All-solid-state battery

Abstract

To provide an all-solid battery that can exhibit excellent load characteristics even when having a thick electrode body, relating to Goals 12, 3, 7, and 11 of Sustainable Development Goals (SDGs).SOLUTION: An all-solid battery has an electrode body in which a positive electrode that includes a positive electrode mixture containing a solid electrolyte, and a negative electrode are laminated via a solid electrolyte layer containing a solid electrolyte. At least one of the positive electrode and the negative electrode is a concavo-convex shaped electrode that has a convex part extending in a thickness direction of the electrode body on a counter electrode side surface. The convex part has such a slope that a width becomes narrower toward the counter electrode side, and has an inclination angle θ with respect to a direction parallel to the thickness direction of the electrode body is 5° to 45°.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an all-solid-state battery that can exhibit excellent load characteristics even when having a thick electrode body.

Background Art

[0002] In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers, and the practical application of electric vehicles, there has been an increasing need for batteries that are small, lightweight, and have high capacity and high energy density.

[0003] Currently, in lithium batteries, particularly lithium-ion batteries, which can meet this requirement, an organic electrolyte solution containing an organic solvent and a lithium salt is used as a non-aqueous electrolyte.

[0004] With the further development of applicable devices for lithium-ion batteries, further improvements in long life, high capacity, and high energy density are required for lithium-ion batteries, and at the same time, high reliability of long-life, high-capacity, and high-energy-density lithium-ion batteries is also highly demanded.

[0005] However, since the organic electrolyte solution used in lithium-ion batteries contains an organic solvent that is a flammable substance, when an abnormal situation such as a short circuit occurs in the battery, the organic electrolyte solution may generate abnormal heat. In addition, with the increasing energy density of recent lithium-ion batteries and the increasing tendency of the amount of organic solvent in the organic electrolyte solution, higher reliability of lithium-ion batteries is required.

[0006] Under the above circumstances, all-solid-state lithium batteries (all-solid-state batteries) that do not use organic solvents have attracted attention. An all-solid-state battery uses a molded body of a solid electrolyte that does not use an organic solvent instead of a conventional organic solvent-based electrolyte, and has no risk of abnormal heat generation of the solid electrolyte and has high safety.

[0007] In addition, all-solid-state batteries are expected to be maintenance-free batteries that can contribute to the development of society and continue to contribute to peace of mind and safety, as they not only have high safety but also high reliability, high environmental resistance, and long life. By providing all-solid-state batteries to society, among the 17 goals of the Sustainable Development Goals (SDGs) established by the United Nations, it is possible to contribute to the achievement of Goal 12 (ensuring sustainable production and consumption patterns), Goal 3 (ensuring healthy lives and promoting well-being for all people of all ages), Goal 7 (ensuring access for all people to affordable, reliable, and sustainable modern energy), and Goal 11 (making cities and human settlements inclusive, safe, resilient, and sustainable).

[0008] By the way, currently, in all-solid-state batteries, the application fields are rapidly expanding. For example, since it is conceivable to apply them to applications that require discharge at a large current value, in order to meet this requirement, for example, it is required to reduce the internal resistance of the battery and improve the load characteristics.

[0009] For example, in Patent Documents 1 to 4, technologies have been proposed to make the surfaces of electrodes and solid electrolyte layers have uneven shapes in order to reduce the internal resistance of batteries using solid electrolytes and improve the load characteristics (output characteristics).

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, for example, in the case of a battery having a thick electrode body in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated and the thickness is 1 mm or more, even if the above-described technology is applied, the positive electrode or the negative electrode may remain thick, and it is difficult to improve the load characteristics.

[0012] The present invention has been made in view of the above circumstances, and an object thereof is to provide an all-solid-state battery that can exhibit excellent load characteristics even when having a thick electrode body.

Means for Solving the Problems

[0013] The all-solid-state battery of the present invention has an electrode body in which a positive electrode containing a positive electrode mixture containing a solid electrolyte and a negative electrode are laminated via a solid electrolyte layer containing a solid electrolyte, and at least one of the positive electrode and the negative electrode is a concavo-convex shaped electrode having a convex portion extending in the thickness direction of the electrode body on the surface on the counter electrode side. The convex portion has a gradient in which the width becomes narrower toward the counter electrode side, and the gradient angle θ with respect to the direction parallel to the thickness direction of the electrode body is 5 to 45°.

Effects of the Invention

[0014] According to the present invention, it is possible to provide an all-solid-state battery that can exhibit excellent load characteristics even when having a thick electrode body.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0016] FIG. 1 shows a cross-sectional view schematically showing a part of an example of an electrode body according to the all-solid-state battery of the present invention. The electrode body 10 shown in FIG. 1 is configured by laminating a positive electrode 1 and a negative electrode 2 with a solid electrolyte layer 3 interposed therebetween. And the negative electrode 2 has an uneven shape having a convex portion 2a extending toward the positive electrode 1 side which is a counter electrode, and a concave portion 2b existing between adjacent convex portions 2a.

