All-solid-state batteries

Abstract

To provide an all-solid-state battery capable of suppressing the deterioration of characteristics due to moisture entering inside the all-solid-state battery, the all-solid-state battery of the present invention relating to the goals 12, 3, 7 and 11 of the SDGs.SOLUTION: An all-solid-state battery of the present invention is characterized in that an electrode laminate including a positive electrode, a negative electrode and a solid electrolyte layer disposed between the positive electrode and the negative electrode is enclosed inside an exterior body, and particles (A) of a sulfide-based solid electrolyte are disposed in a void part inside the exterior body. In the all-solid-state battery of the present invention, it is preferable that at least one of the positive electrode, the negative electrode and the solid electrolyte layer constituting the electrode laminate contains a sulfide-based solid electrolyte.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery capable of suppressing deterioration of characteristics due to moisture entering the battery. [Background technology]

[0002] In recent years, with the development of portable electronic devices such as mobile phones and laptop personal computers, and the practical application of electric vehicles, there has been a growing demand for small, lightweight batteries with high capacity and high energy density.

[0003] Currently, lithium batteries, particularly lithium ion batteries, that can meet this demand use an organic electrolyte solution containing an organic solvent and a lithium salt as the non-aqueous electrolyte.

[0004] Furthermore, with the further development of devices that use lithium-ion batteries, there is a demand for longer life, higher capacity, and higher energy density of lithium-ion batteries, as well as a high demand for the reliability of these longer life, higher capacity, and higher energy density lithium-ion batteries.

[0005] However, the organic electrolyte used in lithium-ion batteries contains flammable organic solvents, which can cause the organic electrolyte to generate excessive heat in the event of an abnormality such as a short circuit. Furthermore, with the recent trend toward higher energy density in lithium-ion batteries and an increasing amount of organic solvent in the organic electrolyte, there is a growing demand for greater reliability in lithium-ion batteries.

[0006] In light of the above, all-solid-state lithium batteries (all-solid-state batteries) that do not use organic solvents are attracting attention. All-solid-state batteries use a molded body of a solid electrolyte that does not use organic solvents instead of the conventional organic solvent-based electrolyte, and are highly safe as they do not pose the risk of abnormal heat generation by the solid electrolyte.

[0007] Furthermore, because all-solid-state batteries are not only highly safe but also highly reliable, environmentally resistant, and have a long lifespan, they are expected to be maintenance-free batteries that can continue to contribute to social development while also contributing to safety and security.By providing all-solid-state batteries to society, we can contribute to the achievement of Goal 12 (Ensure sustainable consumption and production patterns), Goal 3 (Ensure healthy lives and promote well-being for all at all ages), Goal 7 (Ensure access to affordable, reliable, sustainable, and modern energy for all), and Goal 11 (Make cities inclusive, safe, resilient, and sustainable).

[0008] Various improvements have also been attempted in all-solid-state batteries. For example, Patent Document 1 proposes a technology in which one of the positive and negative electrodes is covered with a solid electrolyte layer to prevent short circuits caused by contamination of the electrolyte layer interposed between the positive and negative electrodes by active material particles detached from the positive and negative electrodes during battery production.

[0009] However, lithium batteries have a problem in that moisture entering the battery interior can cause deterioration in various characteristics, such as an increase in internal resistance and a decrease in capacity, and there is a demand for preventing such problems from occurring.

[0010] For example, Patent Document 2 proposes a technology for avoiding the occurrence of the above-mentioned problems by using a housing (exterior body) made of synthetic resin, which allows external moisture to penetrate more easily than a metal container, and by disposing a moisture absorbent inside a battery that uses a non-fluidic electrolyte layer containing, for example, a supporting electrolyte, a solvent, and a polymer for gelation.

[0011] However, in batteries with electrolytes containing solvents, some of the elements constituting the moisture absorbent may dissolve into the solvent, causing a deterioration in performance due to the moisture absorbent disposed inside the battery. In addition, there is a risk that the moisture absorbent will no longer function as a moisture absorbent if its surface becomes wet with the solvent. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-64644 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-243357 Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an all-solid-state battery that can suppress deterioration of characteristics due to moisture penetrating into the battery. [Means for solving the problem]

[0014] The all-solid-state battery of the present invention is characterized in that an electrode laminate having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode is enclosed inside an exterior body, and sulfide-based solid electrolyte particles (A) are disposed in a void portion inside the exterior body. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an all-solid-state battery capable of suppressing deterioration of characteristics due to moisture entering the inside. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a longitudinal sectional view schematically illustrating an example of an all-solid-state battery of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The all-solid-state battery of the present invention is an electrode laminate having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, enclosed inside an exterior body, and further, sulfide-based solid electrolyte particles (A) are disposed in a void portion inside the exterior body, i.e., a gap portion in which components such as the electrode laminate housed in the exterior body of the all-solid-state battery are not disposed.

