Abstract:Li_1.03Co_0.10Mn_1.90F_zO_4-z (z=0, 0.05, 0.10, 0.15 and 0.20) cathode materials were synthesized by solid-state reaction using Mn₂O₃, Li₂CO₃, Co₂O₃ and LiF as raw materials. The chemical compositions of Li_1.03Co_0.1Mn_1.9F_zO_4-z were examined by inductively coupled plasma (ICP) and potentiometric analysis, the effects of F-substitution contents on structure, morphology and electrochemical performance of spinel Li_1.03Co_0.10Mn_1.90O₄ were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. It is found that the Li_1.03 Co_0.10Mn_1.90F_zO_4-z samples display a single phase of cubic spinel structure. The lattice parameters increase with the increase of F content when z≤0.10. However, the lattice parameters begin to decrease when F content continues to increase. The results show that an appropriate amount of F substitution for O element with Li⁺, Co³⁺ improves discharge capacity and structure stability of the materials. The Li_1.03Co_0.10Mn_1.90F_0.15O_3.85 sample shows an initial discharge capacity of 111.0 mA·h/g and has capacity retention of 97.0% after 30 cycles at 0.2C.

Key words: cathode materials; solid-state reaction; F-substitution; cycle performance