Nonaqueous electrolyte secondary battery positive electrode active material and method for manufacturing same, and nonaqueous electrolyte secondary battery

Abstract

Provided are: a nonaqueous electrolyte secondary battery positive electrode active material that has high crystallinity, that causes less amount of Mn deposition on a negative electrode, and that can form a secondary battery having excellent cycle characteristics; and a nonaqueous electrolyte secondary battery using the nonaqueous electrolyte secondary battery positive electrode active material. The nonaqueous electrolyte secondary battery positive electrode active material according to the present invention is formed of a lithium-manganese-nickel complex oxide including a spinel-type crystal structure, wherein the lithium-manganese-nickel complex oxide has a crystallite diameter not smaller than 1000 Å and is formed of primary particles that have a polyhedron shape having more than eight surfaces. The proportion of ungrown particles not having the polyhedron shape of the primary particles in the lithium-manganese-nickel complex oxide is preferably not higher than 5%.

1 . A nonaqueous electrolyte secondary battery positive electrode active material comprising lithium-manganese-nickel complex oxide including a spinel-type crystal structure, wherein
 the lithium-manganese-nickel complex oxide   is formed of primary particles having a polyhedral shape having more than eight faces and   has a crystallite diameter of 1000 Å or more.   
     
     
         2 . The nonaqueous electrolyte secondary battery positive electrode active material according to  claim 1 , wherein
 an atomic ratio among Li, Mn, Ni, and element M in the lithium-manganese-nickel complex oxide has a relationship of Li:Mn:Ni:M=1+x:2−y−x−z:y:z (where 0≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, and M is one or more selected from the group consisting of Mg, Al, Si, Ti, Cr, Fe, Co, Cu, and Zn).   
     
     
         3 . The nonaqueous electrolyte secondary battery positive electrode active material according to  claim 1 , wherein
 a proportion of ungrown particles which are contained in the lithium-manganese-nickel complex oxide and of which primary particles do not have a polyhedral shape is 5% or less.   
     
     
         4 . A method for manufacturing a nonaqueous electrolyte secondary battery positive electrode active material formed of lithium-manganese-nickel complex oxide, the method comprising:
 a crystallization step of crystallizing manganese-nickel complex hydroxide from a mixed solution of manganese chloride and nickel chloride;   a calcination step of mixing the manganese-nickel complex hydroxide obtained and a lithium compound and calcining the mixture at 800° C. or higher and 1000° C. or lower to obtain lithium-manganese-nickel complex oxide; and   a recalcination step of recalcining the lithium-manganese-nickel complex oxide obtained at 500° C. or higher and 800° C. or lower for 5 hours or longer and 40 hours or shorter.   
     
     
         5 . A nonaqueous electrolyte secondary battery comprising the nonaqueous electrolyte secondary battery positive electrode active material according to  claim 1 . 
     
     
         6 . The nonaqueous electrolyte secondary battery positive electrode active material according to  claim 2 , wherein
 a proportion of ungrown particles which are contained in the lithium-manganese-nickel complex oxide and of which primary particles do not have a polyhedral shape is 5% or less.   
     
     
         7 . A nonaqueous electrolyte secondary battery comprising the nonaqueous electrolyte secondary battery positive electrode active material according to  claim 2 . 
     
     
         8 . A nonaqueous electrolyte secondary battery comprising the nonaqueous electrolyte secondary battery positive electrode active material according to  claim 3 . 
     
     
         9 . A nonaqueous electrolyte secondary battery comprising the nonaqueous electrolyte secondary battery positive electrode active material according to  claim 6 .