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

Abstract

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 LiCoxMn2−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 LiCo0.05Mn1.95O4 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.