High-capacity high-Ni low-Co Li-rich layered oxides via adjusting Li2MnO3 content and Li/Ni mixing defects

Li-rich layered oxides (LLOs) have been considered as the promising candidate cathodes for the next high-energy Li-based batteries, but suffer from poor rate capability, lower discharge voltage, and persistent voltage fade. Appropriately increasing the Ni content in LLOs tends to improve rate capability, discharge voltage, and stability. However, the high-Ni LLOs are likely to have inferior O2-/- redox activities, causing lower capacities, typically < 250 mAh/g. Herein, the rationally regulated Li2MnO3 phase content and Li/Ni disordering defects via two-step adjustment of the Ni/Mn and Li/Mn ratios are proposed to obtain a high-capacity high-Ni low-Co LLO Li1.167Ni0.222Mn0.537Co0.074O2 (L2-1). Compared to a typical Li1.2Ni0.13Mn0.54Co0.13O2 (Ls), the as-prepared L2-1 cathode delivers higher reversible capacity (267.2 vs 288.2 mAh/g), higher voltage, and better rate capability. Such an improvement is demonstrated by experiments and theoretical calculations that a suitable Li2MnO3 content (36.6%) and a high Li/Ni disordering (5.93%) for LLOs play a crucial role in the O2-/- redox processes. This work contributes to the design of high-capacity high-Ni LLOs.