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 Cofree 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 Lirich layered oxides.

Automated summary

This study proposes a strategy to alleviate the segregation of Li2MnO3 component in Co-free Li-rich layered cathodes by tailoring oxygen partial pressure during heat treatment. Experimental results show that this strategy can accelerate the activation of Li2MnO3 component and improve the capacity and cycling stability of the material.