文摘
The severe capacity fading of LiMn<sub>2sub>O<sub>4sub> at elevated temperature hinders its wide application in lithium ion batteries despite several advantages over present cathode materials in terms of cost, rate capability, and environmental benignity. In this study, porous nanosized TiO<sub>2sub>-coated LiMn<sub>2sub>O<sub>4sub> is prepared via a modified sol–gel process of controlling hydrolysis and condensation of titanium tetrabutoxide in ethanol/ammonia mixtures, and the phenomenon of homogeneous nucleation has been almost entirely avoided. The X-ray diffraction patterns and transmission electron microscopy images show that a porous nanosized TiO<sub>2sub> layer is uniformly coated on the surface of spinel LiMn<sub>2sub>O<sub>4sub>. Electrochemical tests reveal that the optimal coating content is 3 wt % which shows remarkably improved capacity retentions at both room temperature of 25 °C and elevated temperature of 55 °C. Even after long-term charge and discharge cycles, the TiO<sub>2sub> layer is still robust enough to prevent LiMn<sub>2sub>O<sub>4sub> particles from the attack of electrolyte. The inductively coupled plasma-atomic emission spectrometry, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy results indicate that the obvious improvement of TiO<sub>2sub>-coated LiMn<sub>2sub>O<sub>4sub> electrodes is attributed to the suppression of Mn dissolution, as well as the enhancement of kinetics of Li<sup>+sup> diffusion.