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 Li1.2 Mn0.54 Ni0.13 Co0.13 O1.95 F0.05 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 diffractionanalysis 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.