[0018] Sulfide-based solid electrolytes are prone to absorbing and reacting with moisture. For example, when incorporated into the solid electrolyte layer or electrodes of an all-solid-state battery, this reaction can impair the function of the sulfide-based solid electrolyte, potentially resulting in a deterioration in battery performance. However, when sulfide-based solid electrolyte particles (A) are placed in the voids inside the exterior body, other than the solid electrolyte layer or electrodes, the particles (A) absorb moisture within the exterior body, thereby reducing the amount of moisture in the solid electrolyte layer and electrodes that can cause degradation of the solid electrolyte and active materials. Furthermore, because the sulfide-based solid electrolyte particles (A) themselves are not involved in the function of the solid electrolyte layer or electrodes, moisture-induced degradation of the particles (A) does not result in a deterioration in battery performance. This allows the all-solid-state battery of the present invention to suppress performance degradation due to moisture intrusion.

[0019] Examples of sulfide-based solid electrolyte particles (A) include particles of Li2S-P2S5, Li2S-SiS2, Li2S-P2S5-GeS2, and Li2S-B2S3-based glass, as well as thio-LISICON type particles [Li 10 GeP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 12-12a-b+c+6d-e M 1 3+a-b-c-d M 2 b M 3 c M 4 d M 5 12-e X e (However, M1 is Si, Ge or Sn, M 2 is P or V, M 3 is Al, Ga, Y or Sb, M 4 is Zn, Ca, or Ba, M 5 is either S or S and O, X is F, Cl, Br or I, 0 ≦ a < 3, 0 ≦ b + c + d ≦ 3, 0 ≦ e ≦ 3), or those of the argyrodite type [such as Li6PS5Cl, Li 7-f+g PS 6-x Cl x+y (however, 0.05 ≦ f ≦ 0.9, -3.0f + 1.8 ≦ g ≦ -3.0f + 5.7), those represented by Li 7-h PS 6-h Cl i Br j (however, h = i + j, 0 < h ≦ 1.8, 0.1 ≦ i / j ≦ 10.0), etc.] and the like particles can also be used.

[0020] The particles (A) of the sulfide-based solid electrolyte are in particulate form, and can efficiently absorb the moisture inside the exterior of the all-solid-state battery. The particles (A) have no particular limitation on their shape, and can be either primary particles or secondary particles, but their specific surface area is preferably 0.7 m 2 / g or more, and more preferably 5.0 m 2 / g or more. With particles (A) having such a specific surface area, the moisture inside the exterior of the all-solid-state battery can be absorbed more efficiently.

[0021] The adjustment of the specific surface area of the particles (A) of the sulfide-based solid electrolyte is possible, for example, by adjusting the average particle diameter of the particles (A). However, if the specific surface area is increased too much, the particle diameter becomes too small and the handleability deteriorates. Therefore, the specific surface area of the particles (A) of the sulfide-based solid electrolyte is preferably 30 m 2 / g or less.

[0022] The specific surface area of ​​the sulfide-based solid electrolyte particles (A) referred to in this specification is a value determined by the BET method in accordance with Japanese Industrial Standards (JIS) K 6217, and can be measured, for example, using a specific surface area measuring device ("Macsorb HM model e-1201" manufactured by Mountech Co., Ltd.) using a nitrogen adsorption method.

[0023] The sulfide-based solid electrolyte particles (A) preferably have an average particle size of 0.1 to 5.0 μm.

[0024] FIG. 1 shows a schematic longitudinal cross-sectional view of an example of an all-solid-state battery of the present invention. The all-solid-state battery 1 shown in FIG. 1 has a coin-shaped (also called button-shaped) exterior body consisting of an exterior can 3, a sealing can 4, and a gasket 5, and has a pellet-shaped electrode laminate 2 sealed therein, the pellet-shaped electrode laminate 2 having a positive electrode 21, a negative electrode 22, and a solid electrolyte layer 23 interposed between the positive electrode 21 and the negative electrode 22. That is, in the all-solid-state battery 1, the sealing can 4 is fitted into the opening of the exterior can 3 via the gasket 5, and the open end of the exterior can 3 is tightened inward, thereby abutting the gasket 5 against the sealing can 4, sealing the opening of the exterior can 3 and sealing the interior of the battery. The exterior can 3 also serves as the positive electrode terminal, and the sealing can 4 also serves as the negative electrode terminal. In the all-solid-state battery 1 shown in FIG. 1, the electrode laminate 2 is housed so that the positive electrode 21 contacts the outer can 3 and the negative electrode 22 contacts the sealed can 4, but in the all-solid-state battery of the present invention, the electrode laminate may be housed so that the positive electrode contacts the sealed can and the negative electrode contacts the outer can.

