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 Ti 3 C 2 MXene fibers by tuning of coagulation conditions, such as bath rotating speed, temperature, and ionic composition. We show that increasing the speed improves the Ti 3 C 2 flakes' alignment in the fibers. In addition, slowing the coagulation rate by reducing the temperature to −10 °C leads to the formation of the dense fibers. By using various coagulants (K + , Ca 2+ , Fe 3+ ) with different hydrated radii at −10 °C and 6.3 mm s −1 , we also indicate that Ca 2+ 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.

Ion-exchange membrane-based reverse electrodialysis (RED) shows great potential for harvesting osmotic energy from seawater and converting it to electricity. However, their low energy conversion efficiency and huge ionic resistance hinder...