[0017] Further, the convex portion 2a in the negative electrode 2 which is an uneven-shaped electrode has a gradient in which the width (the length in the horizontal direction in FIG. 1) becomes narrower toward the positive electrode 1 side which is a counter electrode.

[0018] Thus, in the all-solid-state battery of the present invention, in addition to making at least one of the positive electrode and the negative electrode have an uneven shape, the convex portion of the uneven-shaped electrode has a gradient in which the width becomes narrower toward the counter electrode side, and further, the gradient angle θ (the angle of θ in FIG. 1) between the direction parallel to the thickness direction of the electrode body is 45° or less, preferably 30° or less.

[0019] In increasing the capacity of the battery, it is generally performed to thicken the positive electrode and the negative electrode and increase the amount of the active material contained therein. In that case, however, the total thickness of the electrode body formed by interposing the solid electrolyte layer between the positive electrode and the negative electrode also increases. In a battery having such an electrode body, especially when charging (in the case of a secondary battery) or discharging with a large current value, in particular, the active material near the surface on the side opposite to the counter electrode side of the electrode cannot sufficiently participate in the battery reaction, and the capacity originally provided in the electrode cannot be sufficiently drawn out, and the load characteristics usually deteriorate.

[0020] Therefore, it is conceivable to make at least one of the positive electrode and the negative electrode have a concavo-convex shape as shown in FIG. 1. In this case, in the concavo-convex shaped electrode, for example, the distance from the solid electrolyte layer can be shortened at any location near the surface on the side opposite to the counter electrode side. Therefore, a certain improvement in the load characteristics of the battery can be expected. However, for example, when the electrode body is thickened so that the total thickness is 0.7 mm or more, the effect of improving the load characteristics is also limited.

[0021] In the concavo-convex shaped electrode, in a cross-section of the electrode body passing through the center and parallel to the thickness direction, when a perpendicular line is drawn from the central portion of the surface on the counter electrode side of the convex portion to the surface on the side opposite to the counter electrode side, the intersection point of the perpendicular line and the surface on the side opposite to the counter electrode side of the concavo-convex shaped electrode (the intersection point of the broken line in FIG. 1 and the surface on the side opposite to the positive electrode 1 of the negative electrode 2) is the location where the distance from the solid electrolyte layer is the longest.

[0022] Therefore, if the convex portion of the concavo-convex shaped electrode is provided with a gradient as shown in FIG. 1 and the gradient angle θ is 45° or less, preferably 30° or less, the shortest distance Rm (the length of Rm in FIG. 1) from the intersection point to the solid electrolyte layer can be limited to a specific value or less. Therefore, even when a thick electrode body is used, the proportion of the active material that can participate in the battery reaction within the concavo-convex shaped electrode can be increased during charging (in the case of a secondary battery) and discharging at a large current.

[0023] Furthermore, in the all-solid-state battery of the present invention, it is preferable to use a molded body obtained by compressing materials such as an active material and a solid electrolyte for the positive electrode, the solid electrolyte, and further the negative electrode by pressure molding or the like. However, by setting the gradient angle θ of the convex portion of the concavo-convex shaped electrode to 5° or more, preferably 10° or more, the stress during pressure molding can be favorably dispersed over the entire convex portion. Therefore, the density of the molded body is improved, and its internal resistance can be made smaller.

[0024] In the all-solid-state battery of the present invention, by setting the hook angle θ of the convex portion in the concavo-convex shaped electrode within a specific range, excellent load characteristics can be exhibited even when a thick electrode body is applied due to each of the above actions.

[0025] Fig. 2 shows a cross-sectional view schematically showing a part of another example of the electrode body according to the all-solid-state battery of the present invention. The electrode body 11 shown in Fig. 2 has a concavo-convex shape having a convex portion 1a extending toward the negative electrode 2 and a concave portion 1b existing between adjacent convex portions 1a, together with the negative electrode 2 and the positive electrode 1.

[0026] In the all-solid-state battery of the present invention, as shown in Fig. 1, only the negative electrode may be a concavo-convex shaped electrode, or only the positive electrode may be a concavo-convex shaped electrode, but as shown in Fig. 2, it is more preferable that both the positive electrode and the negative electrode are concavo-convex shaped electrodes.

[0027] The electrode body according to the all-solid-state battery has no particular limitation on its total thickness: h (the total value of the thickness of the positive electrode, the thickness of the negative electrode, and the thickness of the solid electrolyte layer; the length of h in Fig. 1). However, even if the capacity of the battery is increased with a thickness (for example, 0.7 mm or more, further 1.0 mm or more, particularly 1.5 mm or more) at which the load characteristics of the battery are likely to deteriorate, it is possible to ensure good load characteristics. The total thickness: h of the electrode body is usually 6.0 mm or less.

