Calcium Alginate Based Gel Electrolyte for Continuous Preparation of Fiber Supercapacitor

Solution-extrusion method enables effective continuous fabrication of fiber energy storage devices. The design and development of gel electrolytes with high ion conductivities are the key to producing these fiber energy storage devices in a single step. Here, calcium alginate was used as the gel electrolyte framework to prepare a high-concentration calcium alginate/ lithium nitrate gel electrolyte, which exhibited a high ion conductivity of 145.3 mS/cm. This gel electrolyte was extruded together with electrode inks via a spinneret and solidified by a coagulation bath, enabling a direct and continuous fabrication of fiber supercapacitors. The fiber supercapacitors based on this gel electrolyte could maintain high stability upon 1.8 V and stably work under current densities ranging from 0.05 A/g to 2.0 A/g. The current density of the fiber supercapacitor was increased from 0.05 A/g to 0.5 A/g, and the discharge capacity retention rate of fiber supercapacitor reached 99.7%. The resulting fiber supercapacitor could preserve 99.3% of the initial capacity after 1000 cycles. By adjusting the composition of gel electrolyte, structure of fiber electrode, concentration and temperature of coagulation bath, we had achieved a production speed of 20 m/min for continuous fiber supercapacitors with lengths over 3000 meters. This fiber supercapacitor is expected to serve as a power source for wearable electronic devices.