Ammonium Ion Intercalation Enabled Stable 1T-VS2/WS2-Nb2CTx Heterostructures during Electrochemical Charge Storage

The performance of energy storage devices utilizing multilayered materials is governed by the complex interactions between electrolyte ions and the electrode. Consequently, inhibiting the irreversible oxidative failure of the electrodes is crucial. Herein, an in situ modification strategy that introduces NH4+ species in Nb2CTx MXene electrodes and integrates them with 1T phase VS2/WS2 heteronanosheets is evaluated. The resulting VS2/WS2–Nb2CTx–NH4+ electrodes demonstrate a specific capacity of up to 217.48 mA h g–1 at 1 A g–1 with excellent electrochemical stability at high current densities. Density functional theory simulations confirmed the strong electronic interaction between the NH4+-intercalated Nb2CTx and 1T-WS2/VS2 nanosheets, resulting in higher OH– adsorption energies. Operando Raman analysis revealed that the process involves cation dehydration and K+ rehydration. These results highlight the importance of NH4+ dynamics, thermodynamic stability, and interfacial interactions. A VS2/WS2–Nb2CTx–NH4+//N-doped nanocube-based asymmetric supercapacitor was fabricated, exhibiting a peak energy density of 54 Wh kg–1 and long-term cycling stability without significant performance degradation.