Structural and Electrochemical Properties of Spherical LiMgxMn2–xO4 (x ≤ 0.10) for Secondary Lithium Ion Batteries

Abstract

A series of spherical LiMgxMn2–xO4 (x ≤ 0.10) cathode materials were successfully synthesized by a co-precipitation technique and solid state route. The morphologies and crystal structures of LiMgxMn2–xO4 were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. All LiMgxMn2–xO4 samples exhibited a single phase LiMn2O4 spinel structure with good crystallinity. Mg2+ ions could completely occupy the octahedral (16d) site to substitute Mn3+ and Mn4+ ions. The effect of Mg2+ ions on the electrochemical performance of LiMgxMn2–xO4 was investigated by galvanostatic charge–discharge test and electrochemical impedance spectroscopy (EIS). The results showed that the Mg-doped LiMn2O4 possessed better cycling stability. For the LiMg0.06Mn194O4, the initial discharge capacity was 115 mAh/g and remained 111 mAh/g after 50 cycles at a constant current density of 148 mA/g (1 C-rate) during the voltage range 3.0–4.3 V. The capacity retention could reach 96.5%, which was higher than that of the LiMn2O4.