Assembly of flexible Ti3C2Tx fiber with promoted ionic transport by constructing hierarchical flakes size for high-performance fiber shaped supercapacitors

With the booming development of wearable system, the flexible fiber-shaped supercapacitor (FSC) has received sufficient attention. However, impeding by the sinuous electrolyte diffusion pathway and limited surface area, the fiber electrode usually causes low energy density and mediocre rate capability. Here, small-sized Ti₃C₂T_x MXene (s-M) intercalated Ti₃C₂T_x flakes (s-M/M) fiber is constructed by microfluidic spinning method. Encouragingly, the existence of s-M flakes can prevent the layer restacking of adjacent Ti₃C₂T_x sheets significantly, constructing porous architectures for fast ion diffusion and exposing abundant active sites for ion adsorption. Moreover, due to homogeneous crosslink via hydrogen bond, s-M/M fiber appears stable interface coupling, which imparts fast electron migration and excellent deformation endurance. As a result, the s-M/M fiber displays huge mass-capacitance (271.35 F g⁻¹ at 1 A g⁻¹), good rate performance (197.92 F g⁻¹ at 10 A g⁻¹) and outstanding long-term cycling properties (80.7 % capacitance retention after 10000 cycling). More importantly, matching with the graphene fiber, the asymmetrical FSC shows large capacitance of 62.98 F g⁻¹ at 0.1 A g⁻¹, high energy density and favorable deformation ability. This work raises an effective strategy for the design of high-performance FSC and the application in wearable system.