[0025] In the all-solid-state battery 1, sulfide-based solid electrolyte particles (A) 6 are accommodated around the radial periphery of the electrode laminate 2, i.e., in a position outside the outer end of the electrode laminate 2 in a plan view from the flat surface side of the electrode laminate 2 (for example, a plan view from above in FIG. 1 ). Note that in FIG. 1 , the position where the particles (A) 6 are arranged is shown as a whole, since illustrating each individual particle of the sulfide-based solid electrolyte particles (A) 6 would make the drawing complicated.

[0026] In an all-solid-state battery, the arrangement of the sulfide-based solid electrolyte particles (A) is not particularly limited, and the particles may be arranged anywhere in the void portion of the exterior body. However, in the case of a coin-type battery having an exterior body (battery container) having an exterior can and a sealing can as shown in FIG. 1, for example, moisture is likely to penetrate from the vicinity of the peripheral edge of the exterior can (between the exterior can 3 and the gasket 5 in the case of the battery 1 in FIG. 1) or the vicinity of the peripheral edge of the sealing can (between the sealing can 4 and the gasket 5 in the case of the battery 1 in FIG. 1), so it is desirable to arrange the particles (A) near these locations; specifically, it is preferable to arrange them around the radial direction of the electrode laminate as shown in FIG. 1.

[0027] From the viewpoint of ensuring the above-mentioned effects obtained by disposing the sulfide-based solid electrolyte particles (A) more effectively, it is preferable that the mass of the sulfide-based solid electrolyte particles (A) disposed in the battery be a certain percentage or more relative to the mass of the electrode laminate (the total mass of the electrode laminate including the positive electrode, the negative electrode, and the solid electrolyte layer).

[0028] More specifically, although it depends on the size of the battery, the mass of the sulfide-based solid electrolyte particles (A) disposed in the battery is, for example, preferably 0.2% or more, more preferably 1% or more, and particularly preferably 1.5% or more, relative to the total mass of the electrode laminate. There are no particular restrictions on the mass of the sulfide-based solid electrolyte particles (A) disposed in the battery as long as they can be accommodated inside the battery, but for example, it is preferably 5% or less, more preferably 4% or less, and particularly preferably 3% or less, relative to the total mass of the electrode laminate.

[0029] As will be described later, in all-solid-state batteries, the solid electrolyte layer contains a solid electrolyte, and the positive electrode also usually contains a solid electrolyte, and the negative electrode also sometimes contains a solid electrolyte. However, when at least one of the positive electrode, negative electrode, and solid electrolyte layer contains a solid electrolyte that is highly reactive with moisture, such as a sulfide-based solid electrolyte, a hydride solid electrolyte, or a part of an oxide-based solid electrolyte, the effect of the present invention, which suppresses deterioration of characteristics due to moisture that has penetrated inside, becomes more pronounced.

[0030] The all-solid-state battery of the present invention includes a primary battery and a secondary battery.

[0031] (positive electrode) The positive electrode of the all-solid-state battery includes a positive electrode mixture containing a positive electrode active material and a solid electrolyte, and examples thereof include a positive electrode consisting of only a compact of the positive electrode mixture, and a positive electrode mixture having a structure in which a layer (positive electrode mixture layer) consisting of a compact of the positive electrode mixture is formed on a current collector.

[0032] When the all-solid-state battery is a primary battery, the same positive electrode active material as that used in conventionally known non-aqueous electrolyte primary batteries can be used. Specifically, for example, manganese dioxide, lithium-containing manganese oxides (e.g., LiMn3O6, or composite oxides having the same crystal structure as manganese dioxide (e.g., β-type, γ-type, or a mixed structure of β-type and γ-type) and 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 Examples include lithium-containing composite oxides such as O4 (4 / 3≦a<7 / 3); vanadium oxide; niobium oxide; titanium oxide; sulfides such as iron disulfide; graphite fluoride; silver sulfides such as Ag2S; and nickel oxides such as NiO2.

[0033] In addition, when the all-solid-state battery is a secondary battery, the same positive electrode active material as that used in conventionally known non-aqueous electrolyte secondary batteries, that is, the same active material capable of absorbing and releasing Li (lithium) ions, can be used. 1-x M r Mn 2-r Spinel-type lithium manganese composite oxide represented by LiO4 (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≦x≦1, 0≦r≦1), Li r Mn (1-s-t) Ni s M t O (2-u) F v(However, 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, 0 ≦ 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, Li 1-x Co 1-r M r O2 (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, 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5) A lithium cobalt composite oxide represented by, Li 1-x Ni 1-r M r O2 (However, M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5) A lithium nickel composite oxide represented by, Li 1+s-x M 1-r N r PO4F s (However, M is at least one element selected from the group consisting of Fe, Mn, and Co, and 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 ≦ x ≦ 1, 0 ≦ r ≦ 0.5, 0 ≦ s ≦ 1) An olivine-type composite oxide represented by, Li 2-x M 1-r N r P2O7 (However, M is at least one element selected from the group consisting of Fe, Mn, and Co, and 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 ≦ x ≦ 2, 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.

