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

Abstract

• 2D graphene oxide (GO) nanosheets are employed to improve the electrode performance of layer double hydroxide (LDH). • Nanohybrids of Ni–Cr-LDH and GO nanosheets (NCG) are prepared via electrostatic self-assembly method. • NCG nanohybrids enables self-assembly with high surface area, mesoporous morphology, high electrical conductivity, and high charge transfer kinetics. • The aqueous hybrid supercapacitors device displays high energy density (ED) of 51.85 Wh kg –1 and power density (PD) of 1.34 kW kg –1 . • All-solid-state hybrid supercapacitor displays exceptional ED of 38.51 Wh kg–1 and PD of 1.33 kW kg –1 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. Exfoliation-reassembly strategy is use to synthesize 2D-2D Ni–Cr-LDH–GO nanohybrids. Owing to the high surface area and high electrical conductivity, Ni–Cr-LDH–GO nanohybrids demonstrated excellent electrochemical performance as a redox electrode in hybrid asymmetric supercapacitor.