All-inorganic solvents for electrolytes
An all-inorganic electrolyte formulation for use in a lithium ion battery system comprising at least one of each a phosphoranimine, a phosphazene, a monomeric organophosphate and a supporting lithium salt. The electrolyte preferably has a melting point below 0° C., and a vapor pressure of combustible components at 60.6° C. sufficiently low to not produce a combustible mixture in air, e.g., less than 40 mmHg at 30° C. The phosphoranimine, phosphazene, and monomeric phosphorus compound preferably do not have any direct halogen-phosphorus bonds. A solid electrolyte interface layer formed by the electrolyte with an electrode is preferably thermally stable ≥80° C.
1. An electrolyte solvent formulation comprising:
a phosphoranimine; and
a cyclic phosphazene,
the electrolyte solvent formulation:
being adapted to solvate lithium ions at a charge carrier density of at least 0.1M,
having a viscosity of ≤30 cp at 35° C., and
having a vapor pressure of combustible components at 60.6° C. sufficiently low to not produce a combustible mixture in air.
2. The electrolyte solvent formulation according to claim 1 , further comprising a monomeric phosphorus compound.
3. The electrolyte solvent formulation according to claim 2 , wherein none of the phosphoranimine, the cyclic phosphazene, and the monomeric phosphorus compound has any direct halogen-phosphorus bonds.
4. The electrolyte solvent formulation according to claim 2 , wherein the electrolyte solvent formulation comprises at least 95% by weight phosphorus-containing compounds.
5. The electrolyte solvent formulation according to claim 2 , wherein the electrolyte solvent formulation comprises less than 2% by weight organic compounds consisting essentially of carbon, oxygen and hydrogen.
6. The electrolyte solvent formulation according to claim 1 , further comprising a supporting salt in an amount sufficient to provide a concentration of at least 0.1M charge carrier ions.
7. The electrolyte solvent formulation according to claim 6 , wherein the supporting salt comprises a supporting lithium salt.
8. The electrolyte solvent formulation according to claim 7 , wherein the supporting salt comprises LiPF 6 .
9. The electrolyte solvent formulation according to claim 1 , further comprising a monomeric phosphorus compound selected from the group consisting of a phosphate, phosphonate, phosphinate, phosphine, and a phosphine oxide, having at least two different types of pendent groups.
10. The electrolyte solvent formulation according to claim 1 , wherein the phosphoranimine has the structure:
wherein R 1 , R 2 , and R 3 are independently selected from the group consisting of at least two different organic functional groups, and X is selected from the group consisting of an organosilyl group and a tert-butyl group.
11. The electrolyte solvent formulation according to claim 10 , wherein R 1 , R 2 , and R 3 are independently selected from the group consisting of an alkoxy group, and an aryloxy group.
12. The electrolyte solvent formulation according to claim 1 , wherein the cyclic phosphazene comprises substituents selected from the group consisting of alkoxy and fluorinated alkoxy groups.
13. The electrolyte solvent formulation according to claim 12 , wherein the cyclic phosphazene comprises at least one of an ethoxy substituent and a 2,2,2-trifluoroethoxy substituent.
14. The electrolyte solvent formulation according to claim 1 , where the cyclic phosphazene is present in an amount of between 20-50% by volume.
15. The electrolyte solvent formulation according to claim 1 , where the phosphoranimine is present in an amount of between 10% and 20% by volume.
16. The electrolyte solvent formulation according to claim 1 , further comprising a monomeric organophosphate compound present in an amount of between 10% and 50% by volume.
17. The electrolyte solvent formulation according to claim 1 , wherein the phosphoranimine is present in an amount of between 20-50% by volume, and the cyclic phosphazene is present in an amount of between 3-15% by volume, further comprising a monomeric phosphorus compound present in an amount of 20-50% by volume, wherein the electrolyte solvent formulation has at least 95% phosphorus-containing compounds.
18. The electrolyte solvent formulation according to claim 1 , having a vapor pressure of less than 40 mmHg at 30° C.
19. An electrolyte solvent formulation comprising:
a phosphoranimine;
a cyclic phosphazene; and
a monomeric phosphorus compound,
wherein the electrolyte solvent formulation comprises at least 95% by weight phosphorus compounds,
the electrolyte solvent formulation:
being adapted to solvate lithium ions at a charge carrier density of at least 0.1M,
having a vapor pressure of less than 40 mm Hg at 30° C.,
having a viscosity of ≤30 cp at 35° C.,
having a vapor pressure of combustible components at 60.6° C. sufficiently low to not produce a combustible mixture in air, and
being adapted to form a solid electrolyte interphase layer at an electrode of a lithium ion battery which is stable for at least 245 days at 60° C.
20. An electrolyte solvent formulation comprising:
a mixture of at least 95% by weight phosphorus compounds, selected from the group consisting of two or more of a phosphoranimine, a cyclic phosphazene, and a monomeric phosphorus compound, formulated to:
have a charge carrier density of lithium ions of at least 0.1M,
have a viscosity of ≤30 cp at 35° C.,
have a vapor pressure of less than 40 mm Hg at 30° C.,
have a vapor pressure of combustible components at 60.6° C. sufficiently low to not produce a combustible mixture in air, and
form a solid electrolyte interphase layer at an electrode of a lithium ion battery which is stable for at least 245 days at 60° C.