Polyimide electrode binders
View Patent ↗Irreversible first cycle capacity loss in lithium secondary cells having a cell electrode based on a powdered material and a binder may be significantly decreased or eliminated by using an aliphatic or cycloaliphatic polyimide binder. Compared to conventional polyimide binders prepared by reacting an aromatic dianhydride and a diamine, the disclosed polyimide binders have decreased aromatic carbonyl content, may be less likely to undergo electrochemical reduction, and may be less likely to consume electrons that might otherwise help lithiate the electrode.
1. A secondary battery electrode composition comprising a powdered material capable of undergoing lithiation and delithiation and an aliphatic or cycloaliphatic polyimide binder, wherein the polyimide binder comprises repeating units of Formula I:
wherein
R 1 is aliphatic or cycloaliphatic and
R 2 is aromatic, aliphatic, cycloaliphatic, or a combination thereof,
wherein R 1 and R 2 contain only carbon, hydrogen, nitrogen or oxygen ring atoms.
2. A composition according to claim 1 wherein the powdered material comprises silicon, silver, lithium, tin, bismuth, lead, antimony, germanium, zinc, gold, platinum, palladium, arsenic, aluminum, gallium, indium, thallium or an alloy thereof.
3. A composition according to claim 1 wherein the powdered material comprises a silicon alloy.
4. A composition according to claim 1 wherein the powdered material comprises a lithium alloy.
5. A composition according to claim 1 wherein the powdered material comprises graphitic carbon.
6. A composition according to claim 1 wherein the polyimide binder has a plurality of imide groups bonded to aliphatic or cycloaliphatic moieties.
7. A composition according to claim 1 wherein the polyimide binder also comprises imide groups bonded to aromatic moieties.
8. A composition according to claim 7 wherein about 10 to about 90 mole percent of the imide groups are bonded to aliphatic or cycloaliphatic moieties and about 90 to about 10 mole percent of the imide groups are bonded to aromatic moieties.
9. A composition according to claim 7 wherein about 20 to about 80 mole percent of the imide groups are bonded to aliphatic or cycloaliphatic moieties and about 80 to about 20 mole percent of the imide groups are bonded to aromatic moieties.
10. A composition according to claim 7 wherein about 5 to about 95 mole percent of the imide groups are bonded to aliphatic or cycloaliphatic moieties and about 95 to about 5 mole percent of the imide groups are bonded to aromatic moieties.
11. A composition according to claim 1 wherein the polyimide has a majority of imide groups bonded to aliphatic or cycloaliphatic moieties.
12. A composition according to claim 1 wherein an R 1 or R 2 moiety is substituted with one or more groups that do not interfere with use of the polyimide in a lithium ion cell.
13. A composition according to claim 1 wherein an R 1 moiety is substituted with one or more electron-donating groups.
14. A composition according to claim 1 wherein R 1 is a tetrafunctional radical derivable from butane, cyclobutane, cyclopentane, cyclohexane, cyclohexene, bicyclooctane, bicyclooctene, bicycloheptane or bicyclooxetane.
15. A composition according to claim 1 wherein R 2 is a polyfunctional radical derivable from benzene, dibenzene, diphenyl ether, diphenylmethane, diphenylpropane, naphthalene, pyridine, pyrimidine, triazine, propane, butane, heptane, hexane, cyclohexane, heptane, octane, nonane, decane or dodecane.
16. A composition according to claim 1 wherein the polyimide can be prepared from 1,2,3,4-butanetetracarboxylic dianhydride.
17. A composition according to claim 1 wherein the polyimide can be prepared from 4,4′-oxydianiline.
18. A composition according to claim 1 wherein the polyimide can be prepared via a condensation reaction between an aliphatic or cycloaliphatic polyanhydride and an aromatic, aliphatic or cycloaliphatic polyamine to form a polyamic acid, followed by chemical or thermal cyclization to form the polyimide.
19. A composition according to claim 18 wherein the polyimide can be prepared via a condensation reaction additionally employing an aromatic polyanhydride.
20. A rechargeable lithium-ion cell comprising a negative electrode comprising a powdered material capable of undergoing lithiation and delithiation and an aliphatic or cycloaliphatic polyimide binder, a positive electrode, and an electrolyte comprising a lithium salt and a charge carrying medium, wherein the aliphatic or cycloaliphatic polyimide contains only carbon, hydrogen, nitrogen or oxygen ring atoms,
wherein the polyimide binder comprises repeating units of Formula I:
wherein
R 1 is aliphatic or cycloaliphatic and
R 2 is aromatic, aliphatic, cycloaliphatic, or a combination thereof,
wherein R 1 and R 2 contain only carbon, hydrogen, nitrogen or oxygen ring atoms.
21. An electronic device comprising a rechargeable lithium-ion cell according to claim 20 .
22. A battery pack comprising a rechargeable lithium-ion cell according to claim 20 .