Insights to pseudocapacitive charge storage of binary metal-oxide nanobelts decorated activated carbon cloth for highly-flexible hybrid-supercapacitors

Abstract

Abstract Although cobalt/zinc-based bimetallic oxides are regarded as auspicious pseudocapacitive electrode materials owing to their high specific-capacitance and rich electrochemistry; however, relatively large capacitance fading during charge/discharge process and low energy-density hinder their real applications. In this work, we rationally designed a bimetallic oxide (ZnCo2O4) nanobelt-decorated activated carbon-cloth composite (ZCO@CC) electrode by economical hydrothermal method for hybrid supercapacitors. The binder-free ZCO@CC electrode displays excellent electrochemical properties by attaining the high specific-capacitance of 1197.14 F g−1 (838 C g−1) at 2 A g−1 with good rate-capability of 75.18 % at 10 A g−1. The hybrid nature of the stored charge is analyzed by manipulating power's law, which reveals that the diffusion-controlled and pseudocapacitive charge storage are contributed equally at a scan rate of 25 mV s−1. The ex-situ X-ray powder diffraction and X-ray photoelectron spectroscopy confirmed the pseudocapacitive charge storage rather than capacitive. Moreover, the assembled hybrid supercapacitor (ZCO@CC||AC@CC) provides excellent specific energy of 79.48 Wh kg−1 at a specific power of 894.24 W kg−1. Further, the ZCO@CC||AC@CC shows superior flexible performance while bending at various angles and demonstrate a negligible change in capacitance by repeating 1000 GCD cycles at each bent state. Therefore, the achieved fascinating pseudocapacitive charge storage properties ensure that the ZCO@CC electrode is a potential material for high-performance hybrid supercapacitors.