Non-aqueous secondary battery having negative electrode including graphite powder

Abstract

Objects of the present invention is to provide a carbon material having a superior reversibility in lithium intercalation-deintercalation reaction, and a non-aqueous secondary battery using the carbon material as an active material for a negative electrode, which has a high energy density and an excellent rapid charging and discharging characteristics. Graphite powder having a maximum particle diameter of less than 100 μm and an existing fraction of rhombohedral structure in the crystalline structure of less than 20% is used as an active material for the negative electrode of the non-aqueous secondary battery. The graphite powder can be obtained by pulverizing raw graphite with a jet mill, and subsequently treating the powder at a temperature equal to or higher than 900° C.

1 . A non-aqueous secondary battery comprising: 
 a positive electrode,    a negative electrode of graphite, the graphite being an active material of the negative electrode, and    electrolytic solution, wherein    the graphite active material of said negative electrode comprises graphite powder having substantially completely a crystal structure, and wherein a rhombohedral fraction, of the crystal structure of the graphite powder, is in a range of 0-20% by weight, a particle size of the graphite powder is equal to or smaller than 100 μm, and the graphite powder has a deintercalating capacity for lithium of at least 320 mAh/g.    
     
     
         2 . A non-aqueous secondary battery as claimed in  claim 1 , wherein the crystal structure of said graphite powder includes at least a fraction having hexagonal crystal structure.  
     
     
         3 . A non-aqueous secondary battery as claimed in  claim 1 , the graphite active material having been produced by heat treating pulverized graphite so as to transform rhombohedral structure of the pulverized graphite to hexagonal structure.  
     
     
         4 . A non-aqueous secondary battery as claimed in  claim 1 , the graphite active material having been produced by treating pulverized graphite with an acidic solution so as to eliminate rhombohedral structure graphite.  
     
     
         5 . A non-aqueous secondary battery comprising: 
 a positive electrode,    a negative electrode of graphite, the graphite being an active material of said negative electrode, and    electrolytic solution, wherein    the graphite active material of said negative electrode comprises graphite powder having substantially completely a crystal structure, and wherein a hexagonal fraction, of the crystal structure of the graphite powder, is in a range of at least 80% by weight, a particle size of the graphite powder is equal to or smaller than 100 μm, and the graphite powder has a deintercalating capacity for lithium of at least 320 mAh/g.    
     
     
         6 . A non-aqueous secondary battery comprising: 
 a positive electrode,    a negative electrode of graphite, the graphite being an active material of said negative electrode, and    electrolytic solution, which is charged or discharged by repeating a reaction of intercalating and deintercalating ions at said positive electrode and said negative electrode, respectively, wherein    the graphite active material of said negative electrode comprises graphite powder having substantially completely a crystal structure, wherein a fraction of a rhombohedral crystal structure of the crystal structure of the graphite powder is equal to or less than 20% by weight, a particle size of the graphite powder is equal to or smaller than 100 μm, and the graphite powder has a deintercalating capacity for lithium of at least 320 mAh/g.    
     
     
         7 . A non-aqueous secondary battery as claimed in  claim 6 , wherein 
 said graphite powder has a fraction of a hexagonal crystal structure of the crystal structure of the graphite powder which is equal to or more than 80% by weight.    
     
     
         8 . A non-aqueous secondary battery as claimed in  claim 6 , wherein the crystal structure of said graphite powder includes at least a fraction having hexagonal crystal structure.  
     
     
         9 . A non-aqueous secondary battery as claimed in  claim 6 , the graphite active material having been produced by heat treating pulverized graphite so as to transform rhombohedral structure of the pulverized graphite to hexagonal structure.  
     
     
         10 . A non-aqueous secondary battery as claimed in  claim 6 , the graphite active material having been produced by treating pulverized graphite with an acidic solution so as to eliminate rhombohedral structure graphite.  
     
     
         11 . A non-aqueous secondary battery comprising: 
 a positive electrode,    a negative electrode of graphite, the graphite being an active material of said negative electrode, and    electrolytic solution, which is charged or discharged by repeating a reaction of intercalating and deintercalating ions at said positive electrode and said negative electrode, respectively, wherein    the graphite active material of said negative electrode comprises graphite powder having a particle size equal to or smaller than 100 μm,    said graphite powder has substantially completely a crystal structure which includes both a hexagonal crystal structure and a rhombohedral crystal structure, and    the crystal structure of said graphite powder has a fraction of the rhombohedral crystal structure equal to or less than 20% by weight, and a fraction of the hexagonal crystal structure equal to or more than 80% by weight, and the graphite powder has a deintercalating capacity for lithium of at least 320 mAh/g.