Honeycomb nickel-cobalt layered double hydroxides supported on carbon skeleton as high-performance electrodes in supercapacitors

Abstract

Nickel-cobalt layered double hydroxide (NiCo-LDH) is an attractive electrode material for supercapacitors (SCs) due to its high theoretical capacitance. However, the poor electrical conductivity greatly limits the charge transfer characteristic of NiCo-LDH, preventing its wide applications. Herein, the honeycomb NiCo-LDH nanosheet supported by carbonized polydopamine (PDA-C/NiCo-LDH) is constructed by polymerization, carbonization and electrodeposition. The active NiCo-LDH nanosheets are tightly embedded on the conductive framework of PDA-C, which can hinder the aggregation of NiCo-LDH nanosheets and accelerate the charge transfer and redox reactions. Benefiting from the honeycomb structure of NiCo-LDH and conductive framework of PDA-C, the optimal PDA-C/NiCo-LDH electrode exhibits a high capacitance of 2458.1 F g−1 at 1 A g−1, along with superior rate performance and cyclic stability. Furthermore, an asymmetric supercapacitor (ASC) is assembled with the PDA-C/NiCo-LDH as cathode and active carbon (AC) as anode. The ASC exhibits a high energy density of 62.7 Wh kg−1 at a power density of 714.3 W kg−1 and exceptional cyclic performance (92.5 % retention after 10,000 cycles), indicating a huge potential of the PDA-C/NiCo-LDH electrode in energy storage fields.