Modifying Electronic Structure of Cation‐Exchanged Bimetallic Sulfide/Metal Oxide Heterostructure through In Situ Inclusion of Silver (Ag) Nanoparticles for Extrinsic Pseudocapacitor

Abstract

The inferior electrical conductivity of conventional electrodes and their slow charge transport impose limitations on the electrochemical performance of supercapacitors (SCs) using those electrodes, necessitating strategies to overcome the limitations. An in situ Ag ion‐incorporated cation‐exchanged bimetallic sulfide/metal oxide heterostructure (Ag‐Co9‐xFexS8@α‐FexOy) is synthesized using a two‐step hydrothermal method. The coordination bond formation and Ag nanoparticle (NP) incorporation improve the electrical conductivity and adhesion of the heterostructure and reduce its interface resistance and volume expansion throughout the charge/discharge cycles. Density functional theory investigations indicate that the remarkable interlayer and interparticle conductivities of the heterostructure resulting from Ag doping have changed its electronic states, leading to an enhanced electrical conductivity. The optimized electrode has an excellent specific capacity (213.6 mA h g−1 at 1 A g−1) and can maintain 93.2% capacity retention with excellent Coulombic efficiency over 20 000 charge/discharge cycles. A flexible solid‐state extrinsic pseudocapacitor (EPSC) is fabricated using Ag‐Co9‐xFexS8@α‐FexOy and Ti3C2TX electrodes. The EPSC has specific and volumetric capacitances of 259 F g−1 and 2.7 F cm−3 at 0.7 A g−1, respectively, an energy density of 80.9 Wh kg−1 at 525 W kg−1, and a capacity retention of 92.8% over 5000 charge/discharge cycles.

Stretchable flexible fiber supercapacitors for wearable integrated devices

“…6 Metal oxide electrodes are also highly conductive electrodes, and supercapacitors prepared from them are called pseudo capacitor supercapacitors, which derive their energy storage properties from Faraday charge transfer reactions. 7 During charging and discharging, the electrically active material undergoes a rapid redox reaction in the electrode material, which results in the rapid transfer of electrons. 8,9 Pseudo capacitors are not only able to react on the surface of the electrodes, but also inside the electrodes, so that their capacitance and energy density are higher than those of double-layer capacitors.…”