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

A freestanding binder-free novel electrode material, a Ni3S2@Co3S4/Mn3O4-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 Ni3S2. After the interrogation of Mn3O4, the crystallinity of the Co3S4 particles increased with decreasing band gap, which resulted in the improvement of electrochemical properties. The flexible CSMRGN electrode exhibited a high specific capacitance of similar to 3140 F g(-1) at 2 A g(-1). The (TRGO//CSMRGN) FSSASC device demonstrated a high energy density of similar to 51.6 Wh kg(-1) at a power density of 1400 W kg(-1). The asymmetric device retained similar to 43.5 Wh kg(-1) (similar to 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 similar to 96 and 83% of initial capacitance after 1000 GCD cycles under normal and 90 degrees bending conditions, respectively.

Automated summary

A novel freestanding binder-free electrode material for flexible solid-state asymmetric supercapacitors was synthesized through a multistep hydrothermal route. The material exhibited high specific capacitance and energy density, with the ability to retain energy density even at high power densities. Capacitive properties varied significantly at different bending angles, but the device showed stable performance during cycle testing.