[0034] When the all-solid-state battery is a secondary battery, the average particle size of the positive electrode active material is preferably 1 μm or more, more preferably 2 μm or more, and preferably 10 μm or less, more preferably 8 μm or less. The positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. When a positive electrode active material having an average particle size within the above range is used, a large interface with the solid electrolyte contained in the positive electrode can be secured, thereby further improving the load characteristics of the battery.

[0035] The average particle diameter of various particles (positive electrode active material, solid electrolyte, etc.) referred to in this specification is the 50% diameter value (D ) in the volume-based integrated fraction when calculating the integrated volume from small particles using a particle size distribution analyzer (e.g., a Microtrac particle size distribution analyzer "HRA9320" manufactured by Nikkiso Co., Ltd.). 50 ) means

[0036] When the all-solid-state battery is a secondary battery, the positive electrode active material preferably has a reaction suppression layer on its surface to suppress reaction with the solid electrolyte contained in the positive electrode.

[0037] If the positive electrode active material and the solid electrolyte come into direct contact within the positive electrode mixture compact, the solid electrolyte may oxidize to form a resistance layer, resulting in a decrease in ionic conductivity within the compact. By providing a reaction suppression layer on the surface of the positive electrode active material that suppresses reaction with the solid electrolyte and preventing direct contact between the positive electrode active material and the solid electrolyte, it is possible to suppress a decrease in ionic conductivity within the compact due to oxidation of the solid electrolyte.

[0038] The reaction suppression layer may be made of any material that has ion conductivity and can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of materials that can form 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, and Zr, more specifically, Nb-containing oxides such as LiNbO3, Li3PO4, Li3BO3, Li4SiO4, Li4GeO4, LiTiO3, LiZrO3, and Li2WO4. The reaction suppression layer may contain only one of these oxides, or may contain two or more of them, or may even form a composite compound of two or more of these oxides. Among these oxides, Nb-containing oxides are preferred, and LiNbO3 is more preferred.

[0039] The reaction suppression layer is preferably present on the surface in an amount of 0.1 to 1.0 part by mass per 100 parts by mass of the positive electrode active material, which allows for effective suppression of the reaction between the positive electrode active material and the solid electrolyte.

[0040] Examples of methods for forming a reaction suppression layer on the surface of a positive electrode active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0041] The content of the positive electrode active material in the positive electrode mixture is preferably 60 to 98 mass %.

[0042] The positive electrode mixture may contain a conductive additive. Specific examples include carbon materials such as graphite (natural graphite, artificial graphite), graphene, carbon black, carbon nanofibers, and carbon nanotubes. For example, when Ag2S is used as the active material, conductive Ag is generated during the discharge reaction, so a conductive additive need not be included. When a conductive additive is included in the positive electrode mixture, its content is preferably 1 to 10 mass %.

[0043] The positive electrode mixture may contain a binder. Specific examples include fluororesins such as PVDF. Note that, for example, when a sulfide-based solid electrolyte is contained in the positive electrode mixture (described in detail below), the positive electrode mixture may not contain a binder if good moldability can be ensured in forming a compact from the positive electrode mixture without using a binder.

[0044] When a binder is required in the positive electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when the positive electrode mixture contains a sulfide-based solid electrolyte and thus can obtain formability without the need for a binder, the content thereof 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 contained).

[0045] The solid electrolyte contained in the positive electrode mixture is not particularly limited as long as it has lithium ion conductivity, and for example, a sulfide-based solid electrolyte, a hydride-based solid electrolyte, a halide-based solid electrolyte, an oxide-based solid electrolyte, etc. can be used.

[0046] The sulfide-based solid electrolyte may be the same as the sulfide-based solid electrolyte for the sulfide-based solid electrolyte particles (A). The sulfide-based solid electrolyte contained in the positive electrode mixture may be the same type as the sulfide-based solid electrolyte for the sulfide-based solid electrolyte particles (A), or may be a different type.

[0047] Examples of the hydride-based solid electrolyte include, for example, LiBH4, a solid solution of LiBH4 and the following alkali metal compound (for example, those having a molar ratio of LiBH4 to the alkali metal compound of 1:1 to 20:1), and the like. Examples of the alkali metal compound in the solid solution include at least one selected from the group consisting of lithium halides (such as LiI, LiBr, LiF, LiCl), rubidium halides (such as RbI, RbBr, RbF, RbCl), cesium halides (such as CsI, CsBr, CsF, CsCl), lithium amide, rubidium amide, and cesium amide.

[0048] [[ID=�]]Examples of the halide-based solid electrolyte include, for example, monoclinic LiAlCl4, defective spinel-type or layered LiInBr4, monoclinic Li 6-3m Y m X6 (where 0 < m < 2 and X = Cl or Br), and the like. In addition, for example, known ones described in International Publication No. 2020 / 07095 and International Publication No. 2020 / 070955 can also be used.

