Elucidation of intercalation-pseudocapacitor mechanism in Binder-free Bi2S3@Ni foam electrodes towards high-performance supercapattery

Abstract

Pseudocapacitance has been commonly correlated with surface or near-surface reversible redox reactions of active electrode material in the electrolyte. However, we recently demonstrated an intercalated pseudocapacitor mechanism into the mesoporous 2-D orthorhombic Bi2S3 nanomaterial over nickel foam for supercapattery application. Such a mechanism effectively reduces the gap between a battery and a supercapacitor for achieving both high energy and power densities. A facile binder-free electrode has been architectured by a coating of Bi2S3 nanoflakes over the Nickel (Ni) foam at a constant 80 °C temperature and pressure resulting in better adhesion and electrochemical functioning. The process-controlled morphologies led to an enhanced electrochemical activity obtained due to enhanced surface area (149.698 m2/g) and high binding of Bi2S3 and Ni foam. The electrochemical supercapacitor studies revealed its battery-type characteristics which show a semi-infinite diffusion-controlled faradaic process that occurs in the bulk of the nanomaterial. The material exhibits an enhanced capacity of 1906 A h g − 1 at a constant high-discharging current density of 5 Ag−1. Furthermore, it provides a very high capacitive retention up to 97.22% till 2000 cycles owing to its unique structural and morphological stability. The principal interest realized from the intercalation mechanism is that high charge storage is achieved within a short period because of the negligible solid-state diffusion. The novel method of electrode design and its morphological changes have enabled it to surpass the electrochemical performance of many other previously reported Bi2S3-related materials.