Aqueous and hybrid electrolytes with wide electrochemical stability windows

1. An electrolyte, comprising:

(a) at least one metal salt; and

(b) a solvent comprising between about 1% and about 100% water by weight;

wherein the molal concentration of the at least one metal salt in the electrolyte is between about 15 m and 100 m when water is the only solvent or the molal concentration of the at least one metal salt in the electrolyte is between about 5 m and 100 m when the solvent comprises water and at least one non-aqueous solvent, and wherein the electrochemical stability window of the electrolyte is between about 2.0 V and about 5.0 V.

2. The electrolyte of claim 1 , wherein the at least one metal salt comprises an anion selected from the group consisting of bis(trifluoromethane sulfonyl)imide (TF SI), trifluoromethane sulfonate (TF), bis(fluorosulfonyl)imide (FSI), tetrafluorophosphate (BF 4 ), hexafluorophosphate (PF 6 ), bis(pentafluoroethane sulfonyl) imide (BETI), 4,5-dicyano-2-trifluoromethanoimidazole (DCMI), [fluoro(nonafluorobutane) sulfonyl]imide (FNF), perchlorate (ClO 4 ), sulfate (SO 4 ), and nitrate (NO 3 ).

3. The electrolyte of claim 2 , wherein the at least one metal salt is selected from the group consisting of LiTFSI, LiTF, LiFSI, LiBETI, LiDCMI, LiFNF, LiClO 4 , LiSO 4 , LiNO 3 , NaTFSI, NaTF, NaFSI, NaBETI, NaDCMI, NaFNF, NaClO 4 , NaSO 4 , NaNO 3 , KTFSI, KTF, KFSI, KBETI, KDCMI, KFNF, KClO 4 , KSO 4 , KNO 3 , Mg(TFSI) 2 , Mg(TF) 2 , Mg(FSI) 2 , Mg(BETI) 2 , Mg(DCMI) 2 , Mg(FNF) 2 , Mg(ClO 4 ) 2 , Mg(SO 4 ) 2 , Mg(NO 3 ) 2 , Al(TFSI) 3 , Al(TF) 3 , Al(FSI) 3 , Al(BETI) 3 , Al(DCMI) 3 , Al(FNF) 3 , Al(ClO 4 ) 3 , Al(SO 4 ) 3 , and Al(NO 3 ) 3 .

4. The electrolyte of claim 3 , wherein the at least one metal salt is selected from the group consisting of LiTFSI, LiTF, NaTFSI, NaFSI, KTFSI, KBETI, and Mg(TFSI) 2 .

5. The electrolyte of claim 1 , wherein the solvent comprises water and at least one non-aqueous solvent.

6. The electrolyte of claim 5 , wherein the weight ratio of the at least one non-aqueous solvent in the solvent is between about 10% and about 90%.

7. The electrolyte of claim 5 , wherein the at least one non-aqueous solvent is an organic solvent.

8. The electrolyte of claim 5 , wherein the at least one non-aqueous solvent is an organic solvent selected from the group consisting of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, γ-butyrolactone, and vinylene carbonate.

9. The electrolyte of claim 5 , comprising two non-aqueous solvents, wherein at least one non-aqueous solvent is ethylene carbonate or fluoroethylene carbonate.

10. The electrolyte of claim 1 , wherein the electrolyte has an electrochemical stability window of between about 2.3 V and about 4.9 V.

11. The electrolyte of claim 1 , wherein the at least one metal salt is selected from the group consisting of LiTFSI, NaTFSI, NaFSI, Na(SO 3 CF 3 ), KTFSI, and Mg(TFSI) 2 , wherein the solvent comprises water and at least one non-aqueous solvent selected from the group consisting of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butyrolactone, and vinylene carbonate, and wherein the solvent comprises water at a weight ratio of between about 40% and about 100%.

12. The electrolyte of claim 1 , comprising:

(a) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 90%;

(b) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises ethylene carbonate, wherein the solvent comprises water at a weight ratio of 50%;

(c) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises ethylene carbonate and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 47.5%;

(d) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises polyethylene carbonate, wherein the solvent comprises water at a weight ratio of 50%;

(e) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises polyethylene carbonate and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 47.5%;

(f) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises γ-butyrolactone and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 47.5%;

(g) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises ethylene carbonate, wherein the solvent comprises water at a weight ratio of 80%;

(h) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises ethylene carbonate and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 72%; or

(i) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises vinylene carbonate and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 87%;

(j) the at least one metal salt comprises NaTFSI and the at least one non-aqueous solvent comprises ethylene carbonate, wherein the solvent comprises water at a weight ratio of 50%;

(k) the at least one metal salt comprises NaTFSI and the at least one non-aqueous solvent comprises ethylene carbonate and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 47.5%;

(l) the at least one metal salt comprises KTFSI and the at least one non-aqueous solvent comprises polyethylene carbonate, wherein the solvent comprises water at a weight ratio of 50%;

(m) the at least one metal salt comprises KBETI and the at least one non-aqueous solvent comprises polyethylene carbonate and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 47.5%;

(n) the at least one metal salt comprises Mg(TFSI) 2 and the at least one non-aqueous solvent comprises γ-butyrolactone and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 47.5%;

(o) the at least one metal salt comprises NaTFSI and the at least one non-aqueous solvent comprises ethylene carbonate, wherein the solvent comprises water at a weight ratio of 80%;

(p) the at least one metal salt comprises NaTFSI and the at least one non-aqueous solvent comprises ethylene carbonate and fluoroethylene carbonate, wherein the solvent comprises water at a weight ratio of 72%; or

(q) the at least one metal salt comprises LiTFSI and the at least one non-aqueous solvent comprises vinylene carbonate and ethylene carbonate, wherein the solvent comprises water at a weight ratio of 87%.

13. A battery cell comprising the electrolyte of claim 1 ; a positive electrode; and a negative electrode.

14. The battery cell of claim 13 , wherein the positive electrode is selected from the group consisting of LiMn 2 O 4 , LiCoO 2 , LiNi 0.33 Mn 0.33 Co 0.33 O 2 , LiNi 0.5 Mn 1.5 O 2 , LiCoPO 4 , and LiNiPO 4 .

15. The battery cell of claim 13 , wherein the negative electrode is selected from the group consisting of lithium, magnesium, aluminum, zinc, chromium, iron, nickel, tin, lead, hydrogen, copper, silver, palladium, mercury, platinum, gold, molybdenum, sulfur, combinations thereof, and oxides thereof.

16. The battery cell of claim 13 , wherein the negative electrode is Mo 6 S 8 and the positive electrode is LiMn 2 O 4 .

17. The battery cell of claim 13 , wherein the number of cycles of the battery cell at a C-rate of about 4.5 C is between about 10 and about 500.

18. The battery cell of claim 13 , wherein the number of cycles of the battery cell at a C-rate of about 1.5 C is between about 500 and about 2000.