[0028] From the viewpoint of further improving the load characteristics of the all-solid-state battery, the height of the convex portion in the concavo-convex shaped electrode (the length of a in Figs. 1 and 2) is preferably h / 3 (mm) or more, and more preferably h / 2 (mm) or more. On the other hand, if the height of the convex portion is too high, it is difficult to maintain the shape during formation. Therefore, the height of the convex portion in the concavo-convex shaped electrode is preferably 4.0 (mm) or less.

[0029] From the perspective of further improving the load characteristics of the all-solid-state battery, the length of the Rm in the concavo-convex electrode is preferably h (mm) or less, and more preferably h / 3 (mm) or less. On the other hand, if Rm is made too small, the interval between the concavities and convexities becomes narrow, the proportion occupied by the solid electrolyte layer increases, leading to a decrease in the energy density of the battery. Therefore, the length of the Rm in the concavo-convex electrode is preferably h / 10 (mm) or more.

[0030] Figs. 3 to 5 show a plan view schematically showing an example of the concavo-convex electrode for an all-solid-state battery. Figs. 3 to 5 show the surface on the side where the convex portion 2a of the negative electrode 2, which is the concavo-convex electrode, is formed (the surface facing the positive electrode which is the counter electrode).

[0031] The shape of the convex portion in the concavo-convex electrode may be a continuous shape as shown in Figs. 3 and 4 in plan view, or a shape in which a large number of convex portions are formed discontinuously as shown in Fig. 5. The shape of each convex portion in plan view when formed discontinuously may be, for example, a polygon such as a quadrangle as shown in Fig. 5, or a circle (a perfect circle, an ellipse). Further, when the shape of the convex portion in plan view is a polygon, the corners thereof may be curves.

[0032] Also, there is no particular limitation on the shape of the tip of the convex portion. It may have a shape with corners as shown in Figs. 1 and 2, or may have a curved shape in side view.

[0033] Also, there is no particular limitation on the arrangement of the convex portions in the concavo-convex electrode. For example, as shown in Fig. 3, they may be arranged concentrically in plan view, or as shown in Figs. 4 and 5, they may be arranged parallel to each other in plan view. However, in order to equalize the current distribution, it is preferably symmetric in plan view, so it is more preferable to arrange them concentrically.

[0034] In the concave-convex shaped electrode, the distance from the rising portion of a convex portion to the rising portion of an adjacent convex portion (i.e., the pitch, the length of L1 in FIG. 1) is preferably 0.2 mm or more, more preferably 0.4 mm or more, preferably 3.0 mm or less, and more preferably 2.0 mm or less.

[0035] Also, the width of the convex portion in the concave-convex shaped electrode (the length from one rising portion to the other rising portion in one convex portion, the length of L2 in FIG. 1) is preferably 0.1 mm or more, more preferably 0.2 mm or more, preferably 1.5 mm or less, and more preferably 1.0 mm or less.

[0036] The included angle θ of the convex portion, the length of Rm, the pitch of the convex portion, and the width of the convex portion (the length of L2 in FIG. 1) in the concave-convex shaped electrode as referred to in this specification can be measured using computed tomography (CT). In this specification, specifically, after acquiring a plurality of images with a slice pitch of 25 μm perpendicular to the thickness direction of the electrode body using "inspeXio SMX-225CT" manufactured by Shimadzu Corporation, among the planes passing through the center of the electrode body constructed by multi-planar reformation (MPR) and parallel to the thickness direction, the dimensions of each part are obtained using the image of the plane that gives the minimum length of Rm.

[0037] In the all-solid-state battery of the present invention, an electrode having a current collector composed of a metal foil or the like is also applicable. In such an electrode, the "surface of the concave-convex shaped electrode on the side opposite to the counter electrode side" when obtaining the above-mentioned "Rm" means the surface of the portion excluding the current collector [the surface of the layer containing the active material (such as the positive electrode mixture layer and the negative electrode mixture layer)].

[0038] Fig. 6 shows a cross-sectional view schematically showing an example of the all-solid-state battery of the present invention. The all-solid-state battery 100 shown in Fig. 6 is a flat battery in which an electrode body in which a positive electrode 1 having an uneven shape and a negative electrode 2 having an uneven shape are laminated via a solid electrolyte layer 3 is enclosed in an exterior body composed of a battery container having an exterior can 4 and a sealing can 5, with a gasket 6 interposed therebetween. In the all-solid-state battery 100, the sealing can 5 is fitted to the opening of the exterior can 4 via the gasket 6, and the opening end of the exterior can 4 is tightened inward, whereby the gasket 6 abuts against the sealing can 5, so that the opening of the exterior can 4 is sealed and the inside of the battery has a sealed structure. And, the exterior can 4 also serves as a positive electrode terminal, and the sealing can 5 also serves as a negative electrode terminal. In the all-solid-state battery 100 shown in Fig. 6, the positive electrode 1 is housed in the exterior can 4 and the negative electrode 2 is housed in the sealing can 5, but in the all-solid-state battery of the present invention, the positive electrode can also be housed in the sealing can and the negative electrode can be housed in the exterior can.

