Flexible MXene/Laser-Induced Porous Graphene Asymmetric Supercapacitors: Enhanced Energy Density of Lateral and Sandwich Architectures Under Different Electrolytes.

Deployment of 2D layered materials beyond graphene, i.e., MXene (TiCT, T = ─OH, F, O) is rigorously explored for generation-II electrochemical energy storage systems. The strategic development of asymmetric supercapacitors (ASCs) comprising MXene as negative and laser-induced porous graphene (LIPG) as a positive electrode (i.e., MXene//LIPG) is reported to improve electrochemical energy storage in lateral (coplanar) and sandwich (cofacial) device configurations. Moreover, the interdigitated lateral device is scalable, flexible, current-collector, and binder-free. Electrochemical performance is evaluated under various electrolyte compositions: aqueous (AE), organic (OE), and ionic liquid (ILE). Notably, ASCs operate up to ≈1.0 V with AE, 1.6-2.0 V with OE, and 2.4-3.0 V with ILE exhibit enhanced energy densities depending upon the electrolyte and 100% Coulombic efficiency while retaining 75-95 % of initial capacitance after thousands of cycles (≥10 000-200 000). Specifically, the highest specific energy density (289 mW h cm at power density 0.2 W cm) is recorded for ILE-sandwich, seven times higher as compared with AE-sandwich (40 mW h cm at power density 0.4 W cm) followed by intermediate value for OE-lateral (8.5 mW h cm at power density 0.14 W cm) device. On the other hand, symmetric (MXene//MXene) device provided for sandwich (ILE: 12 W h cm at power density 0.5 W cm; OE: 8.8 mW h cm at power density 0.1 W cm, AE: 4.2 mW h cm at power density 0.1 W cm) and lateral (OE: 3 mW h cm at power density 0.2 W cm) configurations. Experimental findings are discussed within the framework of novel and constructive dual functionality of asymmetric electrodes' charging mechanism offer a benchmark for high-performing next-generation flexible microscale supercapacitors.