Controls of oxygen-partial pressure to accelerate the electrochemical activation in Co-free Li-rich layered oxide cathodes

The degree of electrochemical activation of Li2MnO3 component has a vital role in achieving high capacity in Co-free Li-rich layered cathodes. However, due to the segregation of Li2MnO3 component in these cathodes sintering at high temperature, it is difficult to be fully activated. Herein, a strategy is proposed to alleviate segregation of Li2MnO3 component by reducing the oxidation state of partial Mn with tailoring oxygen partial pressure during heat treatment. Combined with X-ray photoelectron spectroscopy, electron energy loss spectrum and soft X-ray absorption spectroscopy, some slight Mn3+ have been confirmed to be introduced into the bulk lattice. Monte Carlo simulation is applied to identify the Mn3+ positive effect on alleviating LiMn6 segregation. As a result, the material sintered in the O2-deficient environment exhibits an accelerated activation of Li2MnO3 component at the pre-cycles and delivers a high capacity over 250 mAh g−1 with the capacity retention about 92% over 100 cycle. This strategy provides a simple but effective method to exploit the electrochemical activity in Co-free Li-rich layered oxides.