Electrochemical storage mechanism of interstratification-assembled Ti3C2Tx MXene/NiCo-LDHs electrode in alkaline, acid and neutral electrolytes

Different kinds of two-dimensional hybrid electrodes have high theoretical capacitance and energy density. However, the origin of the electrochemical storage mechanism still remains elusive in alkaline, acid and neutral electrolytes. Herein, the interstratification-assembled Ti3C2Tx MXene/NiCo-LDHs electrodes were successfully prepared and studied in different electrolytes by in-situ Raman spectroscopy. The results show that H2O molecules in neutral electrolyte combine with -OH at the end of Ti3C2Tx MXene during charging, and debonding occurs during discharge. Similarly, this reaction also occurs in the discharge process with NiCo-LDHs and provides smaller pseudocapacitance characteristics. Although this pseudocapacitance reaction also occurs in acidic and alkaline electrolytes, however, the difference is that the hydrogen ions will promote the electrochemical performance of Ti3C2Tx MXene and has a certain corrosion consumption effect on NiCo-LDHs, but generally improve the electrochemical performance of Ti3C2Tx MXene/NiCo-LDHs. Interestingly, the OH- in alkaline electrolyte can promote the electrochemical performance of NiCo-LDHs, and produce a new electrochemical reaction with -F between the layers of Ti3C2Tx MXene, which greatly improves the overall electrochemical performance of this hybrid electrodes. As a result, Ti3C2Tx MXene/NiCo-LDHs electrodes have the best electrochemical performance in alkaline electrolyte with capacitance of 283 F g-1, energy density of 14.2 Wh kg- 1 and power density of 3007.1 W kg- 1. This work lays a foundation for the preparation of high-performance twodimensional hybrid electrochemical energy storage devices.