Co9S8@MnO2 core–shell defective heterostructure for High-Voltage flexible supercapacitor and Zn-ion hybrid supercapacitor

Abstract

Flexible and wearable energy storage devices have drawn increasing attention owing to the rapid development of smart and portable electronic gadgets. Herein, vertically oriented Co9S8@MnO2 core–shell heterostructure nanotube arrays are in situ grown on the carbon cloth surface and activated by oxygen vacancy engineering via a fast NaBH4 reduction method. The introduction of oxygen vacancy can effectively improve the conductivity, reaction kinetics and thus increase the capacitance performance. The as-prepared high-active electrode material can assemble into high-performance flexible supercapacitor and Zn-ion hybrid supercapacitor. The assembled flexible all-solid asymmetric supercapacitors (AAS) show a wide potential window of 2.4 V, the excellent areal capacitance of 0.8058F cm−2 at 2 mA cm−2, high energy density of 92.14 Wh kg−1 and power density of 342.86 W kg−1. Further, the assembled Zn-ion hybrid supercapacitor has a higher energy density of 198.857 Wh kg−1, which is about twice than that of AAS devices. This work provides a rational strategy for design energy storage devices with high energy density and voltage window.