[0049] Examples of the oxide-based solid electrolyte include, for example, garnet-type Li7La3Zr2O 12 、NASICON-type Li 1+O Al 1+O Ti 2-O (PO4)3, Li 1+p Al 1+p Ge 2-p (PO4)3, perovskite-type Li 3q La 2 / 3-q TiO3, and the like.

[0050] Among these solid electrolytes, sulfide-based solid electrolytes are preferred because of their high lithium ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferred, and particularly, argyrodite-type sulfide-based solid electrolytes having high lithium ion conductivity and high chemical stability are even more preferred.

[0051] The average particle size of the solid electrolyte is preferably 0.1 μm or more, and more preferably 0.2 μm or more, from the viewpoint of reducing grain boundary resistance, while it is preferably 10 μm or less, and more preferably 5 μm or less, from the viewpoint of forming a sufficient contact interface between the active material and the solid electrolyte.

[0052] The content of the solid electrolyte in the positive electrode mixture is preferably 4 to 40 mass %.

[0053] When a current collector is used for the positive electrode, the current collector may be made of a metal foil such as aluminum or stainless steel, a punched metal, a mesh, an expanded metal, a foamed metal, a carbon sheet, or the like.

[0054] The compact of the positive electrode mixture can be formed, for example, by compressing a positive electrode mixture prepared by mixing a positive electrode active material with a conductive additive, a binder, a solid electrolyte, and the like, which are added as needed, by pressure molding or the like.

[0055] In the case of a positive electrode having a current collector, it can be produced by bonding a molded body of the positive electrode mixture formed by the above-mentioned method to the current collector by, for example, pressing.

[0056] Alternatively, the positive electrode mixture and a solvent may be mixed to prepare a positive electrode mixture-containing composition, which may then be applied to a substrate such as a current collector or a solid electrolyte layer that faces the positive electrode, dried, and then pressed to form a molded body of the positive electrode mixture.

[0057] The solvent for the positive electrode mixture-containing composition can be water or an organic solvent such as N-methyl-2-pyrrolidone (NMP). When a solid electrolyte is also included in the positive electrode mixture-containing composition, it is preferable to select a solvent that is less likely to deteriorate the solid electrolyte. In particular, sulfide-based solid electrolytes and hydride-based solid electrolytes undergo chemical reactions with trace amounts of water, so nonpolar aprotic solvents such as hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene are preferred. Ultra-dehydrated solvents with a water content of 0.001% by mass (10 ppm) or less are particularly preferred. Fluorine-based solvents such as "Vertrel®" from Mitsui DuPont Fluorochemicals, "Zeorolla®" from Nippon Zeon, and "Novec®" from Sumitomo 3M can also be used, as well as nonaqueous organic solvents such as dichloromethane and diethyl ether.

[0058] From the viewpoint of increasing the density and reducing the porosity of the positive electrode mixture, and further reducing the internal resistance of the positive electrode, it is more preferable that the positive electrode mixture be compressed and molded by pressure molding or the like.

[0059] The thickness of the positive electrode mixture compact is usually 50 μm or more, but is preferably 200 μm or more from the viewpoint of increasing the capacity of the battery. The thickness of the positive electrode mixture compact is usually 3000 μm or less, but is preferably 500 μm or less from the viewpoint of increasing the output of the battery.

[0060] In the case of a positive electrode produced by forming a positive electrode mixture layer made of a compact of a positive electrode mixture on a current collector using a positive electrode mixture-containing composition containing a solvent, the thickness of the positive electrode mixture layer is preferably 50 to 1000 μm, and from the viewpoint of increasing the output of the battery, it is preferably 500 μm or less.

[0061] (Negative electrode) The negative electrode of the all-solid-state battery has, for example, a molded body of a negative electrode mixture containing a negative electrode active material, a lithium sheet, or a lithium alloy sheet.

[0062] When the negative electrode is a molded body of a negative electrode mixture containing a negative electrode active material, examples of the negative electrode include a molded body (pellet, etc.) obtained by molding the negative electrode mixture, and a structure in which a layer (negative electrode mixture layer) made of a molded body of the negative electrode mixture is formed on a current collector.

[0063] When the negative electrode has a molded body of a negative electrode mixture, examples of the negative electrode active material include carbon materials such as graphite, simple substances containing elements such as Si and Sn, compounds (oxides, etc.), and alloys thereof. Lithium metal and lithium alloys (lithium-aluminum alloys, lithium-indium alloys, etc.) can also be used as the negative electrode active material.

[0064] The content of the negative electrode active material in the negative electrode mixture is preferably 10 to 99 mass %.

[0065] The negative electrode mixture may contain a conductive additive. Specific examples include the same conductive additives as those exemplified above as those that may be contained in the positive electrode mixture. The content of the conductive additive in the negative electrode mixture is preferably 1 to 10 mass %.

