Alleviating the initial coulombic efficiency loss and enhancing the electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2 using β-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 β-MnO₂ with Li-rich layered Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ compound at different weight ratios effectively controls the initial IC loss and thereby enhances the ICE. It was observed that addition of β-MnO₂ increased the ICE from 80.0% for the pristine material to 97.0% for composite containing 20 wt% β-MnO₂. The dQ/dV plots of the composites showed that β-MnO₂ becomes electrochemically active at lower potentials (<3.0 V) than the layered MnO₂ component derived from the activation of pristine Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode. Identical performance of composite and pristine electrodes after first cycle activation implies that there is a synergistic electrochemical behavior between the β-MnO₂ and layered Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode. Among the various composite materials with differing ratios of β-MnO₂ investigated, the composite with 15 wt% β-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.