Nonaqueous electrolyte compositions
Electrolyte compositions comprising fluorinated acyclic carboxylic acid esters, fluorinated acyclic carbonates, and/or fluorinated acyclic ethers; co-solvents; and certain film-forming chemical compounds are described. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries where they provide the improved performance of a combination of high capacity and high cycle life.
1. An electrolyte composition comprising:
a) at least one fluorinated solvent selected from the group consisting of:
(i) a fluorinated acyclic carboxylic acid ester represented by the formula: R 1 —COO—R 2 ,
wherein R 1 represents a linear or branched alkyl group with 1, 3, 4, or 5 carbon atoms, R 2 represents a linear or branched alkyl group, the sum of carbon atoms in R 1 and R 2 is 2 to 7, at least two hydrogens in R 1 and/or R 2 are replaced by fluorines; and neither R 1 nor R 2 contains a FCH 2 or FCH group; and the electrolyte composition does not contain any acyclic carboxylic ester represented by the formula R 1 —COO—R 2 , wherein R 1 represents a linear or branched alkyl group with 2 carbon atoms;
b) at least one co-solvent selected from the group consisting of ethylene carbonate, and propylene carbonate;
c) at least one cyclic carboxylic acid anhydride selected from the group consisting of
where R 7 to R 14 are independently H, F, C 1 to C10 linear or branched alkyl optionally substituted with one or more of fluorine, alkoxy, or thioalkyl, C2 to C10 alkene, or C6 to C10 aryl; and
where the at least one cyclic carboxylic acid anhydride is present in an amount of about 0.01% to about 10% by weight of the total electrolyte composition; and
d) at least one electrolyte salt.
2. The electrolyte composition of claim 1 , wherein the fluorinated solvent is a fluorinated acyclic carboxylic ester and the number of carbon atoms in R 1 is 1, 3, 4, or 5.
3. The electrolyte composition of claim 1 , wherein the fluorinated solvent is a fluorinated acyclic carboxylic ester, R 1 does not contain fluorine, and R 2 contains fluorine.
4. The electrolyte composition of claim 1 , wherein the at least one cyclic carboxylic acid anhydride is selected from one or more members of the group consisting of maleic anhydride, succinic anhydride, glutaric anhydride, 2,3-dimethylmaleic anhydride, citraconic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, 2,3-diphenylmaleic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 2,3-dihydro-1,4-dithiono-[2,3-c]furan-5,7 dione, and phenylmaleic anhydride.
5. The electrolyte composition of claim 4 , wherein the at least one cyclic carboxylic acid anhydride is maleic anhydride.
6. The electrolyte composition of claim 1 , wherein the fluorinated acyclic carboxylic acid ester is selected from one or more members of the group consisting of CH 3 —COO—CH 2 CF 2 H, CH 3 CH 2 —COOCH 2 CF 2 H, F 2 CHCH 2 —COO—CH 3 , F 2 CHCH 2 —COO—CH 2 CH 3 , CH 3 —COO—CH 2 CH 2 CF 2 H, CH 3 CH 2 —COO—CH 2 CH 2 CF 2 H, F 2 CHCH 2 CH 2 —COO—CH 2 CH 3 , and CH 3 —COO—CH 2 CF 3 .
7. The electrolyte composition of claim 6 , wherein the fluorinated acyclic carboxylic acid ester is 2,2-difluoroethyl acetate.
8. The electrolyte composition of claim 1 , wherein the at least one cyclic carboxylic acid anhydride is present in an amount of about 0.1% to about 5.0% by weight of the total electrolyte composition.
9. The electrolyte composition of claim 1 , wherein the electrolyte composition comprises 2,2-difluoroethyl acetate, ethylene carbonate, and maleic anhydride.
10. The electrolyte composition of claim 1 , wherein the electrolyte composition comprises about 50% to about 80% of 2,2-difluoroethyl acetate; about 10% to about 40% of ethylene carbonate; and about 0.25% to about 5.0% of maleic anhydride by weight of the total electrolyte composition.
