Nanotechnology engineering of polyanionic Na₃V₂(PO₄)₂F₃ cathodes toward high-performance sodium-ion batteries

Polyanionic Na₃V₂(PO₄)₂F₃ (NVPF) cathodes enable a high operating voltage for sodium-ion batteries (SIBs) by virtue of the valence-electron decoupling properties from vanadium metal transition-metal redox centers and polyanionic groups. However, the low intrinsic conductivity and restricted ion diffusion kinetics have led to undesirable electrochemical performance, thereby limiting the further application of NVPF cathodes. The appropriate nanotechnologies can address the intrinsic deficiencies of materials and serve as a key strategy to break through performance bottlenecks. Herein, we summarize the recent progress made to improve the comprehensive performance of NVPF-based cathode materials from the perspective of nanoengineering, typically including nanoarchitecture, nanoscale surface modification and nanostructure tuning to clarify the structural properties, electrochemical behavior and their interplay. Moreover, the remaining challenges and future suggestions for the design of higher-performance NVPF cathodes towards practical SIBs are presented. The current review provides profound insights into the structure-performance relationship and valuable guidance to develop polyanionic NVPF cathodes for practical SIBs toward commercialization.