2D-2D nanohybrids of Ni-Cr-layered double hydroxide and graphene oxide nanosheets: Electrode for hybrid asymmetric supercapacitors

Nanohybrids of 2D Ni-Cr-layered double hydroxide (Ni-Cr-LDH) and graphene oxide (GO) nanosheets (Ni-Cr-LDH-GO) are prepared by electrostatic self-assembly between cationic Ni-Cr-LDH nanosheets and anionic GO nanosheets. Anionic GO nanosheets provide charge-transporting conducting channels leading to remarkably improved electrochemical activity of Ni-Cr-LDH-GO nanohybrid. The unique Ni-Cr-LDH-GO nanohybrid electrodes enable stable electrochemical structure, abundant active electrochemical sites, and fast electron transporting channels, which play a crucial role in improving the specific capacities, cycle stability, and rate capacity. As a result, Ni-Cr-LDH-GO nanohybrid electrodes demonstrate excellent electrochemical performance with a specific capacity of 815 C g(-1) at 1 A g(-1), superior to pristine Ni-Cr-LDH (354 C g(-1)). An aqueous hybrid supercapacitor (AHS) device displays outstanding electrochemical performance with improved energy density (ED) of 51.85 Wh kg(-1) and power density (PD) of 1.34 kW kg(-1). An all-solid-state hybrid supercapacitor (ASSHS) displays ED of 38.51 Wh kg(-1) and PD of 1.33 kW kg(-1). Furthermore, AHS and ASSHS show excellent cycling stability of 89% and 86% capacitance retention after 10,000 galvanostatic charge/discharge (GCD) cycles, respectively. The present exfoliation-restacking strategy provides a useful method for developing a 2D-2D Ni-Cr-LDH-GO structure for a highly active hybrid-type supercapacitor structure.