Exploration of a Novel Vanadium Source for the Synthesis of a Na3V2(PO4)3 Cathode of Sodium-Ion Batteries

The NASICON (sodium super ion conductor)-type Na3V2(PO4)3 (NVP) possesses a high voltage plateau and structural robustness and thus demonstrates enormous potential in energy storage applications. Traditionally, high-purity vanadium pentoxide (V2O5) and ammonium vanadate (NH4VO3) have been employed as vanadium sources for NVP@C synthesis, resulting in lengthy and expensive procedures. This study demonstrates the potential of utilizing sodium vanadate (NaVO3) solution, which can be obtained as an intermediate product during V2O5 extraction from vanadium slag, as a vanadium source through a solid-state method. Two different types of red cakes (xNa2O·yV2O5·zH2O) from a pure NaVO3 solution and sodium roasting leachate of vanadium slag were analyzed to evaluate their effect on the resulting NVP@C. The findings indicate that phase-pure NVP@C can be synthesized from both red cake sources, demonstrating the feasibility of this new synthesis route. Moreover, the NVP@C material prepared from a red cake of NaVO3 solution exhibits superior properties, which may be attributed to the sparser particles and narrower particle size distribution. It maintained reversible capacities of 104.7, 101.2, 94.5, and 66.7 mA h g–1 at 0.1, 1, 5, and 10 C, respectively, in the first week. After 500 cycles at 1 C, the capacity retention rate is 93.12%, demonstrating good cycling stability. Using an intermediate product of industrial V2O5 production as a raw material to achieve the synthesis of NVP@C expanded the range of vanadium sources for the synthesis of NVP@C, simplified the production process, avoided the generation of ammonia nitrogen wastewater, and opened up a more industrially viable synthesis pathway for NVP@C.