Electrochemical Active Mesoporous Hollow Carbon Sphere Supported High-Rate Performance Mxene Electrodes

Abstract

The development of electrode materials with a hierarchically porous structure and good electrical connection is key to improve the charging-discharging rate and energy density of supercapacitors. However, the restacking issue of two-dimensional nanomaterials, such as MXene, seriously hinders the diffusion of electrolyte ions. Different from the extensively used sacrificing template method, an electrically conducting mesoporous hollow carbon spheres (MHCS)-supported three-dimensional (3D) porous MXene/MHCS electrode is designed and achieved through simple vacuum filtration without further template removing procedures. This direct preparation strategy not only effectively improves the specific surface area of the electrode but also enhances the abundant surface pores and good conductivity of MHCS, improving the penetration of the electrolyte solution and shortening the ion transport path, leading to a pronounced improvement in specific capacitance and rate performance of the electrodes. Additionally, the influence of sheath thickness of MHCSs on ion transfer rate is deeply discussed. The introduction of carbon nanotubes (CNTs) further improves conductivity and stability while maintaining good flexibility. Consequently, the MXene/MHCS/CNT film delivers a high specific capacitance (395 F g-1 at 2 mV s-1), outstanding rate performance (70.9% at 1000 mV s-1), and excellent cycling stability (98.3 % capacity retention after 10000 cycles). Furthermore, the assembled symmetric supercapacitor provides a maximum energy density of 14.48 Wh kg-1. This work provides a quick and effective approach for constructing high performance 3D MXene architectures for fast ion transfer electrodes.

Keywords: MXene, mesoporous hollow carbon spheres, porous films, fast charging-discharging rate, Supercapacitors