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

Abstract Co-doped samples are synthesized by a sol–gel method and investigated in detail to improve the high-rate discharge performance of the spinel LiMn 2 O 4 cathode in high-temperature lithium batteries. The results of X-ray diffraction and scanning electron microscopy confirm that the cobalt additive incorporates into the LiMn 2 O 4 lattice and that the lattice parameters decrease gradually with increasing Co substitute content. The galvanostatic discharge results indicate that the Co-doped LiMn 2 O 4 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 LiMn 1.7 Co 0.3 O 4 and LiMn 1.5 Co 0.5 O 4 , 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.