Sol–gel synthesis of Co-doped LiMn2O4 with improved high-rate properties for high-temperature lithium batteries

Co-doped samples are synthesized by a sol–gel method and investigated in detail to improve the high-rate discharge performance of the spinel LiMn2O4 cathode in high-temperature lithium batteries. The results of X-ray diffraction and scanning electron microscopy confirm that the cobalt additive incorporates into the LiMn2O4 lattice and that the lattice parameters decrease gradually with increasing Co substitute content. The galvanostatic discharge results indicate that the Co-doped LiMn2O4 satisfies both high-capacity and high-rate discharge requirements at 200–300 °C when proper substitute contents are chosen. At a high current density of 30 mA cm−2, enhanced high-rate capacities of 219.71 mAh g−1 at 200 °C and 307.38 mAh g−1 at 300 °C are obtained in LiMn1.7Co0.3O4 and LiMn1.5Co0.5O4, respectively, which have promising applications in high-temperature lithium batteries. These improvements are partly attributed to the enhanced electrical conductivity, as observed through electrochemical impedance spectroscopy.