Development of Asymmetric Lateral and Vertical Configuration Flexible Micro-Supercapacitors from MXene and Laser Induced Porous Graphene (MXene-LIPG)

Associated with the rapid development of layered materials beyond graphene, two-dimensional transition metal carbides i.e., MXenes derivatives have been exploited and exhibited unique physical/chemical properties that hold promise for applications in electrochemical energy storage and conversion systems, especially micoscale devices [1]. Current microfabrication of micro-supercapacitors often involves multistep processing and time-consuming lithography protocols. In this study, we report a facile method of fabrication to develop an asymmetric MXene-based micro-supercapacitor, which is flexible and current-collector-free. Specifically, the interdigitated device architectures are designed while fabricating scalable laser-induced porous graphene (LIPG) onto flexible substrates created. The electrode materials consisted of titanium carbide MXene (Ti₃C₂T_x) and LIPG, which are both 2D layered materials that contribute to the faster ion diffusion in the interdigitated electrode architectures. The MXene-based asymmetric micro-supercapacitor operates at ≥ 1 V working voltage window with polymer gel or aqueous electrolytes while retaining > 85% of the initial capacitance after five thousand cycles, and exhibiting an energy density of 7.3 mW h cm⁻³ at a power density of 0.14 W cm⁻³. Further, these MSCs can 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 LIG as a positive electrode in asymmetric architectures appears to be a promising strategy for increasing both stored energy and power densities simultaneously. We also fabricated and characterized vertical (or traditionally parallel) asymmetric MXene || LIPG (< 1V, 3 mW h cm⁻³ at a power density of 0.1 W) and symmetric LIPG || LIPG (< 0.8 V, <1 mW h cm⁻³ at a power density of < 0.01 W) and MXene || MXene (1V, 3 mW h cm⁻³ at a power density of 0.1 W) devices. The intrinsic relationship among microscopic structure, physicochemical properties, and applications for termination-tailored MXene derivatives is emphasized [2]. *The author (S.G.) acknowledges the support from an internal Grant (Nobelium Award under IDUB).