All-in-One Compact Architecture toward Wearable All-Solid-State, High-Volumetric-Energy-Density Supercapacitors

High-performance flexible energy storage devices are an important prerequisite to the utilization of various advanced wearable electronics, such as healthcare sensors and smart textiles. In this work, we design a wearable all-solid-state, all-in-one asymmetric supercapacitor by integrating current collectors, a separator, and negative and positive electrodes into a thin, flexible, and porous polyamide nanofiber film. The positive and negative electrodes are, respectively, electrodeposited onto each side of the carbon nanotube-modified porous polyamide nanofiber film to form the integrated and compact asymmetric cell. The all-in-one thin-film asymmetric supercapacitor is binder-, additive-, and metal current collector-free, which can effectively decrease the cost, simplify the assembly procedures, and increase the energy density. The assembled flexible all-in-one asymmetric supercapacitor with a compact structure shows high gravimetric and volumetric specific capacitances of 70 F g^-1 and 3.1 F cm^-3 under a current density of 0.5 A g^-1 in a neutral polyvinyl alcohol/LiCl gel electrolyte, respectively. Additionally, the all-in-one asymmetric cell displays a favorable volumetric energy density of 1.1 W h L^-3, which is among the highest compared with other reported flexible solid-state supercapacitors. Notably, multiple cell units can be integrated in one piece of polyamide nanofiber film and connected in series to satisfy the need of high output voltage.