Polygonal CuS Nanoprisms Fabricated by Grinding Reaction for Advanced Quasi-Solid-State Asymmetry Supercapacitors

The construction of advanced electrode materials with well-connected channels and a satisfactory specific surface area for energy storage techniques, such as supercapacitors, is promising but still challenging. Herein, applying the copper Prussian blue analogue (CuFe-PBA) as the precursor, a polygonal prism-like CuS was synthesized through a grinding method at ambient temperature. The reaction between CuFe-PBA and Na2S led to the substitution of S2– for [Fe(CN)6]3–, and then, CuS was obtained. Benefitting from the porous precursor, the increased electrochemically active surface area enabled CuS to fully expose the electrochemically active sites and facilitated the effective contact between them and the electrolyte. Moreover, the energy storage mechanism was investigated based on ex situ X-ray photoelectron spectroscopy. The results demonstrated that both the copper and sulfur in CuS are electrochemically active sites, contributing to the distinguished specific capacitance. When used as a negative electrode, the as-fabricated CuS showed the excellent specific capacitance of 1850 F g–1 at 1 A g–1. Then, a quasi-solid-state asymmetry supercapacitor was assembled with CuS as the negative electrode and CuFe-PBA as the positive electrode, possessing an energy density of 56.01 W h kg–1 at a power density of 250.05 W kg–1. Furthermore, the capacitance retention of the asymmetry supercapacitor after 5000 cycles is 83.3%, showing good cycle stability. This work provides an effective strategy toward the design of CuS negative electrode materials with continuously connected channels and outstanding electrochemical properties for energy storage applications.