[0066] The negative electrode mixture may contain a binder. Specific examples include the same binders as those exemplified above as binders that may be contained in the positive electrode mixture. Note that, for example, when a sulfide-based solid electrolyte is contained in the negative electrode mixture (described in detail below), if good moldability can be ensured in forming a compact from the negative electrode mixture without using a binder, the negative electrode mixture may not contain a binder.

[0067] When a binder is required in the negative electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when the negative electrode mixture contains a sulfide-based solid electrolyte and thus can be molded without a binder, the content thereof 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 contained).

[0068] In a negative electrode having a molded body of a negative electrode mixture, a solid electrolyte is contained in the negative electrode mixture. Specific examples include the same solid electrolytes as those exemplified above as those that can be contained in the positive electrode mixture. Among the solid electrolytes exemplified above, it is more preferable to use a sulfide-based solid electrolyte because it has high lithium ion conductivity and also has the function of improving the moldability of the negative electrode mixture. The sulfide-based solid electrolyte contained in the negative electrode mixture may be the same type as the sulfide-based solid electrolyte related to the sulfide-based solid electrolyte particles (A), or may be a different type.

[0069] The content of the solid electrolyte in the negative electrode mixture is preferably 4 to 49 mass %.

[0070] When a current collector is used in a negative electrode having a molded body of a negative electrode mixture, the current collector can be made of copper or nickel foil, punched metal, mesh, expanded metal, foamed metal; carbon sheet; or the like.

[0071] The compact of the negative electrode mixture can be formed, for example, by compressing a negative electrode mixture prepared by mixing a negative electrode active material, and optionally a conductive additive, a solid electrolyte, a binder, etc., by pressure molding, etc. A negative electrode composed only of a compact of the negative electrode mixture can be produced by the above-mentioned method.

[0072] In the case of a negative electrode having a current collector, it can be produced by bonding a molded body of the negative electrode mixture formed by the above-mentioned method to the current collector by, for example, pressing.

[0073] Furthermore, in the case of a negative electrode having a current collector, the negative electrode can also be produced by a method in which a negative electrode mixture-containing composition (paste, slurry, etc.) in which a negative electrode active material, and further, optionally added conductive additives, a solid electrolyte, a binder, etc. are dispersed in a solvent is applied to a current collector, dried, and then pressure-molded, as necessary, by calendering or other means, to form a molded body of the negative electrode mixture (negative electrode mixture layer) on the surface of the current collector.

[0074] As the solvent for the negative electrode mixture-containing composition, an organic solvent such as water or NMP can be used. However, when the negative electrode mixture-containing composition also contains a solid electrolyte, it is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte. It is preferable to use the same solvents as those exemplified above as the solvent for the positive electrode mixture-containing composition containing a solid electrolyte.

[0075] From the viewpoint of increasing the density and reducing the porosity of the negative electrode mixture, and further reducing the internal resistance of the negative electrode, it is more preferable that the negative electrode mixture be formed by compressing the negative electrode mixture by pressure molding or the like.

[0076] The thickness of the negative electrode mixture compact is usually 50 μm or more, but from the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. The thickness of the negative electrode mixture compact is usually 3000 μm or less, but from the viewpoint of increasing the output of the battery, it is preferably 500 μm or less.

[0077] In the case of a negative electrode produced by forming a negative electrode mixture layer made of a compact of a negative electrode mixture on a current collector using a negative electrode mixture-containing composition containing a solvent, the thickness of the negative electrode mixture layer is preferably 50 to 1000 μm, and from the viewpoint of increasing the output of the battery, it is preferably 500 μm or less.

[0078] In the case of a negative electrode having a lithium sheet or a lithium alloy sheet, one consisting of only this sheet or one consisting of this sheet stuck to a current collector is used.

[0079] Examples of alloying elements for lithium alloys include aluminum, lead, bismuth, indium, and gallium, with aluminum and indium being preferred. The proportion of alloying elements in the lithium alloy (the total proportion when multiple alloying elements are included) is preferably 50 atomic % or less (in this case, the remainder is lithium and inevitable impurities).

[0080] In addition, in the case of a negative electrode having a lithium alloy sheet, a laminate can be used in which a layer containing an alloying element for forming a lithium alloy is laminated on the surface of a lithium layer (a layer containing lithium) composed of a metal lithium foil or the like by pressure bonding, and this laminate is brought into contact with a solid electrolyte in a battery to form a lithium alloy on the surface of the lithium layer, thereby forming a negative electrode. In such a negative electrode, a laminate having a layer containing an alloying element on only one side of the lithium layer may be used, or a laminate having a layer containing an alloying element on both sides of the lithium layer may be used. The laminate can be formed, for example, by pressure bonding a metal lithium foil and a foil composed of an alloying element.

[0081] The current collector can also be used when a lithium alloy is formed in a battery to form a negative electrode. For example, a laminate having a lithium layer on one side of the negative electrode current collector and a layer containing an alloying element on the side of the lithium layer opposite the negative electrode current collector may be used, or a laminate having lithium layers on both sides of the negative electrode current collector and a layer containing an alloying element on the side of each lithium layer opposite the negative electrode current collector may be used. The negative electrode current collector and the lithium layer (metallic lithium foil) may be laminated by compression bonding or the like.

