Cathode active material and non-aqueous electrolyte secondary battery using the same

Abstract

A cathode active material having a large capacity and improved charge/discharge cycle characteristics is disclosed. A battery has a cathode ( 2 ) having a cathode active material, an anode ( 3 ) and a non-aqueous electrolyte, and uses a cathode active material composed of a mixture of a first lithium-transition metal composite oxide containing Ni and Co and comprising a layer structure and a second lithium-transition metal composite oxide containing Ni and Mn and comprising a layer structure.

1 . A cathode active material used for a lithium ion non-aqueous electrolyte secondary battery, characterized in that a cathode active material contains a lithium composite oxide having a layer structure, containing at least lithium and nickel as components, and in which a shift width of 50% position of jump height of nickel-K shell absorption edge obtainable by measurement using X-ray absorption fine structure (XAFS) analysis technology is equal to or more than 1.0 eV when 50% of the whole lithium contents was extracted. 
     
     
         2 . The cathode active material according to  claim 1 , wherein said lithium composite oxide includes Ni and Co. 
     
     
         3 . The cathode active material according to  claim 1 , wherein said lithium composite oxide is expressed by the following chemical formula: LixNi1−y−zCoyMzO2
 where M is one or more transition metals or elements selected from Group 2, 3 and 4 elements of the periodic table, and x, y and z respectively satisfy 0.9≦x<1.10, 0.05≦y≦0.50, and 0.01≦z≦0.10). 
 
     
     
         4 . The cathode active material according to  claim 1 , wherein said lithium composite oxide further contains manganese and/or titanium. 
     
     
         5 . The cathode active material according to  claim 4 , characterized in that said lithium composite oxide contains Ni, Co, and manganese and/or titanium in an atomic ratio of Ni:Co:(Mn and/or Ti)=x:y:z, wherein 0.5≦x≦0.6, y=0.2, 0.2≦Z≦0.3 and x+y+z is substantially 1. 
     
     
         6 . The cathode active material according to  claim 1 , wherein a mean particle size of each of cathode active material is 2 μm or more and 30 μm or less. 
     
     
         7 . The cathode active material according to  claim 1 , characterized in that an amount of nickel contained in the cathode active material is in a range of 5% to 40% in molar ratio to the total amount of the cathode active material. 
     
     
         8 . A lithium ion non-aqueous electrolyte secondary battery comprising the cathode active material according to  claim 1 . 
     
     
         9 . The lithium ion non-aqueous electrolyte secondary battery according to  claim 8 , wherein said lithium composite oxide includes Ni and Co. 
     
     
         10 . The lithium ion non-aqueous electrolyte secondary battery according to  claim 8 , wherein said lithium composite oxide is expressed by the following chemical formula: LixNi1−y−zCoyMzO2
 where M is one or more transition metals or elements selected from Group 2, 3 and 4 elements of the periodic table, and x, y and z respectively satisfy 0.9≦x<1.10, 0.05≦y≦0.50, and 0.01≦z≦0.10). 
 
     
     
         11 . The lithium ion non-aqueous electrolyte secondary battery according to  claim 8 , wherein said lithium composite oxide further contains manganese and/or titanium. 
     
     
         12 . The lithium ion non-aqueous electrolyte secondary battery according to  claim 11 , characterized in that said lithium composite oxide contains Ni, Co, and manganese and/or titanium in an atomic ratio of Ni:Co:(Mn and/or Ti)=x:y:z, wherein 0.5≦x≦0.6, y=0.2, 0.2≦Z≦0.3 and x+y+z is substantially 1. 
     
     
         13 . The lithium ion non-aqueous electrolyte secondary battery according to  claim 8 , wherein a mean particle size of each of cathode active material is 2 μm or more and 30 μm or less. 
     
     
         14 . The lithium ion non-aqueous electrolyte secondary battery according to  claim 8 , characterized in that an amount of nickel contained in the cathode active material is in a range of 5% to 40% in molar ratio to the total amount of the cathode active material.