Ultralight coaxial fiber-shaped zinc-ion hybrid supercapacitor with high specific capacitance and energy density for wearable electronics

Abstract

Zinc-ion hybrid supercapacitors (ZHSs) with a fiber-shaped form are strongly desired for flexible electronics, but the construction still remains a great challenge. Herein, by using a graphene/multi-walled carbon nanotubes (MWCNTs) hybrid tube (GMHT) as cathode and a 2D nanostructured Zn modified graphene/MWCNTs tube (Zn@GMHT) as anode, we, for the first time, fabricate a ‘sword-scabbard’ like coaxial fiber-shaped all-solid-state ZHSs. The core-sheath structure notably accelerates electron transport and ion diffusion, and in comparison with the commonly used Zn metal electrode, an astounding 84.1 % anode mass reduction has been realized. Specifically, the optimized GMHT//Zn@GMHT ZHSs presents a superb length specific capacitance of 470.6 mF cm−1 (relevant to an outstanding areal/volumetric capacitance of 735.3 mF cm−2/19.6 F cm−3) at the current density of 1 mA cm−1, which is obviously better than most of the reported fiber-shaped ZHSs. Meanwhile, the device shows a maximum energy density of 167.3 μWh cm−1 at the power density of 533.5 μW cm−1, and an attractive power density of 5988.1 μW cm−1 at 16.8 μWh cm−1. Moreover, the capacitance retentions of 84.6 % after 5000 charge–discharge cycles and 100–88.3 % under bending angles from 0 to 150° demonstrate great electrochemical stability and mechanical flexibility of the device. The admirable properties, together with this creative architecture and ultralight function, endow GMHT//Zn@GMHT with a broad prospect in wearable application.