Synthesis and application of NiLa-layered double hydroxides on nickel-coated carbon nanotubes with Co-ZIF-67 composite in supercapacitors

Abstract

Owing to the global climate emergency, there is considerable interest in new energy generation and storage solutions. Supercapacitors have many desirable properties of particular interest for energy storage. However, they have low energy densities, which must be improved. Materials based on zeolite imidazole skeletons (ZIFs) have uniform pores, large specific surface areas, and simple structures. Moreover, Co-ZIF-67 has high electrical conductivity, which makes it a promising candidate for energy storage applications. In this study, a Co-ZIF-67 precursor with a regular cubic structure is synthesized. This precursor is combined with Ni-coated carbon nanotubes (Ni-CNTs) and NiLa-layered double hydroxides (NiLa-LDHs). Thus, by controlling the hydrothermal reaction time, an electrode material with a nanosheet structure is applied to the CNTs. Electrochemical analysis shows that the resulting Co-ZIF-67/Ni-CNT@NiLa-LDH composite has a specific capacitance of 1710 F g−1 at a current density of 1 A g−1. The composite is combined with activated carbon (AC) to produce a Co-ZIF-67/Ni-CNT@NiLa-LDH//AC asymmetric supercapacitor, which exhibits outstanding capacitive performance (150.1 F g−1 at a current density of 1 A g−1), a wide operating voltage window (1.7 V), and outstanding stability.