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.

What is claimed is: 
     
         1 . A method of preparing a nickel-iron battery comprising the steps of:
 i) preparing a paste formulation which comprises an iron active material comprising iron metal, an iron oxide or a mixture thereof from 0.25 to 1.5 wt % elemental sulfur, from 8 to 20 wt % nickel, and from 2.5 to 4 wt% of a polyvinyl alcohol binder;   ii) providing a substrate;   iii) coating the paste formulation on at least one side of the substrate to provide an iron active material coating on the substrate;   iv) drying the coating on the substrate to thereby provide an iron anode;   v) subjecting the iron anode to electrochemical cycling to thereby effectively fuse together the iron particles; and   vi) combining the iron anode from v) with a nickel cathode to prepare the nickel-iron battery.   
     
     
         2 . The method of  claim 1 , wherein the amount of polyvinyl alcohol binder in the paste is about 3.5 wt %. 
     
     
         3 . The method of  claim 1 , wherein the amount of nickel in the paste ranges from 16 to 20 wt %. 
     
     
         4 . The method of  claim 1 , wherein the substrate comprises a conductive material. 
     
     
         5 . The method of  claim 4 , wherein the conductive material comprises a perforated metal foil or sheet, metal mesh or screen, woven metal, or expanded metal. 
     
     
         6 . The method of  claim 5 , wherein the conductive material comprises a nickel plated perforated foil. 
     
     
         7 . The method of  claim 1 , wherein the substrate comprises a three dimensional material. 
     
     
         8 . The method of  claim 7 , wherein the three-dimensional material comprises a metal foam or metal felt. 
     
     
         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 iron oxide material comprises Fe 3 O 4 . 
     
     
         11 . The method of  claim 1 , wherein the polyvinyl alcohol binder comprises polyvinyl alcohol that is hydrolyzed between 98.5 and 100%. 
     
     
         12 . The method of  claim 1 , wherein the polyvinyl alcohol binder comprises polyvinyl alcohol that is hydrolyzed between 99 and 100%.