Lithium-sulfur solid-state battery

Abstract

To provide a lithium-sulfur solid-state battery that can achieve high voltage and high energy density.SOLUTION: A lithium-sulfur solid-state battery includes: a housing having an internal space formed by a first pole which is formed into a cover shape, and a second pole which is insulated from and fixed to the first pole and is formed into a cover shape; a sulfur positive electrode that is provided on a first pole side, in the internal space; a lithium negative electrode that is provided on a second pole side in the internal space, and is arranged so as to face the sulfur positive electrode; a solid electrolyte that is formed so as to partition the internal space, and is provided between the sulfur positive electrode and the lithium negative electrode; an elastic body that is provided at least on the first pole side or the second pole side, and has electroconductivity; a first tabular body having electroconductivity; and a pressing portion that presses the sulfur positive electrode, the solid electrolyte, and the lithium negative electrode, by the first tabular body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lithium-sulfur solid-state battery with improved electrical density. [Background technology]

[0002] In recent years, lithium-ion secondary batteries have been used as power sources for electronic devices and electric vehicles. Development of secondary batteries with even higher voltages and higher energy densities is desired for next-generation electronic devices and electric vehicles. The applicant has proposed next-generation lithium-sulfur solid-state batteries that achieve high voltages and high energy densities in, for example, Patent Documents 1 to 3.

[0003] Lithium-sulfur solid-state batteries are easier to handle than lithium-ion batteries, which are prone to leaks and fires, because their solid electrolyte is non-flammable. Furthermore, lithium-sulfur solid-state batteries are less likely to produce reaction products during charging and discharging, causing little degradation, and have a higher storage capacity than lithium-ion batteries. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-181633 [Patent Document 2] Patent No. 6313491 [Patent Document 3] Patent No. 6385486 Summary of the Invention [Problem to be solved by the invention]

[0005] The basic principles of lithium-sulfur solid state batteries are proposed in Patent Documents 1 to 3. The inventors have been diligently researching specific configurations of lithium-sulfur solid state batteries with a view to mass production of lithium-sulfur solid state batteries.

[0006] An object of the present invention is to provide a lithium-sulfur solid state battery that can achieve high voltage and high energy density. [Means for solving the problem]

[0007] The lithium-sulfur solid state battery according to the present invention comprises: a housing having an internal space formed by a first electrode formed in a lid shape and a second electrode formed in a lid shape and insulated and fixed to the first electrode; a sulfur positive electrode provided on the first electrode side in the internal space; a lithium negative electrode provided on the second electrode side in the internal space and arranged opposite the sulfur positive electrode; a solid electrolyte formed so as to separate the internal space and provided between the sulfur positive electrode and the lithium negative electrode; a conductive elastic body provided on at least the first electrode side or the second electrode side; and a pressing part having a conductive first plate-like body and pressing the sulfur positive electrode, the solid electrolyte, and the lithium negative electrode with the first plate-like body.

[0008] According to the present invention, a solid-state battery having high voltage and high energy density can be realized. According to the present invention, a pressing portion that presses the sulfur positive electrode, the solid electrolyte, and the lithium negative electrode between the first electrode and the second electrode is provided, thereby reliably ensuring electrical conductivity.

[0009] In one aspect of the present invention, the solid electrolyte divides the internal space into a first space containing the sulfur positive electrode and a second space containing the lithium negative electrode, and a separator is provided between the lithium negative electrode and the solid electrolyte in the second space.

[0010] According to the present invention, the sulfur positive electrode and the lithium negative electrode can be physically separated while ensuring ionic conductivity.

[0011] In one aspect of the present invention, the device further includes a seal member that ensures airtightness between the first space and the second space.

[0012] According to the present invention, the sealing member ensures airtightness between the first space and the second space, thereby preventing the electrolyte, such as an ionic liquid, contained in the positive electrode material of the sulfur positive electrode on the first space side from flowing into the second space, thereby maintaining battery performance.

[0013] In one aspect of the present invention, the sealing member seals between the solid electrolyte and the second electrode in the second space.

