Enhancement of the Electrochemical Performance of a Novel Binder-Free Ni₃S₂@Co₃S₄/Mn₃O₄-RGO Heterostructure through Crystallinity and Band Gap Modification for Flexible Supercapacitors

Abstract

A freestanding binder-free novel electrode material, a Ni 3 S 2 @Co 3 S 4 /Mn 3 O 4 -RGO (CSMRGN) composite, was synthesized for flexible solid-state asymmetric supercapacitors (FSSASCs) through a multistep hydrothermal route. The more electronegative sulfur atoms were arranged regularly to form the land-lotus flower-like structure that enhanced the electrical conductivity and reacted with a nickel foam substrate to form Ni 3 S 2 . After the interrogation of Mn 3 O 4 , the crystallinity of the Co 3 S 4 particles increased with decreasing band gap, which resulted in the improvement of electrochemical properties. The flexible CSMRGN electrode exhibited a high specific capacitance of ∼3140 F g −1 at 2 A g −1 . The (TRGO//CSMRGN) FSSASC device demonstrated a high energy density of ∼51.6 Wh kg −1 at a power density of 1400 W kg −1 . The asymmetric device retained ∼43.5 Wh kg −1 (∼84.5%) energy density even at a high power density of 7 kW kg −1 . The capacitive properties and charge transfer resistance of the FSSASC device were calculated at different bending angles. In comparison to the kinetic controlled process, the diffusion-controlled specific capacitance decreased significantly when the bending angle of the device increased. The device retained ∼96 and 83% of initial capacitance after 1000 GCD cycles under normal and 90°b ending conditions, respectively.

Ultrastable Asymmetric Supercapacitor Device with Chemically Derived and Mechanically Activated NiCo2O4

“…To explain the conductive behavior of these two milled samples, EIS spectroscopy (Figure 9a,b) has been considered a proper tool in which an AC perturbation potential of 10 mV has been applied within the frequency range of 0.01−10 5 Hz at a fixed dc potential in Na 2 SO 4 electrolyte. EIS plots of these three samples show a small semicircular arc at a very high frequency (Figure 9b).…”

“…Typically, the charge storage mechanism of a supercapacitor is of two types: one is the capacitive type and the other is the pseudocapacitive type. Generally, the charge storage process of the capacitive type is an electric double-layer capacitor that relies on electrostatic charge storage separation of ions at the electron electrolyte interface. , …”

“…Generally, the charge storage process of the capacitive type is an electric double-layer capacitor that relies on electrostatic charge storage separation of ions at the electron electrolyte interface. 4,5 In contrast, in a pseudocapacitor, capacitance is produced by a fast multielectron faradaic surface redox reaction. The capacitance performance is much better than the electric double-layer capacitor (EDLC), especially in energy density.…”

A short review on transition metal chalcogenides/carbon nanocomposites for energy storage

“…Ghosh et al prepared Ni 3 S 2 @Co 3 S 4 /Mn 3 O 4 -rGO composite for flexible solid-state asymmetric supercapacitors. The flexible electrode showed a high capacitance of 3140 F g −1 at 2 A g −1 , and the asymmetric device showed a high energy density of ∼51.6 Wh kg −1 at a power density of 1400 W kg −1 [16]. The synergic effect between elements in TMOs and sulfides makes more active sites for adsorption of ions hence enhancing the capacitive performance of the electrode.…”

Heteroatom Modification of Heterostructured CuS/Mn3O4 with Rich Defects for Solid-State Supercapacitors

“…Therefore, it is a rational choice to integrate CuS with other electrode materials to construct a heterojunction structure. Mn 3 O 4 is a suitable candidate material with the advantages of good environmental compatibility, easy room-temperature synthesis, and high theoretical capacity, and presents significant advantages in electrode materials for supercapacitors. , However, Mn 3 O 4 has poor electrical conductivity (10 –7 –10 –8 S cm –1 ) and is prone to agglomeration, resulting in its actual capacity much lower than its theoretical capacity (936 mA h g –1 ). − Therefore, combining Mn 3 O 4 with CuS to prepare composites can remove the obstacles faced by both. In this heterojunction structure, CuS contributes to enhancing the conductivity of Mn 3 O 4 and inhibiting the latter from agglomeration.…”