Improving the composite-structured supercapacitor assembled with Ni–Co-layered double hydroxide and polymer cement electrolyte through structural optimization

Abstract

In order to solve the problem of low energy density of previous cement-based supercapacitors, the capacitor performance was optimized in four aspects: positive electrode performance, positive and negative capacity matching, and electrolyte performance. The effects of electrodeposition solution ratio and scan rate on the electrochemical properties of nickel–cobalt double hydroxide were investigated. The microscopic morphology and elements of nickel–cobalt double hydroxide were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The optimized nickel–cobalt double hydroxide electrode demonstrates an excellent areal capacitance of 10.53 F cm⁻² and excellent cycling stability (106% capacitance retention after 10 000 cycles) at a current density of 1 mA cm⁻². In this paper, an electrode made of activated carbon was used as the negative electrode and the loading of activated carbon was strictly controlled to better match the high specific capacitance of the nickel–cobalt double hydroxide electrode. An optimally proportioned cementitious-polymer electrolyte was selected as the electrolyte for the supercapacitor. The three-step optimized supercapacitor exhibits a high areal capacitance of 1.442 F cm⁻², good cycle retention (69.4%), and a remarkable energy density of 0.444 mW h cm⁻² (0.75 mW cm⁻²). This paper is expected to provide a new way to mitigate the issue of “curtailed light” and to construct large-scale buildings integrating light, electricity, and energy storage.