[0014] According to the present invention, it is possible to prevent the electrolyte in the first space and the electrolyte in the second space from mixing with each other.

[0015] In addition, one aspect of the present invention includes a conductive second plate-like body provided between the second electrode and the lithium negative electrode, and the sealing member seals between the second plate-like body and the solid electrolyte.

[0016] According to the present invention, the sealing member seals the gap between the second plate-shaped body and the solid electrolyte, thereby reliably separating the second space containing the lithium negative electrode from the first space containing the sulfur positive electrode.

[0017] In addition, one aspect of the present invention includes a semi-solid substance applied between the sealing member and the second plate-like body and between the sealing member and the solid electrolyte to improve adhesion.

[0018] According to the present invention, a semi-solid substance is applied between the sealing member and the second plate-like body and between the sealing member and the solid electrolyte, thereby improving the sealing performance of the sealing member.

[0019] In one aspect of the present invention, the pressing portion includes a first pressing portion provided between the first plate-like body and the first pole, and a second pressing portion provided between the second plate-like body and the second pole.

[0020] According to the present invention, since the pressing portions are provided on the first electrode side and the second electrode side, electrical conductivity between the sulfur positive electrode, the solid electrolyte, and the lithium negative electrode can be reliably ensured. [Effects of the Invention]

[0021] It is possible to realize high-voltage, high-energy density lithium-sulfur solid-state batteries. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view showing the configuration of a lithium-sulfur solid state battery according to the present invention. [Figure 2] FIG. 3 is a cross-sectional view showing the configuration of a sealing member. [Figure 3] FIG. 10 is a cross-sectional view showing the configuration of a lithium-sulfur solid state battery according to a modified example. [Figure 4] FIG. 10 is a diagram comparing the performance of a lithium-sulfur solid state battery and a lithium-sulfur solid state battery according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, the lithium-sulfur solid state battery according to the present invention will be described with reference to the drawings.

[0024] As shown in Fig. 1, the lithium-sulfur solid state battery 1 is formed, for example, as a circular button battery. The lithium-sulfur solid state battery 1 is formed, for example, with a diameter of about 20 mm and a thickness of about 3.2 mm. The size of the lithium-sulfur solid state battery 1 is one example, and the battery may be formed into any size or shape other than a circle depending on the intended purpose of the battery.

[0025] In the lithium-sulfur solid state battery 1, a button-type housing 2 is formed by a first electrode 3 formed in a lid shape and a second electrode 4 formed in a lid shape and insulated and fixed to the first electrode 3. An internal space S is formed inside the housing 2. The lithium-sulfur solid state battery 1 is a secondary battery in which a solid is used as the electrolyte filled in the internal space S. Hereinafter, the surface of a plate-like member constituting the lithium-sulfur solid state battery 1 as viewed in the +z direction of the figure will be referred to as the bottom side (one side), and the surface as viewed in the -z direction will be referred to as the top side (other side), etc.

[0026] The first electrode 3 is made of a conductive material such as metal. The first electrode 3 is formed, for example, in the shape of a circular lid. The first electrode 3 includes a disk-shaped electrode terminal 3A and a side wall 3B extending around the electrode terminal 3A.

[0027] The second electrode 4 is formed of, for example, a conductive material such as metal, similar to the first electrode 3. The second electrode 4 is formed, for example, in the shape of a circular lid. The second electrode 4 includes a disk-shaped electrode terminal 4A and a side wall 4B extending around the electrode terminal 4A. The outer diameter of the side wall 4B is formed, for example, to be slightly smaller than the outer shape of the side wall 3B. The side wall 4B is inserted inside the side wall 3B.

[0028] A gasket G made of, for example, resin is press-fitted between the outer wall of side wall 4B and the inner wall of side wall 3B. The second electrode 4 is fixed to the first electrode 3 via the gasket G in a non-contact, insulated manner. A sealed internal space S is formed between the first electrode 3 and the second electrode 4 when they are fixed together.

