Tailored synthesis of nano-corals nickel-vanadium layered double hydroxide@Co2NiO4 on nickel foam for a novel hybrid supercapacitor

At present, it is still a challenge for developing hybrid supercapacitors with outstanding electrochemical performance. Herein, a step-by-step approach was tailored to fabricate a novel electrode material as nickelvanadium layered double hydroxide (NiV-LDH)@Co2NiO4 nano-coral arrays anchored on nickel foam. Thanks to the three-dimensional interconnected nanostructure, the electrode fully immersed in electrolyte participates in faradaic redox reaction, which promotes the transfer of ions and charges, leading to the enhancement of electrochemical performance. The optimal NiV-LDH@Co2NiO4/NF (nickel foam) exhibits 1381.8 C g(-1) at 1 A g(-1), which is the best among the prepared samples (compared with NiV-LDH/NF and Co2NiO4/NF). Benefitting from the coral-like interconnect morphology, NiV-LDH@Co2NiO4/NF retains 79.8% of the initial capacity after 5000 cycles at 5 A g(-1). Besides, NiV-LDH@Co2NiO4/NF and activated carbon (AC) act as positive and negative electrodes, assembling a hybrid asymmetric supercapacitor, which delivers an ideal energy density of 68.7 W h kg(-1) at a power density of 878.6 W kg(-1) and leaves 88.6% of specific capacity remaining after 5000 cycles. To evaluate the practical application of NiV-LDH@Co2NiO4/NF//AC, two devices are connected in series and acted as a continuous energy supply for a 2.2 V LED light.