Linking Local Atomic Structure and Carbon Network Architecture to Electrochemical Performance and Na+ Diffusivity in Na4VMn(PO4)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.