Enhanced electrochemical performance of NaTi₂(PO₄)₃ as an electrode in KOH solution for supercapacitor applications

Abstract

We present the influence of electrolyte solutions on the electrochemical performance of NaTi₂(PO₄)₃, as an electrode material for supercapacitor applications. The NaTi₂(PO₄)₃ ceramic material was successfully synthesised in the rhombohedral phase with R$\bar{3}$c space group, as confirmed by the Rietveld refinement of the x-ray diffraction data. Electrochemical impedance spectroscopy studies revealed that charge transfer resistance in KOH electrolyte is significantly lower than in NaOH, indicating higher ionic conduction in KOH. The specific discharge capacities of the NaTi₂(PO₄)₃ electrode material in KOH and NaOH solutions were found to be 75.46 mAh/g and 6.3 mAh/g, respectively. Moreover, the energy density reached 54.16 Wh/kg at a power density of 1612 W/kg in KOH electrolyte, which is significantly higher than the 3.73 Wh/kg at 1532 W/kg observed in NaOH electrolyte. The electrode also exhibited excellent cycling behaviour, with less than 2% capacitance loss after 10,000 cycles in KOH electrolyte, compared to 15% in NaOH electrolyte. Further, the mechanisms of electrochemical behaviour and associated chemical reactions in KOH and NaOH electrolytes were investigated using density functional theory (DFT) calculations. These findings highlight NaTi₂(PO₄)₃ as a promising electrode material for KOH electrolyte-based supercapacitors.