Asymmetric Flexible MXene-Reduced Graphene Oxide Micro-Supercapacitor

Current microfabrication of micro-supercapacitors often involves multistep processing and delicate lithography protocols. In this study, simple fabrication of an asymmetric MXene-based micro-supercapacitor that is flexible, binder-free, and current-collector-free is reported. The interdigitated device architecture is fabricated using a custom-made mask and a scalable spray coating technique onto a flexible, transparent substrate. The electrode materials are comprised of titanium carbide MXene (Ti₃C₂T_x) and reduced graphene oxide (rGO), which are both 2D layered materials that contribute to the fast ion diffusion in the interdigitated electrode architecture. This MXene-based asymmetric micro-supercapacitor operates at a 1 V voltage window, while retaining 97% of the initial capacitance after ten thousand cycles, and exhibits an energy density of 8.6 mW h cm⁻³ at a power density of 0.2 W cm⁻³. Further, these micro-supercapacitors show a high level of flexibility during mechanical bending. Utilizing the ability of Ti₃C₂T_x-MXene electrodes to operate at negative potentials in aqueous electrolytes, it is shown that using Ti₃C₂T_x as a negative electrode and rGO as a positive one in asymmetric architectures is a promising strategy for increasing both energy and power densities of micro-supercapacitors.