Li1.2Ni0.25Mn0.55O2: A high-capacity cathode material with a homogeneous monoclinic Li2MnO3-like superstructure

High-energy lithium-rich and manganese-based layered materials are one of the most promising candidates for the cathode materials of lithium-ion batteries. These cathode materials can deliver anomalously high capacity due to multiple electron transfers involving both cationic and anionic redox processes. An unprecedented homogeneous monoclinic LiMnO-like structured material LiNiMnO, which with the highest nickel content among the Li-rich materials, is first disclosed in this work. Our proposed LiNiMnO material can deliver a reversible capacity exceeding 295 mAh·g with a high and stable discharge voltage. It is especially encouraging that the as-prepared LiNiMnO cathode material displays high charge-discharge efficiency and good capacity retention during cycling. In this work, we applied in-situ EIS and ex-situ XPS methods to systematically investigate the reversible structural evolution of LiNiMnO cathode material and cathode-electrolyte interfaces (CEI). These findings will shed light on the design of high-performance cathode materials for lithium-ion batteries.