posted on 2021-05-11, 07:48authored byGyan Prakash Sharma, Prashant Kumar Gupta, Shilendra Kumar Sharma, Raj Ganesh S Pala, Sri Sivakumar
We explore the effect of sulfur doping
in Co3V2O8 on the electrochemical
performance of supercapacitors
in terms of enhanced lattice spacing, electrochemical surface area
(ECSA), electronic conductivity, and density of states. The sulfur-doped
Co3V2O8 (S-Co3V2O8) nanosheets were grown in situ as a binder-free synthesis
on nickel foam by the hydrothermal method. The electrochemical performance
was analyzed in an aqueous alkaline electrolyte where the S-Co3V2O8 electrode exhibited a specific
capacity of 410 mAh/g at 2 A/g with enhanced rate capability and capacity
retention of 94.2% at 5 A/g specific currents after 4000 cycles, whereas
the undoped Co3V2O8 electrode exhibited
a specific capacity of 337.8 mAh/g at 2 A/g. The high capacity of
S-Co3V2O8 is attributed to the enhanced
ECSA (by ∼45%) and improved electrical conductivity (by ∼22%)
upon doping with sulfur. Furthermore, these results corroborated with
density functional theory results. The calculations suggest an increase
in lattice parameters and the introduction of additional density of
states near the valence-band edge due to the doping of sulfur, resulting
in a decrease in charge-transfer resistance. An asymmetric supercapacitor
was fabricated, using S-Co3V2O8 nanosheets
as the cathode and activated carbon as the anode, which shows a high
specific capacity (or capacitance) value of 485 mAh/g, an energy density
of 36.4 W h/kg, and a power density of 740 W/kg at 2 A/g with 98.4%
specific capacity retention after 4000 consecutive charge–discharge
cycles. Furthermore, the analysis was extended in a nonaqueous medium
for Li-ion storage where S-Co3V2O8 exhibits a specific capacity of 994 mA h/g and a specific energy
density of 828 W h/kg at 1 A/g making it a promising candidate for
future high-energy storage systems. The concept of doping is extended
to other chalcogenide (e.g., selenium) doping (Se-Co3V2O8), which also shows improved device performance
and makes this a versatile approach for high-performance devices.