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 lithium mixed transition metal oxide having a composition represented by Formula I and comprising mixed transition metal oxide (MO) layers comprising Ni ions, and reversible lithium layers which allow intercalation and deintercalation of lithium ions, wherein the MO layers and the reversible lithium layers are disposed alternately and repeatedly to form a layered crystal structure, and a portion of Ni ions derived from the MO layer are inserted into the reversible lithium layers at a level of 3% to 7% measured by Rietveld refinement of X-ray diffraction patterns to interconnect the MO layers and the reversible lithium layers:
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.