Application of WCT MXenes obtained by hydrothermal etching as an additive to enhance the electrochemical energy storage properties of binder-free TiCT MXene films.

In this study, the electrochemical energy storage properties of TiCT MXene films have been improved by the addition of WCT MXenes with ordered vacancies in their structure. The WCT i-MXene was obtained from the (WY)AlC i-MAX phase by etching in a HCl/LiF mixture under hydrothermal conditions followed by delamination by the intercalation of tetramethylammonium ions. TiCT/WCT composite electrode films were prepared from colloidal solutions, which were mixed in an appropriate ratio to achieve the WCT concentrations of 10, 20, 30 and 40 wt%. MXenes were characterized by XRD, SEM, TEM and XPS methods. The electrochemical energy storage properties of binder-free MXene films were studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) methods. It has been shown that the addition of 20 wt% WCT can significantly improve the pseudocapacitive intercalation of electrolyte ions. The specific capacitance of TiCT/WCT (20 wt%) electrodes in HSO, LiCl and KOH electrolytes was 375, 171 and 235 F g, respectively, at a scan rate of 5 mV s. The composite electrode showed good cycling stability (more than 93% capacity retention after 10 000 cycles). The results obtained indicated that the synthesised composite could be considered a promising electrode material for energy storage systems.