Co2(OH)3Cl/WC for improved high-energy aqueous asymmetric supercapacitors

Abstract

Modified cobalt hydroxide structures are promising new energy storage materials that offer many advantages. Owing to their novelty and unique structures, these materials are increasingly being studied. Herein, a novel Co₂(OH)₃Cl/WC composite was synthesized via a simple solution process by varying the tungsten carbide (WC) concentrations (0.5 wt%, 1 wt%, and 1.5 wt%) with respect to Co₂(OH)₃Cl. The as-prepared materials were subjected to various structural and morphological characterisations, including XRD, XPS, FESEM, and HRTEM. The electrochemical characteristics of bare Co₂(OH)₃Cl and the as-prepared composites were analyzed using three-electrode configurations in a KOH electrolyte medium. The Co₂(OH)₃Cl/WC composite with 0.5 wt% of WC delivered the best overall electrochemical performance, outperforming bare Co₂(OH)₃Cl (CC-0) by offering a specific capacity of 99 C g⁻¹ at 1 A g⁻¹. A flexible pouch-type PVA-KOH gel electrolyte-based AC‖PVA-KOH‖Co₂(OH)₃Cl/WC asymmetric supercapacitor (ASC) was fabricated. It exhibited a maximum specific energy of 33.4 W h kg⁻¹ at a specific power of 3200 W kg⁻¹, which was much better than the specific energy of 22.5 W h kg⁻¹ observed for WC-free electrode-based AC‖PVA-KOH‖Co₂(OH)₃Cl device. Furthermore, the ASCs were fabricated using CR2032-coin cell components, where 2 M KOH is used as an electrolyte. The AC‖KOH‖Co₂(OH)₃Cl/WC ASC showed 96.52% retention with a coulombic efficiency of 99.55% even after 20 000 cycles at a current rate of 1 A g⁻¹, which was much better than the cycle life obtained for AC‖PVA-KOH‖Co₂(OH)₃Cl. This reveals that incorporating WC, in minimal concentration, can greatly augment the cycling performance of Co₂(OH)₃Cl electrode materials. Thus, Co₂(OH)₃Cl/WC will be a futuristic addition to the high-energy aqueous asymmetric supercapacitor horizon as a positive electrode.