Fluorinated electrolytes with nitrile groups
Perfluoropolyether electrolytes have either one or two terminal nitrile groups and an alkali metal salt. The alkali metal salt can be a lithium salt, a sodium salt, a potassium salt, or a cesium salt. The salt can make up between 5 and 30 wt % of the electrolyte composition. Such electrolytes have shown high ionic conductivities, making them useful as lithium cell electrolytes.
1. An electrolyte, comprising:
a mixture of
perfluoropolyethers, each having either one or two terminal nitrile groups covalently coupled thereto; and
an alkali metal salt;
wherein the perfluoropolyethers are selected from the group consisting of:
and combinations thereof, and
wherein x is the mole fraction of difluoromethyleneoxy groups in the perfluoropolyether, and x ranges between 0 and 1;
y is the mole fraction of tetrafluoroethyleneoxy groups in the perfluoropolyether, y is equal to (1−x) and y ranges between 0 and 1;
n is the average total number of randomly co-distibuted difluoromethyleneoxy and tetrafluoroethyleneoxy groups in the perfluoropolyether, and n ranges between 1 and 50;
Rf is a perfluorinated C1-C8 straight alkyl group or a perfluorinated C1-C8 branched alkyl group; and
R 1 is selected from the group consisting of C1-C8 straight alkyl groups, C1-C8 branched alkyl groups, polyethers, cyanoethyls, pyrrolidine, piperidine, morpholine, 4-methylpiperazine, and C5-C8 heterocycloalkyl groups that contain nitrogen.
2. The electrolyteof claim 1 , wherein the alkali metal salt is a lithium salt.
3. The electrolyte of claim 1 , wherein the alkali metal salt is a sodium salt.
4. The electrolyte of claim 1 , wherein the alkali metal salt comprises between 5 to 30 wt % of the electrolyte.
5. The electrolyte of claim 1 wherein the polyethers are selected from the group consisting of 2-methoxyethyl and 2-(2-ethoxy)ethoxyethyl.
6. An electrolyte composing:
a mixture of:
perfluoropolyethers, each having one or two terminal nitrile groups covalently coupled thereto; and
an alkali metal salt;
wherein the perfluoropolyethers are selected from the group consisting of:
and combinations thereof, and
wherein x is the mole fraction of difluoromethyleneoxy groups in the perfluoropolyether, and x ranges between 0 and 1;
y is the mole fraction of tetrafluoroethyleneoxy groups in the perfluoropolyether, y is equal to (1−x) and y ranges between 0 and 1;
n is the average total number of randomly co-distributed difluoromethyleneoxy and tetrafluoroethyleneoxy groups in the perfluoropolyether and n ranges between 1 and 50; and
Rf is a perfluorinated C1-C8 straight alkyl group or a perfluorinated C1-C8 branched alkyl group; and
R 2 and R 3 are each selected independently from the group consisting of —CN, C1-C8 straight alkyl groups, C1-C8 branched alkyl groups, polyethers, cyanoethyls, hydrogen, pyrrolidine, piperidine, morpholine, 4-methylpiperazine, and C5-C8 heterocycloalkyl groups that contain nitrogen.
7. An electrochemical cell, comprising:
an anode;
a cathode; and
an electrolyte between the anode and the cathode, the electrolyte in ionic communication with both the anode and the cathode;
wherein the electrolyte comprises:
the electrolyte of claim 1 or the electrolyte of claim 6 .
8. The cell of claim 7 , wherein the anode comprises a material selected from the group consisting of lithium metal and alloys, graphite, lithium titanante, silicon, silicon alloys, and combinations thereof.
9. The cell of claim 7 , wherein the cathode comprises a material selected from the group consisting of nickel cobalt aluminum oxide (NCA), nickel cobalt manganese oxide (NCM), LiCoO 2 , LiFePO 4 , LiMnPO4, LiNiPO 4 , LiCoPO 4 , LiNi 0.5 Mn 1.5 O 4 , Li 2 MnSiO 4 , Li 2 FeSiO 4 and LiMn 2 O 4 particles, and combination thereof.
10. An electrochemical cell, comprising:
an anode configured to absorb and release lithium ions;
a cathode comprising cathode active material particles, an electronically-conductive additive, a catholyte, and an optional binder material;
a current collector adjacent to an outside surface of the cathode; and
a separator region between the anode and the cathode, the separator region comprising a separator electrolyte configured to facilitate movement of lithium ions back and forth between the anode and the cathode;
wherein the catholyte comprises:
the electrolyte of claim 1 or the electrolyte of claim 6 .
11. The electrolyte of claim 6 , wherein the alkali metal salt is a lithium salt.
12. The electrolyte of claim 6 , wherein the alkali metal salt is a sodium salt.
13. The electrolyte of claim 6 , wherein the alkali metal salt comprises between 5 to 30 wt % of the electrolyte.