Synthesis and characterization of LiMeO2 (Me = Ni, Ni/Co and Co) for 4-volts secondary nonaqueous lithium cells

Abstract

LiNiO2, LiNi1/2Co1/2O2, and LiCoO2 were prepared and characterized by XRD and FT-IR. XRD data for these three samples indicated that lithium ions were located at octahedral 3(b) sites and transition metal ions at 3(a) sites in a cubic close packed oxygen array (space group; R3̄m). XRD and IR methods to estimate the degree of contamination of rock-salt domain in the solid matrix were described. Electrochemical examinations for the well-characterized samples were also carried out in lithium nonaqueous cells. These three samples exhibited 130-140 mAh·g-1 of rechargeable capacity in the working voltage above 3.5 V with charge/discharge coulombic efficiency of ca.97%. The key technology to establish 4-volts secondary nonaqueous lithium cells was briefly described together with a concept on the active material design based on the lithium-transition metal-oxygen ternary phase for a secondary system therefrom.