Aqueous electrolyte with carbonate and batteries using the same
An electrolyte composition has a fluoroalkylsulfonyl salt and water. The water is present, relative to the fluoroalkylsulfonyl salt, at a molar ratio within a range of 0.1:1 to 10:1, inclusive. This creates a “water-in-salt” in which individual water molecules are surrounded by salt rather than vice versa. Water contained in this environment is electrochemically stabilized relative to a bulk water. The electrolyte also has an organic carbonate present, relative to the fluoroalkylsulfonyl salt, at a molar ratio within a range of 0.1:1 to 50:1, inclusive. It has been discovered that inclusion of the organic carbonate further increases the electrochemical stability of the water within the “in-salt” environment.
1. An electrolyte composition having:
a lithium fluoroalkylsulfonyl salt selected from the group consisting of:
lithium bis(fluorosulfonyl)imide (LiFSI);
lithium bis(trifluoromethane)sulfonamide (LiTFSI);
lithium bis(perfluoroethanesulfonyl)imide (LiBETI); and
mixtures thereof;
an organic carbonate selected from the group consisting of:
dimethyl carbonate;
diethyl carbonate;
ethylene carbonate;
propylene carbonate; and
mixtures thereof,
the organic carbonate present at a first molar ratio, relative to the lithium fluoroalkylsulfonyl salt, within a range of 0.1:1 to 50:1, inclusive; and
water, present at a second molar ratio, relative to the lithium fluoroalkylsulfonyl salt, within a range of 1:1 to 5:1.
2. The electrolyte composition as recited in claim 1 , wherein the first molar ratio is within a range of 0.5:1 to 20:1, inclusive.
3. The electrolyte composition as recited in claim 1 , wherein the lithium fluoroalkylsulfonyl salt is present at a mole fraction of at least 0.3 of the electrolyte composition.
4. The electrolyte composition as recited in claim 1 , wherein the lithium fluoroalkylsulfonyl salt comprises LiTFSI.
5. The electrolyte composition as recited in claim 1 , wherein the organic carbonate comprises propylene carbonate.
6. A Li-ion cell comprising:
an anode;
a cathode; and
an electrolyte composition placing the anode and the cathode in ionic communication with one another, the electrolyte composition comprising:
a lithium fluoroalkylsulfonyl salt selected from the group consisting of:
lithium bis(fluorosulfonyl)imide (LiFSI);
lithium bis(trifluoromethane)sulfonamide (LiTFSI);
lithium bis(perfluoroethanesulfonyl)imide (LiBETI); and
mixtures thereof; and
an organic carbonate selected from the group consisting of:
dimethyl carbonate;
diethyl carbonate;
ethylene carbonate;
propylene carbonate; and
mixtures thereof,
the organic carbonate present at a first molar ratio, relative to the lithium fluoroalkylsulfonyl salt, within a range of 0.1:1 to 50:1, inclusive; and
water, present at a second molar ratio, relative to the lithium fluoroalkylsulfonyl salt, within a range of 1:1 to 5:1.
7. The Li-ion cell as recited in claim 6 , wherein the first molar ratio is within a range of 0.5:1 to 20:1, inclusive.
8. The Li-ion cell as recited in claim 6 , wherein the lithium fluoroalkylsulfonyl salt is present at a mole fraction of at least 0.3 of the electrolyte composition.
9. The Li-ion cell as recited in claim 6 , wherein the lithium fluoroalkylsulfonyl salt comprises LiTFSI.
10. The Li-ion cell as recited in claim 6 , wherein the organic carbonate comprises a cyclic organic carbonate.
11. The Li-ion cell as recited in claim 6 , wherein the organic carbonate comprises at least one of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate.
12. The Li-ion cell as recited in claim 6 , wherein the cathode has a redox potential at least 2.5 V more positive than a redox potential of the anode.
13. The Li-ion cell as recited in claim 6 , wherein the cathode has a redox potential at least 3.0 V more positive than a redox potential of the anode.
14. The Li-ion cell as recited in claim 6 , wherein the cathode comprises at least one of: LiMn 2 O 4 ; LiCoO 2 ; LiFe(PO 4 ); LiMn 1/3 Ni 1/3 Co 1/3 O 2 ; LiNi 0.5 Mn 1.5 O 4 ; and LiCoPO 4 .
15. The Li-ion cell as recited in claim 6 , wherein the anode comprises at least one of: Li 4 Ti 5 O 12 , Mo 6 S 8 , Cu 2 V 2 O 7 , TiS 4 , NbS 5 , Li terephthalate (C 8 H 4 Li 2 O 4 ), silicon, sulfur, and graphite.
16. The Li-ion cell as recited in claim 6 , wherein the anode comprises Li 4 Ti 5 O 12 and the cathode comprises LiNi 0.5 Mn 1.5 O 4 .
17. The Li-ion cell as recited in claim 6 , wherein the anode comprises Li 4 Ti 5 O 12 ; the cathode comprises LiNi 0.5 Mn 1.5 O 4 ; the lithium fluoroalkylsulfonyl salt comprises LiTFSI; the organic carbonate comprises propylene carbonate; the first molar ratio is 1:1; and the second molar ratio is 1:1.
18. An electrolyte composition having:
a lithium fluoroalkylsulfonyl salt;
an organic carbonate, present at a first molar ratio, relative to the lithium fluoroalkylsulfonyl salt, within a range of 0.1:1 to 50:1, inclusive; and
water, present at a second molar ratio, relative to the lithium fluoroalkylsulfonyl salt, within a range of 1:1 to 5:1;
wherein the lithium fluoroalkylsulfonyl salt is present at a mole fraction of at least 0.3 of the electrolyte composition.