Material for lithium secondary battery of high performance

摘要

Provided is a lithium mixed transition metal oxide having a composition represented by Formula I of LixMyO2 (M, x and y are as defined in the specification) having mixed transition metal oxide layers (“MO layers”) comprising Ni ions and lithium ions, wherein lithium ions intercalate into and deintercalate from the MO layers and a portion of MO layer-derived Ni ions are inserted into intercalation/deintercalation layers of lithium ions (“reversible lithium layers”) thereby resulting in the interconnection between the MO layers. The lithium mixed transition metal oxide of the present invention has a stable layered structure and therefore exhibits improved stability of the crystal structure upon charge/discharge. In addition, a battery comprising such a cathode active material can exhibit a high capacity and a high cycle stability. Further, such a lithium mixed transition metal oxide is substantially free of water-soluble bases, and thereby can provide excellent storage stability, decreased gas evolution and consequently superior high-temperature stability with the feasibility of low-cost mass production.

主权项

1. A cathode active material comprising: a lithium transition metal oxide of the general formula
Lix((Ni1−a−b(Ni1/2Mn1/2)aCob)1−kAk)2−xO2, wherein 0.65≦a+b≦0.85, 0.1≦b≦0.4, A is a dopant, 0≦k<0.05, and 0.95≦x≦1.05,said lithium transition metal oxide being substantially free of soluble bases such that less than about 20 ml of 0.1M HCl is necessary to titrate 200 ml of a solution containing substantially all of the soluble bases present in 10 g of said lithium transition metal oxide to a pH less than 5, said solution being prepared by repeated soaking and decanting of said lithium transition metal oxide.