Formation of NaTi(PO) Coating Layers to Enhance the High-temperature Performance of NaNiFeMnO Cathode Materials

The insufficient structure and interfacial stability of O3-type layered oxide cathode materials hinder their practical application in sodium-ion batteries, particularly at high temperatures. In this study, a thin, island-like NaTi(PO) coating layer (∼15 nm) is constructed on the surface of NaNiFeMnO through an reaction involving nano-TiO, NaCO and NHHPO. During the high-temperature calcination process, partial Ti-atom diffusion into the NaNiFeMnO lattice results in the expansion of the interslab of the sodium layer and a reduction in lattice oxygen vacancies. Benefitting from the stable NaTi(PO)-modified interface and enhanced structural stability, the NaNiFeMnO coated with 2 wt% NaTi(PO) exhibits optimal cycle stability at high temperature. It retains 90.3% of its initial capacity after 100 cycles at 0.5C (1C = 130 mA g, 45 °C). This dual-modification strategy, obtained from a facile approach, has the potential to facilitate the practical application of O3-type layered oxide cathode materials.