Process of preparing a chemically pre-formed (CPF) iron negative electrode with oxidizing compounds
Provided is a process for preparing an electrode comprising an iron active material. The process comprises first fabricating an electrode comprising an iron active material, and then treating the surface of the electrode with an oxidant solution to thereby create an oxidized surface. The resulting iron electrode is thereby preconditioned prior to any charge-discharge cycle to have the assessable surface of the iron active material in the same oxidation state as in discharged iron negative electrodes active material.
1. A process for preparing an electrode comprising an iron active material, which comprises:
i) fabricating an electrode comprising an iron active material, a polyvinyl alcohol binder and sulfur, and
ii) treating the surface of the electrode with an oxidant solution to thereby create an oxidized surface prior to any charge-discharge cycle.
2. The process of claim 1 , therein the oxidant solution comprises, hydrogen peroxide, nitric acid, hypochlorite, bromine, iodine, permanganate compounds, or sodium perborate.
3. The process of claim 2 , wherein the oxidant solution comprises hydrogen peroxide.
4. The process of claim 1 , wherein the iron electrode surface is treated with an oxidant solution prior to any charge-discharge cycle to have the accessible surface of the iron material in the same oxidation state as discharged iron negative electrode active material.
5. The process of claim 4 , wherein the oxidation state of the oxidized iron active material is +2, +2/+3, +3 or +4.
6. The process of claim 1 , wherein the electrode further comprises a conductive additive.
7. The process of claim 6 , wherein the conductive additive comprises nickel, copper or carbon black.
8. The process of claim 1 , wherein the electrode comprises an iron active material comprising about:
50-90 wt % iron powder
5-30 wt % nickel powder
0.5-5.0 w % polyvinyl alcohol binder, and
0.25-2.0 w % sulfur.
9. The process of claim 1 , wherein the electrode comprises a single layer of conductive substrate coated on at least one side with a coating comprising the iron active material, polyvinyl alcohol binder and sulfur.
10. The process of claim 9 , wherein the substrate is comprised of nickel plated steel.
11. The process of claim 1 , wherein the porosity of the electrode is in the range of about 15-50%.
12. The process of claim 1 , wherein the oxidant solution comprises nitric acid.
13. The process of claim 1 , wherein the oxidant solution comprises sodium perborate.
14. The process of claim 1 , wherein the treatment of the surface of the electrode comprises coating, dipping, spraying, or brushing the oxidant solution on the surface of the electrode.