Supercapacitors are amongst the most prominent electrochemical energy storage devices and fill the gap between batteries and capacitors with their high power and energy density. Pseudocapacitive materials have been found to be promising electrode materials for supercapacitor applications. They achieve high power output and fast charging/discharging by fast faradaic redox reactions at the surface, which has made them the focus of super capacitor research in recent years [1]. Two-dimensional (2D) materials, especially MXenes, such as titanium carbides (Ti₃C₂T_x), have been shown to hold significant promise, as they offer great pseudocapacitive properties combined with a high electronic conductivity. For example, thin film electrodes made up of Ti₃C²T_x have shown exceptional capacitance of up to 450 F/g and a good rate performance even up to 100 V/s [3]. However, when trying to increase the areal capacitance by increasing the film thickness, conventional thin film approaches (e.g. thickness < 100 nm) for the fabrication of MXene electrodes suffer in electrochemical performance from mass transport and diffusion limitations.
Herein is a novel method for the fabrication of interconnected 2D thin films in a 3D macroscopic assembly using a template-based approach which can overcome these limitations [4][5]. We demonstrate supercapacitor electrodes with a thickness of 50 µm and areal loadings of more than 5 mg/cm2 that  achieve volumetric and specific capacitances of up 140 F/cm³ and 240 F/g respectively, at a scan rate of up to 200 mV/s. At the same scan rate an areal capacitance of ~1.4 F/cm² is recorded, outperforming that of state-of-the-art MXene based electrodes by a factor of ~2.
The electrochemical performance of the electrodes can be further modified by combining the MXene interconnected thin films with thin films of functional polymers, such as PEDOT:PSS. It has been shown, that the incorporation of PEDOT into the MXene structure can greatly enhance electrochemical properties [2]. This modification has the potential to further increase the electrochemical performance of the pure 3D-Mxene electrodes, e.g. by increasing layer separation and opening up of ionic pathways as well as enhance the mechanical stability of the electrodes [2].