[0039] The all-solid-state battery of the present invention includes a primary battery and a secondary battery.

[0040] (Positive electrode) The positive electrode for the all-solid-state battery includes a positive electrode mixture containing a positive electrode active material and a solid electrolyte. For example, it may be composed only of a molded body of the positive electrode mixture, or may have a structure in which a layer (positive electrode mixture layer) composed of a molded body of the positive electrode mixture is formed on a current collector.

[0041] When the all-solid-state battery is a primary battery, the same positive electrode active material as that used in a conventionally known non-aqueous electrolyte primary battery can be used. Specifically, for example, manganese dioxide, lithium-containing manganese oxide [for example, LiMn3O6, and a composite oxide 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 the Li content is 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 / 3Lithium-containing composite oxides such as O4 (4 / 3 ≤ a < 7 / 3); vanadium oxides; niobium oxides; titanium oxides; sulfides such as iron disulfide; graphite fluoride; silver sulfides such as Ag2S; nickel oxides such as NiO2: and the like can be mentioned.

[0042] Further, when the all-solid-state battery is a secondary battery, the same positive electrode active material as that used in a conventionally known non-aqueous electrolyte secondary battery, that is, an active material capable of occluding and releasing Li (lithium) ions can be used. Specifically, Li 1-x M r Mn 2-r O4 (where 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, 0 ≤ x ≤ 1, 0 ≤ r ≤ 1), spinel-type lithium manganese composite oxide represented by r Mn (1-s-t) Ni s M t O (2-u) F v (where 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), layered compound represented by 1-x Co 1-r M r O2 (where 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), lithium cobalt composite oxide represented by 1-x Ni 1-r M r O2 (where 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), lithium nickel composite oxide represented by 1+s-xM 1-r N r PO4F 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 ≦ x ≦ 1, 0 ≦ r ≦ 0.5, 0 ≦ s ≦ 1), an olivine-type composite oxide, 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, 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), a pyrophosphate compound, etc. can be exemplified, and only one of these may be used, or two or more thereof may be used in combination.

[0043] When the all-solid-state battery is a secondary battery, the average particle diameter 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. Note that the positive electrode active material may be primary particles or secondary particles in which the primary particles are aggregated. When the positive electrode active material having an average particle diameter within the above range is used, since more interfaces with the solid electrolyte contained in the positive electrode can be obtained, the load characteristics of the battery are further improved.

[0044] The average particle diameter of various particles (positive electrode active material, solid electrolyte, etc.) referred to in this specification is the value (D 50 ) of the 50% diameter in the volume-based integrated fraction when obtaining the integrated volume from the particles with a small particle size using a particle size distribution measuring device (such as the Microtrac particle size distribution measuring device "HRA9320" manufactured by Nikkiso Co., Ltd.).

[0045] When the all-solid-state battery is a secondary battery, the positive electrode active material preferably has a reaction suppression layer on its surface for suppressing the reaction with the solid electrolyte contained in the positive electrode.

[0046] In the molded body of the positive electrode active material, if the positive electrode active material and the solid electrolyte come into direct contact, the solid electrolyte may be oxidized to form a resistance layer, and the ionic conductivity in the molded body may decrease. By providing a reaction inhibition layer on the surface of the positive electrode active material to prevent direct contact between the positive electrode active material and the solid electrolyte, it is possible to suppress a decrease in ionic conductivity in the molded body due to oxidation of the solid electrolyte.

[0047] The reaction inhibition layer may be composed of a material having ionic conductivity and capable of suppressing the reaction between the positive electrode active material and the solid electrolyte. Examples of materials that can constitute the reaction inhibition 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, Li2WO4, etc. may be mentioned. The reaction inhibition layer may contain only one of these oxides, or may contain two or more of them. Furthermore, a plurality of these oxides may form a composite compound. Among these oxides, it is preferable to use Nb-containing oxides, and more preferably to use LiNbO3.

[0048] The reaction inhibition layer is preferably present on the surface in an amount of 0.1 to 1.0 parts by mass with respect to 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 favorably suppressed.

[0049] Examples of methods for forming the reaction inhibition layer on the surface of the positive electrode active material include the sol-gel method, the mechanofusion method, the CVD method, the PVD method, the ALD method, etc.

[0050] The content of the positive electrode active material in the positive electrode mixture is preferably 60 to 98% by mass.

