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

The restacking of single-layer MXene has seriously hampered its wide applications. To address this issue, Bi₂Se₃-modified porous MXene (Bi₂Se₃-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 Bi₂Se₃ 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, Bi₂Se₃ can provide more active sites to further improve the electrochemical performance in capacitor application. Benefiting from these properties, the Bi₂Se₃-MXene-P film electrode shows outstanding volumetric capacities of 1407.6 F cm⁻³ at 0.5 A g⁻¹ in 1M AlCl₃ electrolyte. To assess the electrochemical behavior for practical applications, the Bi₂Se₃-MXene-P//Al soft-pack devices were assembled. Volumetric capacities of the Bi₂Se₃-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 Bi₂Se₃-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 Bi₂Se₃-MXene-P film electrode in flexible energy storage devices.