Electrolyte liquid, method for preparing the same, and lithium sulfur battery using the same

Patent metadata

Field	Value
Publication number	US-10665898-B2
Application number	US-201615763440-A
Country	US
Kind code	B2
Filing date	Sep 9, 2016
Priority date	Sep 25, 2015
Publication date	May 26, 2020
Grant date	May 26, 2020

Abstract

The present disclosure provides an electrolyte liquid of a lithium sulfur battery comprising a carbonate ester organic solvent, a lithium salt, and a flame-retardant cosolvent, the flame-retardant cosolvent being a phosphazene compound, wherein a mass percentage of the flame-retardant cosolvent is 20% to 50%, a concentration of the lithium salt is 0.8 mol/L to 1.2 mol/L. The present disclosure also provides a lithium sulfur battery and a method for preparing the electrolyte liquid.

First claim

What is claimed is:

1. An electrolyte liquid of a lithium sulfur battery comprising a carbonate ester organic solvent, a lithium salt, and a flame-retardant cosolvent, the flame-retardant cosolvent being a phosphazene compound having a molecular structure represented by one of formulas (1) to (3), wherein R 1 and R 2 are hydrocarbon groups, and only a hydrogen atom is replaced by a fluorine atom, R 1 and R 2 have different carbon chain lengths, and carbon chains of R 1 and R 2 have a difference of 3 or more in carbon atom number,

2. The electrolyte liquid of claim 1 , wherein a mass percentage of the flame-retardant cosolvent is 20% to 50%.

3. The electrolyte liquid of claim 1 , wherein a concentration of the lithium salt is 0.8 mol/L to 1.2 mol/L.

4. The electrolyte liquid of claim 1 , wherein R 1 and R 2 respectively have 1 to 8 carbon atoms.

5. The electrolyte liquid of claim 1 , wherein in the phosphazene compound, a ratio between fluorine atoms and hydrogen atoms is greater than 3.

6. The electrolyte liquid of claim 1 , wherein the carbonate ester organic solvent is two or three selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, and ethyl propionate.

7. The electrolyte liquid of claim 1 , wherein the lithium salt is selected from the group consisting of LiCl, LiPF 6 , LiBF 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiAsF 6 , LiClO 4 , LiBOB, LiN(CF 3 SO 2 ) 2 and combinations thereof.

8. The electrolyte liquid of claim 1 , wherein a number of carbon atoms of the carbon chain of the R 1 is 5 to 8, and a number of carbon atoms of the carbon chain of R2 is 1 to 4.

9. A lithium sulfur battery comprising a cathode electrode, an anode electrode, a separator, and an electrolyte liquid,
wherein the cathode electrode and the anode electrode are spaced, the separator is disposed between the cathode electrode and the anode electrode, and the electrolyte liquid infiltrates the cathode electrode, the anode electrode, and the separator;
the electrolyte liquid comprises a carbonate ester organic solvent, a lithium salt, and a flame-retardant cosolvent, the flame-retardant cosolvent is a phosphazene compound having a molecular structure represented by one of formulas (1) to (3), wherein R 1 and R 2 are hydrocarbon groups, and only a hydrogen atom is replaced by a fluorine atom, R 1 and R 2 have different carbon chain lengths, and carbon chains of R 1 and R 2 have a difference of 3 or more in carbon atom number,

10. The lithium sulfur battery of claim 9 , wherein the cathode electrode comprises sulfur.

11. The method of claim 9 , wherein a number of carbon atoms of the carbon chain of R 1 is 5 to 8, and a number of carbon atoms of the carbon chain of R2 is 1 to 4.

12. A method for preparing an electrolyte liquid of a lithium sulfur battery comprising following steps:
S1, respectively reacting sodium metal or sodium hydride in a first organic solvent with a first fluorine-containing alcohol and a second fluorine-containing alcohol to form a first fluorine-containing sodium alkoxide solution and a second fluorine-containing sodium alkoxide solution, the first fluorine-containing alcohol and the second fluorine-containing alcohol having different carbon chain lengths, and carbon chains of the first fluorine-containing alcohol and the second fluorine-containing alcohol have a difference of 3 or more in carbon atom number;
S2, dissolving hexachlorocyclotriphosphazene in a second organic solvent to form a hexachlorocyclotriphosphazene solution; adding the first fluorine-containing sodium alkoxide solution into the hexachlorocyclotriphosphazene solution to have a first reaction; then adding the second fluorine-containing sodium alkoxide solution, raising the temperature to 45° C. to 55° C., and carrying a second reaction to obtain a milky turbid liquid;
S3, drying the milky turbid liquid, and washing a dried product thereof with an alkaline water solution;
S4, purifying the dried product to obtain an orange-yellow transparent liquid; and
S5, mixing the orange-yellow transparent liquid and a carbonate ester organic solvent to form a mixed solvent, and adding a lithium salt into the mixed solvent;
the electrolyte liquid comprising the carbonate ester organic solvent, the lithium salt, and a flame-retardant cosolvent, the flame-retardant cosolvent being a phosphazene compound having a molecular structure represented by one of formulas (1) to (3), wherein R 1 and R 2 are hydrocarbon groups, and only a hydrogen atom is replaced by a fluorine atom, R 1 and R 2 have different carbon chain lengths, and carbon chains of R 1 and R 2 have a difference of 3 or more in carbon atom number,

13. The method of claim 12 , wherein the first fluorine-containing alcohol and the second fluorine-containing alcohol respectively have 1 to 8 carbon atoms.

14. The method of claim 12 , wherein the first and second organic solvents are respectively selected from the group consisting of tetrahydrofuran, dioxane, dichloromethane, chloroform, and a combination thereof.

15. The method of claim 12 , wherein a molar ratio of the first fluorine-containing sodium alkoxide to the hexachlorocyclotriphosphazene is 1:1 to 3:1, and a molar ratio of the second fluorine-containing sodium alkoxide to the hexachlorocyclotriphosphazene is 3:1 to 5:1.

16. The method of claim 12 , wherein a number of carbon atoms of the carbon chain of the first fluorine-containing alcohol is 5 to 8, and a number of carbon atoms of the carbon chain of the second fluorine-containing alcohol is 1 to 4.

Assignees

• Jiangsu Huadong Inst Of Li Ion Battery Co Ltd
• Univ Tsinghua

Inventors

• Liu Zhen
• Shang yu-ming
• He xiang-ming
• Wang Li

Classifications

• H01M10/0569 Primary

  characterised by the solvents · CPC title

• H01M2300/0037

  Mixture of solvents · CPC title

• H01M10/0568

  characterised by the solutes · CPC title

• H01M10/0567 Primary

  characterised by the additives · CPC title

• H01M4/382

  Lithium (H01M4/405 takes precedence) · CPC title