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

A series of spherical LiMg x Mn 2– x O 4 ( x ≤ 0.10) cathode materials were successfully synthesized by a co-precipitation technique and solid state route. The morphologies and crystal structures of LiMg x Mn 2– x O 4 were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. All LiMg x Mn 2– x O 4 samples exhibited a single phase LiMn 2 O 4 spinel structure with good crystallinity. Mg 2+ ions could completely occupy the octahedral (16 d ) site to substitute Mn 3+ and Mn 4+ ions. The effect of Mg 2+ ions on the electrochemical performance of LiMg x Mn 2– x O 4 was investigated by galvanostatic charge–discharge test and electrochemical impedance spectroscopy (EIS). The results showed that the Mg-doped LiMn 2 O 4 possessed better cycling stability. For the LiMg 0.06 Mn 194 O 4 , 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 LiMn 2 O 4 .