Non-aqueous fluoride salts, solutions, and their uses
Electrolyte solutions including at least one anhydrous fluoride salt and at least one non-aqueous solvent are presented. The fluoride salt includes an organic cation having a charge center (e.g., N, P, S, or O) that does not possess a carbon in the β-position or does not possess a carbon in the β-position having a bound hydrogen. This salt structure facilitates its ability to be made anhydrous without decomposition. Example anhydrous fluoride salts include (2,2-dimethylpropyl)trimethylammonium fluoride and bis(2,2-dimethylpropyl)dimethylammonium fluoride. Combining these fluoride salts with at least one fluorine-containing non-aqueous solvent (e.g., bis(2,2,2-trifluoroethyl)ether; (BTFE)) promotes solubility of the salt within the non-aqueous solvents. The solvent may be a mixture of at least one non-aqueous, fluorine-containing solvent and at least one other non-aqueous, fluorine or non-fluorine containing solvent (e.g., BTFE and propionitrile or dimethoxyethane). The electrolyte solutions may be employed in electrochemical cells, such as batteries, fuel cells, electrolysis systems, and capacitors.
1. A method of making a fluoride ion containing solution, the method comprising:
dissolving a fluoride salt into one or more non-aqueous solvents, the fluoride salt being provided to the one or more non-aqueous solvents in an anhydrous form;
wherein the fluoride salt comprises:
one or more fluoride ions; and
an organic cation, wherein:
the organic cation does not possess a carbon in the β-position having a bound hydrogen; and
the cation charge center is N, P, S, or O;
wherein the one or more non-aqueous solvents are fluorinated and comprise at least one functional group characterized by the form [X—(CH 2 ) n —Y], where X and Y are polar functional groups having a combined effect to confer a partial positive charge on the CH 2 group or groups and n=1 or 2;
wherein the fluoride salt is a substituted or unsubstituted (2,2-dimethylpropyl)trimethylammonium fluoride (NpMe 3 NF) or a substituted or unsubstituted bis(2,2-dimethylpropyl)dimethylammonium fluoride (Np 2 Me 2 NF); and
wherein the concentration of said fluoride ions dissolved in said solution is selected from the range of 0.5 M to 20 M.
2. The method of claim 1 , wherein the concentration of said fluoride ions dissolved in said solution is greater than or equal to 1 M and less than or equal to 20 M.
3. The method of claim 1 , wherein Y is O or S and X is a functional group selected from the group consisting of ethers, esters, acid anhydrides, amines, amides, carbonates, sulfones, sulfonyl esters, phosphites, phosphates, nitriles, nitro, aldehydes, acetates, SF 5 , or fluorocarbons.
4. The method of claim 1 , wherein the one or more non-aqueous solvents are characterized by the formula (FX7a) (FX7b), (FX7c), (FX7d), (FX7e), or (FX7g):
5. The method of claim 1 , wherein the non-aqueous solvent is a fluorinated phosphite or any combination thereof and the fluorinated phosphite is characterized by the formula (FX8a):
6. The method of claim 1 , wherein the non-aqueous solvent is a fluorinated ester or anhydride or any combination thereof and the fluorinated ester or anhydride is characterized by the formula (FX9b):
7. The method of claim 1 , wherein the non-aqueous solvent is a nitrile or any combination thereof and the nitrile is characterized by the formula (FX10c):
8. The method of claim 1 , wherein the non-aqueous solvent is characterized by the formula (FX12a):
wherein R 7 is a halo group or a halogen-substituted C 1 -C 20 alkyl, C 3 -C 20 cycloalkyl, C 5 -C 30 aryl, C 5 -C 30 heteroaryl, C 1 -C 20 acyl, C 2 -C 20 alkenyl, C 3 -C 20 cycloalkenyl, C 2 -C 20 alkynyl, C 5 -C 20 alkylaryl, C 1 -C 20 alkyl, C 2 -C 20 alkoxycarbonyl, C 4 -C 30 aliphatic, C 4 -C 30 cycloaliphatic, or C 4 -C 30 aromatic; and
wherein n is an integer selected from the range of 1 to 20.
9. The method of claim 1 , the solution further comprising a second non-aqueous solvent different from the one or more non-aqueous solvents.
10. The method of claim 9 , wherein the second non-aqueous solvent is an ether or a glyme.
11. The method of claim 9 , wherein a ratio of amounts of the first solvent and the second solvent is selected from the range from 1:20 to 20:1.
12. The method of claim 1 , wherein the fluoride salt is a first fluoride salt and the step of dissolving comprises dissolving a second fluoride salt in the fluoride ion containing solution, wherein the second fluoride salt is different than the first fluoride salt, and the second fluoride salt comprises:
one or more second fluoride ions; and
a second organic cation, wherein
the cation charge center of the second organic cation is N, P, S, or O;
wherein the total concentration of fluoride ions from the first fluoride salt and the second fluoride salt dissolved in the solution is selected from the range of 0.5 M to 20 M.
13. The method of claim 1 , wherein the solution provides an ionic conductivity greater than or equal to 0.1 mS/cm at 25° C.
14. The method of claim 1 , wherein the one or more non-aqueous solvents are selected from the group consisting of bis(2,2,2-trifluoroethyl)ether (BTFE), tris(2,2,2-trifluoroethyl)phosphite (TTFP), 2,2,2-trifluoroethyl trifluoroacetate (TFE-TFA), methoxyacetonitrile (MeOAN), 3-methoxypropionitrile (3-MeOPN), and fluoroethylene carbonate (FEC).