Compositions and methods for passivation of electrode binders
Passivation methods and compositions for electrode binders are disclosed. A coated binder particle for use in an electrode film of an energy storage device is provided. The coated binder particle can comprise a coating over the surface of a binder particle, wherein the coating provides ionic insulation to the binder particle. In some embodiments, the coating covers the entire surface of the binder particle. In still further embodiments, a coated binder particle in an energy storage device blocks ionic contact between the binder and an electrolyte.
1. A method for fabricating an energy storage device electrode film, comprising:
mixing binder particles and an ionically insulating coating material to form coated binder particles, wherein mixing does not fibrillize the binder particles, and wherein mixing coats at least about 70% of an average surface of the binder particles with the ionically insulating coating material;
combining the coated binder particles with active material particles to form a first mixture;
milling at least some of the first mixture to form an electrode film mixture; and
calendering the electrode film mixture to form a free-standing electrode film.
2. The method of claim 1 , wherein the polymeric binder particles comprise a binder selected from the group consisting of polytetrafluoroethylene (PTFE), ultra-high molecular weight polyethylene (UHMWPE), polyvinylidene fluoride (PVDF), a PVDF co-polymer, poly(ethylene oxide) (PEO), and combinations thereof.
3. The method of claim 1 , wherein the active material particles comprise a material selected from the group consisting of graphite, hard carbon, soft carbon, graphene, mesoporous carbon, silicon, a silicon oxide, tin, a tin oxide, germanium, lithium titanate, combinations thereof, and composites thereof.
4. The method of claim 1 , wherein the coated binder particles comprise composite particles of binder and ionically insulating coating material.
5. The method of claim 1 , wherein the ionically insulating coating material comprises a material selected from the group consisting of carbon black, conductive carbon, graphene-containing carbon, graphite, and combinations thereof.
6. The method of claim 1 , wherein the ionically insulating coating material comprises an electrically conductive material.
7. The method of claim 1 , wherein mixing comprises pre-milling.
8. The method of claim 7 , wherein the pre-milling is conducted in a mill comprising media.
9. The method of claim 8 , further comprising removing the media prior to forming the electrode film.
10. The method of claim 8 , wherein the media comprises a material shape selected from the group consisting of balls, beads, cylinders, and combinations thereof.
11. The method of claim 7 , wherein the pre-milling is performed in a jar roller mill.
12. The method of claim 1 , wherein milling at least some of the first mixture is a high shear process at a shear velocity sufficient to fibrillize the binder particles.
13. The method of claim 12 , wherein the high shear process comprises jet-milling.
14. The method of claim 1 , wherein surface color of the binder particles is not visible to the naked eye following the mixing step.
15. The method of claim 1 , wherein the coated binder particles do not aggregate.
16. The method of claim 1 , wherein the coated binder particles comprise binder particles covering about 80% to 90% of an average surface of the coated binder particles.
17. The method of claim 1 , wherein during the mixing step the mass of the coating material is about 1-50% the mass of the binder particles.
18. The method of claim 1 , wherein the mixing step consists essentially of mixing the binder particles and the ionically insulating coating material to form the coated binder particles.
19. The method of claim 1 , wherein the mixing step comprises mechanically fusing the binder particles and the ionically insulating coating material to form the coated binder particles.
20. The method of claim 19 , wherein mechanically fusing comprises a process selected from the group consisting of low-velocity milling, tumbling, and combinations thereof.
21. The method of claim 1 , wherein the ionically insulating coating material further comprises a ductile metal.
22. The method of claim 21 , wherein the ductile metal is selected from the group consisting of Cu, Sn, Sb, and combinations thereof.