[0051] The positive electrode active material can contain a conductive aid. Specific examples thereof include carbon materials such as graphite (natural graphite, artificial graphite), graphene, carbon black, carbon nanofibers, and carbon nanotubes. When, for example, Ag2S is used as the active material, since conductive Ag is generated during the discharge reaction, it is not necessary to contain a conductive aid. When a conductive aid is contained in the positive electrode active material, the content thereof is preferably 1 to 10% by mass.

[0052] In addition, the positive electrode active material can contain a binder. Specific examples thereof include fluororesins such as polyvinylidene fluoride (PVDF). When, for example, a sulfide-based solid electrolyte is contained in the positive electrode active material (details will be described later), if good moldability can be ensured in forming a molded body of the positive electrode active material without using a binder, it is not necessary to contain a binder in the positive electrode active material.

[0053] When a binder is required in the positive electrode active material, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when a sulfide-based solid electrolyte is contained in the positive electrode active material and moldability can be obtained without requiring a binder, the content thereof is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and most preferably 0% by mass (that is, no binder is contained).

[0054] The solid electrolyte to be contained in the positive electrode active material is not particularly limited as long as it has lithium ion conductivity. For example, sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, oxide-based solid electrolytes, etc. can be used.

[0055] Examples of the sulfide-based solid electrolyte include particles such as Li2S-P2S5, Li2S-SiS2, Li2S-P2S5-GeS2, and Li2S-B2S3-based glasses. In recent years, thio-LISICON type materials [Li 10 GeP2S 12, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 such as 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 (where M 1 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 (where 0.05 ≦ f ≦ 0.9, -3.0f + 1.8 ≦ g ≦ -3.0f + 5.7), Li 7-h PS 6-h Cl i Br j (where h = i + j, 0 < h ≦ 1.8, 0.1 ≦ i / j ≦ 10.0), etc.] can also be used.

[0056] Examples of the hydride-based solid electrolyte include LiBH4, a solid solution of LiBH4 and the following alkali metal compounds (for example, those with a molar ratio of LiBH4 to the alkali metal compound of 1:1 to 20:1). 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.

[0057] Examples of halide-based solid electrolytes include monoclinic LiAlCl4, defective spinel-type or layered-structured LiInBr4, monoclinic Li 6-3m Y m X6 (where 0 < m < 2 and X = Cl or Br), etc. In addition, for example, known ones described in International Publication No. 2020 / 070958 and International Publication No. 2020 / 070955 can be used.

[0058] Examples of oxide-based solid electrolytes include 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, etc.

[0059] 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. Particularly, argyrodite-type sulfide-based solid electrolytes with high lithium ion conductivity and high chemical stability are even more preferred.

[0060] Note that from the perspective of reducing grain boundary resistance, the average particle size of the solid electrolyte is preferably 0.1 μm or more, more preferably 0.2 μm or more. On the other hand, from the perspective of forming a sufficient contact interface between the active material and the solid electrolyte, it is preferably 10 μm or less, more preferably 5 μm or less.

[0061] The content of the solid electrolyte in the positive electrode mixture is preferably 4 to 40% by mass.

[0062] When using a current collector for the positive electrode, as the current collector, metal foils such as aluminum and stainless steel, punching metal, mesh, expanded metal, foamed metal; carbon sheet; etc. can be used.

[0063] The molded body of the positive electrode active material can be formed, for example, by compressing a positive electrode active material prepared by mixing a conductive assistant, a binder, a solid electrolyte, etc., which are added as necessary, with a positive electrode active material by pressure molding or the like.

[0064] In the case of a positive electrode having a current collector, it can be manufactured by bonding a molded body of the positive electrode active material formed by the above method to the current collector by pressure bonding or the like.

[0065] Alternatively, a positive electrode active material-containing composition may be prepared by mixing the above positive electrode active material and a solvent, and this may be applied onto a substrate such as a current collector or a solid electrolyte layer facing the positive electrode, dried, and then subjected to a pressing treatment to form a molded body of the positive electrode active material.

[0066] As the solvent of the positive electrode active material-containing composition, water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) can be used. When the positive electrode active material-containing composition also contains a solid electrolyte, it is preferable to select a solvent that hardly deteriorates the solid electrolyte. In particular, sulfide-based solid electrolytes and hydride-based solid electrolytes cause chemical reactions due to a small amount of moisture, so it is preferable to use an aprotic nonpolar solvent typified by hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene. In particular, it is more preferable to use an ultra-dehydrated solvent having a water content of 0.001% by mass (10 ppm) or less. In addition, fluorine-based solvents such as "Bartrel (registered trademark)" manufactured by Mitsui DuPont Fluorochemical Co., Ltd., "Zeorola (registered trademark)" manufactured by Nippon Zeon Co., Ltd., and "Novec (registered trademark)" manufactured by Sumitomo 3M Co., Ltd., as well as non-aqueous organic solvents such as dichloromethane and diethyl ether can also be used.

