Processes for the manufacture of conductive particle films for lithium ion batteries and lithium ion batteries
The invention is directed to a process for forming a particle film on a substrate. Preferably, a series of corona guns, staggered to optimize film thickness uniformity, are oriented on both sides of a slowly translating grounded substrate (copper or aluminum for the anode or cathode, respectively). The substrate is preferably slightly heated to induce binder flow, and passed through a set of hot rollers that further induce melting and improve film uniformity. The sheeting is collected on a roll or can be combined in-situ and rolled into a single-cell battery. The invention is also directed to products formed by the processes of the invention and, in particular, batteries.
1. A method for forming a conductive particle film comprising:
spraying a mixture of conductive particles and a binder toward a substrate at a spray deposition site;
passing a current through the substrate between a first electrode in electrical contact with the substrate and a second electrode in electrical contact with the substrate to generate heat in the substrate, wherein the first electrode is disposed upstream of the spray deposition site and the second electrode is disposed downstream of the spray deposition site; and
applying the sprayed mixture to a first side and a second opposing side of the heated substrate at the spray deposition site to form the conductive particle film.
2. The method of claim 1 , further comprising moving a portion of the substrate from the first electrode toward the second electrode while the mixture is sprayed toward the substrate.
3. The method of claim 1 , wherein electrical current is passed through an uncoated section of the substrate by the first electrode and through the conductive particle film by the second electrode.
4. The method of claim 1 , wherein at least one of the first electrode and the second electrode include one or more rollers in electrical contact with the substrate.
5. The method of claim 4 , wherein the electrical current passes into and out of the one or more rollers using at least one of conductive brushes and conductive bearings.
6. The method of claim 4 , further comprising calendering the particle film using at least one of the one or more rollers.
7. The method of claim 6 , wherein the current is passed through the calendered particle film by the second electrode.
8. The method of claim 4 , wherein both the first electrode and second electrode are rollers in electrical contact with the substrate.
9. The method of claim 1 , wherein the substrate is a metal foil.
10. The method of claim 1 , wherein the conductive particles comprise an anodic or cathodic material.
11. The method of claim 10 , wherein the anodic or cathodic material comprises at least one of carbon, lithium titanate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium iron manganese phosphate.
12. The method of claim 10 , wherein the binder is selected from the group comprising PVDF, PTFE and SBR.
13. The method of claim 1 , further comprising mixing the conductive particles with the binder.
14. The method of claim 1 , wherein spraying the mixture comprises aerosolizing the mixture.
15. The method of claim 1 , further comprising spraying a separator material onto a surface of the conductive particle film disposed on the substrate to form a separator disposed on the conductive particle film.
16. The method of claim 15 , wherein the separator material is a polymer powder.