Material for lithium secondary battery of high performance

摘要

Provided is a cathode active material containing a Ni-based lithium mixed transition metal oxide. More specifically, the cathode active material comprises the lithium mixed transition metal oxide having a composition represented by Formula I of LixMyO2 wherein M, x and y are as defined in the specification, which is prepared by a solid-state reaction of Li2CO3 with a mixed transition metal precursor under an oxygen-deficient atmosphere, and has a Li2CO3 content of less than 0.07% by weight of the cathode active material as determined by pH titration. The cathode active material in accordance with the present invention and substantially free of water-soluble bases such as lithium carbonates and lithium sulfates and therefore has excellent high-temperature and storage stabilities and a stable crystal structure. A secondary battery comprising such a cathode active material exhibits a high capacity and excellent characteristics, and can be produced by an environmentally friendly method with low production costs and high production efficiency.

主权项

1. A cathode active material comprising a lithium mixed transition metal oxide having a composition represented by Formula I:
LixMyO2  (I) wherein: M=M′1−kAk, wherein M′ is Ni1−a−b (Ni1/2Mn1/2)aCob, 0.65≦a+b≦0.85 and 0.1≦b≦0.4; A is a dopant; 0≦k<0.05; and x+y=2 and 0.95≦x≦1.05, wherein the lithium mixed transition metal oxide has a Li2CO3 content of less than 0.07% by weight of the cathode active material as determined by pH titration, and is prepared by a solid-state reaction of Li2CO3 and a mixed transition metal precursor under an oxygen-deficient atmosphere, wherein the solid-state reaction includes a sintering process at 600° C. to 1100° C. for 3 to 20 hours, and wherein an amount of air exceeding 2 m3/kg of LixMyO2 during the sintering process is supplied to a reaction vessel equipped with a heat exchanger for pre-warming of the air.