Electrochemical Cell With A Catalytic Electrode And Process For Making The Electrode And The Cell

Abstract

A process for making a catalytic electrode containing a transition metal nano-catalyst without using spray or thermal decomposition, and a process for making an electrochemical cell with a catalytic electrode. The nano-catalyst is a particulate material that includes particles that are at least partially oxidized, preferably to include at least oxide shells, before mixing with an activated carbon and binder in a liquid medium to adhere particles of the nano-catalyst to internal and external surfaces of the particles of activated carbon. Oxidation of the nano-catalyst particles allows the mixing of the nano-catalyst, activated carbon and binder in air rather than an inert gas atmosphere and can avoid the use of potentially dangerous liquid media such as highly volatile alcohols.

1 . A process for making a catalytic electrode, the process being a non-spray, non-thermal decomposition process comprising the steps:
 providing a nano-catalyst, comprising one or more transition metals, transition metal alloys or transition metal oxides;   providing a particulate carbon;   providing a binder material capable of binding particles of the carbon together;   mixing in air the nano-catalyst, carbon and binder together in a liquid medium in which the nano-catalyst is essentially insoluble to form a catalytic mix, the mix comprising particles of the carbon with particles of the nano-catalyst adhered to internal and external surfaces of the carbon particles to form a catalytic mix, wherein the particles of the nano-catalyst comprise particles that are at least partially oxidized before mixing with the carbon and binder;   forming the catalytic mix into a catalytic layer; and   combining the catalytic layer with a current collector and a hydrophobic layer to form the catalytic electrode.   
     
     
         2 . The process for making a catalytic electrode according to  claim 1 , wherein the nano-catalyst comprises a single transition metal or transition metal oxide. 
     
     
         3 . The process for making a catalytic electrode according to  claim 1 , wherein the one or more transition metals, transition metal alloys or transition metal oxides comprise manganese. 
     
     
         4 . The process for making a catalytic electrode according to  claim 1 , wherein the particles of the nano-catalyst further comprise essentially unoxidized particles of the one or more transition metals or transition metal alloys. 
     
     
         5 . The process for making a catalytic electrode according to  claim 4 , wherein the majority of the particles of the nano-catalyst are at least partially oxidized before mixing with the carbon and binder. 
     
     
         6 . The process for making a catalytic electrode according to  claim 5 , wherein the majority of nano-catalyst particles that are at least partially oxidized before mixing with the carbon and binder have oxide shells before mixing with the carbon and binder. 
     
     
         7 . The process for making a catalytic electrode according to  claim 1 , wherein the carbon comprises an activated carbon. 
     
     
         8 . The process for making a catalytic electrode according to  claim 7 , wherein the activated carbon is a steam-activated carbon derived from coal. 
     
     
         9 . The process for making a catalytic electrode according to  claim 8 , wherein the carbon has a BET specific surface area of from 600 to 1000 m 2 /g. 
     
     
         10 . The process for making a catalytic electrode according to  claim 1 , wherein the binder comprises a fluorocarbon material. 
     
     
         11 . The process for making a catalytic electrode according to  claim 10 , wherein the fluorocarbon material comprises tetrafluoroethylene. 
     
     
         12 . The process for making a catalytic electrode according to  claim 10 , wherein the fluorocarbon material is fibrillated in the mixing step. 
     
     
         13 . The process for making a catalytic electrode according to  claim 1 , wherein the dry mix is fluffed before forming the catalytic layer. 
     
     
         14 . The process for making a catalytic electrode according to  claim 1 , wherein the catalytic mix is formed into a catalytic sheet with two major surfaces. 
     
     
         15 . The process for making a catalytic electrode according to  claim 14 , wherein the current collector is pressed into one major surface of the catalytic sheet, and a hydrophobic sheet is adhered to the opposite major surface of the catalytic sheet to provide a catalytic electrode sheet. 
     
     
         16 . The process for making a catalytic electrode according to  claim 15 , wherein the hydrophobic sheet is adhered by pressure lamination. 
     
     
         17 . The process for making a catalytic electrode according to  claim 1 , wherein the liquid medium comprises water and essentially no alcohol, and the mix is dried to remove at least a portion of the water prior to forming the catalytic layer. 
     
     
         18 . A process for making an electrochemical cell comprising a catalytic electrode made by the process according to  claim 1 , the process for making the cell further comprising the steps:
 adhering at least one separator layer to the catalytic electrode sheet; and   combining the catalytic electrode sheet with an opposing electrode in a cell housing; wherein:   the separator layer disposed between the catalytic layer and the opposing electrode;   the hydrophobic sheet is disposed between the catalytic layer and a fluid entry port in the cell housing, the fluid entry port allowing a fluid from outside the cell housing to enter the cell to react with in catalytic layer of the catalytic electrode.   
     
     
         19 . The process for making an electrochemical cell according to  claim 18 , wherein the cell is a cell with an aqueous alkaline electrolyte, and oxygen contained in air entering through the fluid entry port is reduced at the catalytic electrode. 
     
     
         20 . The process for making an electrochemical cell according to  claim 19 , wherein the cell is a zinc-air cell, and the opposing electrode comprises zinc. 
     
     
         21 . The process for making an electrochemical cell according to  claim 20 , wherein the zinc is an unamalgamated zinc with no added mercury. 
     
     
         22 . The process for making an electrochemical cell according to  claim 18 , wherein the nano-catalyst comprises nano-manganese. 
     
     
         23 . The process for making an electrochemical cell according to  claim 18 , wherein the cell is a cylindrical cell or a prismatic cell. 
     
     
         24 . The process for making an electrochemical cell according to  claim 22 , wherein the cell is a prismatic cell. 
     
     
         25 . The process for making an electrochemical cell according to  claim 20 , wherein the separator layer comprises a layer of a rayon bound with an acrylic acid. 
     
     
         26 . The process for making an electrochemical cell according to  claim 20 , wherein the density of the catalytic sheet prior to adhering the hydrophobic sheet is from 8 to 20 mg/cm 2 . 
     
     
         27 . The process for making an electrochemical cell according to  claim 20 , wherein the catalytic electrode has a bond strength between the catalytic layer and the hydrophobic layer of from 65 to 250 g per 25.4 mm. 
     
     
         28 . The process for making an electrochemical cell according to  claim 20 , wherein the catalytic electrode has a thickness of from 0.15 to 0.35 mm.