Facile Fabrication of Highly Oriented Dense Ti3C2 Fibers with Enhanced Strength and Supercapacitance Performance by Coagulation Condition Tuning

Portable, wearable, and lightweight fiber-shaped supercapacitors (FSCs) are promising candidates for powering microscale electronics. However, the preparation of the fiber electrodes with high electrochemical performance, mechanical strength, and electrical conductivity is challenging due to a trade-off between these properties. We propose a simple wet-spinning method to produce Ti3C2 MXene fibers by tuning of coagulation conditions, such as bath rotating speed, temperature, and ionic composition. We show that increasing the speed improves the Ti3C2 flakes' alignment in the fibers. In addition, slowing the coagulation rate by reducing the temperature to -10 degrees C leads to the formation of the dense fibers. By using various coagulants (K+, Ca2+, Fe3+) with different hydrated radii at -10 degrees C and 6.3 mm s-1, we also indicate that Ca2+ minimizes the trade-off between charge storage (2668.7 F cm-3 at 2.5 A cm-3) and mechanical/electrical properties (154 MPa/8558 S cm-1). Assembled FSC-based fibers deliver high energy and power densities of 44.9 mW h cm-3 and 7686.9 mW cm-3, respectively. The FSC also shows good elasticity with 98.8% capacitance retention after 200 bending cycles. This work proposes a scalable method for fabrication of high-performance fiber electrodes for energy storage applications.