CN-115668572-B - Electrolyte for lithium-sulfur battery and lithium-sulfur battery comprising same

CN115668572BCN 115668572 BCN115668572 BCN 115668572BCN-115668572-B

Abstract

The present invention relates to an electrolyte for a lithium sulfur battery including a nonaqueous organic solvent including specific three compounds, and a lithium sulfur battery including the same.

Inventors

LI ZAIJI
HAN CHENGXUN
Jin Yitai
Pu Chengxiao

Assignees

株式会社LG新能源

Dates

Publication Date: 20260512
Application Date: 20211115
Priority Date: 20201123

Claims (11)

1. An electrolyte for a lithium sulfur battery, the electrolyte comprising: Lithium salt, and A non-aqueous organic solvent, which is not an organic solvent, Wherein the nonaqueous organic solvent comprises: a first solvent comprising a conjugated cyclic ether compound; the second solvent is used for the preparation of the second solvent, the second solvent comprises dimethoxyethane; and A third solvent comprising a glycol diether compound represented by the following chemical formula 1: [ chemical formula 1] R 1 (CH 2 CH 2 O) n R 2 In the chemical formula 1, the chemical formula is shown in the drawing, R 1 and R 2 are identical or different from one another and are each independently an alkyl or alkoxy radical having from 1 to 10 carbon atoms, and N is an integer of 2 to 4, Wherein, based on 100% by volume of the nonaqueous organic solvent comprising the first solvent, the second solvent and the third solvent, The content of the first solvent is 20 to 49% by volume; The second solvent is contained in an amount of 50 to 79% by volume, and The content of the third solvent is greater than or equal to 1% by volume and less than 25% by volume.
2. The electrolyte for lithium-sulfur battery according to claim 1, wherein the conjugated cyclic ether compound comprises a 4-to 15-membered heterocyclic compound containing an oxygen atom or a sulfur atom while containing two or more double bonds.
3. The electrolyte for lithium sulfur battery according to claim 1, wherein the conjugated cyclic ether compound comprises one or more selected from the group consisting of furan compounds and thiophene compounds.
4. The electrolyte for lithium-sulfur battery according to claim 3, wherein the furan-based compound comprises one or more selected from the group consisting of furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2, 3-dimethylfuran, 2, 4-dimethylfuran, 2, 5-dimethylfuran, pyran, 2-methylpyrane, 3-methylpyrane, 4-methylpyrane, benzofuran and 2- (2-nitrovinyl) furan.
5. The electrolyte for lithium sulfur battery according to claim 3, wherein the thiophene-based compound comprises one or more selected from the group consisting of thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2, 3-dimethylthiophene, 2, 4-dimethylthiophene and 2, 5-dimethylthiophene.
6. The electrolyte for lithium sulfur battery according to claim 1, wherein the glycol diether compound comprises one or more selected from the group consisting of diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol dimethyl ether and tetraethylene glycol methyl ethyl ether.
7. The electrolyte for a lithium sulfur battery according to claim 1, wherein in chemical formula 1, R 1 and R 2 are the same or different from each other and are each independently an alkyl group or an alkoxy group having 1 to 5 carbon atoms.
8. The electrolyte for lithium sulfur battery according to claim 1, wherein the glycol diether compound comprises one or more selected from the group consisting of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.
9. A lithium sulfur battery, the lithium sulfur battery comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material, and The electrolyte of claim 1.
10. The lithium sulfur battery of claim 9, wherein the positive electrode active material comprises one or more selected from the group consisting of: An inorganic sulfur-containing compound such as an inorganic sulfur, Li 2 S n , where n≥1), A disulfide compound, which is a compound having a disulfide moiety, An organic sulfur compound, and Carbon-sulfur polymers (C 2 S x ) n , where x=2.5 to 50, n≥2).
11. The lithium sulfur battery of claim 9, wherein the negative active material comprises one or more selected from lithium metal and lithium alloy.

