Structural Optimization of NVP/C Composites by an Advanced Two-Step Spray Technique for High Energy Density and Long-Life Symmetric Sodium-Ion Batteries

Sodium superionic conductor (NASICON)-type Na₃V₂(PO₄)₃ (NVP) has emerged as a pivotal cathode material for the development of high-durability sodium-ion batteries, owing to its distinctive 3D open framework and exceptional chemical stability. Enhancing the electrochemical performance of NVP through the incorporation of conductive materials and precise control of the pore structure requires refining and optimizing the synthesis methodologies. In this study, robust NVP composites combined with dextrin-derived carbon (D-NVP/Dex) and carbon nanotubes (D-NVP/CNT) are developed with stable cycling characteristics and high energy densities, exhibiting high capacities of 99.0 and 93.0 mA h g⁻¹, respectively, at 1.0 C after the 300 cycles, via a two-step synthesis approach utilizing spray techniques. These structural features, including the conformal carbon layer encapsulating the NVP particles and the connections formed through CNT networks, are validated to enhance their electrical and ionic conductivities, as demonstrated by evaluations of both half-cell and symmetric full-cell configurations. Specifically, symmetric D-NVP/Dex||D-NVP/Dex and D-NVP/Dex||P-NVP sodium-ion batteries exhibit excellent cyclability, achieving capacities of 46.5 and 49.0 mA h g⁻¹, respectively, after 150 cycles at 0.5 C.