Application of W1.33CTz MXene obtained by hydrothermal etching as an additive to enhance the electrochemical energy storage properties of binder-free Ti3C2Tx MXene films

In this study, the electrochemical energy storage properties of Ti3C2Tx MXene films have been improved by the addition of W1.33CTz MXenes with ordered vacancies in their structure. W1.33CTz i-MXene was obtained from (W2/3Y1/3)2AlC i-MAX phase by etching in HCl/LiF mixture under hydrothermal conditions with following delamination by intercalation of tetramethylammonium ions. Ti3C2Tx/W1.33CTz composite electrode films were prepared from colloidal solutions, which were mixed in the appropriate ratio to achieve the W1.33CTz 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.% W1.33CTz can significantly improve the pseudocapacitive intercalation of electrolyte ions. The specific capacitance of Ti3C2Tx/W1.33CTz (20 wt.%) electrodes in H2SO4, LiCl and KOH electrolytes was 375, 171 and 235 F•g-1, respectively, at a scan rate of 5 mV•s-1. 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 as a promising electrode material for energy storage systems.