MXene-carbon nanotubes layer-by-layer assembly based on-chip micro-supercapacitor with improved capacitive performance

The development of miniaturized flexible energy storage devices has attracted tremendous research interests for their wide spectrum of applications in various advanced wearable and smart electronic devices. In this work, we have developed a new type of on-chip micro-supercapacitor (mSC) using MXene (i.e., Ti3C2TX)-carbon nanotubes (CNTs) composite as the electrode material via photolithography technique and subsequent vacuum-filtration process. While preparing electrode material for mSC, Ti3C2TX holds several merits such as flat and flexible layered structure, huge surface area and high electrical conductivity. The integration of CNTs with Ti3C2TX leads to the formation of layer-by-layer (LbL) assembly, where CNTs act as the spacer to prevent the stacking and aggregation of Ti3C2TX nanosheets during the assembly process. Consequently, the resultant Ti3C2TX-CNTs electrode material offers flexible layered channels and controllable electronic structures for rapid diffusion of electrolyte ions, which give rise to a significant improvement in the capacitive performance. The as-fabricated mSC device based on Ti3C2TX-CNTs LbL assembly exhibits good areal capacitance of 61.38 mF/cm2 at a current density of 0.5 mA/cm2, outperforming most of MXene or carbon materials based mSCs. Furthermore, it also demonstrates the capability to be operated in serial and parallel configuration to provide a large energy storage or high power output to satisfy the practical use. Therefore, this strategy for the construction of high-performance flexible mSC based on Ti3C2TX-CNTs LbL assembly shows great potential in flexible microelectronic devices.