Electrolytes for lithium sulfur cells
View Patent ↗Disclosed is an electrochemical cell comprising a lithium anode and a sulfur-containing cathode and a non-aqueous electrolyte. The cell exhibits high utilization of the electroactive sulfur-containing material of the cathode and a high charge-discharge efficiency.
1. An electrochemical cell comprising:
(a) a cathode comprising an electroactive sulfur-containing material;
(b) an anode comprising lithium; and
(c) a nonaqueous electrolyte, wherein the electrolyte comprises:
(i) one or more nonaqueous solvents selected from the group consisting of acyclic ethers, cyclic ethers, polyethers, and sulfones;
(ii) one or more lithium salts; and
(iii) one or more N—O additives, wherein the one or more N—O additives comprise an inorganic nitrite selected from one or more of the group consisting of lithium nitrite, potassium nitrite, cesium nitrite, and ammonium nitrite:
wherein the cell exhibits utilization of the electroactive sulfur-containing material of at least 60% and a charge-discharge efficiency of at least 80% over at least 10 cycles at a charge rate of about 0.2 mA/cm 2 and a discharge rate of about 0.4 mA/cm 2 .
2. The cell of claim 1 that exhibits a charge-discharge efficiency of at least 90%.
3. The cell of claim 1 that exhibits utilization of the electroactive sulfur-containing material of at least 60% over at least 20 cycles at a discharge rate of about 0.4 mA/cm 2 .
4. The cell of claim 1 that exhibits utilization of the electroactive sulfur-containing material of at least 60% over at least 50 cycles at a discharge rate of about 0.4 mA/cm 2 .
5. The cell of claim 4 that exhibits a charge-discharge efficiency of at least 90% at a discharge rate of about 0.4 mA/cm 2 .
6. The cell of claim 1 that exhibits utilization of the electroactive sulfur-containing material of at least 60% over at least 20 cycles at a discharge rate of about 2.8 mA/cm 2 .
7. The cell of claim 1 wherein the one or more N—O additives further comprise one or more of the group consisting of inorganic nitrates, organic nitrates, inorganic nitrites, organic nitrites, and organic nitro compounds.
8. The cell of claim 1 wherein the one or more lithium salts is selected from one or more of the group consisting of LiSCN, LiCF 3 SO 3 , and LiN(CF 3 SO 2 ) 2 .
9. The cell of claim 1 wherein the concentration of the one or more N—O additives in the electrolyte is from about 0.02 m to 2.0 m.
10. The cell of claim 1 wherein the concentration of the one or more N—O additives in the electrolyte is from about 0.1 m to 1.5 m.
11. The cell of claim 1 wherein the concentration of the one or more N—O additives in the electrolyte is from about 0.2 m to 1.0 m.
12. The cell of claim 1 wherein the concentration of the one or more lithium salts in the electrolyte is from about 0.2 m to about 2.0 m.
13. The cell of claim 1 wherein the electroactive sulfur-containing material comprises elemental sulfur.
14. The cell of claim 1 wherein the anode comprises lithium metal.
15. The cell of claim 1 that further includes a separator interposed between the anode and the cathode.
16. A battery comprising a casing and one or more cells of claim 1 .
17. The cell of claim 1 wherein the nonaqueous solvent comprises dioxolane.
18. The cell of claim 17 wherein the nonaqueous solvent comprises greater than 40% by weight dioxolane.
19. The cell of claim 1 wherein the one or more solvents consists of dimethoxyethane and dioxolane.
20. The cell of claim 19 wherein the nonaqueous solvent comprises greater than 40% by weight dioxolane.
21. The cell of claim 1 wherein the one or more lithium salts are selected from one or more of the group consisting of LiSCN, LiBr, LiI, LiClO 4 , LiAsF 6 , LiSO 3 CF 3 , LiSO 3 CH 3 , LiBF 4 , LiB(Ph) 4 , LiPF 6 , LiC(SO 2 CF 3 ) 3 , and LiN(SO 2 CF 3 ) 2 .
