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

Abstract Deployment of 2D layered materials beyond graphene, i.e., MXene (Ti 3 C 2 T x , 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 −3  at power density 0.2 W cm −3 ) is recorded for ILE‐sandwich, seven times higher as compared with AE‐sandwich (40 mW h cm −3 at power density 0.4 W cm −3 ) followed by intermediate value for OE‐lateral (8.5 mW h cm −3  at power density 0.14 W cm −3 ) device. On the other hand, symmetric (MXene//MXene) device provided for sandwich (ILE: 12 W h cm −3  at power density 0.5 W cm −3 ; OE: 8.8 mW h cm −3  at power density 0.1 W cm −3 , AE: 4.2 mW h cm −3  at power density 0.1 W cm −3 ) and lateral (OE: 3 mW h cm −3  at power density 0.2 W cm −3 ) 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.