Synergistic Strain Suppressing and Interface Engineering in Na4MnV(PO4)3/C for Wide-Temperature and Long-Calendar-Life Sodium-Ion Storage

A Na₄MnV(PO₄)₃ (NMVP) cathode is regarded as a promising cathode candidate for sodium-ion batteries (SIBs). However, issues such as low electronic conductivity and partial cation dissolution contribute to high polarization and structure distortion. Herein, we engineered the local electron density and reaction kinetic properties of NMVP cathodes with varying oxygen vacancies by introducing varying amounts of Zr doping and carbon coating. The optimized sample exhibited a high-rate capacity of 71.8 mAh g^-1 at 30 C (83.1% capacity retention after 1000 cycles) and excellent performance over a wide temperature range (84.1 mAh g^-1 at 60 °C and 61.4 mAh g^-1 at -30 °C). In situ X-ray diffraction technology confirmed a redox solid solution and a two-phase reaction mechanism, revealing minor changes in cell volume and slight strain variations after Zr doping, effectively suppressing the structural distortion. Theoretical calculations illustrated that Zr doping largely shrinks the band gap of NMVP, enriches local electron density, and slightly alters the local element distribution and bond lengths. Moreover, full-cells have shown high energy density (259.9 Wh kg^-1) and outstanding cycling stability (200 cycles). The work provides fresh insights into the synergistic effect of strain suppressing and interface engineering in promoting the development of wide temperature range and long-calendar-life SIBs.