[0067] From the viewpoint of increasing the density of the molded body of the positive electrode active material, reducing the porosity, and further reducing the internal resistance of the positive electrode, it is more preferable that the molded body of the positive electrode active material is formed by compressing the positive electrode active material by pressure molding or the like.

[0068] The thickness of the molded body of the positive electrode active material (the thickness excluding the convex portion; in the case of an electrode having a current collector, the thickness of the molded body of the positive electrode active material per side of the current collector; the same applies hereinafter) is usually 50 μm or more, but from the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. Further, the thickness of the molded body of the positive electrode active material is usually 3000 μm or less, and from the viewpoint of increasing the output of the battery, it is preferably 500 μm or less.

[0069] In the case of a positive electrode manufactured by forming a positive electrode active material layer composed of a molded body of a positive electrode active material on a current collector using a positive electrode active material-containing composition containing a solvent, the thickness of the positive electrode active material 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.

[0070] (Negative electrode) The negative electrode of the all-solid-state battery has, for example, a molded body of a negative electrode active material-containing negative electrode active material, a lithium sheet, or a lithium alloy sheet.

[0071] When the negative electrode is a molded body of a negative electrode active material-containing negative electrode active material, examples thereof include a molded body (such as a pellet) formed by molding the negative electrode active material and a structure in which a layer (negative electrode active material layer) composed of a molded body of the negative electrode active material is formed on a current collector.

[0072] When the negative electrode has a molded body of a negative electrode active material, examples of the negative electrode active material include carbon materials such as graphite, simple substances containing elements such as Si and Sn, compounds (such as oxides), and alloys thereof. Further, lithium metal and lithium alloys (such as lithium-aluminum alloys and lithium-indium alloys) can also be used as the negative electrode active material.

[0073] The content of the negative electrode active material in the negative electrode active material is preferably 10 to 99% by mass.

[0074] A conductive aid can be contained in the negative electrode active material. Specific examples thereof include the same conductive aids as those exemplified above that can be contained in the positive electrode active material. The content of the conductive aid in the negative electrode active material is preferably 1 to 10% by mass.

[0075] In addition, a binder can be contained in the negative electrode active material. Specific examples thereof include the same binders as those exemplified above that can be contained in the positive electrode active material. Note that, for example, when a sulfide-based solid electrolyte is contained in the negative electrode active material (details will be described later), if good moldability can be ensured in forming a molded body of the negative electrode active material without using a binder, the negative electrode active material may not contain a binder.

[0076] In the case where a binder is required in the negative electrode active material, the content is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, in the case where the negative electrode active material contains a sulfide-based solid electrolyte and moldability can be obtained without requiring a binder, the content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (that is, no binder is contained).

[0077] In a negative electrode having a molded body of the negative electrode active material, a solid electrolyte is contained in the negative electrode active material. Specific examples thereof include the same solid electrolytes as those exemplified above that can be contained in the positive electrode active material. Among the exemplified solid electrolytes, a sulfide-based solid electrolyte is more preferably used because it has high lithium ion conductivity and a function of enhancing the moldability of the negative electrode active material.

[0078] The content of the solid electrolyte in the negative electrode active material is preferably 4 to 49% by mass.

[0079] When a current collector is used for a negative electrode having a molded body of the negative electrode active material, as the current collector, a copper or nickel foil, punching metal, net, expanded metal, foamed metal; carbon sheet; etc. can be used.

[0080] The molded body of the negative electrode mixture can be formed by compressing, such as by pressure molding, a negative electrode mixture prepared by mixing, for example, a negative electrode active material, and further, if necessary, a conductive auxiliary agent, a solid electrolyte, a binder, etc. In the case of a negative electrode composed only of the molded body of the negative electrode mixture, it can be manufactured by the above method.

[0081] In the case of a negative electrode having a current collector, it can be manufactured by bonding, such as by pressure bonding, the molded body of the negative electrode mixture formed by the above method to the current collector.

[0082] Also, in the case of a negative electrode having a current collector, a negative electrode mixture-containing composition (paste, slurry, etc.) in which a negative electrode active material, and further, if necessary, a conductive auxiliary agent, a solid electrolyte, a binder, etc. are dispersed in a solvent is applied to the current collector, dried, and then, if necessary, pressure molding such as calendering is performed to form a molded body (negative electrode mixture layer) of the negative electrode mixture on the surface of the current collector. It can also be manufactured by this method.

[0083] As the solvent of the negative electrode mixture-containing composition, water or an organic solvent such as N-methyl-2-pyrrolidone (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 less likely to deteriorate the solid electrolyte, and it is preferable to use the same various solvents as those exemplified above as the solvent for the positive electrode mixture-containing composition containing the solid electrolyte.