[0029] In the internal space S, a sulfur positive electrode 5 is provided on the first electrode 3 side. In the internal space S, a lithium negative electrode 6 is provided on the second electrode 4 side. A solid electrolyte 7 is provided between the sulfur positive electrode 5 and the lithium negative electrode 6 so as to separate the internal space S. The solid electrolyte 7 separates the internal space S into a first space S1 containing the sulfur positive electrode 5 and a second space S2 containing the lithium negative electrode 6.

[0030] In the first space S1, a pressing portion 8 is provided between the first electrode 3 and the sulfur positive electrode 5. The pressing portion 8 has, for example, a conductive elastic body 9 provided on the first electrode 3 side and a conductive first plate-like body 10. In the first space S1, one surface of the elastic body 9 contacts the inner wall of the electrode terminal portion 3A, providing electrical continuity. The other surface of the elastic body 9 contacts one surface of the first plate-like body 10, providing electrical continuity.

[0031] The elastic body 9 is made of a conductive material such as metal. The elastic body 9 is, for example, a wave washer in which a washer formed in a circular shape is deformed into a wave shape when viewed in a cross-sectional direction. The elastic body 9 is a leaf spring that elastically deforms so that its thickness is reduced when viewed in a cross-sectional direction when a compressive force is applied to both sides. The wave washer used for the elastic body 9 is just one example, and other members such as a coil spring may be used as long as they are conductive and elastically deform so that their thickness is reduced when viewed in a cross-sectional direction when a compressive force is applied to one side and the other side.

[0032] The elastic body 9 does not necessarily have to be made of a conductive material as long as the first electrode 3 and the first plate-like body 10 are electrically connected by a wire, a metal plate, etc., and may be made of a resin, a liquid, a semi-solid substance, a gas, a composite of the above materials, etc. The elastic body 9 may be made of not only one member, but also a plurality of members arranged side by side.

[0033] The first plate 10 is formed into a circular plate shape made of, for example, a conductive material such as metal. The diameter of the first plate 10 is formed to be, for example, slightly smaller than the inner diameter of the side wall portion 4B of the second electrode 4. The first plate 10 is formed to be, for example, 15 mm in diameter and 0.5 mm in thickness. The size of the first plate 10 is an example, and the first plate 10 may be formed into any size or shape other than a circle depending on the purpose of the battery to which it is applied. The other side of the first plate 10 is in contact with one side of the sulfur positive electrode 5 and is electrically conductive.

[0034] With the above-described configuration, the pressing portion 8 presses one surface of the sulfur positive electrode 5 with the first plate-like body 10 in the first space S1. The pressing portion 8 generates a pressing force by the first plate-like body 10 on the sulfur positive electrode 5, the solid electrolyte 7, and the lithium negative electrode 6 in the internal space S in the direction from the first electrode 3 to the second electrode 4, thereby increasing the contact area between the surfaces of the respective components and reliably ensuring electrical conductivity. The pressing portion 8 may be provided between the second electrode and the lithium negative electrode 6. That is, the pressing portion 8 only needs to be provided on at least the first electrode side or the second electrode side.

[0035] The sulfur positive electrode 5 is formed, for example, so that its diameter on the first space S1 side fits within the inner diameter 4A of the second electrode 4. The sulfur positive electrode 5 is formed, for example, to have a diameter of 8 mm and a thickness of 0.2 mm. The size of the sulfur positive electrode 5 is an example, and the sulfur positive electrode 5 may be formed into any size and shape other than a circle depending on the purpose of the battery to which it is applied.

[0036] The sulfur positive electrode 5 may have the configurations described in, for example, Patent Documents 1 to 3. The sulfur positive electrode 5 includes a conductive sheet 5A having numerous voids formed therein and a positive electrode material 5B contained in the conductive sheet 5A. The conductive sheet 5A functions as a positive electrode current collector. The conductive sheet 5A is formed, for example, from carbon cloth. The positive electrode material 5B is contained in the voids of the conductive sheet 5A. The positive electrode material 5B is formed, for example, from sulfur, a conductive additive, a binder, and an ionic liquid. The components of the positive electrode material 5B may be changed as appropriate. The voids in the conductive sheet 5A are open to the material surface. The other surface of the sulfur positive electrode 5 is in contact with one surface of the solid electrolyte 7 and is electrically conductive.

