until the voltage reached 2.6V, and then constant voltage charging was performed while maintaining the voltage at 2.6V until the voltage reached 0.01C. After constant voltage charging, the open-circuit voltage of each battery was measured for 10 minutes, and then constant current discharge was performed at a current of 0.1C until the voltage reached 1.0V. After measuring the open-circuit voltage for 1 hour, constant current charging was performed at a current of 0.2C until the voltage reached 2.6V, and then constant voltage charging was performed while maintaining the voltage at 2.6V until the voltage reached 0.01C, and the initial resistance value of the battery (impedance at 1MHz) was measured.

[0135] (Load Characteristics Evaluation) For each all-solid-state secondary battery in the examples and comparative examples, constant current charging was performed at a current of 0.1C until the voltage reached 2.6V, then constant voltage charging was performed while maintaining the voltage at 2.6V until it reached 0.01C, and then constant current discharge was performed at a current of 0.1C until the voltage reached 1.0V to determine the initial capacity. Next, constant current charging and constant voltage charging were performed again for each battery under the same conditions as above, and then constant current step discharge was performed to measure the discharge capacity at each current value (constant current step discharge capacity). The constant current step discharge was performed by discharging the charged battery at a current of 1C until the voltage reached 1.5V, then at a current of 0.6C until the voltage reached 1.0V, then at a current of 0.3C until the voltage reached 1.0V, then at a current of 0.1C until the voltage reached 1.0V, and then at a current of 0.02C until the voltage reached 1.0V. Then, the sum of all constant current step discharge capacities from 1C to 0.02C (0.02C discharge capacity) was calculated, and the 1C discharge capacity (which is the same as the step discharge capacity when discharged at 1C during constant current step discharge) was divided by the 0.02C discharge capacity to evaluate the load characteristics.

[0136] The evaluation results for each of the above are shown in Table 1. Note that the "value of relational expression (1)" in Table 1 refers to the "(|L" in relational expression (1). Ｓ / L Ｃ -L Ａ / L Ｃ | + | L Ｓ / L Ｃ This represents the value of "-1|) × 100".

[0137]

[0138] As shown in Table 1, the all-solid-state secondary batteries of Examples 1 to 5, which have electrode stacks that satisfy the above relation (1), had lower impedance and better characteristics compared to the battery of Comparative Example 1, which used an electrode stack that did not satisfy the above relation (1), because structural destruction of the solid electrolyte layer due to integral molding of the electrode stack was well suppressed.

[0139] Furthermore, the batteries in Examples 1 to 3 exhibited a shrinkage amount during the initial charge of LiCoO. ２Although a Li-containing composite oxide with a larger Ni content than that was used as the positive electrode active material, the structural destruction of the solid electrolyte layer due to this shrinkage was well suppressed, resulting in LiCoO ２ The load characteristics were better than those of the batteries in Examples 4 and 5, which used Ni as the positive electrode active material, and the effects of the Ni-containing Li-containing composite oxide were effectively utilized.

[0140] The present invention can also be implemented in forms other than those described herein, without departing from its spirit. The embodiments disclosed herein are examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the claims attached, which take precedence over the description herein, and all modifications within the scope equivalent to the claims are included in the claims.

[0141] The all-solid-state battery of the present invention has low internal resistance and excellent properties, making it suitable for applications requiring such properties, as well as for other applications where known all-solid-state batteries are used.

[0142] 100 All-solid-state battery 110 Positive electrode 111 Molded positive electrode mixture 112 Positive electrode current collector 120 Negative electrode 121 Molded negative electrode mixture 122 Negative electrode current collector 130 Solid electrolyte layer 140 Electrode stack 150 Conductive sheet 160 Outer container 170 Lid 180, 190 External terminals 181, 191 Conductive path 200 Lead 210 Spacer

Claims

1. A all-solid-state battery having a positive electrode containing a molded body of a positive electrode mixture containing a positive electrode active material and a negative electrode containing a molded body of a negative electrode mixture containing a negative electrode active material, the electrodes being laminated via a solid electrolyte layer, wherein the electrode laminate is an integrally molded body of the molded body of the positive electrode mixture, the solid electrolyte layer, and the molded body of the negative electrode mixture, and in a plan view of the molded body of the positive electrode mixture, the length of the portion having the longest distance among the points from one outer peripheral end point to another outer peripheral end point is defined as L Ｃ and in a plan view of the molded body of the negative electrode mixture, the length of the portion having the longest distance among the points from one outer peripheral end point to another outer peripheral end point is defined as L Ａ and in a plan view of the solid electrolyte layer, the length of the portion having the longest distance among the points from one outer peripheral end point to another outer peripheral end point is defined as L Ｓ When this is the case, the all-solid-state battery is characterized by satisfying the following relational expression (1). 0 ≦ (|L Ｓ / L Ｃ −L Ａ / L Ｃ | + |L Ｓ / L Ｃ −1|) × 100 ≦ 0.7 (1) 2. The all-solid-state battery according to claim 1, wherein the molded body of the positive electrode mixture, the molded body of the negative electrode mixture, and the solid electrolyte have the same shape in plan view.

3. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer contains an anti-expansion agent.

4. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer contains a sulfide-based solid electrolyte, a chloride-based solid electrolyte, or an oxide-based solid electrolyte.

5. The all-solid-state battery according to claim 1, wherein the positive electrode has a Li-containing composite oxide containing Ni as the positive electrode active material.

6. The molded body of the positive electrode mixture extends from the outer edge to L Ｃ The thickness of the thinnest part in the region inward from a distance of 10 is 98% or more of the thickness of the thickest part, and the molded body of the negative electrode mixture extends from the outer edge L Ａ The thickness of the thinnest part in the region inward from a distance of 10 is 98% or more of the thickness of the thickest part, and the solid electrolyte layer extends from the outer edge L Ｓ The all-solid-state battery according to claim 1, wherein the thickness of the thinnest part in the region inside a distance of 10 is 95% or more of the thickness of the thickest part.

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