Electrode composition comprising doped tungsten oxides, method of preparation thereof and electrochemical cell comprising same

Abstract

Provided is a novel electrode composition suitable for use in an electrochemical cell. The composition includes a polymeric binder material and a doped tungsten (IV) oxide active material. The active material includes a tungsten (IV) oxide host material and a metal dopant in the host material effective to increase the charge-discharge capacity per unit weight of the active material when used in an electrochemical cell. Also provided is a method for forming the electrode composition and an electrochemical cell comprising the composition. The invention results in an electrochemical cell having improved charge-discharge capacity per unit weight of the electrode active material, and is additionally chemically and electrochemically stable.

What is claimed is:  
     
         1 . An electrode composition suitable for use in an electrochemical cell, comprising a polymeric binder material and a doped tungsten (IV) oxide active material, the active material comprising a tungsten (IV) oxide host material and a metal dopant in the host material effective to increase the charge-discharge capacity per unit weight of the active material when used in an electrochemical cell.  
     
     
         2 . The electrode composition according to  claim 1 , wherein the metal dopant is a metal selected from the group consisting of aluminum, manganese, barium, cobalt, molybdenum, tin, titanium, yttrium, zirconium and combinations thereof.  
     
     
         3 . The electrode composition according to  claim 2 , wherein the metal dopant is aluminum or manganese.  
     
     
         4 . The electrode composition according to  claim 1 , wherein the active material is of general formula A x W 1-x O 2 , wherein A is a metal, and x is a number from 0.05 to 0.15.  
     
     
         5 . The electrode composition according to  claim 1 , wherein the active material has an X-ray diffraction pattern which comprises peaks at substantially the same positions as tungsten oxide.  
     
     
         6 . The electrode composition according to  claim 1 , wherein the polymeric binder material is polyvinylidene fluoride or TEFLON powder.  
     
     
         7 . The electrode composition according to  claim 1 , further comprising a conductive carbon material.  
     
     
         8 . A method of forming an electrode composition suitable for use in an electrochemical cell, comprising the steps of: 
 (a) forming an electrode paste or slurry from components comprising a first solvent, a polymeric binder material and a doped tungsten (IV) oxide active material, wherein the active material is formed by a process comprising the steps of: 
 (i) mixing a tungsten (VI) oxide or a tungsten salt with a salt of the metal dopant and a second solvent, thereby forming a mixture;  
 (ii) heating the mixture to substantially remove the solvent therefrom;  
 (iii) performing a further heat treatment of the mixture; and  
 (iv) cooling the resulting product to ambient temperature;  
   (b) forming a coating of the electrode slurry; and    (c) evaporating the solvent.    
     
     
         9 . The method of  claim 8 , wherein the salt of the metal dopant is a salt of a metal selected from the group consisting of aluminum, manganese, barium, cobalt, molybdenum, tin, titanium, yttrium and zirconium.  
     
     
         10 . The method of  claim 9 , wherein the salt of the metal dopant is a salt of aluminum or manganese.  
     
     
         11 . The method of  claim 10 , wherein the tungsten salt is ammonium tungstate.  
     
     
         12 . The method of  claim 8 , wherein the tungsten salt is ammonium tungstate.  
     
     
         13 . The method according to  claim 8 , wherein the step (a)(ii) heating is conducted at a temperature of from about 100 to 120° C.  
     
     
         14 . The method according to  claim 8 , wherein the step (a)(iii) further heat treatment is conducted in pure hydrogen or in an inert gas/hydrogen mixture.  
     
     
         15 . The method according to  claim 14 , wherein the step (a)(iii) further heat treatment comprises a step of heating at a temperature of from about 650 to 800° C. for a period of from about 30 to 200 hours.  
     
     
         16 . The method according to  claim 8 , wherein the polymeric binder material is polyvinylidene fluoride or TEFLON powder.  
     
     
         17 . The method according to  claim 8 , wherein the components forming the electrode paste or slurry further comprise a conductive carbon material.  
     
     
         18 . An electrochemical cell, comprising: 
 an anode, a cathode and an electrolyte providing a conducting medium between said anode and said cathode, wherein said anode or said cathode comprises an electrode composition comprising a polymeric binder material and a doped tungsten (IV) oxide active material, the active material comprising a tungsten (IV) oxide host material and a metal dopant in the host material effective to increase the charge-discharge capacity per unit weight of the active material.    
     
     
         19 . The electrochemical cell according to  claim 18 , wherein the metal dopant is a metal selected from the group consisting of aluminum, manganese, barium, cobalt, molybdenum, tin, titanium, yttrium, zirconium and combinations thereof.  
     
     
         20 . The electrochemical cell according to  claim 19 , wherein the metal dopant is aluminum or manganese.  
     
     
         21 . The electrochemical cell according to  claim 18 , wherein the active material is of general formula A x W 1-x O 2 , wherein A is a metal, and x is a number from 0.05 to 0.15.  
     
     
         22 . The electrochemical cell according to  claim 18 , wherein the active material has an X-ray diffraction pattern which comprises peaks at substantially the same positions as tungsten oxide.  
     
     
         23 . The electrochemical cell according to  claim 18 , wherein the polymeric binder material is polyvinylidene fluoride or TEFLON powder.  
     
     
         24 . The electrochemical cell according to  claim 18 , wherein the electrode composition further comprises a conductive carbon material.  
     
     
         25 . The electrochemical cell according to  claim 18 , wherein the cell comprises a plurality of anodes and a plurality of cathodes.  
     
     
         26 . The electrochemical cell according to  claim 18 , further comprising a separator interposed between the anode and cathode.  
     
     
         27 . The electrochemical cell according to  claim 18 , wherein the electrolyte comprises LiPF 6  in ethylene carbonate and diethylcarbonate, or LiPF 6  in ethylene carbonate and dimethylcarbonate.  
     
     
         28 . A mobile telephone comprising the electrochemical cell according to  claim 18 .  
     
     
         29 . An electrically powered vehicle comprising the electrochemical cell according to  claim 18 .  
     
     
         30 . A medical device comprising the electrochemical cell according to  claim 18 .  
     
     
         31 . A security system comprising the electrochemical cell according to claim  18 .