Separator for lithium-sulfur batteries and lithium-sulfur batteries containing the same

Abstract

This invention aims to develop a separator for lithium-sulfur batteries that overcomes the shortcomings of conventional technology, and in particular to provide a separator for lithium-sulfur batteries having a high energy density of 400 Wh / kg and 600 Wh / L or more, so that the lithium-sulfur battery is driven to approach the theoretical capacity of sulfur (S) as closely as possible, thereby improving the life characteristics of the lithium-sulfur battery. [Solution] The lithium-sulfur battery according to the present invention can achieve a high sulfur (S) discharge capacity even with a small amount of positive electrode material used. The lithium-sulfur battery according to the present invention can reduce the process cost for manufacturing the positive electrode by manufacturing the positive electrode using a dry manufacturing method in which positive electrode active material powder is pressed into a predetermined shape without the manufacturing process of a slurry for the electrode active material layer. The lithium-sulfur battery according to the present invention can eliminate variations in the reaction of the positive electrode manufactured by the dry manufacturing method by using a multilayer separator.

Claims

1. A lithium-sulfur battery having a high energy density of 400 Wh / kg or more, The aforementioned battery is Includes an electrode assembly and an electrolyte, The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the negative electrode and the positive electrode. The positive electrode includes a positive electrode active material layer, and the positive electrode active material layer includes a sulfur-based material containing sulfur and / or a sulfur compound. The separator includes a first layer having a porosity of 50 vol% or more. The first layer is placed on one surface of the separator, The thickness of the first layer is 50% or more compared to the thickness of the separator (100%). The separator includes a second layer having a porosity of 25 vol% or more and less than 50 vol%, and the second layer is disposed on the other surface of the separator which is the opposite surface to the one surface. A lithium sulfur battery in which the first layer of the separator faces the positive electrode active material layer.

2. The lithium sulfur battery according to claim 1, wherein the first layer has a porosity of 80 vol% or less.

3. The lithium sulfur battery according to claim 1, wherein the separator is composed of the first layer and the second layer, and the first layer and the second layer are stacked in this order.

4. The lithium sulfur battery according to claim 1, wherein the first layer is a monolayer or a multilayer comprising two or more unit layers, and if comprising two or more unit layers, each unit layer has a porosity of 50 vol% or more and 80 vol% or less.

5. The lithium sulfur battery according to claim 4, wherein, if the first layer is a multilayer, the unit layers are arranged such that the porosity increases toward one surface with respect to the thickness direction of the separator.

6. The lithium sulfur battery according to claim 1, wherein the second layer is a monolayer or a multilayer comprising two or more unit layers, and if the second layer comprises two or more unit layers, each unit layer has a porosity of less than 50 vol% and 25 vol% or more.

7. The lithium sulfur battery according to claim 6, wherein, if the second layer is a multilayer, the unit layers are arranged such that the porosity decreases toward the other surface with respect to the thickness direction of the separator.

8. The lithium sulfur battery according to claim 1, wherein the thickness of the separator is 20 μm to 500 μm.

9. The lithium sulfur battery according to claim 1, wherein the first layer comprises one or more selected from a porous polymer film, a porous nonwoven fabric containing a polymer material, glass fiber, and carbon paper.

10. The lithium sulfur battery according to claim 1, wherein the second layer comprises a porous polymer film, a porous nonwoven fabric containing a polymer material, or both.

11. The lithium sulfur battery according to claim 1, wherein the electrolyte comprises a lithium salt and an organic solvent, and the organic solvent comprises a first organic solvent containing a fluorine-based ether compound and a second organic solvent containing a glyme-based compound.

12. The lithium sulfur battery according to claim 1, wherein the sulfur-based material containing sulfur and / or a sulfur compound is included in the positive electrode active material layer in the form of a sulfur-carbon composite, and the sulfur-based material is present in an amount of 60 wt% or more relative to 100 wt% of the positive electrode active material layer.

13. The lithium sulfur battery according to claim 12, wherein the sulfur-carbon composite contains sulfur and carbon in a weight ratio of 60:40 to 80:

20.

14. The lithium sulfur battery according to claim 1, wherein the positive electrode includes a current collector and a positive electrode active material layer disposed on at least one surface of the current collector, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material is present in an amount of 99 wt% or more relative to 100 wt% of the positive electrode active material layer, the positive electrode active material contains an amount of 90 wt% or more of a sulfur-carbon composite relative to 100 wt% of the positive electrode active material layer, and the sulfur-carbon composite includes a sulfur-based material containing sulfur and / or a sulfur compound.

15. The lithium sulfur battery according to claim 1, wherein the negative electrode includes a lithium metal and / or a lithium alloy as a negative electrode active material, and the lithium alloy is an alloy of lithium and another metal.

16. The lithium sulfur battery according to claim 11, wherein the first and second organic solvents are present in an amount of 90 vol% or more relative to 100 vol% of the total organic solvent.

17. The lithium sulfur battery according to claim 11, wherein the first organic solvent comprises one or more of the following: 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), bis(fluoromethyl) ether, 2-fluoromethyl ether, bis(2,2,2-trifluoroethyl) ether, propyl 1,1,2,2-tetrafluoroethyl ether, isopropyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl isobutyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,2'H,3H-decafluorodipropyl ether, and 1H,1H,2'H-perfluorodipropyl ether.

18. The lithium sulfur battery according to claim 11, wherein the second organic solvent is fluorine-free and contains one or more of the following: dimethoxyethane, diethoxyethane, methoxyethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, and polyethylene glycol methyl ethyl ether.

19. The lithium sulfur battery according to claim 11, wherein the electrolyte comprises lithium-bis(trifluoromethanesulfonyl)imide, dimethoxyethane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

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