22. The cell of claim 1 wherein the nonaqueous electrolyte comprises two or more solvents selected from acyclic ethers, glymes and cyclic ethers.
23. The cell of claim 22 wherein one of the two or more non aqueous solvents is dioxolane.
24. The cell of claim 1 wherein the one or more nonaqueous solvents consist of:
1,3-dioxolane and dimethoxyethane; or
1,3-dioxolane and diethyleneglycol dimethyl ether; or
1,3-dioxolane and triethyleneglycol dimethyl ether; or
1,3-dioxolane and sulfolane.
25. The cell of claim 24 wherein the electrolyte comprises a binary mixture and the weight ratio of the components of the binary mixture are from about 5 to 95 to 95 to 5.
26. The cell of claim 24 wherein the non aqueous solvent comprises greater than 40% by weight dioxolane.
27. An electrochemical cell comprising:
(a) a cathode comprising an electroactive sulfur-containing material;
(b) an anode comprising lithium; and
(c) a nonaqueous electrolyte, wherein the electrolyte comprises
(i) one or more nonaqueous solvents selected from the group consisting of acyclic ethers, cyclic ethers, polyethers, and sulfones; and
(ii) one or more N—O additives, wherein the one or more N—O additives is lithium nitrate;
wherein the cell exhibits utilization of the electroactive sulfur-containing material of at least 60% and a charge-discharge efficiency of at least 80% over at least 10 cycles at a charge rate of about 0.2 mA/cm 2 and a discharge rate of about 0.4 mA/cm 2 .
28. The cell of claim 27 wherein the electrolyte further consists of LiSCN or LiN(CF 3 SO 2 ) 2 .
29. The cell of claim 27 that exhibits a charge-discharge efficiency of at least 90%.
30. The cell of claim 27 that exhibits utilization of the electroactive sulfur-containing material of at least 60% over at least 20 cycles at a discharge rate of about 0.4 mA/cm 2 .
31. The cell of claim 27 that exhibits utilization of the electroactive sulfur-containing material of at least 60% over at least 50 cycles at a discharge rate of about 0.4 mA/cm 2 .
32. The cell of claim 27 wherein the concentration of the one or more N—O additives in the electrolyte is from about 0.02 m to 2.0 m.
33. The cell of claim 27 wherein the electroactive sulfur-containing material comprises elemental sulfur.
34. The cell of claim 27 wherein the electrolyte further comprises one or more lithium salts, wherein the lithium salts are selected from one or more of the group consisting of LiSCN, LiBr, LiI, LiClO 4 , LiAsF 6 , LiSO 3 CF 3 , LiSO 3 CH 3 , LiBF 4 , LiB(Ph) 4 , LiPF 6 , LiC(SO 2 CF 3 ) 3 , and LiN(SO 2 CF 3 .
35. The cell of claim 34 wherein the concentration of the one or more lithium salts in the electrolyte is from about 0.2 m to about 2.0 m.
36. The cell of claim 27 wherein the nonaqueous electrolyte comprises two or more solvents selected from acyclic ethers, glymes and cyclic ethers.
37. The cell of claim 27 wherein the nonaqueous solvent comprises dioxolane.
38. The cell of claim 37 wherein the non aqueous solvent comprises greater than 40% by weight dioxolane.
39. The cell of claim 27 wherein the one or more nonaqueous solvents consist of:
1,3-dioxolane and dimethoxyethane; or
1,3-dioxolane and diethyleneglycol dimethyl ether; or
1,3-dioxolane and triethyleneglycol dimethyl ether; or
1,3-dioxolane and sulfolane.
40. The cell of claim 39 wherein the electrolyte comprises a binary mixture and the weight ratio of the components of the binary mixture are from about 5 to 95 to 95 to 5.
41. The cell of claim 39 wherein the non aqueous solvent comprises greater than 40% by weight dioxolane.