Surface modification of silicon-containing electrodes using carbon dioxide

1. A method of forming an electrochemical cell, the method comprising:

providing a first electrode, a second electrode, a separator between the first and second electrodes, and an electrolyte in a cell container, wherein the first electrode comprises silicon-dominant electrochemically active material, wherein the silicon-dominant electrochemically active material comprises greater than 50% silicon by weight;

exposing at least a part of the electrochemical cell to CO 2 ; and

forming a solid electrolyte interphase (SEI) layer on the first electrode using the CO 2 ;

wherein the first electrode, the second electrode, and the separator are held together with a polymer adhesive on the separator in order to maintain adhesion between the first electrode, second electrode, and separator while the at least a part of the electrochemical cell is exposed to CO 2 ;

wherein said SEI layer is about 1 nm to about 20 nm thick and wherein the first electrode is a self-supported film.

2. The method of claim 1 , wherein the SEI layer comprises solid carbonate on LiF particles.

3. The method of claim 1 , wherein forming the SEI layer occurs during lithiation.

4. The method of claim 1 , wherein the silicon-dominant electrochemically active material comprises the silicon at about 60% to about 100% by weight.

5. The method of claim 4 , wherein the silicon-dominant electrochemically active material comprises the silicon at about 70% to about 100% by weight.

6. The method of claim 1 , wherein the second electrode comprises nickel cobalt aluminum (NCA).

7. The method of claim 6 , wherein the CO 2 is produced from Li 2 CO 3 on a surface of the NCA.

8. The method of claim 1 , wherein the second electrode comprises lithium cobalt oxide (LCO), lithium manganese oxide (LMO), or nickel manganese cobalt (NMC).

9. The method of claim 1 , wherein the CO 2 is provided in the cell container.

10. The method of claim 9 , wherein the CO 2 is provided in an amount of about 0.01 to about 0.6 mg per mg of the silicon.

11. The method of claim 10 , wherein the CO 2 is provided in an amount of about 0.1 to about 0.6 mg per mg of the silicon.

12. The method of claim 9 , wherein the CO 2 is provided by adding dry ice to the electrolyte.

13. The method of claim 1 , wherein the CO 2 is dissolved in the electrolyte.

14. The method of claim 13 , wherein the CO 2 is dissolved in an amount of about 0.01 to about 0.6 mg per mg of the silicon.

15. The method of claim 1 , wherein the CO 2 is produced from a carbonate in the cell container.

16. The method of claim 1 , wherein the electrolyte comprises greater than about 10% to about 90% carbonate solvent by weight.

17. The method of claim 1 , wherein the electrolyte comprises a cyclic carbonate solvent.

18. The method of claim 17 , wherein the solvent comprises fluoroethylene carbonate (FEC), difluoroethylene carbonate (F2EC), trifluoroethylene carbonate (F3EC), ethylene carbonate (EC), propylene carbonate (PC), trifluoropropylene carbonate (TFPC), or a mixture thereof.

19. The method of claim 1 , wherein the electrolyte comprises a linear carbonate solvent.

20. The method of claim 19 , wherein the solvent comprises ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl 2,2,2-trifluoroethyl carbonate (TFEMC), ethyl 2,2,2-trifluoroethyl carbonate (TFDEC), difluoromethyl fluoromethyl carbonate (TFDMC), or a mixture thereof.

21. The method of claim 1 , wherein the separator comprises polyolefin, cellulose, or a combination thereof.

22. The method of claim 1 , wherein the adhesive comprises poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA).

23. The method of claim 1 , wherein the first electrode is an anode and the second electrode is a cathode.

24. The method of claim 1 , wherein the first electrode comprises a Si-composite electrochemically active film.