Artificial SEI transplantation
An anode for a Li-ion cell, protected with an SEI by pre-treatment in an SEI-formation cell, is stable for cell cycling even in the presence of substantial water in the cell electrolyte. A method for making the protected anode includes forming an SEI on a lithium electrode by performing multiple charge/discharge cycles on the electrode in a first cell having an SEI formation electrolyte to produce the protected anode. The SEI formation electrolyte includes an ionic liquid having at least one of eight organic cations.
1. A method for preparing a lithium-ion cell having a protected anode with a pre-formed solid electrolyte interphase (SEI), the method comprising:
forming an SEI on a lithium electrode by performing multiple charge/discharge cycles on the electrode in a first cell having an SEI formation electrolyte to produce the protected anode, the SEI formation electrolyte comprising:
lithium bis(fluorosulfonyl)imide (LiFSI); and
an ionic liquid comprising:
an organic cation selected from the group consisting of: 1-methyl-1-propylpyrrolidinium; N-methyl-N,N-diethyl-N-propylammonium; N,N-diethyl-N-methyl-N-(2-methoxyethyl)-ammonium; 1,1-methylpropylpiperidinium; N-methyl-N-(2-methoxyethyl)-pyrrolidinium; trimethylisopropylphosphonium; methyltriethylphosphonium; methyltributylphosphonium; and mixtures thereof; and
a (fluorosulfonyl)imide anion (FSI)
assembling a wet Li-ion voltaic cell comprising:
the protected anode; and
a wet electrolyte in contact with the protected anode, the wet electrolyte comprising at least 50 ppm water.
2. The method as recited in claim 1 , wherein LiFSI is present at a molar ratio, relative to ionic liquid of: at least 1:1.
3. The method as recited in claim 1 , wherein LiFSI is present at its saturation point in the ionic liquid.
4. The method as recited in claim 1 , further comprising, prior to assembling the wet Li-ion voltaic cell, washing the protected anode with a solvent in which the SEI formation electrolyte is soluble.
5. The method as recited in claim 1 , wherein the SEI formation electrolyte has a water content of less than 50 ppm.
6. The method as recited in claim 1 , wherein the wet electrolyte comprises water present at a concentration of at least 100 ppm.
7. The method as recited in claim 1 , wherein the wet electrolyte comprises water present at a concentration of at least 500 ppm.
8. The method as recited in claim 1 , wherein the wet electrolyte comprises water present at a concentration of at least 1000 ppm.
9. The method as recited in claim 1 , wherein the wet electrolyte comprises water present at a concentration of at least 4000 ppm.
10. The method as recited in claim 1 , wherein the wet electrolyte comprises water present at a concentration of at least 16000 ppm.
11. The method as recited in claim 1 , wherein the cation comprises Pyr13.
12. The method as recited in claim 1 , wherein the cation comprises N1223.
13. The method as recited in claim 1 , wherein the cation comprises DEME.
14. The method as recited in claim 1 , wherein the cation comprises Pip13.
15. The method as recited in claim 1 , wherein the cation comprises P111 i 4.
16. The method as recited in claim 1 , wherein the cation comprises Pyr12 o 1.
17. The method as recited in claim 1 , wherein the cation comprises P1222.
18. The method as recited in claim 1 , wherein the cation comprises P1444.