Description

Electrolyte for lithium-sulfur battery and lithium-sulfur battery comprising same Technical Field The invention provides an electrolyte for a lithium-sulfur battery and a lithium-sulfur battery comprising the same. The present application claims priority based on korean patent application No. 10-2020-0157907, filed 11/23 in 2020, the entire contents of which are incorporated herein by reference. Background As the application range of lithium secondary batteries is extended not only to portable electronic devices and communication devices but also to Electric Vehicles (EVs) and power storage systems (ESS), the demand for higher capacities of lithium secondary batteries used as their power sources has grown. Among various lithium secondary batteries, lithium sulfur batteries are battery systems using a sulfur-based material containing a sulfur-sulfur bond as a positive electrode active material and using lithium metal, a carbon-based material having intercalation/deintercalation of lithium ions, or silicon, tin, or the like alloyed with lithium as a negative electrode active material. Sulfur, which is a main material of a positive electrode active material in a lithium-sulfur battery, has advantages of low atomic weight, easy supply due to abundant resources, low price, non-toxicity, and environmental friendliness. Further, the lithium-sulfur battery has a theoretical discharge capacity of up to 1675mAh/g obtained from the conversion reaction (S 8+16Li++16e-→8Li2 S) of lithium ions in the positive electrode with sulfur, and when lithium metal (theoretical capacity: 3860 mAh/g) is used as the negative electrode, the theoretical energy density is 2600Wh/kg. This is a very high value compared with the theoretical energy densities of other battery systems currently under study (Ni-MH battery: 450Wh/kg; li-FeS battery: 480Wh/kg; li-MnO 2 battery: 1000Wh/kg; na-S battery: 800 Wh/kg) and lithium ion battery (250 Wh/kg), and therefore, among the secondary batteries that have been developed so far, lithium-sulfur batteries have been attracting attention as high-capacity, environmentally friendly and low-cost lithium secondary batteries, and various studies have been made thereon as next-generation battery systems. In such a lithium-sulfur battery, sulfur accepts electrons upon discharge to initiate a reduction reaction in the positive electrode, specifically, sulfur as a positive electrode active material is finally reduced to lithium sulfide (Li 2 S) through lithium polysulfide (Li 2Sx, x=8, 6, 4, 2). However, lithium sulfide, which is a final product of a reduction reaction (discharge) of sulfur, is a material having low conductivity and is deposited on an electrode to passivate the surface of the electrode on which an electrochemical reaction is performed, and since electrochemical reactivity of the electrode is lowered due to this, a problem that theoretical discharge capacity cannot be completely achieved occurs in actual operation. In addition, since the deposited lithium sulfide no longer participates in the electrochemical reaction, loss of the positive electrode active material occurs, which accelerates the decrease in discharge capacity of the battery. Due to the problems described above, capacity and charge and discharge efficiency performance in lithium sulfur batteries rapidly decrease as cycles proceed, which also shortens the life, and has not been successfully commercialized because it is difficult to secure sufficient performance and operation stability. Most of the research to solve these problems has focused on the modification of the positive electrode. In particular, as one of methods of improving the conductivity of an electrode, attempts have been made to minimize the decrease in conductivity of an electrode in which lithium sulfide accumulates by adding a conductive material made of a carbon material, or to control the generation and accumulation of intermediate products and lithium sulfide using a sulfur carrier having a nanostructure. However, most of the technologies are difficult to be commercially used, and the effect of improving capacity performance is insufficient. Accordingly, there is still a need to develop a lithium-sulfur battery capable of obtaining excellent capacity performance by suppressing passivation of an electrode caused by lithium sulfide and a resulting decrease in electrochemical reactivity of the electrode. Disclosure of Invention [ Technical problem ] As a result of extensive studies in view of the above-described circumstances, the inventors of the present invention have found that when a conjugated cyclic ether compound, dimethoxyethane and a glycol diether compound are contained as a nonaqueous organic solvent in an electrolyte for a lithium-sulfur battery, the discharge capacity of the battery can be improved by preventing electrode passivation due to lithium sulfide, and have completed the present invention. Accordingly, the present invention aims to provide an e