Boosting Long‐Life Sodium Storage of Na ₄ MnV(PO ₄ ) ₃ via Synergistic Bond Structure Regulation and Interfacial Modification

ABSTRACT Na 4 MnV(PO 4 ) 3 (NMVP) is a promising cathode alternative for Na 3 V 2 (PO 4 ) 3 in sodium‐ion batteries (SIBs) due to its cost‐effectiveness and relatively high average working voltage. However, the inferior electronic conductivity and negative Jahn‐Teller (J–T) distortion of Mn 3+ ions lead to structural degradation and unsatisfactory electrochemical performance, limiting its practical utilization in SIBs. Herein, we propose a Mn─O bond regulation strategy through high‐valence‐state Mo 6+ substitution, supplemented by interfacial Al 2 O 3 coating to suppress the dissolution of Mn in NMVP, thus enhancing its electrochemical performance. Multiple characterizations and density functional theory (DFT) calculations show that Mo 6+ substitution can strengthen Mn─O bonds and mitigate MnO 6 octahedral distortion in NMVP, enhancing the electrical conductivity and Na + diffusion kinetics due to the reduced band gap and Na + transport energy barrier. In addition, the well‐established Al 2 O 3 coating layer can stabilize the electrode/electrolyte interface and further accelerate Na⁺ transport. Hence, the prepared Na 3.91 MnV 0.97 Mo 0.03 (PO 4 ) 3 @Al 2 O 3 (NMVMP@Al 2 O 3 ) cathode delivers a superior electrochemical performance with 84.5% of capacity retention after 3000 cycles at 10 C. The regulation of bond structure and interfacial modification provides a novel idea for further developing long‐life SIBs V‐based polyanionic cathodes.