Sodium vanadium phosphate cathodes for Na-ion batteries: Carbon modification strategies and electrolyte compatibility

Sodium Vanadium Phosphate (Na 3 V 2 (PO 4 ) 3 , (NVP)) is a promising cathode for sodium-ion batteries (SIBs) due to its stable Sodium Super Ionic Conductor (NASICON) structure, high operating voltage, and fast Na + diffusion. However, its inherently low electronic conductivity limits rate performance and cycling stability. Carbon modification effectively mitigates these challenges by enhancing the electronic conductivity of NVP particles, improving ion movement, and reducing charge transfer resistance. This review systematically analyzes major carbon-modification strategies, such as in-situ carbon coating, integration of carbon nanostructures, hetero-atom-doped carbon, and composite architectures, and their influence on the electrochemical performance of NVP cathodes. Special emphasis is given to how carbon coating thickness and morphology affect conductivity, ion transport, and interface stability of the NVP cathode. Furthermore, the interplay between carbon modification and electrolyte compatibility is examined to clarify their combined role in solid electrolyte interface (SEI) and cathode electrolyte interface (CEI) formation and long-term stability. Finally, the review highlights existing challenges and future directions toward optimizing carbon-modified NVP cathodes for next-generation sodium ion batteries.