Synthesis and characterization of LiNi1-x-yCoxMnyO2 as the cathode materials of secondary lithium batteries

Abstract

LiNi1-x-yCoxMnyO2 (0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.3) were prepared by heating Ni1-x-yCoxMny(OH)2 and LiNO3 in flowing oxygen for 10 h at 550°C, followed by another heating at 750°C. The XRD patterns of LiNi1-x-yCoxMnyO2 (0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.3) samples with different x and y values show a pure phase of layered hexagonal structure. The lattice parameters a, c and the unit cell volume are found to decrease with increasing x in LiNi1-xCoxO2 The partial substitution of Ni by Co and Mn as in LiNi1-xCoxO2 and LiNi1-yCo0.2MnyO2 has a positive effect on lithium stoichiometry. However, lithium deficiency is still found after a prolonged thermal treatments (24 h). Among the doped materials synthesized, LiNi0.8Co0.2O2 and LiNi0.7Co0.2Mn0.1O2 have shown the best characteristics in terms of initial capacity and cycle life. © 1999 Elsevier Science S.A. All rights reserved.