Unveiling the Effect of Voltage Regulation System on the Structure and Electrochemical Properties of Lithium-Rich Cathode Materials

Abstract

© The Author(s) 2019. Lithium-rich layered oxides exhibit a superior specific capacity more than 280 mAh g–1 in the range of 2.0–4.8 V. Meanwhile, capacity attenuation and voltage decay are also caused by such a wide voltage range. The structure evolution and electrochemical properties of materials at different voltage regulation systems have been studied. Complex phase transition and interplanar spacing increase can be blocked under the lower voltage cycle and the diffusion ability of Li+ has been significantly improved after pre-cycling treatment, especially at the condition of 4.5 V. Li1.2Ni0.13Co0.13Mn0.54O2 exhibits excellent capacity retention of 92.77% with slight voltage attenuation of 0.3731 V compared to 55.74% and 0.7883 V at high voltage after 200 cycles under the synergistic effect of pre-cycling and lower voltage operation. Such superior electrochemical performance is attributed to that: (1) pre-cycling can gentle the activation process and rationalize the intercalation/deintercalation interval of Li+; (2) the lower voltage operation will restrain the release of oxygen in high voltage region to stabilize the phase structure and inhibit the decomposition of electrolyte. The rational voltage regulation system can improve the reversibility of anion redox and maintain excellent cycle performance.