High capacity bilayer cathode for aqueous Zn-ion batteries
Bilayer structured hydrated Ca—V oxide is disclosed as a high capacity cathode for rechargeable aqueous Zn-ion batteries, as well as methods for forming same to provide an improved cathode with significant improvements over existing cathode structures and materials.
1. An improved cathode for batteries comprising:
at least one nanobelt further comprising;
CaVO; and
a fernandinite bilayer structure; and
wherein the bilayer is hydrated.
2. The improved cathode of claim 1 , wherein the nanobelt CaVO stoichiometry comprises Ca 0.67 V 8 O 20 .3.5H 2 O.
3. The improved cathode of claim 1 , wherein the cathode has a discharge capacity of 466 mAh g −1 at 0.1 A g −1 .
4. The improved cathode of claim 1 having a capacity retention rate of 100%, 95% and 74% at 5.0 A g −1 for 500, 1,000, 2,000 cycles.
5. The improved cathode of claim 1 , wherein the fernandinite bilayer comprises a ρ-CaVO structure.
6. The improved cathode of claim 5 , wherein Ca 2+ structurally s tabilizes the ρ-CaVO structure and undergoes ion-exchange with Zn 2+ in an electrolyte solution.
7. The improved cathode of claim 6 , wherein the ρ-CaVO structure has a monoclinic structure with space group of C2/m and lattice parameters of a=11.4817(2) A, b=3.6497(2) Å, c=10.8486(7) Å, α=γ=90.0°, and β=101.8°.
8. The improved cathode of claim 6 , wherein the ρ-CaVO structure comprises a bilayer of ρ-V 2 O 5 .
9. The improved cathode of claim 8 , wherein bilayer sheets in the ρ-V 2 O 5 are congruently stacked and contain apical oxygen atoms within adjacent bilayer sheets substantially adjacent to one another.
10. The improved cathode of claim 6 , wherein the ρ-CaVO structure remains unchanged throughout Zn 2+ /H + storage cycles.
11. A method of forming an improved nanobelt for use as a cathode comprising:
employing a hydrothermal method further comprising;
dissolving ammonium metavanadate (NH 4 VO 3 ) in deionized water to form an ammonium metavanadate solution;
dispersing calcium chloride and sodium dodecyl sulfate in deionized water to form a calcium chloride and sodium dodecyl sulfate solution;
mixing the ammonium metavanadate and calcium chloride and sodium dodecyl sulfate solutions to form a resulting solution;
adding hydrochloric acid to the resulting solution; and
heating the resulting solution to form a nanobelt precipitate.
12. The method of claim 11 , further comprising:
forming a cathode via:
mixing the nanobelt precipitate, Super-P, and polyvinylidene fluoride;
dispersing the nanobelt precipitate, Super-P, and polyvinylidene fluoride into N-Methyl pyrrolidone to form a slurry;
coating the slurry onto a substrate; and
vacuum drying the substrate.
13. The method of claim 11 , further comprising forming the nanobelt to have CaVO stoichiometry comprising Ca 0.67 V 8 O 20 .3.5H 2 O.
14. The method of claim 12 , further comprising forming the cathode to have a discharge capacity of 466 mAh g −1 at 0.1 A g −1 .
15. The method of claim 12 , further comprising forming the cathode to have a capacity retention rate of 100%, 95% and 74% at 5.0 A g −1 for 500, 1,000, 2,000 cycles.
16. The method of claim 12 , further comprising forming the cathode such that Ca 2+ structurally stabilizes ρ-CaVO and undergoes ion-exchange with Zn 2+ in an electrolyte solution.
17. The method of claim 16 , further comprising forming the cathode such that the ρ-CaVO has a monoclinic structure with space group of C2/m and lattice parameters of a=11.4817(2) Å, b=3.6497(2) Å, c=10.8486(7) Å, α=γ=90.0°, and β=101.8°.
18. The method of claim 17 , further comprising forming the ρ-CaVO to comprise a bilayer of ρ-V 2 O 5 .
19. The method of claim 17 , further comprising forming the ρ-V 2 O 5 bilayer as sheets, which are congruently stacked with apical oxygen atoms in adjacent sheets substantially adjacent to one another.
20. The method of claim 17 , further comprising forming the ρ-CaVO structure such that it remains unchanged throughout Zn 2+ /H + storage cycles.