[0037] The solid electrolyte 7 may have the configurations described in Patent Documents 1 to 3, for example. For example, lithium composite oxides or lithium-containing sulfides known in lithium ion batteries may be used for the solid electrolyte 7. It is more preferable to use a lithium composite oxide for the solid electrolyte 7. For example, a lithium composite oxide such as lithium-lanthanum-zirconium composite oxide (hereinafter referred to as "LLZ") is preferable.

[0038] The basic composition of LLZ is Li7La3Zr2O 12 LLZ is a composite oxide of lithium, lanthanum, and zirconium, with the following structure: LLZ may contain one or more elements selected from aluminum, tantalum, niobium, and bismuth, as necessary. The components of the solid electrolyte 7 may be changed as appropriate. The solid electrolyte 7 is formed in a disk shape with a diameter slightly smaller than the inner diameter of the side wall portion 4B of the second electrode 4. The solid electrolyte 7 is formed, for example, with a diameter of 15 mm and a thickness of 0.5 mm to 1 mm. The size of the solid electrolyte 7 is an example, and the solid electrolyte 7 may be formed in any size or shape other than a circle depending on the purpose of the battery to which it is applied.

[0039] A gasket G is filled between the outer periphery of the solid electrolyte 7 and the inner wall of the side wall portion 4B, separating the first space S1 from the second space S2. The other side of the solid electrolyte 7 forms the second space S2 and faces one side of the lithium negative electrode 6.

[0040] In the second space S2, a separator 11 may be provided between the lithium negative electrode 6 and the solid electrolyte 7. The separator 11 is a film-like member used in existing batteries. The separator 11 is a member that physically separates the sulfur positive electrode 5 and the lithium negative electrode 6 while ensuring ionic conductivity between the sulfur positive electrode 5 and the lithium negative electrode 6. The separator 11 is formed, for example, with a diameter of 10 mm and a thickness of 0.015 mm. The size of the separator 11 is an example, and the separator 11 may be formed into any size and shape other than a circle depending on the purpose of the battery to which it is applied. The separator 11 is not necessarily provided.

[0041] The lithium negative electrode 6 is disposed opposite the sulfur positive electrode 5 with a solid electrolyte 7 and a separator 11 interposed therebetween. The lithium negative electrode 6 is electrically connected to the solid electrolyte 7 via the separator 11. The lithium negative electrode 6 may have the configurations described in Patent Documents 1 to 3, for example. The lithium negative electrode 6 is formed of, for example, lithium metal. The components of the lithium negative electrode 6 may be changed as appropriate.

[0042] The lithium negative electrode 6 is formed, for example, so that its diameter fits within the inner diameter of the sealing member 15 described below. The lithium negative electrode 6 is formed, for example, so that its diameter is 10 mm and its thickness is 0.6 mm. The size of the lithium negative electrode 6 is an example, and the lithium negative electrode may be formed into any size or shape other than a circle depending on the purpose of the battery to which it is applied. A conductive second plate-like body 12 is provided between the lithium negative electrode 6 and the second electrode 4.

[0043] The second plate-like body 12 is disposed, for example, inside the electrode terminal portion 4A in the second space S2. The second plate-like body 12 has, for example, the same configuration as the first plate-like body 10. The second plate-like body 12 is formed in a circular plate shape with a diameter slightly smaller than the diameter of the electrode terminal portion 4A. The second plate-like body 12 is formed, for example, with a diameter of 15 mm and a thickness of 0.5 mm. The size of the second plate-like body 12 is an example, and the second plate-like body 12 may be formed in any size or shape other than a circle depending on the purpose of the battery to which it is applied.