[0084] From the viewpoint of increasing the density of the molded body of the negative electrode mixture, reducing the porosity, and further reducing the internal resistance of the negative electrode, it is more preferable that the molded body of the negative electrode mixture is formed by compressing the negative electrode mixture by pressure molding or the like.

[0085] The thickness of the molded body of the negative electrode mixture (the thickness excluding the convex portions; in the case of an electrode having a current collector, the thickness of the molded body of the negative electrode mixture per side of the current collector; the same shall apply hereinafter) is usually 50 μm or more, but from the viewpoint of increasing the capacity of the battery, it is preferably 200 μm or more. Further, the thickness of the molded body of the negative electrode mixture is usually 3000 μm or less, and from the viewpoint of increasing the output of the battery, it is preferably 500 μm or less.

[0086] In the case of a negative electrode produced by forming a negative electrode mixture layer composed of a molded body 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.

[0087] In the case of a negative electrode having a lithium sheet or a lithium alloy sheet, those composed only of these sheets or those in which these sheets are bonded to a current collector are used.

[0088] Examples of alloy elements for the lithium alloy include aluminum, lead, bismuth, indium, gallium, etc., with aluminum and indium being preferred. The proportion of alloy elements in the lithium alloy (in the case of containing a plurality of types of alloy elements, their total proportion) is preferably 50 atomic% or less (in this case, the balance is lithium and unavoidable impurities).

[0089] Further, in the case of a negative electrode having a lithium alloy sheet, a laminate obtained by laminating, for example, by pressing a layer containing an alloy element for forming a lithium alloy on the surface of a lithium layer (a layer containing lithium) composed of a metal lithium foil or the like is used, and by bringing this laminate into contact with a solid electrolyte in the battery, a lithium alloy can be formed on the surface of the lithium layer to form a negative electrode. In the case of such a negative electrode, a laminate having a layer containing an alloy element on only one side of the lithium layer may be used, or a laminate having a layer containing an alloy element on both sides of the lithium layer may be used. The laminate can be formed, for example, by pressing a metal lithium foil and a foil composed of an alloy element.

[0090] In addition, a current collector can also be used when forming a lithium alloy in the battery to serve as the negative electrode. For example, a laminate having a lithium layer on one side of the negative electrode current collector and a layer containing an alloy element on the surface of the lithium layer opposite to the negative electrode current collector may be used. A laminate having lithium layers on both sides of the negative electrode current collector and a layer containing an alloy element on the surface of each lithium layer opposite to the negative electrode current collector may also be used. The negative electrode current collector and the lithium layer (metallic lithium foil) may be laminated by means of pressure bonding or the like.

[0091] For the layer containing the alloy element in the laminate for use as the negative electrode, for example, a foil made of these alloy elements can be used. The thickness of the layer containing the alloy element is preferably 1 μm or more, more preferably 3 μm or more, preferably 20 μm or less, and more preferably 12 μm or less.

[0092] For the lithium layer in the laminate for use as the negative electrode, for example, metallic lithium foil or the like can be used. The thickness of the lithium layer is preferably 0.1 to 1.5 mm. Also, the thickness of the sheet in the negative electrode having a sheet of lithium or a lithium alloy is preferably 0.1 to 1.5 mm.

[0093] In addition, when the negative electrode having a sheet of lithium or a lithium alloy has a current collector, the same current collectors as those exemplified above that can be used for the negative electrode having a molded body of a negative electrode mixture can be used for the current collector.

[0094] (Solid electrolyte layer) As the solid electrolyte that constitutes the solid electrolyte layer interposed between the positive electrode and the negative electrode, 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 those that can be used for the positive electrode can be used. However, in order to make the battery characteristics more excellent, it is desirable to contain a sulfide-based solid electrolyte, and it is more desirable to contain an argyrodite-type sulfide-based solid electrolyte. And it is further desirable to contain a sulfide-based solid electrolyte in both the positive electrode and the solid electrolyte layer, and it is further desirable to contain an argyrodite-type sulfide-based solid electrolyte.

[0095] The solid electrolyte layer may have a porous body such as a resin nonwoven fabric as a support.

[0096] The solid electrolyte layer can be formed by a method of compressing the solid electrolyte by pressure molding or the like; a method of applying a composition for forming a solid electrolyte layer prepared by dispersing the solid electrolyte in a solvent onto a base material, a positive electrode, or a negative electrode, drying it, and performing pressure molding such as pressing as necessary: etc. However, it is more preferable to adopt the method of compressing the above solid electrolyte.

[0097] It is desirable to select a solvent for the composition for forming the solid electrolyte layer that is difficult to deteriorate the solid electrolyte, and it is preferable to use the same solvents as the various solvents exemplified above as the solvents for the composition containing the positive electrode mixture containing the solid electrolyte.

