NiCo layered double hydroxide with multi-dimensional nanostructures optimized by Mo-doping and electrochemical reconstruction strategies for asymmetric supercapacitors

NiCo layered double hydroxide (NiCo-LDH)/ZIF-67 was in situ grown on the surface of Ni foam (NF) through hydrothermal method and subsequent solution growth method. The ZIF-67 was then hydrothermally converted into hydroxide in the presence of Mo and Ni salts for the preparation of Mo-doped NiCo-LDH (NiCoMo-LDH), and the doping of Mo endowed the NiCo-LDH with more active sites. The obtained NiCoMo-LDH showed a unique multi-dimensional “lollipop” nanostructure, which was then optimized through electrochemical reconstruction in KOH solution. During the electrochemical reconstruction, rich oxygen vacancies were generated in the NiCoMo-LDH via continuous doping/de-doping of hydroxyl ions (OH − ). Moreover, the crystallinity of the NiCoMo-LDH was greatly lowered after the electrochemical reconstruction, resulting in the generation of internal disorders and effective exposure of active sites. Owing to the abundant active sites, variable valence states, multi-dimensional nanostructure as well as rich oxygen vacancies, the electrochemical reconstructed NF@NiCoMo-LDH (ER-NF@NiCoMo-LDH) showed superior electrochemical performances. Finally, an asymmetric supercapacitor (ASC) was fabricated by using the ER-NF@NiCoMo-LDH as cathode and NF supported active carbon as anode, which had a high energy density of 0.32 mWh cm −2 (at 1.60 mW cm −2 ) and a nearly 100 % coulombic efficiency. The ASC could be used to power light-emitting diodes (LEDs) for a long time.