Dry electrode for energy storing devices
Electrical energy storage devices made using a wet electrode application technique are associated with high energy consumption. Herein, a dry electrode or electrolyte application process involves mixing activated carbon with a binder and then fibrillating the mixture. The mixture is roll-pressed into a film, which is then actively cooled. Optionally, tension in the cooled portion of the film is increased for spooling the film. The film is adhered to a pre-treated current collector and then wound into a jelly roll for the manufacture of an electrical energy storage device.
1. A process for manufacturing a film for an energy storage device, comprising:
mixing dry, powdered active material with a binder to form a mixture;
fibrillating the mixture, thereby forming a fibrillated mixture;
sieving the fibrillated mixture, thereby forming a sieved, fibrillated mixture;
heating the sieved, fibrillated mixture between rollers to form the film, the rollers being at a temperature between 50° C. and 160° C.; and
actively cooling the film to between 10° C. and 70° C. within a distance of 30 cm from a location of formation of the film, resulting in a cooled film;
wherein the film is a dry electrode film or a dry electrolyte film.
2. The process of claim 1 , wherein:
the film is the dry electrode film;
the dry, powdered active material is activated carbon; and
the binder is PTFE (polytetrafluoroethylene).
3. The process of claim 2 , further comprising mixing carbon black with the activated carbon and the binder, the carbon black being present in the mixture from over 0% to 20% by weight.
4. The process of claim 1 , wherein:
the mixture comprises 1-30% by weight of the binder, and
the binder is PTFE (polytetrafluoroethylene).
5. The process of claim 1 , wherein:
the mixture comprises 10-15% by weight of the binder; and
the binder is PTFE (polytetrafluoroethylene).
6. The process of claim 1 , wherein the mixture comprises by weight:
50-99% of the dry, powdered active material;
1-30% of the binder, and
0-20% of a conductive additive.
7. The process of claim 1 , wherein the mixture comprises by weight:
75-98% of the dry, powdered active material;
2-15% of the binder, and
0-10% of a conductive additive.
8. The process of claim 1 , wherein the mixture comprises by weight:
80-95% of the dry, powdered active material, the dry, powdered active material being activated carbon;
1.5-15% of the binder, the binder being a fluoropolymer, and
0-15% of a conductive additive.
9. The process of claim 1 , wherein the mixture comprises by weight:
5-20% of the binder, the binder being a fluoropolymer.
10. The process of claim 1 , comprising passing the fibrillated mixture over a vibrating surface before said sieving, said sieving being through a vibrating sieve.
11. The process of claim 1 , wherein the film is actively cooled with a current of chilled gas.
12. The process of claim 1 , wherein the film is actively cooled with a chilled roller.
13. The process of claim 1 , further comprising trimming the cooled film to result in a trimmed, cooled film.
14. The process of claim 1 , further comprising:
trimming the cooled film to result in a trimmed, cooled film;
applying a first tension to the film, the cooled film and a first portion of the trimmed, cooled film that is adjacent to the cooled film; and
applying a second tension to a second portion of the trimmed, cooled film;
wherein the second tension is greater than the first tension.
15. The process of claim 14 , further comprising spooling the trimmed, cooled film under the second tension.
16. The process of claim 15 , wherein the trimmed, cooled film is uncalendered.
17. The process of claim 14 , wherein:
the first tension is between 6.7μN-0.13N per mm 2 cross-section of the second portion of the trimmed, cooled film; and
the second tension is between 0.033N-0.4N per mm 2 cross-section of the second portion of the trimmed, cooled film.
18. The process of claim 13 , further comprising adhering at least some of the trimmed, cooled film to an aluminum foil.
19. The process of claim 18 , further comprising prior to said adhering:
removing oil residue from the aluminum foil; and
applying adhesive to the aluminum foil.
20. The process of claim 19 , wherein the aluminum foil is heated to between 50° C. and 200° C. to remove the oil residue.
21. The process of claim 19 , comprising drying the applied adhesive prior to said adhering.
22. The process of claim 18 , comprising winding, in layers, into a jelly roll:
a first piece of the aluminum foil with the adhered, trimmed, cooled film;
a first separator;
a second piece of the aluminum foil with the adhered, trimmed, cooled film; and
a second separator.
23. The process of claim 22 , comprising manufacturing the energy storage device using the jelly roll.
24. The process of claim 1 , further comprising depositing the sieved, fibrillated mixture between the rollers to a height that is not greater than uppermost points of the rollers.
25. The process of claim 1 , wherein the fibrillated mixture is sieved through a 3-10 mm mesh.
26. The process of claim 1 , wherein a maximum dwell time of the sieved, fibrillated mixture between the rollers is 5 minutes.
27. The process of claim 1 , wherein a maximum dwell time of the sieved, fibrillated mixture between the rollers is 1 minute.
28. The process of claim 1 , wherein a maximum dwell time of the sieved, fibrillated mixture between the rollers is 30 seconds.
29. The process of claim 1 comprising mixing a non-aqueous lubricant with the dry, powdered active material and the binder to form the mixture.
30. The process of claim 1 comprising mixing a conductive additive with the dry, powdered active material and the binder to form the mixture.
31. The process of claim 1 , wherein the rollers are at a temperature between 80° C. and 140° C.
32. The process of claim 1 , wherein the film is actively cooled to below 25° C.
33. The process of claim 14 , wherein the mixture comprises by weight:
10-15% of the binder, the binder being PTFE (polytetrafluoroethylene).
34. The process of claim 1 , wherein:
the film is the dry electrolyte film;
the dry, powdered active material comprises an ion-conducting inorganic ceramic oxide, a Li-superionic conductor, a sodium superionic conductor, lithium sulfide, lithium sulfide boron sulfide, lithium germanium sulfide, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polyethylene glycol (PEG), LiTFSi, LiCIO 4 , LiPF 6 , or any combination selected therefrom; and
the binder is PTFE (polytetrafluoroethylene).