“Salt-in-Fiber” Electrolyte Enables High-Voltage Solid-State Supercapacitors

The design of functional solid electrolytes is crucial to develop flexible nonsealing supercapacitors for lightweight, wearable, and portable electronics. Herein, an innovative method was used to fabricate LiCl electrospun electrolyte. A solid-state supercapacitor was assembled using LiCl-containing nanofibers as both an electrolyte and separator, and commercial activated carbon as the positive and negative electrodes, respectively. The morphology and chemical composition of the novel electrolyte was revealed using scanning electron microscopy, energy-dispersive X-ray, Fourier transform infrared, and Brunauer–Emmett–Teller analyses. The electrochemical properties of the solid-state supercapacitor were characterized by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. Additionally, the performance of the supercapacitor device with the nanofiber electrolyte was compared with that of the aqueous electrolyte-based and hydrogel-based devices. The supercapacitor with the LiCl nanofiber electrolyte exhibited an extended potential window of 2.3 V compared to 1.8 V for the aqueous-based device and 2 V for the hydrogel-based device. Consequently, the specific capacitance and energy density were increased by 9.6 and 44.6%, respectively, when both devices are measured at 1 A/g.