Applied Surface Science, Vol.489, 336-345, 2019
Alleviating the initial coulombic efficiency loss and enhancing the electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2 using beta-MnO2
The surface reactivity and chemical instability of de-lithiated Li-rich layered oxide at high voltages often leads to huge irreversible capacity (IC) loss in the first cycle leading to low initial coulombic efficiency (ICE). Herein we demonstrate that simple physical mixing of electrochemically active beta-MnO2 with Li-rich layered Li1.2Mn0.54Ni0.13Co0.13O2 compound at different weight ratios effectively controls the initial IC loss and thereby enhances the ICE. It was observed that addition of beta-MnO2 increased the ICE from 80.0% for the pristine material to 97.0% for composite containing 20 wt% beta-MnO2. The dQ/dV plots of the composites showed that beta-MnO2 becomes electrochemically active at lower potentials (< 3.0 V) than the layered MnO2 component derived from the activation of pristine Li1.2Mn0.54Ni0.13Co0.13O2 cathode. Identical performance of composite and pristine electrodes after first cycle activation implies that there is a synergistic electrochemical behavior between the beta-MnO2 and layered Li1.2Mn0.54Ni0.13Co0.13O2 cathode. Among the various composite materials with differing ratios of beta-MnO2 investigated, the composite with 15 wt% beta-MnO2 showed better performance in terms of deliverable capacity, material stability, and rate capability with an ICE of 94.1% compared to other composite cathodes.