High discharge electrolytic manganese dioxide and an electrode and alkaline cell incorporating the same

Abstract

An alkaline electrochemical cell is disclosed having a positive electrode, a negative electrode, and an electrolyte. The positive electrode comprises electrolytic manganese dioxide having a pH-voltage of at least about 0.860 volt. The electrolytic manganese dioxide also preferably has less than about 250 ppm and more preferably less than about 150 ppm of potassium impurities by weight. Electrolytic manganese dioxide having these properties exhibits significant synergistic and unexpected improvements in high-rate service, which translates to improved high-rate service life of the electrochemical cell containing the improved electrolytic manganese dioxide in its positive electrode.

The invention claimed is:  
     
         1 . An electrode for an electrochemical cell comprising electrolytic manganese dioxide that, when tested, has a pH-voltage value of at least about 0.860 volt.  
     
     
         2 . The electrode as defined in  claim 1 , wherein the electrolytic manganese dioxide, when tested, has a pH-voltage value of at least about 0.870 volt.  
     
     
         3 . The electrode as defined in  claim 1 , wherein the electrolytic manganese dioxide has less than 250 ppm of potassium impurities by weight.  
     
     
         4 . The electrode as defined in  claim 1  and further including a conductive agent.  
     
     
         5 . The electrode as defined in  claim 1 , wherein the electrode comprises particles, and all of the particles are capable of passing through a 70-mesh screen.  
     
     
         6 . An electrochemical cell comprising a negative electrode, an electrolyte, and a positive electrode comprising electrolytic manganese dioxide that, when tested has a pH-voltage value of at least about 0.860 volt.  
     
     
         7 . The electrochemical cell as defined in  claim 6 , wherein the electrolytic manganese dioxide, when tested, has a pH-voltage value of at least about 0.870 volt.  
     
     
         8 . The electrochemical cell as defined in  claim 6 , wherein said positive electrode further includes a conductive agent.  
     
     
         9 . The electrochemical cell as defined in  claim 6 , wherein said negative electrode comprises zinc or an alloy including zinc.  
     
     
         10 . An electrochemical cell comprising: 
 a negative electrode comprising zinc;    an electrolyte comprising an aqueous solution of potassium hydroxide; and    a positive electrode comprising electrolytic manganese dioxide that, when tested, has a pH-voltage value of at least about 0.860 volt.    
     
     
         11 . The electrochemical cell as defined in  claim 10 , wherein the electrolytic manganese dioxide, when tested, has a pH-voltage value of at least about 0.870 volt.  
     
     
         12 . The electrochemical cell as defined in  claim 10 , wherein the positive electrode further comprises graphite.  
     
     
         13 . The electrochemical cell as defined in  claim 12 , wherein the graphite comprises expanded graphite.  
     
     
         14 . The electrochemical cell as defined in  claim 10 , wherein the positive electrode further comprises electrolytic manganese dioxide that, when tested, has a pH-voltage value of less than 0.860 volt.  
     
     
         15 . The electrochemical cell as defined in  claim 10 , wherein the cell has a bobbin construction.  
     
     
         16 . An electrolytic manganese dioxide for use in an electrochemical cell, wherein the electrolytic manganese dioxide, when tested, has a pH-voltage value of at least about 0.860 volt.  
     
     
         17 . The electrolytic manganese dioxide as defined in  claim 16 , wherein the electrolytic manganese dioxide, when tested, has a pH-voltage value of at least 0.870 volt.  
     
     
         18 . The electrolytic manganese dioxide as defined in  claim 16 , wherein the electrolytic manganese dioxide has less than 250 ppm of potassium impurities by weight.