Improve First-Cycle Efficiency and Rate Performance of Layered-Layered Li1.2Mn0.6Ni0.2O2 Using Oxygen Stabilizing Dopant.

The poor first-cycle Coulombic efficiency and rate performance of the Li-rich layered-layered oxides are associated with oxygen gas generation in the first activation charging and sluggish charge transportation along the layers. In this work, we report that barium doping improves the first-cycle efficiency of Li-rich layered-layered Li1.2Mn0.6Ni0.2O2 via suppression of the oxidation of O(2-) ions in the first charging. This effect can be attributed to the stabilizing effect of the barium cations on the oxygen radical intermediates generated during the oxidation of O(2-). Meanwhile, because the stabilized oxygen radicals likely facilitate the charge transportation in the layered-layered structure, the barium-doped Li1.2Mn0.6Ni0.2O2 exhibits significant improvement in rate performance. Stabilizing the oxygen radicals could be a promising strategy to improve the electrochemical performance of Li-rich layered-layered oxides.