Enhanced Performance of Li‐Rich Manganese Oxide Cathode Synergistically Modificated by F‐Doping and Oleic Acid Treatment

Abstract

Even lithium-rich manganese oxides (LRMOs) are considered as promising cathode materials for next-generation lithium-ion batteries, their commercialization is hindered mainly by the low initial Coulombic efficiency, poor cyclability and unexpected capacity fade. Here, a synergistic modification strategy by using both F doping and weak organic acid surface treatment is proposed to improve the electrochemical performances of LRMOs significantly. Optimized Li_1.2Mn_0.54Ni_0.13Co_0.13O_1.95F_0.05 sample with surface oxygen vacancy defects and thin carbon coating layer exhibits profound electrochemical performances, for example, discharging capacities of 298.6 and 212.5 mAh g^-1 at 0.1 C and 1 C rate, respectively. In addition, it can own an initial Coulombic efficiency of 84.4%, which is much higher than that of untreated sample. In situ X-ray diffraction analysis implies that synergistic modification can enhance the skeleton stability of LRMOs , especially at a high state of charge. Galvanostatic intermittent titration technique analysis suggests that as-developed synergistic modification can accelerate the lithium ions diffusion. Theoretical calculations reveal that substituted F and oxygen vacancy defects can diminish the diffusion energy barrier of Li⁺ ions. This work provides a new synergistic modification strategy to improve the comprehensive properties of LRMO cathode effectively.