Dual-Role Surface Modification of Layered Oxide Cathodes for High-Power Sodium-Ion Batteries

P2-type layered oxides have attracted extensive attentions due to their high reversible capacity and operating voltage when applied as cathode materials for sodium-ion batteries (SIBs). However, the large ionic radius of Na+ and restricted 2D diffusion channels account for the inferior Na+ conductivity, limiting their practical application under large current densities. Herein, a facile dual-role surface treatment on oxide precursors using KMnO4 solution is employed to generate K+ pillar and spinel-like surface nanolayer in the layered oxide cathodes simultaneously. The substantial enhancement of Na kinetics is ascribed to the enlarged interlayer spacing in the lattice induced by K+ pillar and the formation of coherent spinel-like surface structure derived from the decomposition of KMnO4, which satisfies the timely Na+ insertion/extraction and improves the rate performance. It is anticipated that this dual-role strategy may provide a promising pathway for the development of the high-power-capability SIBs.