Enhanced electrochemical performance of LiMn2O4 by SiO2 modifying via electrostatic attraction forces method

Abstract

SiO2-modified LiMn2O4 materials were synthesized by the electrostatic attraction forces with the followed heat treatment. The surface morphology, structure, and electrochemical performance were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), CV, and electrochemical impedance spectroscopies (EIS), respectively. SEM and XRD patterns revealed that SiO2 was not only coated on the surface, but also partial Si4+ ions diffused into the crystal structure. As a result, the spinel LiMn2O4 modified with 2.0 wt.% SiO2 (LiMn2O4@SiO2-2.0 wt.%) exhibits a discharge specific capacity of 101.2 mAh g−1 over 3.0–4.3 V and with a capacity retention of 97.6% after 100 cycles at 25 °C. Even cycled at 55 °C, its capacity retention is still 88.7%. The excellent electrochemical performance is attributed to the improved reversibility and dynamic behaviors after SiO2 modification. Partial Si4+ doping in LiMn2O4 assists to stabilize its crystal structure, while the SiO2 coating layer on the surface of LiMn2O4 materials helps to reduce the attacks of electrolyte and the dissolution of Mn2+.