Boosting energy efficiency of Li-rich layered oxide cathodes by tuning oxygen redox kinetics and reversibility

In developing electrode materials for next-generation Li-ion batteries, significant efforts have been given to the energy, power density and cycling stability, with much less (if any) attention paid to the energy efficiency – arguably, the most important practical measure for large-scale applications. This is particularly true for the oxygen-redox active electrodes, such as Li1.2Ni0.13Co0.13Mn0.54O2, the notorious energy-inefficient cathode that has an extremely high capacity but comes with large voltage hysteresis and voltage decay. Herein, we report the rational design of an energy-efficient Li-rich layered cathode along with high energy, power density and cycling stability enabled by tuning oxygen redox activity. Specifically, the target material Li1.12Ni0.22Co0.13Mn0.52O2 exhibits an ultrahigh energy efficiency at 1 C (90.6%), high capacity (> 200 mAh g−1) with 98.9% retention and less than 150 mV decay at the extended 200 cycles. Through direct comparison between the material and Li1.2Ni0.13Co0.13Mn0.54O2, we show that the compositional change, although slightly, greatly improves the oxygen redox kinetics and reversibility, thereby boosts energy efficiency. The findings offer a strategy to narrow the gap between scientific interest and practical application of oxygen-redox chemistry.