Coating on nickelate cathode materials
Alkaline electrochemical cells are provided, containing cathodes with a nickel compound active material, wherein active material particles are coated with at least one of a number of materials so as to improve the shelf life of the electrochemical cell. Methods of preparing such cathodes and electrochemical cells are also provided.
1. An alkaline electrochemical cell, comprising:
a) a container; and
b) an electrode assembly disposed within the container and comprising a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an alkaline electrolyte;
wherein the positive electrode comprises coated active material particles, said coated active material particles comprising active material and a coating, wherein the active material comprises a nickel compound; and
wherein the coating has a thickness of about 0.5 nm-5 nm.
2. The alkaline electrochemical cell of claim 1 , wherein the nickel compound is a nickel oxide or a nickel oxyhydroxide.
3. The alkaline electrochemical cell of claim 2 , wherein the nickel compound is a nickel oxide selected from the group consisting of a nickel (IV) oxide, nickel dioxide (NiO 2 ), Li x NiO 2 (lithium nickelate), wherein 0<x≤1, and Li x A y Ni 1+a−z M z O 2 , wherein 0≤x≤1, 0≤y≤0.3, 0≤a≤0.2, and 0≤z≤0.3, wherein A comprises one or more alkali metals, and wherein M comprises one or more alkaline earth metal, transition metal, other metal, or any combination thereof.
4. The alkaline electrochemical cell of claim 3 , wherein the active material is nickel dioxide.
5. The alkaline electrochemical cell of claim 2 , wherein the active material is a nickel oxyhydroxide.
6. The alkaline electrochemical cell of claim 1 , wherein the coating comprises an insulator.
7. The alkaline electrochemical cell of claim 6 , wherein the insulator is an organic material.
8. The alkaline electrochemical cell of claim 6 , wherein the insulator is an inorganic material.
9. The alkaline electrochemical cell of claim 1 , wherein the coating comprises an electronic conductor or semi-conductor.
10. The alkaline electrochemical cell of claim 9 , wherein the electronic conductor or semi-conductor is selected from the group consisting of manganese oxides, carbon, conductive polymers, cobalt oxyhydroxide, and metallic materials.
11. The alkaline electrochemical cell of claim 10 , wherein the electric conductor or semi-conductor is a manganese oxide having the formula MnO x , wherein x is from 1.5-2.0 inclusive.
12. The alkaline electrochemical cell of claim 10 , wherein the electronic conductor or semi-conductor is a conductive polymer selected from the group consisting of polyaniline, polystyrene sulfonate, and poly(3-hexylthiophene).
13. The alkaline electrochemical cell of claim 1 , wherein the coating comprises a second nickel compound, wherein the second nickel compound comprises nickel having a lower oxidation state than that of the nickel in the active material.
14. The alkaline electrochemical cell of claim 13 , wherein the second nickel compound is nickel oxyhydroxide or nickel hydroxide.
15. The alkaline electrochemical cell of claim 1 , wherein the weight ratio of active material to coating is greater than about 3.
16. The alkaline electrochemical cell of claim 1 , wherein the coating comprises a first coating material and a second coating material.
17. A method of producing the alkaline electrochemical cell of claim 1 , comprising:
i) providing a cathode electrode mix comprising
1) coated active material particles,
2) binder,
3) conductive carbon, and
4) electrolyte,
ii) forming a plurality of rings from the electrode mix; and
iii) inserting the rings into a container.
18. A method of producing the alkaline electrochemical cell of claim 1 , comprising
i) providing a cathode electrode mix comprising
1) coated active material particles,
2) binder,
3) conductive carbon, and
4) electrolyte, and
ii) using a ram to mold the cathode electrode mix into a solid tubular configuration.
19. The method of claim 17 , further comprising, prior to step i), a step of coating cathode active material particles by a method selected from the group consisting of atomic layer deposition, chemical deposition, chemical vapor deposition, electrolytic deposition or plating, electroless deposition or plating, carbon evaporation, laser ablation, and arc discharge.