Urea-assisted mixed gas treatment on Li-Rich layered oxide with enhanced electrochemical performance

Abstract

Lithium-rich manganese-based oxides (LRMOs) have been considered as one of the most promising cathode materials owing to their superior specific capacity and high operating voltage. However, their large-scale commercial applications are limited due to problems such as structural instability, voltage decay, and poor cycle stability. Herein, pre-generated oxygen vacancies and oxygen-deficient phase were introduced to Li1.2Mn0.6Ni0.2O2 (LMNO) using a facile urea-assisted mixed gas treatment (UMGT) method for facilitating electronic and ionic conductivity, reducing the surface oxygen partial pressure, and suppressing the release of lattice oxygen. Compared with the pristine LMNO material, the UMGT sample modified at 200 °C exhibited enhanced discharge capacity, capacity retention, and rate capability. In addition, the Li+ diffusion coefficient significantly improved by 50% than that of the reference LMNO. More importantly, the voltage decay was effectively suppressed, with average potential decreasing from 0.53 V (LMNO) to 0.39 V (UMGT-200) after 200 cycles at 1 C. The proposed UMGT method provides an effective strategy to alleviate the phase transition and improve the electrochemical performance for lithium-rich materials, and identifies a promising research direction to inhibit the voltage decay of layered anion redox cathode materials.