Hf-Doped Na ₄ VMn(PO ₄ ) ₃ NASICON Cathodes with Nanosized Carbon Coatings for Sodium Battery

Nanostructured NASICON-type Na 4 VMn(PO 4 ) 3 (NMVP) is a promising high-voltage cathode alternative to Na 3 V 2 (PO 4 ) 3 for sodium-ion batteries (SIBs). However, its low electronic conductivity, the Jahn–Teller effect, and cation dissolution severely compromise the lattice integrity at the nanoscale, leading to structural distortion and electrode polarization. In order to mitigate nanostructural degradation and improve electrochemical performance, nanostructured NMVP cathodes were synthesized via a combination of freeze-drying and microwave sintering, followed by a synergistic modification strategy involving Hf doping and uniform carbon coating to enhance electronic conductivity and Na + reaction kinetics. The resulting Hf-doped NMVHP/C-0.01 composite delivered an initial discharge specific capacity of 97.79 mAh g –1 at 0.2C, while maintaining 86.79% of its capacity after 900 cycles at 10C. For further validation of its practical applicability, an NMVHP/C-0.01//hard carbon (HC) full-cell configuration was evaluated, which demonstrates the great prospect of NMVP as a high-performance cathode material for SIBs.