Cobalt doped spinel LiMn₂O₄ cathode toward high-rate performance lithium-ion batteries

Great efforts have been devoted to improving the cycling stability and the high-rate performance of spinel LiMn₂O₄ cathode. Herein, we demonstrate that Co doping can improve the electrochemical performance of spinel LiMn₂O₄. We elucidate the atomic position of Co in spinel LiMn₂O₄ configuration and the stability improvement mechanism of the Co-doped LiMn₂O₄ cathode by using the state-of-art spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM). The results show that the Co³⁺ ions occupy the Mn octahedral 16d sites to reconstruct a more robust LiCo_xMn_2−xO₄ framework, which is beneficial for stabilizing the LiMn₂O₄ crystal structure by ameliorating Mn dissolution and inhibiting Jahn-Teller distortion. Concomitantly, the doped Co atoms can offer short path lengths for Li⁺ ions intercalation and deintercalation that leads to accelerated Li⁺ diffusion kinetics. The as-designed optimal LiCo_0.05Mn_1.95O₄ presents a respectable capacity retention of 83.81 % after 1000 cycles at 10C (1C = 148 mAh g⁻¹), with an initial discharge capacity of 86.31 mAh g⁻¹. Especially, excellent capacity retention of 78.52 % is obtained after 1000 cycles even at a high current rate of 15C. Our research shed light on the microscopic mechanism of Co doping on the cycling stability enhancement of spinel LiMn₂O₄ toward high-rate performance LIBs.