Ultrafast All-Solid-State Coaxial Asymmetric Fiber Supercapacitors with a High Volumetric Energy Density

Fiber-supercapacitors (FSCs) are promising energy storage devices that can complement or even replace microbatteries in miniaturized portable and wearable electronics. Currently, a major challenge for FSCs is achieving ultrahigh volumetric energy and power densities simultaneously, especially when the charge/discharge rates exceed 1 V s-1. Herein, an Au-nanoparticledoped- MnOx@CoNi-alloy@carbon-nanotube (Au-MnOx@CoNi@CNT) core/shell nanocomposite fiber electrode is designed, aiming to boost its charge/discharge rate by taking advantage of the superconductive CoNi alloy network and the greatly enhanced conductivity of the Au doped MnOx active materials. An all-solid-state coaxial asymmetric FSC (CAFSC) prototype device made by wrapping this fiber with a holey graphene paper (HGP) exhibits excellent performance at rates up to 10 V s(-1), which is the highest charge rate demonstrated so far for FSCs based on pseudocapacitive materials. Furthermore, our fully packaged CAFSC delivers a volumetric energy density of similar to 15.1 mW h cm(-3), while simultaneously maintaining a high power density of 7.28 W cm(-3) as well as a long cycle life (90% retention after 10 000 cycles). This value is the highest among all reported FSCs, even better than that of a typical 4 V/500 mu A h thin-film lithium battery.