Iron electrode employing a polyvinyl alcohol binder

Abstract

The present invention provides one with an iron electrode employing a binder comprised of polyvinyl alcohol (PVA) binder. In one embodiment, the invention comprises an iron based electrode comprising a single layer of a conductive substrate coated on at least one side with a coating comprising an iron active material and a binder, wherein the binder is PVA. This iron based electrode is useful in alkaline rechargeable batteries, particularly as a negative electrode in a Ni—Fe battery.

1 . A method of preparing an iron electrode comprising the steps of
 i) preparing a paste formulation which comprises an iron active material, sulfur and from 2 to 5 wt % of a polyvinyl alcohol binder;   ii) providing a single layer substrate; and   iii) coating the paste formulation on at least one side of the single layer substrate.   
     
     
         2 . The method of  claim 1 , wherein the paste formulation further comprises a pore former, carbon, graphite or Ni powder. 
     
     
         3 . The method of  claim 1 , wherein the single layer substrate comprises a thin conductive material. 
     
     
         4 . The method of  claim 3 , wherein the thin conductive material comprises a perforated metal foil or sheet, metal mesh or screen, woven metal, or expanded metal. 
     
     
         5 . The method of  claim 4 , wherein the thin conductive material comprises a nickel plated perforated foil. 
     
     
         6 . The method of  claim 1 , wherein the single layer substrate comprises a three dimensional material. 
     
     
         7 . The method of  claim 6 , wherein the three dimensional material comprises a metal foam or metal felt. 
     
     
         8 . The method of  claim 1 , wherein the sulfur is present in the paste formulation in the amount of from 0.25 to 1.5% by weight. 
     
     
         9 . The method of  claim 1 , wherein the paste formulation is coated on both sides of the substrate. 
     
     
         10 . The method of  claim 1 , wherein the sulfur comprises elemental sulfur. 
     
     
         11 . The method of  claim 1 , wherein the active iron material comprises iron metal, an iron oxide material, or a mixture thereof. 
     
     
         12 . The method of  claim 11 , wherein the iron oxide material comprises Fe 3 O 4 . 
     
     
         13 . The method of  claim 1 , wherein the polyvinyl alcohol binder comprises polyvinyl alcohol that is hydrolyzed between 98.5 and 100%. 
     
     
         14 . The method of  claim 1 , wherein the polyvinyl alcohol binder comprises polyvinyl alcohol that is hydrolyzed between 99 and 100%. 
     
     
         15 . The method of  claim 1 , wherein the polyvinyl alcohol binder comprises from 2.5 to 4 wt % of the iron electrode.