O3-Type Ni-Rich NaNi2/3Mn1/6Fe1/6O2: A high-performance cathode material for sodium-ion batteries

Because of relative prominent capacity, layered oxide materials are regarded as promising candidate cathode materials for sodium-ion batteries (SIBs). Nevertheless, the permanent changes in structure accompanied by sodium extraction/insertion restrict their capacity and retention in cycles. The O3-type phase material has a stable structure and can obtain a steady high-capacity output combined with high nickel content. In this paper, a simple high-temperature solid-state approach is used to create Ni-rich NaNi2/3Mn1/6Fe1/6O2 materials aiming to achieve high capacity. Systematic researches are conducted through a combination of electrochemical measurements and structural characterization. The Ni-rich NaNi2/3Mn1/6Fe1/6O2 sample obtained at 850 °C exhibits a well-crystallized O3 phase, as well as comprises hexagonal plate-like particles. In the voltage range of 1.5–4.2 V, this sample demonstrates an impressive initial discharge capacity of 226 mAh/g at a rate of 0.2 C. Furthermore, even after 100 cycles, it still maintains a capacity retention of approximately 76 %, exhibiting outstanding cycling stability. This material demonstrating remarkable electrochemical performance highlights the potential of the Ni-rich layered cathode material candidate, and makes an important supplement to the research on commercialization electrode materials for SIBs.