Metal-air cell with performance enhancing additive
View Patent ↗Systems and methods drawn to an electrochemical cell comprising a low temperature ionic liquid comprising positive ions and negative ions and a performance enhancing additive added to the low temperature ionic liquid. The additive dissolves in the ionic liquid to form cations, which are coordinated with one or more negative ions forming ion complexes. The electrochemical cell also includes an air electrode configured to absorb and reduce oxygen. The ion complexes improve oxygen reduction thermodynamics and/or kinetics relative to the ionic liquid without the additive.
1. A method comprising:
mixing (a) an oxygen reduction enhancing compound that dissociates into oxygen reduction enhancing positive ions, with (b) a low temperature ionic liquid to create a solution comprising an oxygen reduction enhancing positive-negative ion complex formed between the oxygen reduction enhancing positive ions and one or more negative ions in the low temperature ionic liquid;
exposing the solution to oxygen; and
electrochemjcally reducing the oxygen,
wherein the oxygen reduction enhancing compound comprises an additive that is at least one of triflic acid, benzonitrile: HTf, acetophenone: HTf, methanesulfonic acid, hydronium triflate, pyridazinium triflate, acetic acid, pryidinium triflate, 1,2-dimethjylimidaozlium triflate, n,n- diethyl-n-methylammonium triflate, 2,2,2-trifluoroethanol, and 2-butyl-1,1,3,3-tetramethylguanidinium triflate.
2. The method of claim 1 , wherein the reducing the oxygen occurs with improved oxygen reduction thermodynamics, kinetics, or both, relative to electrochemical oxygen reduction in the ionic liquid without the metal-containing additive.
3. The method of claim 1 , wherein the oxygen is electrochemically reduced using a catalyst.
4. The method of claim 1 , wherein the electrochemically reducing the oxygen occurs in an electrochemical cell.
5. The method of claim 1 , wherein the solution further comprises an oxygen reduction enhancing compound comprising a metal-containing additive.
6. The method of claim 5 , wherein the metal of the metal-containing additive is selected from the group consisting of Mg, Al, Mn, Ga, and Zn.
7. The method of claim 1 , wherein the solution further comprises an oxygen reduction enhancing compound comprising a metal, water, an organic molecule, or combinations thereof.
8. The method of claim 1 , wherein the solution further comprises an oxygen reduction enhancing compound comprises a protic organic molecule containing additive.
9. The method of claim 1 , wherein the low temperature ionic liquid is selected from the group consisting of triethylammonium methansulfonate, 1-methyl-3-octylimidazolium tetrachlorogallate, diethylmethylammonium triflate, and 1-butyl-3-methylimidazolium bis(trifluoromethane)sulfonamide.
10. The method of claim 1 , wherein the electrochemically reducing the oxygen occurs in a metal-air ionic liquid battery comprising a metal electrode and an air electrode.
11. The method of claim 1 , wherein the oxygen reduction enhancing positive-negative ion complex enhances reversibility of an air cathode of a metal-air ionic liquid battery.
12. The method of claim 1 , wherein the low temperature ionic liquid is aprotic.
13. The method of claim 1 , wherein the low temperature ionic liquid is a room temperature ionic liquid (RTIL).
14. The method of claim 1 , further comprising flowing the low temperature ionic liquid in a gap between a metal electrode and an air electrode.
15. The method of claim 1 , further comprising forming metal-oxide by-products at a metal fuel electrode.
16. The method of claim 1 , further comprising storing metal-oxide by-products at the metal electrode.
17. The method of claim 1 , further comprising forming metal-oxide by-product at an air electrode.
18. The method of claim 1 , further comprising storing metal-oxide by-products at the air electrode.
19. The method of claim 1 , wherein the electrochemical oxygen reduction half-reaction involves a transfer of at least two electrons per oxygen molecule.