All-inorganic solvents for electrolytes

1. An electrolyte for use in a lithium battery, comprising:

lithium ions in an amount of at least 0.1 M;

at least one cyclic phosphazene;

at least one phosphoranimine; and

at least one monomeric phosphorus compound;

wherein the electrolyte:

is a liquid at ≤0° C.;

has a viscosity of ≤30 cp at 35° C.; and

has a concentration volatile flammable components formed in an air headspace at 30° C. which is non-flammable.

2. The electrolyte according to claim 1 , wherein the at least one cyclic phosphazene is present in an amount of at least 3% and up to 50% by volume.

3. The electrolyte according to claim 2 , wherein the at least one phosphoranimine is present in an amount of at least 20% and up to 50% by volume.

4. The electrolyte according to claim 3 , wherein the at least one monomeric phosphorus compound is present in an amount of at least 10% and up to 50% by volume.

5. The electrolyte according to claim 1 , wherein has a vapor pressure of less than 40 mmHg at 30° C., a melting point above −30 C, and a viscosity ≥1 cp.

6. The electrolyte according to claim 1 , wherein the electrolyte consists essentially of compositions lacking direct phosphorus-halogen bonds.

7. The electrolyte according to claim 1 , in combination with:

an anode,

a cathode, and

a lithium-ion permeable separator configured to separate the anode and the cathode.

8. The electrolyte according to claim 7 , further comprising an electrochemically-formed a solid electrolyte interface layer which stable against degradation at 65° C.

9. The electrolyte according to claim 1 , comprising between 0.1% and 50% by volume of the at least one cyclic phosphazene, between 10% and 50% by volume of the at least one phosphoranimine, and between 10% and 50% by volume of the at least one monophosphorus compound.

10. An electrolyte for use in a lithium battery, which is liquid at 0° C., comprising:

a supporting lithium salt;

and a solvent comprising:

cyclic phosphazenes in an amount of at least 0.1% and less than 70% by volume;

phosphoranimines in an amount of at least 20% and less than 89.9% by volume; and

monomeric phosphorus compounds in an amount of at least 10% and less that 79.1% by volume;

having a vapor pressure of less than 40 mmHg at 30° C.

11. The electrolyte of claim 10 , wherein the cyclic phosphazenes, phosphoranimines, and monomeric phosphorus compounds each lacks direct phosphorus-halogen bonds.

12. The electrolyte according to claim 10 , in combination with:

an anode,

a cathode, and

a separator configured to separate the anode and the cathode and permit lithium ion permeability there-through,

wherein the supporting lithium salt provides a lithium ion concentration of at least 0.2 M, and a solid electrolyte interphase layer selectively forms near a surface of the anode and cathode from degradation products of the electrolyte.

13. The electrolyte of claim 12 , wherein a solid electrolyte interface layer formed by the electrolyte with an electrode is thermally stable at ≥80° C.

14. The electrolyte of claim 12 , wherein the phosphoranimines comprise a plurality of different phosphoranimines, the different phosphoranimines respectively differing by at least having respectfully different substituents.

15. The electrolyte of claim 12 , wherein the electrolyte comprises between 3% and 50% of the cyclic phosphazenes by volume and between 20% and 50% of the phosphoranimines by volume.

16. The electrolyte of claim 15 , wherein the electrolyte comprises up to 50% by volume of the monomeric phosphorus compounds, and less than 2% purely organic compounds consisting essentially of carbon, hydrogen and oxygen.

17. The electrolyte of claim 10 , having a viscosity of ≥1 cp and ≤30 cp at 35° C., a melting point above −30 C, and a concentration of lithium ions of at least 0.2M.

18. The electrolyte of claim 10 , wherein the cyclic phosphazenes comprise a plurality of different cyclic phosphazenes having a plurality of respectfully different substituents.

19. The electrolyte of claim 12 , wherein the solid electrolyte interphase layer is stable against degradation at 65° C.

20. The electrolyte of claim 12 , wherein the solid electrolyte interphase layer is stable for at least 245 days at 60° C.

21. An electrolyte formulation, comprising:

a lithium salt in an amount sufficient to provide at least 0.1 M lithium ions;

a phosphoranimine in an amount of at least 20% and less than or equal to 89.9% by volume;

a cyclic phosphazene in an amount of at least 0.1% and less than or equal to 70% by volume; and

a monomeric phosphorus compound in an amount of at least 10% and less than or equal to 79.9% by volume;

the formulation having: a viscosity of ≤30 cp at 35° C., a melting point below 0° C., and a vapor pressure of ≤40 mmHg at 30° C., wherein none of the phosphoranimine, cyclic phosphazene, and monomeric phosphorus compound has any direct halogen-phosphorus bonds.

22. The formulation of claim 21 , wherein the supporting salt comprises LiPF 6 .

23. The formulation of claim 21 , wherein the monomeric phosphorus compound is selected from the group consisting of a phosphate, phosphonate, phosphinate, phosphine, and a phosphine oxide, having at least two different types of pendent groups.

24. The formulation of claim 21 , wherein the phosphoranimine has the structure:

wherein X, R 1 , R 2 , and R 3 are independently selected from the group consisting of inorganic and organic functional groups, wherein R 1 , R 2 , and R 3 are represented by at least two different substituents.

25. The formulation of claim 24 , wherein X is selected from the group consisting of an organosilyl group and a tert-butyl group and R 1 , R 2 , and R 3 are independently selected from the group consisting of a substituted or unsubstituted alkoxy group, and a substituted or unsubstituted aryloxy group.

26. The formulation of claim 21 , wherein the cyclic phosphazene comprises a plurality of cyclic phosphazenes having respectively different pendent group substitution, having substituents selected from the group consisting of alkoxy groups and fluorinated alkoxy groups.

27. The formulation of claim 21 , comprising less than 2% by weight of organic compounds consisting essentially of at least one of carbon, hydrogen, and oxygen.

28. The formulation of claim 21 , wherein the phosphoranimine is present in an amount of between 20-50% by volume, the cyclic phosphazene is present in an amount of between 3-15% by volume, and the monomeric phosphorus compound is present in an amount of 20-50% by volume, the formulation has a viscosity of at least 1 cp, and a melting point of at least −30 C.

29. A battery comprising the formulation of claim 21 , in combination with an anode, a cathode, and a separator.