Electrochemical deposition of ZnCo2O4/NiCo2S4 nanosheet arrays for high-performance supercapacitors

Abstract

The demand for power density has promoted the application of supercapacitors, and one hot study task for supercapacitors is high-energy-density electrode materials, such as transition metal oxides or sulfides. Here, composites of ZnCo₂O₄/NiCo₂S₄ (ZCO/NCS) nanosheet arrays on hydrophilic carbon cloth were synthesized and were used in high-performance supercapacitors. The ZCO/NCS composite electrodes were obtained via electrochemical deposition using a mixed solution of MOF-drived ZCO nanoclusters and Ni, Co, S sources. It was found that the acid etching pretreatment for 20 min of the ZIF-8/67 templates would lead to better electrochemical performance of the derived product (labeled as ZCO-20) and the composites with NCS (labeled as ZCO-20/NCS) as well. The effects of deposition conditions on the morphologies and electrochemical properties of the ZCO/NCS products were also investigated. The results showed that the ZCO-20/NCS deposited at −0.9 V for 10 min exhibited a high specific capacitance (2385 F g⁻¹ at 1 A g⁻¹) and excellent rate retention (1868 F g⁻¹ at 10 A g⁻¹, and 990 F g⁻¹ even at 50 A g⁻¹). Further, ZCO-20/NCS was used to assemble a quasi-solid-state asymmetric supercapacitor (ASC) with activated carbon (AC) and PVA/KOH gel electrolyte. ZCO-20/NCS//AC ASC showed a good specific capacitance (161 F g⁻¹ at 1 A g⁻¹ and 131 F g⁻¹ at 10 A g⁻¹), high energy density (57.28 W h kg⁻¹ at 1 A g⁻¹ and 46.50 W h kg⁻¹ at 10 A g⁻¹), high power density (8.0 kW kg⁻¹ at 10 A g⁻¹) and good cycle retention (91.5% after 5000 cycles). Thereby, ZCO-20/NCS could serve as a promising supercapacitor electrode material in the future.