Maximizing ion storage in MXene/Kevlar nanofiber composite films for enhanced capacitive energy storage

MXene is a promising two-dimensional (2D) metal carbides and nitrides materials for energy storage devices, due to its efficient, low-cost and eco-friendly synthesis technology. MXene possesses high mechanical strength, metallic conductivity, and excellent capacitance performance. However, traditional electrode films obtained from 2D nanomaterials suffer from restacking issue, which hinders the transmission of ion and results in slow ion transport dynamics between layers. The improvement of ion transfer rate of MXene electrode materials is a hot spot in the current research of 2D nanomaterials. Herein, we fabricated the Ti3C2Tx MXene/aramid nanofiber (ANF) composite film with high specific surface area via a freezing method. The obtained MXene/ANF composite film presents high specific capacitance (174.3 F g−1 at a current density of 0.05 A g−1), excellent rate performance and high cycling stability (∼84.4% capacity retention after 10 000 cycles). The improvement of electrochemical performance is attributed to the smaller size of 2D sheets that effectively shorten ion diffusion path. Thus, both the diffusion rate and storage ability of electrolyte ions increase in the interstitial space between 2D sheets. In addition, ANF obtained from the commercial Kevlar yarns interacted with 2D sheets to enhance the mechanical strength of the composite films. Thus, the self-supporting MXene/ANF composite film with high specific surface area can be used as an electrode material of supercapacitors to present high specific capacitance and excellent cycling stability. This work provides a simple and effective way to construct high specific surface area 2D materials that present huge potential in energy storage fields.