[0044] The other surface of the second plate 12 is in contact with the electrode terminal 4A and is electrically connected to it. One surface of the second plate 12 is in contact with one surface of the lithium negative electrode 6 and is electrically connected to it. The second plate 12 may be formed integrally with the second electrode 4. The second plate 12 may be omitted, or the other surface of the lithium negative electrode 6 may be in direct contact with one surface of the electrode terminal 4A.

[0045] In the second space S2, a seal member 15 is provided to ensure the sealing between the first space S1 and the second space S2. The seal member 15 is, for example, an O-ring formed in a circular ring shape. The seal member 15 is, for example, made of an elastic material such as fluororubber.

[0046] The sealing member 15 seals between the solid electrolyte 7 and the second electrode 4 in the second space S2, preventing the electrolyte in the first space S1 from mixing with the electrolyte in the second space S2. The sealing member 15 seals between the second plate-shaped body 12 and the solid electrolyte 7.

[0047] 2, the sealing member 15 is in contact with the outer periphery of one surface of the second plate-like body 12. The sealing member 15 is in contact with the outer periphery of the other surface of the solid electrolyte 7. The lithium negative electrode 6 and the separator 11 are disposed inside the sealing member 15.

[0048] Between sealing member 15 and second plate-like body 12 and between sealing member 15 and solid electrolyte 7, coating layers 16, 17 are formed, for example, by applying a semi-solid substance such as grease to improve adhesion. In the drawings, coating layers 16, 17 are exaggerated to appear thick, but they need only be applied to an extent that ensures airtightness between sealing member 15 and second plate-like body 12 and between sealing member 15 and solid electrolyte 7. Instead of grease, coating layers 16, 17 may be strip-shaped members made of an elastic material such as sealing tape.

[0049] As shown in FIG. 2(2), when the sulfur positive electrode 5, the solid electrolyte 7, the separator 11, and the lithium negative electrode 6 are pressed toward the second plate-like body 12 by the pressing portion 8, the sealing member 15 is compressed and deformed in the vertical direction (z direction). The sealing member 15 adheres to the second plate-like body 12 and the solid electrolyte 7 via the compressed coating layers 16 and 17. The coating layers 16 and 17 penetrate into gaps formed by the fine unevenness on the surface of the second plate-like body 12 and the surface of the solid electrolyte 7, improving the adhesion with the sealing member 15.

[0050] Furthermore, the sealing member 15 bulges and deforms in the horizontal direction around the z-axis and comes into close contact with the side wall portion 4B, thereby separating the first space S1 from the second space S2 and preventing the ionic liquid contained in the positive electrode material 5B of the sulfur positive electrode 5 from entering the second space S2.

[0051] As described above, in the lithium-sulfur solid state battery 1, the pressing portion 8 applies a pressing force to the sulfur positive electrode 5, the solid electrolyte 7, and the lithium negative electrode 6 in the vertical direction (z direction) in the internal space S of the casing 2, thereby ensuring electrical continuity, and also ensuring electrical continuity between the first electrode 3 and the sulfur positive electrode 5, and between the second electrode 4 and the lithium negative electrode 6. In the lithium-sulfur solid state battery 1, even if the volume of the sulfur positive electrode 5 changes during charging and discharging, the pressing portion 8 applies a pressing force, so that the pressing portion 8 follows the volume change of the sulfur positive electrode 5 and ensures electrical continuity.

[0052] According to the lithium-sulfur solid state battery 1, the pressing portion 8 deforms the sealing member 15, reliably separating the first space S1 from the second space S2, and preventing the ionic liquid contained in the positive electrode material 5B of the sulfur positive electrode 5 from entering the second space S2.

[0053] [Variations] The following describes modified examples of the lithium-sulfur solid state battery 1. In the following description, the same components as those in the above embodiment are designated by the same names and reference numerals, and overlapping descriptions will be omitted as appropriate.

