Electrolyte additives for lithium-ion batteries under high-voltage operation
A non-aqueous electrolyte for a lithium-ion battery comprises a lithium salt and an additive in an organic solvent. The additive comprises a di-substituted malonate silyl ester compound, in which the hydrogens of the malonate methylene group are replaced by substituents R 1 (e.g., alkyl) and X (e.g., halogen). Each of the carboxylic acid groups of the malonate are esterified by a monovalent silyl group such as —Si(R 4 ) 3 ; or the two carboxylic acid groups are esterified by a single divalent silylene group such as —Si(R 5 ) 2 — to form a ring therewith. Each R 4 and R 5 independently is alkyl, phenyl, or alkoxy; and each substituted-alkyl comprises an alkyl moiety substituted with one or more group selected from alkenyl, alkynyl, hydroxy, halogen, alkoxy, carboxylic acid, carboxylic ester, carboxylic amide, phenyl, sulfonic acid, and phosphonic acid.
1. A non-aqueous electrolyte for a lithium-ion battery comprising a lithium salt and an additive in an organic solvent; wherein the solvent comprises one or more solvent selected from a linear dialkyl carbonate, a cyclic alkylene carbonate, a sulfolane, a sulfone, a fluoro-substituted linear dialkyl carbonate, a fluoro-substituted cyclic alkylene carbonate, a fluoro-substituted sulfolane, and a fluoro-substituted sulfone; and wherein the additive comprises a compound of Formula (I):
wherein:
R 1 is selected from alkyl and substituted-alkyl;
X is selected from halogen, alkoxy, cyano, sulfonyl, sulfonylamido, carboxylic acid, carboxylic ester, and carboxylic amide;
R 2 and R 3 each independently is Si(R 4 ) 3 , or R 2 and R 3 together are Si(R 5 ) 2 —;
each R 4 and R 5 independently is selected from alkyl, phenyl, and alkoxy; and
each substituted-alkyl comprises an alkyl moiety substituted with one or more substituent group selected from alkenyl, alkynyl, hydroxy, halogen, amino, alkoxy, carboxylic acid, carboxylic ester, carboxylic amide, phenyl, sulfonic acid, and phosphonic acid.
2. The electrolyte of claim 1 , wherein the additive is present in the electrolyte at a concentration in the range of about 0.005 molar (M) to about 0.5 M.
3. The electrolyte of claim 1 , wherein the lithium salt is present in the electrolyte at a concentration in the range of about 0.1 M to about 3 M.
4. The electrolyte of claim 1 , wherein the lithium salt is selected from one or more of LiF 2 BC 2 O 4 , LiPF 6 , LiBF 4 , LiB(C 2 O 4 ) 2 , LiClO 4 , lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSi), and LiAsF 6 .
5. The electrolyte of claim 1 , wherein the solvent comprises a mixture of a linear dialkyl carbonate and a cyclic alkylene carbonate.
6. The electrolyte of claim 1 , wherein X is F.
7. The electrolyte of claim 1 , wherein R 1 is C 1 to C 4 alkyl.
8. The electrolyte of claim 1 , wherein each R 4 and R 5 independently is a C 1 to C 4 alkyl group.
9. The electrolyte of claim 1 , wherein the additive is a compound of Formula (II):
wherein:
R 1 is selected from alkyl and substituted-alkyl;
each substituted-alkyl comprises an alkyl moiety substituted with one or more substituent group selected from alkenyl, alkynyl, hydroxy, halogen, alkoxy, carboxylic acid, carboxylic ester, carboxylic amide, phenyl, sulfonic acid, and phosphonic acid;
X is selected from halogen, amino, alkoxy, cyano, sulfonyl, sulfonylamido, carboxylic acid, carboxylic ester, and carboxylic amide; and
each R 4 independently is selected from alkyl, phenyl, and alkoxy.
10. The electrolyte of claim 9 , wherein X is F.
11. The electrolyte of claim 9 , wherein R 1 is selected from C 1 to C 4 alkyl and allyl.
12. The electrolyte of claim 9 , wherein each R 4 independently is a C 1 to C 4 alkyl group.
13. The electrolyte of claim 9 , wherein X is F; and R 1 is selected from C 1 to C 4 alkyl and allyl.
14. The electrolyte of claim 9 , wherein X is F; R 1 is selected from C 1 to C 4 alkyl and allyl; and each R 4 independently is a C 1 to C 4 alkyl group.
15. The electrolyte of claim 9 , wherein X is F; R 1 is selected from methyl and allyl; and each R 4 is methyl.
16. The electrolyte of claim 1 , wherein the additive is a compound of Formula
wherein:
R 1 is selected from alkyl and substituted-alkyl;
each substituted-alkyl comprises an alkyl moiety substituted with one or more substituent group selected from alkenyl, alkynyl, hydroxy, halogen, amino, alkoxy, carboxylic acid, carboxylic ester, carboxylic amide, phenyl, sulfonic acid, and phosphonic acid;
X is selected from halogen and alkoxy; and
each R 5 independently is selected from alkyl, phenyl, and alkoxy.
17. The electrolyte of claim 16 , wherein X is F.
18. The electrolyte of claim 16 , wherein R 1 is selected from C 1 to C 4 alkyl and allyl.
19. The electrolyte of claim 16 , wherein each R 5 independently is a C 1 to C 4 alkyl group.
20. The electrolyte of claim 19 , wherein X is F; and R 1 is selected from methyl and allyl.
21. A lithium-ion electrochemical cell comprising a cathode and an anode, with porous separator therebetween, and an electrolyte of claim 1 contacting the anode, the cathode and the separator.
22. A lithium-ion battery comprising a plurality of electrochemical cells of claim 20 electrically connected in series, parallel, or both series and parallel.