Rational Selection of Carbon Source for High‐Performance Na 3 V 2 (PO 4 ) 3 Cathodes: Correlating Carbon Layer Properties With Electrochemical Performance

Sodium vanadium phosphate (Na 3 V 2 (PO 4 ) 3 , NVP) is regarded as a promising cathode material for sodium‐ion batteries (SIBs). However, its practical application is severely impeded by the inherent low electronic conductivity. Carbon coating has been widely adopted to mitigate this limitation, primarily because it can form an interconnected conductive network. Herein, a series of NVP/C composites was synthesized via a sol‐gel method followed by calcination, employing oxalic acid, citric acid, sucrose, and ascorbic acid as distinct carbon sources. The influence of carbon sources on the degree of graphitization, specific surface area, uniformity, and morphology of the derived carbon coating was systematically investigated, and its correlation with the electrochemical performance was established. The results demonstrate that the composite prepared with citric acid as a carbon source (denoted as NVP/C‐N) exhibits the most favorable carbon layer structure, featuring large specific surface area, high graphitization, and uniform coverage, which contribute to its superior sodium storage properties. Specifically, it delivers a high reversible capacity, excellent rate capability, and outstanding cycling stability. This work elucidates the critical role of carbon source selection in determining the interfacial and conductive properties of NVP/C composites and provides practical guidance for the rational design of high‐performance NVP‐based cathodes for advanced SIBs.