Flexible cathodes
View Patent ↗This disclosure relates to methods of making a cathode for a lithium batter. The methods include: (a) treating a cathode current collector with flame or corona; (b) coating a slurry containing iron disulfide, a first solvent, and a binder onto the cathode current collector obtained from step (a) to form a coated cathode current collector, in which the slurry contains about 73-75% by weight solids and the binder contains a polymer selected from the group consisting of linear di- and tri-block copolymers, linear tri-block copolymers cross-linked with melamine resin, ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, tri-block fluorinated thermoplastics, hydrogenated nitrile rubbers, fluoro-ethylene-vinyl ether copolymers, thermoplastic polyurethanes, thermoplastic olefins, and polyvinylidene fluoride homopolymers; and (c) drying the coated cathode current collector obtained from step (b) to provide a cathode, in which the cathode contains no more than 0.5% by volume of the first solvent and is capable of being bent to 180°. This disclosure also relates to methods of making a lithium battery.
1. A method of making a lithium battery, the method comprising:
(a) coating a slurry comprising iron disulfide, a solvent selected from the group consisting of hydrocarbons and paraffinic solvents, and a binder onto the cathode current collector to form a coated cathode current collector, wherein the binder comprises a polymer selected from the group consisting of linear di- and tri-block copolymers, linear tri-block copolymers cross-linked with melamine resin, ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, tri-block fluorinated thermoplastics, hydrogenated nitrile rubbers, fluoro-ethylene-vinyl ether copolymers, thermoplastic polyurethanes, thermoplastic olefins, and polyvinylidene fluoride homopolymers;
(b) drying the coated cathode current collector obtained from step (a) to provide a cathode, wherein the cathode comprises no more than 0.5% by volume of the solvent; and
(c) incorporating the cathode obtained from step (b), an anode comprising lithium, and an electrolyte comprising dimethyloxyethane, dioxolane, and lithium iodide into a housing to form the lithium battery.
2. The method of claim 1 , wherein the binder comprises a linear tri-block copolymer.
3. The method of claim 2 , wherein the binder comprises a styrene-ethylene-butylene-styrene polymer.
4. The method of claim 1 , wherein the cathode current collector comprises aluminum or an aluminum alloy.
5. The method of claim 1 , wherein the cathode current collector comprises an aluminum foil.
6. The method of claim 1 , wherein the solvent is a hydrocarbon solvent.
7. The method of claim 6 , wherein the hydrocarbon solvent is an unbranched hydrocarbon.
8. The method of claim 6 , wherein the hydrocarbon solvent is a branched hydrocarbon.
9. The method of claim 6 , wherein the hydrocarbon solvent is an aromatic hydrocarbon.
10. The method of claim 1 , wherein the solvent is a paraffinic solvent.
11. The method of claim 10 , wherein the paraffinic solvent is an iso-paraffinic solvent.
12. The method of claim 10 , wherein the paraffinic solvent is a cyclo-paraffinic solvent.
13. The method of claim 1 , wherein the coating step comprises applying the slurry onto the cathode current collector using a solution extrusion process.
14. The method of claim 1 , wherein the drying step comprises drying the coated cathode current collector in a first heating zone having a temperature of 45° C. to 80° C.
15. The method of claim 14 , wherein the drying step further comprises drying the coated cathode current collector in a second heating zone having a temperature of 75° C. to 130° C. after drying the coated cathode current collector in the first heating zone.
16. The method of claim 1 , further comprising calendering the cathode after the drying step.
17. The method of claim 16 , wherein the cathode is calendered at an elevated temperature.
18. The method of claim 1 , wherein the cathode has a thickness of from 16 mil to 22 mil.
19. The method of claim 1 , wherein the cathode further comprises a conductive material selected from the group consisting of carbon black and graphite.
20. The method of claim 1 , wherein the cathode has a porosity of from 30% to 35%.
21. The method of claim 1 , wherein the cathode comprises less than about 3% by weight of the binder.
22. The method of claim 1 , wherein the cathode is capable of being wound around a mandrel without forming a crack in the coating of the cathode.
23. The method of claim 1 , wherein the slurry comprises about 65-75% by weight solids.
24. The method of claim 1 , wherein the cathode is capable of bending 180°.