EDTA-induced growth of nickel hydroxychloride nanosheet networks on multilayer graphene for high-performance supercapacitors

The synthesis of high-performance electrode materials at a low cost is essential for the future application of supercapacitors. In this work, multilayer graphene (MLG) prepared by mechanical exfoliation is directly used as a conductive substrate, on which nickel hydroxychloride nanosheet networks are assembled by chemical bath deposition at 90 °C using EDTA (Ethylenediaminetetraacetic acid) as a complexing agent. The effect of EDTA amount on the morphology and electrochemical performance of nickel hydroxychloride (NHC)/MLG composites is studied in detail. The composite prepared with optimized EDTA (NHC/MLG-10) exhibits a specific capacitance of 1952.38 F g ⁻¹ at 1 A g ⁻¹ and a capacitance retention of 70.24 % at 10 A g ⁻¹. An asymmetric supercapacitor is fabricated using NHC/MLG-10 as the positive electrode and activated carbon as the negative electrode. It demonstrates a high specific capacitance of 105.17 F g ⁻¹ at 1 mA cm ⁻², and a capacitance retention of 73.85 % at 10 mA cm ⁻². A high energy density of 36.99 Wh kg ⁻¹ can be delivered at a high power density of 3185.36 W kg ⁻¹. It is a promising material for supercapacitors due to its facile synthesis, low cost and high specific capacitance.