Process of preparing a chemically pre-formed (CPF) iron negative electrode with water
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 water to thereby create an oxidized surface. The resulting iron electrode is 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 water to thereby create an oxidized surface prior to any charge-discharge cycle.
2. The process of claim 1 , wherein the water comprises deionized water.
3. The process of claim 1 , wherein the electrode is treated with water 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.
4. The process of claim 3 , wherein the oxidation state of the oxidized iron active material is +2, +2/+3, +3 or +4.
5. The process of claim 1 , wherein the electrode further comprises a conductive additive.
6. The process of claim 5 , wherein the conductive additive comprises nickel, or copper or carbon black.
7. 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 wt % polyvinyl alcohol binder, and
0.25-20 wt % sulfur.
8. The process of claim 1 , wherein the sulfur is elemental 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 treatment of the surface of the electrode comprises coating, dipping, spraying or brushing the water on the electrode.
13. The process of claim 12 , wherein the water is brushed on the surface of the electrode.
14. The process of claim 12 , wherein the water is sprayed on the surface of the electrode.
15. The process of claim 12 , wherein the electrode is dipped in water.