Synthesis and characterization of spinel Li_1.05Cr_0.1Mn_1.9O_4-zF_z as cathode materials for lithium-ion batteries

Samples with the nominal stoichiometry Li_1.05Cr_0.1Mn_1.9O_4-zF_z (z=0, 0.05, 0.1, 0.15, and 0.2) were synthesized via the solid-state reaction method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge/discharge, and slow rate cyclic voltammetry (SSCV) techniques. The results show that the pure spinel phase indexed to Fd₃m can be obtained when z=0, 0.05, and 0.1. The substitution of F for O with z≤0.1 contributes to the increase of initial capacity compared with Li_1.05Cr_0.1Mn_1.9O₄ spinels. However, when the F-dopant content is designed to be 0.15 and 0.2, the Li_1.05Cr_0.1Mn_1.9O_4-zF_z samples deliver relatively low capacity and poor cycling properties at 55℃.