Positive electrode active substance for non-aqueous electrolyte secondary batteries, and non-aqueous electrolyte secondary battery

Abstract

In accordance with the present invention, there are provided positive electrode active substance particles for non-aqueous electrolyte secondary batteries which is excellent in life characteristics of a battery with respect to a repeated charging and discharging performance thereof, as well as a non-aqueous electrolyte secondary battery. The present invention relates to a positive electrode active substance for non-aqueous electrolyte secondary batteries comprising lithium transition metal layered oxide having a composition represented by the formula: Li a (Ni x Co y Mn 1-x-y )O 2 wherein a is 1.0≦a≦1.15; x is 0<x<1; and y is 0<y<1, in which the positive electrode active substance is in the form of secondary particles formed by aggregating primary particles thereof, and a coefficient of variation of a compositional ratio: Li/Me wherein Me is a sum of Ni, Co and Mn (Me=Ni+Co+Mn) as measured on a section of the secondary particle is not more than 25%.

1 . A positive electrode active substance for non-aqueous electrolyte secondary batteries comprising lithium transition metal layered oxide having a composition represented by the formula:
   Li a (Ni x Co y Mn 1-x-y )O 2      
       wherein a is 1.0≦a≦1.15; x is 0<x<1; and y is 0<y<1,
 in which the positive electrode active substance is in the form of secondary particles formed by aggregating primary particles thereof, and a coefficient of variation of a compositional ratio: Li/Me wherein Me is a sum of Ni, Co and Mn (Me=Ni+Co+Mn) as measured on a section of the secondary particle is not more than 25%. 
 
     
     
         2 . The positive electrode active substance for non-aqueous electrolyte secondary batteries according to  claim 1 , wherein an average secondary particle diameter of the active substance is 3.0 to 16 μm. 
     
     
         3 . The positive electrode active substance for non-aqueous electrolyte secondary batteries according to  claim 1 , wherein an average particle diameter (crystallite size) of primary particles of the active substance is 100 to 600 nm. 
     
     
         4 . A non-aqueous electrolyte secondary battery using the positive electrode active substance for non-aqueous electrolyte secondary batteries as defined in  claim 1 . 
     
     
         5 . A process for producing the positive electrode active substance for non-aqueous electrolyte secondary batteries as defined in  claim 1 , comprising the steps of:
 obtaining spherical nickel-cobalt-manganese-based composite compound particles as a raw material;   mixing the composite compound particles with lithium hydroxide such that a molar ratio of Li to a sum of Ni, Co and Mn (Li/(Ni+Co+Mn)) is in the range of 1.00 to 1.20 to obtain a mixture thereof;   calcining the thus obtained mixture at a temperature of 600 to 900° C. in an oxygen-containing atmosphere; and   subjecting the calcined product to annealing treatment at a temperature of 500 to 750° C. which is lower than the calcination temperature, without subjecting the calcined product to water-washing treatment.