Ion transport dynamics and cation mobility in hydrothermally synthesized MXene-NiWO4 composite electrodes for advanced energy storage

Abstract

Excessive consumption of fossil fuels over the years has severely impacted the global environment, causing air pollution and climate change. Thereby, developing renewable and efficient energy storage systems has become essential to overcome these challenges. In this context, supercapacitors (SCs) have attracted significant attention due to their rapid charge–discharge performance, higher power density (PD), longer cycle life, and environmental friendliness. In this study, NiWO₄/MXene composite electrodes were synthesized via a hydrothermal route with the aim of achieving enhanced cation mobility and accelerated ion transport, thereby improving electrochemical efficiency and charge storage performance. The material's electrochemical performance was tested using cyclic voltammetry (CV) for redox behavior and galvanostatic charge–discharge (GCD) for charge storage capacity and stability. The NiWO₄/MXene electrode delivered a high specific capacitance of 1545.42 F g⁻¹ at a current density of 1.5 A g⁻¹, along with an energy density (ED) of 107.32 Wh kg⁻¹ and a PD of 199.9 W kg⁻¹. The chronoamperometry results confirm that the composite exhibits excellent electrochemical stability over 50 hours and 95.80% capacitance retention from GCD after 2000 cycles. A systematic correlation was observed between the structural features such as the reduction in diffraction peak intensity due to MXene coverage and the preservation of NiWO₄ crystal planes and the ion transport dynamics, indicating that the structural modulation directly influences cation mobility and overall charge transport. These findings demonstrate that careful tuning of the material's structure can effectively enhance ion transport in composite electrode materials.