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.