β-Ni(OH)2/nickel-cobalt layered double hydroxides coupled with fluorine-modified graphene as high-capacitance supercapacitor electrodes with improved cycle life

Abstract

As energy consumption grows, the demand for a new generation of high-security, long-life and large-capacity power supplies is growing rapidly. Here we demonstrate a facile and binder-free strategy to obtain β-Ni(OH)2/nickel–cobalt layered double hydroxides (β-Ni(OH)2/NiCo-LDH) coupled with fluorine-modified graphene (FG) as supercapacitor electrodes (β-Ni(OH)2/NiCo-LDH@FG) via hydrothermal method, synchronous electrochemical exfoliation of graphite into fluorine-modified graphene and assembly on β-Ni(OH)2/NiCo-LDH. This hybrid structure of β-Ni(OH)2/NiCo-LDH and modified graphene as supercapacitor electrode displays high conductivity, high ion diffusivity and strong mechanical strength. As a result, the β-Ni(OH)2/NiCo-LDH@FG electrode possesses excellent capacitance (3996 mF cm−2 at 1 mA cm−2), remarkable rate capability and improved cycle life. The β-Ni(OH)2/NiCo-LDH coupled with undoped electrochemically exfoliated graphene exhibits the significantly improved cycle stability (79% capacitance retention after 1000 cycles at 5 mA cm−2), superior to that of β-Ni(OH)2/NiCo-LDH (31%). Therefore, this strategy has great potential to improve the performance of electrodes.