[0054] 3, in the lithium-sulfur solid state battery 1A according to the modified example, the pressing portion includes a first pressing portion 8A provided between the first plate 10 and the first electrode 3, and a second pressing portion 8B provided between the second plate 12 and the second electrode 4. The first pressing portion 8A includes an elastic body 9 arranged on the other side of the electrode terminal 3A, and the first plate 10 arranged on the other side of the elastic body 9. The second pressing portion 8B includes an elastic body 9 arranged on one side of the electrode terminal 4A, and a second plate 12 arranged on one side of the elastic body 9.

[0055] In the lithium-sulfur solid state battery 1A, the first pressing portion 8A and the second pressing portion 8B apply pressing force to the sulfur positive electrode 5, the solid electrolyte 7, and the lithium negative electrode 6 in the vertical direction (z direction), thereby ensuring electrical continuity, and also ensuring electrical continuity between the first electrode 3 and the sulfur positive electrode 5, and between the lithium negative electrode 6 and the second electrode 4.

[0056] As shown in FIG. 4, the lithium-sulfur solid state battery 1A according to the modified example can reduce the decrease in capacity with respect to the number of charge / discharge cycles compared to the lithium-sulfur solid state battery 1.

[0057] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope and spirit of the invention, as well as the scope of the invention described in the claims and their equivalents. For example, although a button-type secondary battery has been exemplified as the lithium-sulfur solid state battery, the present invention may also be applied to secondary batteries and primary batteries of other shapes. A stacked battery may be constructed by stacking the internal structures of the lithium-sulfur solid state batteries according to the embodiments. [Explanation of symbols]

[0058] DESCRIPTION OF SYMBOLS 1, 1A...Lithium-sulfur solid state battery, 2...Housing, 3...First electrode, 3A...Electrode terminal portion, 3B...Side wall portion, 4...Second electrode, 4A...Electrode terminal portion, 4B...Side wall portion, 5...Sulfur positive electrode, 5A...Conductive sheet, 5B...Cathode material, 6...Lithium negative electrode, 7...Solid electrolyte, 8...Pressing portion, 8A...First pressing portion, 8B...Second pressing portion, 9...Elastic body, 10...First plate-like body, 11...Separator, 12...Second plate-like body, 15...Sealing member, 16...Coating layer, 17...Coating layer, G...Gasket, S...Internal space, S1...First space, S2...Second space

Claims

1. a housing having an internal space formed by a first electrode formed in a lid shape and a second electrode formed in a lid shape and fixed to and insulated from the first electrode; a sulfur positive electrode provided on the first electrode side in the internal space; a lithium negative electrode provided on a second electrode side in the internal space and facing the sulfur positive electrode; a solid electrolyte provided between the sulfur positive electrode and the lithium negative electrode so as to partition the internal space; a pressing portion having a conductive elastic body provided at least on the first electrode side or the second electrode side, and a conductive first plate-like body, and pressing the sulfur positive electrode, the solid electrolyte, and the lithium negative electrode with the first plate-like body; a separator; the solid electrolyte divides the internal space into a first space including the sulfur positive electrode and a second space including the lithium negative electrode, The separator is provided between the lithium negative electrode and the solid electrolyte in the second space. Lithium-sulfur solid-state battery.

2. a seal member for ensuring hermetic sealing between the first space and the second space; The lithium-sulfur solid state battery of claim 1.

3. the sealing member seals between the solid electrolyte and the second electrode in the second space. The lithium-sulfur solid state battery according to claim 2.

4. a second plate-like body having conductivity and provided between the second electrode and the lithium negative electrode; the sealing member seals between the second plate-shaped body and the solid electrolyte. The lithium-sulfur solid state battery according to claim 3.

5. a semi-solid substance for improving adhesion is applied between the sealing member and the second plate-like body and between the sealing member and the solid electrolyte; The lithium-sulfur solid state battery according to claim 4.

6. The pressing portion includes a first pressing portion provided between the first plate-like body and the first pole, and a second pressing portion provided between the second plate-like body and the second pole. The lithium-sulfur solid state battery according to claim 4 or 5.

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