Surface Encapsulation of Layered Oxide Cathode Material with NiTiO3 for Enhanced Cycling Stability of Na-Ion Batteries

In Na-ion batteries,O3-type layered oxide cathode materials encounter challenges such as particle cracking,oxygen loss,electrolyte side reactions,and multi-phase transitions during the charge/discharge process.This study focuses on surface coating with NiTiO 3 achieved via secondary heat treatment using a coating precursor and the surface material.Through in-situ x-ray diffraction（XRD） and differential electrochemical mass spectrometry（DEMS）,along with crystal structure characterizations of post-cycling materials,it was determined that the NiTiO 3 coating layer facilitates the formation of a stable lattice structure,effectively inhibiting lattice oxygen loss and reducing side reaction with the electrolyte.This enhancement in cycling stability was evidenced by a capacity retention of approximately 74% over 300 cycles at 1 C,marking a significant 30% improvement over the initial sample.Furthermore,notable advancements in rate performance were observed.Experimental results indicate that a stable and robust surface structure substantially enhances the overall stability of the bulk phase,presenting a novel approach for designing layered oxide cathodes with higher energy density.