Process of preparing a chemically pre-formed (CPF) iron negative electrode with oxidizing gases
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, a polyvinyl alcohol binder and sulfur, and then treating the electrode with a gaseous oxidant to thereby create an oxidized surface. The resulting iron electrode is treated 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, a polyvinyl alcohol binder and sulfur, which comprises:
i) fabricating an electrode comprising an iron active material, a polyvinyl alcohol binder and sulfur, and
ii) treating the electrode with a gaseous oxidant to thereby create an oxidized surface prior to any charge-discharge cycle.
2. The process of claim 1 , therein the oxidant comprises ozone, chlorine, or nitrous oxide.
3. The process of claim 2 , wherein the oxidant comprises ozone.
4. The process of claim 1 , wherein the electrode is treated 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 treated 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
0.25-20 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%.