Boosting the Performance of a Highly Cobalt-Doped Na3V2(PO4)3/C Nanocomposite via a Dual Doping Strategy for High-Performance SIB Cathodes

In recent years, sodium-ion batteries (SIBs) have emerged as promising alternatives to lithium-ion batteries (LIBs) due to several advantages such as low cost and high abundance of sodium precursors. However, one of the significant drawbacks of SIB cathodes is poor cycling stability at a higher current density than LIBs due to the large size of the Na⁺ ion. We have demonstrated a strategy to boost the cycling stability and overall performance of the SIB cathode via combined dual ion doping and nanostructuring methodologies. We synthesized a series of Na₃V_2–xCo_x(PO₄)₃/C (x = 0.05, 0.1, 0.5) cathode materials via a solid-state sintering process. Structural and morphological properties were analyzed by using XRD, SEM, and TEM analysis. In addition, the successful incorporation of Co was confirmed by an XPS analysis. An aqueous-based electrochemical system was utilized to check the electrochemical performance of the synthesized material. In a 1 M NaOH electrolyte, NCoVP-0.5 delivers the highest discharge time of 175.89 s at a current density of 1 A g^–1. Additional K and Li dopants were utilized to further enhance the performance of NCoVP-0.5. During the initial galvanostatic charge–discharge at a current density of 1 A g^–1 and a voltage window of 0.1–0.58 V, LiNCoVP delivers a discharge time of 202 s with an efficiency of 84.6%, while KNCoVP delivers the highest discharge time of 215 s with an efficiency of 86.2%. Even at a current density of 5 A g^–1, KNCoVP demonstrated a Coulombic efficiency of >97% after 200 cycles. Also, KNCoVP delivers a discharge specific capacity of 116.2 mAh/g at 0.1C. Thus, the introduced material and the demonstrated strategy underscore the inherent problems of the cathode material of SIBs.