High-performance asymmetric supercapacitor device with nickel–cobalt bimetallic sites encapsulated in multilayered nanotubes

Abstract

Enhanced faradaic capacitance can be achieved by using a metallic heterostructure as a result of the intrinsic activity of the electrodes. Optimizing the multimetallic heterostructure is key to improving the intrinsic activity of the electrodes. Herein, a consolidated strategy of a multimetallic design with predominantly nickel, cobalt, and zinc centers on multiwalled nanotubes was developed via pyrolysis of a trimetallic metal–organic framework at 800 °C. The resulting C-ZIF-800 material offers a multiwalled nanotube-like structure that facilitates the encapsulation of multimetallic sites with predominantly nickel and cobalt centers on a nanotube-like N–C interface. XRD, HRTEM, XPS, and EXAFS spectroscopic analysis support the metallic valence state of the Ni and Co centers encapsulated in the N–C nanotubes. C-ZIF-800 offers an outstanding specific capacitance of 849.47 F g⁻¹ at a current density of 1 A g⁻¹. Based on three-electrode electrochemical measurements, an asymmetric supercapacitor (ASC) device (C-ZIF-800//AC) was fabricated with a wide potential window of 1.7 V. The device offers an excellent specific capacity of 599.7 C g⁻¹ at 0.25 A g⁻¹ with an exceptional energy density of 141.59 W h kg⁻¹ at a power density of 212.5 W kg⁻¹, and remaining 4250 W kg⁻¹ after retaining 81.93 W h kg⁻¹ of energy density. The as-fabricated device demonstrated its excellent potential for future energy storage applications by illuminating a red LED light for 60 min by combining two devices in series.