[0098] The thickness of the solid electrolyte layer (the distance from the closest positive electrode to the negative electrode through the solid electrolyte layer) is preferably 100 to 400 μm.

[0099] (Electrode body) The positive electrode and the negative electrode are used in a battery in the form of an electrode body (laminated electrode body) laminated via a solid electrolyte layer or a separator.

[0100] When forming an electrode body having a solid electrolyte layer, it is preferable to perform pressure molding in a state where the positive electrode, the negative electrode, and the solid electrolyte layer are laminated, from the viewpoints of enhancing the mechanical strength of the electrode body and reducing the internal resistance.

[0101] (Outer package) For the outer package of the all-solid-state battery, for example, a battery container having an outer can and a sealing can is used. That is, an all-solid-state battery using such a battery container as the outer package becomes a flat battery.

[0102] In the battery industry, a flat battery with a diameter larger than its height is sometimes called a coin-shaped battery or a button-shaped battery. However, there is no clear difference between the coin-shaped battery and the button-shaped battery. When the all-solid-state battery of the present invention is a flat battery, it includes both coin-shaped batteries and button-shaped batteries.

[0103] When the outer package of the all-solid-state battery is a battery container having an outer can and a sealing can, as shown in FIG. 6, examples include those in which the outer can and the sealing can are caulked and sealed via a gasket, and those in which the outer can and the sealing can are adhered with resin.

[0104] For the outer can and the sealing can, those made of stainless steel can be used. In addition, as the material of the gasket, polypropylene, nylon, etc. can be used. When heat resistance is required in relation to the use of the battery, fluorine resins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), etc. with a melting point exceeding 240 °C can also be used. When the battery is applied to applications where heat resistance is required, a glass hermetic seal can also be used for its sealing.

[0105] In plan view, the shape of the exterior body composed of a battery container having an outer can and a sealing can may be circular, or may be a polygon such as a quadrilateral (square or rectangle). Further, in the case of a polygon, the corners thereof may be curved.

[0106] Furthermore, for the exterior body of the all-solid-state battery, a laminated film exterior body composed of a metal laminated film such as an aluminum laminated film can also be used.

[0107] The all-solid-state battery of the present invention can be applied to the same uses as conventionally known primary batteries and secondary batteries. However, since it has a solid electrolyte instead of an organic electrolyte, it has excellent heat resistance and can be preferably used for applications exposed to high temperatures.

Description of Reference Numerals

[0108] 1 Positive electrode 1a Convex portion of the positive electrode 1b Concave portion of the positive electrode 2 Negative electrode 2a Convex portion of the negative electrode 2b Concave portion of the negative electrode 3 Solid electrolyte layer 4 Outer can 5 Sealing can 6 Gasket 10, 11 Electrode body 100 All-solid-state battery

Claims

1. An all-solid-state battery having an electrode body in which a positive electrode containing a positive electrode mixture containing a solid electrolyte and a negative electrode are laminated via a solid electrolyte layer containing a solid electrolyte, wherein the positive electrode and the negative electrode are concavo-convex electrodes having a convex portion extending in the thickness direction of the electrode body and a concave portion adjacent to the convex portion and having a smaller thickness than the convex portion on the surface on the counter electrode side, in a cross section in the thickness direction of the electrode body, at least a part of the convex portions of the positive electrode is disposed at a position facing the concave portions of the negative electrode, and at least a part of the convex portions of the negative electrode is disposed at a position facing the concave portions of the positive electrode, the convex portion has a gradient such that the width becomes narrower toward the counter electrode side, and the gradient angle θ between the direction parallel to the thickness direction of the electrode body is 5 to 45°, characterized in that it is an all-solid-state battery.

2. The all-solid-state battery according to claim 1, wherein the total thickness h of the electrode body is 0.7 mm or more, and the height of the convex portion in the concavo-convex electrode is h / 3 (mm) or more.

3. The all-solid-state battery according to claim 1 or 2, wherein in a plan view of the concavo-convex electrode, the convex portions are formed continuously or discontinuously.

4. The all-solid-state battery according to claim 3, wherein in a plan view of the concavo-convex electrode, a plurality of the convex portions are formed concentrically or in parallel.

5. The all-solid-state battery according to any one of claims 1 to 4, wherein the positive electrode and the solid electrolyte layer contain a sulfide-based solid electrolyte.

6. The all-solid-state battery according to any one of claims 1 to 5, wherein the positive electrode has a molded body of a positive electrode mixture, the negative electrode has a molded body of a negative electrode mixture containing a negative electrode active material and a solid electrolyte, and the solid electrolyte layer has a molded body containing a solid electrolyte.

7. The all-solid-state battery according to claim 6, wherein the negative electrode contains a sulfide-based solid electrolyte.

8. The all-solid-state battery according to any one of claims 1 to 7, which is a flat battery provided with an exterior body composed of a flat battery container having an exterior can and a sealing can.

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