[0082] The layer containing the alloying elements in the laminate to be used as the negative electrode can be, for example, a foil composed of these alloying elements. The thickness of the layer containing the alloying elements is preferably 1 μm or more, more preferably 3 μm or more, and is preferably 20 μm or less, more preferably 12 μm or less.

[0083] The lithium layer of the laminate for use as a negative electrode may be, for example, a metallic lithium foil. The thickness of the lithium layer is preferably 0.1 to 1.5 mm. In addition, the thickness of the sheet for the negative electrode having a lithium or lithium alloy sheet is also preferably 0.1 to 1.5 mm.

[0084] Furthermore, when a negative electrode having a lithium sheet or a lithium alloy sheet has a current collector, the same current collectors as those exemplified above as those usable for a negative electrode having a molded body of a negative electrode mixture can be used for the current collector.

[0085] (Solid electrolyte layer) The solid electrolyte constituting 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 listed above as examples of solid electrolytes that can be used for the positive electrode. However, to improve battery characteristics, it is preferable to contain a sulfide-based solid electrolyte, and it is more preferable to contain an argyrodite-type sulfide-based solid electrolyte. It is even more preferable to contain a sulfide-based solid electrolyte in both the positive electrode and the solid electrolyte layer, and it is even more preferable to contain an argyrodite-type sulfide-based solid electrolyte. The sulfide-based solid electrolyte contained in the solid electrolyte layer may be the same type as or different from the sulfide-based solid electrolyte of the sulfide-based solid electrolyte particles (A).

[0086] The solid electrolyte layer may have a porous body such as a resin nonwoven fabric as a support.

[0087] The solid electrolyte layer can be formed by a method of compressing the solid electrolyte by pressure molding or the like; a method of dispersing the solid electrolyte in a solvent to prepare a composition for forming the solid electrolyte layer, applying the composition to a substrate, a positive electrode, or a negative electrode, drying the composition, and optionally performing pressure molding such as pressing; or the like; however, it is more preferable to employ the method of compressing the solid electrolyte.

[0088] It is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte as the solvent used in the solid electrolyte layer-forming composition, and it is preferable to use the same solvents as those exemplified above as the solvents for the positive electrode mixture-containing composition containing the solid electrolyte.

[0089] The thickness of the solid electrolyte layer is preferably 100 to 400 μm.

[0090] (electrode laminate) The positive electrode and the negative electrode are stacked with a solid electrolyte layer interposed therebetween to form an electrode laminate, which is used in a battery.

[0091] When forming the electrode stack, it is preferable to pressure-mold the positive electrode, negative electrode, and solid electrolyte layer in a stacked state, from the viewpoint of increasing the mechanical strength of the electrode stack and reducing the internal resistance.

[0092] (exterior body) The exterior body of an all-solid-state battery is, for example, a battery container having an exterior can and a sealing can as shown in Fig. 1. That is, an all-solid-state battery using such a battery container as the exterior body becomes a coin-type (button-type) battery.

[0093] In the case where the exterior body of the all-solid-state battery is a battery container having an exterior can and a sealing can, examples include a case in which the exterior can and the sealing can are crimped and sealed via a gasket, as shown in FIG. 1, and a case in which the exterior can and the sealing can are bonded with a resin.

[0094] The outer can and sealing can can be made of stainless steel or other materials. Materials such as polypropylene and nylon can be used for the gasket. If heat resistance is required for the battery's intended use, heat-resistant resins with melting points exceeding 240°C, such as fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), can also be used. If the battery is intended for use in applications requiring heat resistance, a glass hermetic seal can also be used for the sealing.

[0095] The shape of the exterior body, which is a battery container having an exterior can and a sealing can, in a plan view may be circular or polygonal such as quadrilateral (square or rectangle).In the case of a polygon, the corners may be curved.

[0096] Furthermore, a laminate film exterior made of a metal laminate film such as an aluminum laminate film can also be used as the exterior of the all-solid-state battery.

[0097] The all-solid-state battery of the present invention can be used in the same applications as conventionally known primary batteries and secondary batteries, but since it has a solid electrolyte instead of an organic electrolyte solution, it has excellent heat resistance and can be preferably used in applications where it is exposed to high temperatures. [Example]

[0098] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0099] Example 1 Lithium titanate (Li4Ti5O 12 , negative electrode active material) and a sulfide-based solid electrolyte (Li 5.4 PS 4.4 Cl 0.8Br 0.8 ) and graphene (conductive additive) were mixed in a mass ratio of 50:41:9 to prepare a negative electrode mixture.