11. The electrolyte composition of claim 1 , wherein the electrolyte composition comprises about 50% to about 80% of 2,2-difluoroethyl acetate, about 10% to about 40% of ethylene carbonate, about 0.25% to about 5.0% of fluoroethylene carbonate and about 0.25% to about 5.0% of maleic anhydride by weight of the total electrolyte composition.
12. An electrochemical cell comprising:
(a) a housing;
(b) an anode and a cathode disposed in said housing and in ionically conductive contact with one another;
(c) the electrolyte composition of claim 1 or claim 2 disposed in said housing and providing an ionically conductive pathway between said anode and said cathode; and
(d) a porous separator between said anode and said cathode.
13. The electrochemical cell of claim 12 , wherein said electrochemical cell is a lithium ion battery.
14. The electrochemical cell of claim 13 , wherein the anode is lithium titanate or graphite.
15. The electrochemical cell of claim 13 , wherein the cathode comprises a cathode active material exhibiting greater than 30 mAh/g capacity in a potential range greater than 4.6 V versus a Li/Li + reference electrode.
16. The electrochemical cell of claim 13 , wherein the cathode comprises a cathode active material which is charged to a potential greater than or equal to 4.35 V versus a Li/Li + reference electrode.
17. The electrochemical cell of claim 13 , wherein the cathode comprises a lithium-containing manganese composite oxide having a spinel structure as active material, the lithium-containing manganese composite oxide being represented by the formula:
Li x Ni y M z Mn 2-y-z O 4-d ,
wherein x is 0.03 to 1.0; x changes in accordance with release and uptake of lithium ions and electrons during charge and discharge; y is 0.3 to 0.6; M comprises one or more of Cr, Fe, Co, Li, Al, Ga, Nb, Mo, Ti, Zr, Mg, Zn, V, and Cu; z is 0.01 to 0.18, and d is 0 to 0.3.
18. The electrochemical cell of claim 13 , wherein the cathode comprises Li a Ni b Mn c Co d R e O 2-f Z f , wherein:
R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Zr, Ti, a rare earth element, or a combination thereof, and Z is F, S, P, or a combination thereof; and
0.8≤a≤1.2, 0.1≤b≤0.5, 0.2≤c≤0.7, 0.05≤d≤0.4, 0≤e≤0.2; wherein the sum of b+c+d+e is about 1; and 00.08.
19. An electronic device, transportation device, or telecommunications device, comprising an electrochemical cell according to claim 13 .
20. A method comprising combining to form an electrolyte composition:
a) at least one fluorinated solvent selected from the group consisting of:
(i) a fluorinated acyclic carboxylic acid ester represented by the formula:
R 1 —COO—R 2 ,
wherein R 1 represents a linear or branched alkyl group with 1, 3, 4, or 5 carbon atoms, R 2 represents a linear or branched alkyl group, the sum of carbon atoms in R 1 and R 2 is 2 to 7, at least two hydrogens in R 1 and/or R 2 are replaced by fluorines; and neither R 1 nor R 2 contains a FCH 2 or FCH group; and the electrolyte composition does not contain any acyclic carboxylic ester represented by the formula R 1 —COO—R 2 , wherein R 1 represents a linear or branched alkyl group with 2 carbon atoms;
b) at least one co-solvent selected from the group consisting of ethylene carbonate, and propylene carbonate;
c) at least one cyclic carboxylic acid anhydride selected from the group consisting of
where R 7 to R 14 are independently H, F, C 1 to C10 linear or branched alkyl optionally substituted with one or more of fluorine, alkoxy, or thioalkyl, C2 to C10 alkene, or C6 to C10 aryl; and
d) at least one electrolyte salt.
21. The electrolyte composition of claim 1 , wherein the electrolyte composition comprises about 30% to 70% by weight of the fluorinated solvent, about 10% to 60% by weight co-solvent, and about 0.01% to 10% by weight cyclic carboxylic acid anhydride.
22. The electrolyte composition of claim 1 , wherein the electrolyte composition is free of butyrolactone.