Influence of Co-substitution on Structure and Electrochemical Performances of Li-rich Spinel LiMn₂O₄

Abstract

In this paper, the non-stoichiometric spinel LiMn₂O₄ was synthesized by solid-state reaction using Mn₂O₃ as Mn source, and the influence of Co-substitution on structure and electrochemical performances of spinel LiMn₂O₄ was researched. The structure was characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR), morphology was examined by scanning electron microscopy (SEM), and chemical composition of samples were analyzed by the energy-dispersive X-ray spectrum (EDX), while the doping dosage of Co element was measured by inductively coupled plasma (ICP). The results show that the Co-substituted Li_1.03Mn₂O₄ samples display a single phase of cubic spinel structure, and have enhanced particle size uniformity and surface smoothness. The electrochemical performance tests show that the rate capability and cycling performances of Co-substituted samples are significantly improved compared with that of pristine Li_1.03Mn₂O₄. The sample (Li_1.03Mn_0.85Co_0.15O₄) with 15 mol% of Co-substitution has discharge capacity of 106mAh·g⁻¹ at 2C and shows an improved average capacity retention of 97.2% compared with that of the Li_1.03Mn₂O₄ which shows 87.7% capacity retention after 50 cycles at 1C rate.

Keywords:

• Cathode materials
• Li_1.03Mn₂O₄
• solid-state reaction
• cycling performance