Binder‐Free Highly Porous Bi2Se3‐MXene‐P Film Electrode Toward High‐Performance Asymmetric Capacitor

ABSTRACT The restacking of single‐layer MXene has seriously hampered its wide applications. To address this issue, Bi 2 Se 3 ‐modified porous MXene (Bi 2 Se 3 ‐MXene‐P) films with highly porous structure were selectively prepared using a template method, the prepared films exhibit large specific surface area, good conductivity, high volumetric capacity, and excellent flexibility. The introduction of Bi 2 Se 3 acts as the spacers can not only effectively prevent the restacking of single‐layer MXene but also enlarge the interlayer distance of MXene, leading to increased surface area and improved electrolyte electron transportation. More importantly, Bi 2 Se 3 can provide more active sites to further improve the electrochemical performance in capacitor application. Benefiting from these properties, the Bi 2 Se 3 ‐MXene‐P film electrode shows outstanding volumetric capacities of 1407.6 F cm −3 at 0.5 A g −1 in 1M AlCl 3 electrolyte. To assess the electrochemical behavior for practical applications, the Bi 2 Se 3 ‐MXene‐P//Al soft‐pack devices were assembled. Volumetric capacities of the Bi 2 Se 3 ‐MXene‐P//Al soft‐pack devices decreased from 214.1 F cm −3 at 0.5 A g −1 to 115.7 F cm −3 at 5 A g −1 . Additionally, when it switched back to 0.5 A g −1 , the volumetric capacity could recover to 210.1 F cm −3 demonstrating its excellent rate capability. Moreover, the Bi 2 Se 3 ‐MXene‐P//Al soft‐pack Al‐ion device exhibits the capacitance retention of 77.4% after 5000 charge–discharge cycles. The device also displays a high energy density of 14.8 Wh kg −1 at 130.7 W kg −1 power density. The present work demonstrates the potential application of the Bi 2 Se 3 ‐MXene‐P film electrode in flexible energy storage devices.