Tunable construction of CuS nanosheets@flower-like ZnCo-layered double hydroxide nanostructures for hybrid supercapacitors†

Abstract

Layered double hydroxides (LDHs) are regarded as ideal materials for supercapacitors due to their excellent electrochemical characteristics and unique structural properties. However, unsatisfactory cyclability and poor conductivity have been recognized as the key limitations to LDH performance. To overcome these obstacles, constructing hybrid materials as well as designing porous nanoarchitectures are efficient approaches. Herein, through controlling the sulfide ion concentration during the synthesis of CuS nanosheets and adjusting the amount of urea in the synthesis of flower-like ZnCo-LDH structures, an optimized sample with an exclusive porous texture was fabricated on nickel foam (NF) (identified as NF@CS10-ZC-LDH4) via two-step hydrothermal routes and then employed as a binder-less electrode for a hybrid supercapacitor. The as-fabricated nanoarchitectures provide efficient electron-ion transport channels and preserve the structural integrity during prolonged periods of cycling, which resulted in fantastic supercapacitive properties with a capacity of 1270.5 C g⁻¹ and excellent cyclability (remaining at 90.7% after 7000 cycles). Furthermore, we fabricated a hybrid supercapacitor (NF@CS10-ZC-LDH4//NF@AC) with NF@CS10-ZC-LDH4 as a cathode electrode and activated carbon (AC)-covered NF as an anode electrode. The energy density of NF@CS10-ZC-LDH4//NF@AC was high, at 62.4 W h kg⁻¹ with a power density of 810.4 W kg⁻¹ and splendid cyclability of 88.4%. This innovative study offers valuable inspiration for the synthesis of electrode materials to be used in hybrid supercapacitors.

Keywords: Layered double hydroxides; Flower-like ZnCo-LDH; Hybrid supercapacitors; CuS nanosheets.