Electrochemical device having a solid alkaline ion-conducting electrolyte and an aqueous electrolyte
The present invention relates to an alkaline cation-conducting ceramic membrane covered, over at least a portion of the surface thereof, with a cation-conducting organic polyelectrolyte layer that is insoluble and chemically stable in pH-basic water. The invention also relates to an electrochemical device including such a membrane as a solid electrolyte in contact with a liquid electrolyte formed of an alkali metal hydroxide aqueous solution.
1. An electrochemical device comprising:
a solid, ceramic membrane electrolyte
a liquid aqueous solution of alkali-metal hydroxide electrolyte,
wherein
the ceramic membrane electrolyte is from 30 μm to 500 μm in thickness,
the ceramic membrane electrolyte conducts Li + ions,
at least a first surface of the ceramic membrane covered with an organic cation-conductive halopolymer layer, wherein the ceramic electrolyte membrane does not contact the liquid electrolyte over the entire first surface of the ceramic electrolyte membrane,
wherein said halopolymer layer is between 1 and 50 μm in thickness, insoluble and chemically stable in water at a basic pH, in contact with the liquid aqueous solution of alkali metal hydroxide electrolyte.
2. The electrochemical device as claimed in claim 1 , wherein the solid ceramic membrane has the chemical formula:
Li 1+x (M,Ga,Al) x (Ge 1−y Ti y ) 2−x (PO 4 ) 3 ,
where M is one or more metals chosen from Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and
where 0<x<0.8 and 0<y<1.0.
3. The electrochemical device as claimed in claim 1 , wherein the halopolymer has the formula:
where X represents a —COO − group or an —SO3 − group and M + represents a proton or a metal cation.
4. The electrochemical device as claimed in claim 1 , wherein the halopolymer is a copolymer of tetrafluoroethylene and a comonomer bearing acid group(s).
5. The electrochemical device of claim 4 , wherein the acid group has a formula —SO3 − M + wherein M is a metal cation or proton.
6. The electrochemical device of claim 1 , wherein the halopolymer layer is from 2 to 10 μm in thickness.
7. The electrochemical device as claimed in claim 1 , wherein the second surface of the ceramic electrolyte membrane is covered with a protective coating comprising Li 3 N, Li 3 P, LiI, LiBr, LiF or lithium phosphorus oxynitride (LiPON).
8. The electrochemical device as claimed in claim 1 , wherein the device is a lithium-air battery.
9. The electrochemical device as claimed in claim 1 , wherein the device is a lithium-water battery.
10. The electrochemical device as claimed in claim 1 , wherein the device is an electrolysis cell.
11. The electrochemical device as claimed in claim 1 , wherein the device is a lithium pump.
12. The electrochemical device as claimed in claim 1 , wherein the ceramic membrane electrolyte is from 50 μm to 160 μm in thickness.
13. The electrochemical device as claimed in claim 1 , wherein the second surface of the ceramic membrane is covered with LiPON protective coating.
14. A method for preventing formation of a dense crystalline layer of LiOH at the solid electrolyte/aqueous electrolyte interface, comprising preparing an electrochemical device comprising:
a solid, ceramic membrane electrolyte and
a liquid aqueous solution of alkali-metal hydroxide electrolyte,
wherein
the ceramic membrane electrolyte is from 30 μm to 500 μm in thickness,
the ceramic membrane electrolyte conducts Li + ions,
at least a first surface of the ceramic electrolyte membrane covered with an organic cation-conductive halopolymer layer, and
wherein said halopolymer layer is between 1 and 50 μm in thickness, insoluble and chemically stable in water at a basic pH, and in contact with the liquid aqueous solution of alkali metal hydroxide electrolyte.
15. A method for preventing formation of a dense crystalline layer of LiOH at the solid electrolyte/aqueous electrolyte interface, comprising in an electrochemical device comprising:
a solid, ceramic membrane electrolyte and
a liquid aqueous solution of alkali-metal hydroxide electrolyte,
wherein
the ceramic membrane electrolyte is from 30 μm to 500 μm in thickness, and
the ceramic membrane electrolyte conducts Li + ions,
wherein the method comprises covering
at least a first surface of the ceramic electrolyte membrane with an organic cation-conductive halopolymer layer, wherein the ceramic electrolyte membrane does not contact the liquid electrolyte over the entire first surface of the ceramic electrolyte membrane,
and
wherein said halopolymer layer is between 1 and 50 μm in thickness, insoluble and chemically stable in water at a basic pH, is in contact with the liquid aqueous solution of alkali metal hydroxide electrolyte and conducts cations between said liquid aqueous solution of alkali-metal hydroxide electrolyte and said ceramic membrane electrolyte.
16. The method of claim 14 or 15 wherein in the electrochemical device, the solid ceramic membrane has the chemical formula:
Li 1+x (M,Ga,Al) x (Ge 1−y Ti y ) 2−x (PO 4 ) 3 ,
where M is one or more metals chosen from Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and
where 0<x<0.8 and 0<y<1.0.
17. The method of claim 14 or 15 wherein the halopolymer has the formula:
where X represents a —COO − group or an —SO3 − group and M + represents a proton or a metal cation.
18. The method of claim 14 or 15 wherein the halopolymer is a copolymer of tetrafluoroethylene and a comonomer bearing acid group(s).
19. The method claim 18 , wherein the acid group has a formula —SO3 − M + wherein M is a metal cation or proton.
20. The method of claim 14 or 15 wherein the halopolymer layer is from 2 to 10 μm in thickness.
21. The method of claim 14 or 15 wherein the second surface of the ceramic electrolyte membrane is covered with a protective coating comprising Li 3 N, Li 3 P, LiI, LiBr, LiF or lithium phosphorus oxynitride (LiPON).
22. The method of claim 14 or 15 wherein the device is a lithium-air battery.
23. The method of claim 14 or 15 wherein the device is a lithium-water battery.
24. The method of claim 14 or 15 wherein the device is an electrolysis cell.
25. The method of claim 14 or 15 wherein the device is a lithium pump.
26. The method of claim 14 or 15 wherein the ceramic membrane electrolyte is from 50 μm to 160 μm in thickness.
27. The method of claim 14 or 15 wherein the second surface of the ceramic membrane is covered with LiPON protective coating.