[0100] In addition, a LiCoO2 (positive electrode active material) with an average particle size of 5 μm and a LiNbO3 coating layer formed on its surface and a sulfide-based solid electrolyte (Li 7.0 PS 5.4 Cl 1.2 ) was mixed with carbon black and vapor grown carbon fiber (VGCF) in a mass ratio of 70:26.8:1.1:2.1 to prepare a positive electrode mixture.

[0101] Next, a sulfide-based solid electrolyte (Li 5.4 PS 4.4 Cl 0.8 Br 0.8 ) powder was placed in a powder molding die and subjected to low-pressure molding using a press to form a provisionally molded layer of a solid electrolyte layer. Furthermore, the negative electrode mixture was placed on the upper surface of the provisionally molded layer of the solid electrolyte layer and subjected to low-pressure molding to form a provisionally molded layer of a negative electrode on the provisionally molded layer of the solid electrolyte layer.

[0102] Furthermore, after the mold was turned upside down, the positive electrode mixture was placed on the upper surface of the provisionally molded layer of the solid electrolyte layer in the mold (the surface opposite to the surface having the provisionally molded layer of the negative electrode), and the entire mold was pressurized with 1300 MPa (13 tf / cm 2 ) to obtain an electrode laminate having a thickness of 1.57 mm in which the negative electrode, the solid electrolyte layer, and the positive electrode were integrated.

[0103] Next, the stainless steel sealing can and the stainless steel outer can were crimped and sealed with a polyphenylene sulfide gasket interposed therebetween, and the electrode stack was enclosed inside to produce a coin-shaped all-solid-state battery having the structure shown in FIG. 1.

[0104] When the electrode laminate is sealed, a sulfide-based solid electrolyte (Li ) having an average particle size of 0.7 μm is filled in the gap around the electrode laminate. 5.4 PS 4.4 Cl0.8 Br 0.8 The electrode stack was filled with 3.5 mg of sulfide-based solid electrolyte powder (particles (A) of sulfide-based solid electrolyte), and then sealed. The mass of the solid electrolyte powder was 1.9% of the mass of the electrode stack.

[0105] Although not shown, carbon sheets with a thickness of about 0.1 mm were inserted between the positive electrode and the outer can, and between the negative electrode and the sealing can.

[0106] (Comparative Example 1) A coin-shaped all-solid-state battery was produced in the same manner as in Example 1, except that the gap around the electrode laminate was sealed without being filled with solid electrolyte powder.

[0107] Ten batteries each of the produced Example 1 and Comparative Example 1 were charged and discharged, and then an AC voltage of 1 kHz was applied to measure the internal resistance of the battery, and the average value of the ten batteries was calculated.

[0108] Next, the batteries were stored in a thermostatic chamber at 60°C and a relative humidity of 90% for 36 days, then removed and allowed to cool to room temperature. An alternating current of 1 kHz was then applied to measure the internal resistance of the batteries after high-temperature storage, and the average value for 10 batteries was calculated.

[0109] The difference between the internal resistance of the battery after high-temperature storage and the internal resistance of the battery before storage (increase in internal resistance) was calculated for the batteries of Example 1 and Comparative Example 1 and compared.

[0110] The increase in internal resistance during high-temperature storage for each battery is shown in Table 1, with the value for the battery of Comparative Example 1 set at 100.

[0111] [Table 1]

[0112] When a battery is stored in a high-temperature and high-humidity environment, moisture gradually penetrates into the battery through the sealed portion and reacts with the solid electrolyte, etc., increasing the internal resistance of the battery. However, as shown in Table 1, in the battery of Example 1, by disposing sulfide-based solid electrolyte particles (A) in the voids inside the battery, the amount of moisture reacting with the solid electrolyte, etc. contained in the electrode laminate was reduced, and the increase in internal resistance was suppressed. [Explanation of symbols]

[0113] 1 All-solid-state battery 2-electrode laminate 21 Positive electrode 22 Negative electrode 23 Solid electrolyte layer 3 Outer can 4 Sealed cans 5 Gasket 6. Sulfide-based solid electrolyte particles (A)

Claims

1. An all-solid-state battery in which an electrode stack having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode is sealed inside an exterior body, particles (A) of a sulfide-based solid electrolyte are disposed in a void portion inside the exterior packaging; 1. An all-solid-state battery, characterized in that the mass of the sulfide-based solid electrolyte particles (A) is 0.2% or more of the mass of the electrode laminate.

2. 2. The all-solid-state battery according to claim 1, wherein at least one of the positive electrode, the negative electrode, and the solid electrolyte layer that constitute the electrode stack contains a sulfide-based solid electrolyte.

3. The sulfide-based solid electrolyte particles (A) have a specific surface area of ​​0.7 m ２ The all-solid-state battery according to claim 1 or 2, wherein the SiO2 content is 1 / g or more.

4. The electrode laminate is in the form of a pellet and is enclosed in a coin-shaped exterior body, 4. The all-solid-state battery according to claim 1, wherein the sulfide-based solid electrolyte particles (A) are arranged radially around the electrode stack.

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