Linking Local Atomic Structure and Carbon Network Architecture to Electrochemical Performance and Na ⁺ Diffusivity in Na ₄ VMn(PO ₄ ) ₃ /C Cathodes

Na₄VMn-(PO₄)₃ is a promising cathode material for sodium-ion batteries due to its high operating voltage, structural robustness, and open three-dimensional framework that supports efficient Na⁺ transport. However, its practical deployment is limited by poor intrinsic electronic conductivity and structural instability under cycling. To address these limitations, Na₄VMn-(PO₄)₃/carbon (Na₄VMn-(PO₄)₃/C) composites were investigated, focusing on the interplay between carbon network architecture and local atomic structure. Using advanced characterization techniques, this study reveals that the degree of distortion in MnO₆ and VO₆ octahedra, along with the continuity and distribution of the conductive carbon matrix, plays a pivotal role in determining Na⁺ diffusion kinetics and electrochemical performance. Composites with reduced local structural distortion exhibit enhanced structural integrity and Na⁺ mobility, while a well-integrated carbon network significantly improves the electronic conductivity. Together, these synergistic effects led to markedly improved cycling stability, rate capability, and Na⁺ diffusion coefficients. These findings provide valuable insights into the atomic-scale and mesoscale design principles necessary for optimizing polyanionic cathode materials for high-performance sodium-ion batteries.