Cobalt–Nickel Layered Double Hydroxides on Electrospun MXene for Superior Asymmetric Supercapacitor Electrodes

Abstract

Flexible electrodes for energy storage and conversion require a micro-nanomorphology and stable structure. Herein, MXene fibers (MX-CNF) are fabricated by electrospinning, and Co-MOF nanoarrays are prepared on the fibers to form Co-MOF@MX-CNF. Hydrolysis and etching of Co-MOF@MX-CNF in the Ni 2+ solution produce cobalt–nickel layered double hydroxide (CoNi-LDH). The CoNi-LDH nanoarrays on the MX-CNF substrate have a large specific surface area and abundant electrochemical active sites, thus ensuring effective exposure of the CoNi-LDH active materials to the electrolyte and efficient pseudocapacitive energy storage and fast reversible redox kinetics for enhanced charging–discharging characteristics. The CoNi-LDH@MX-CNF electrode exhibits a discharge capacity of 996 F g –1 at a current density of 1 A g –1 as well as 78.62% capacitance retention after 3,000 cycles at 10 A g –1 . The asymmetric supercapacitor (ASC) comprising the CoNi-LDH@MX-CNF positive electrode and negative activated carbon electrode shows an energy density of 48.4 Wh kg –1 at a power density of 499 W kg –1 and a capacity retention of 78.9% after 3,000 cycles at a current density of 10 A g –1 . Density-functional theory calculations reveal the charge density difference and partial density of states of CoNi-LDH@MX-CNF confirming the large potential of the CoNi-LDH@MX-CNF electrode in energy storage applications.

Efficient improvement in the electrochemical performance of petal-like lamellar NiMn–LDHs with affluent oxygen vacancies derived from Mn MOF-74

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