High pseudocapacitance electrode enabled by heterovalent doping and surface coating for rapid charge storage

Abstract

With admirable energy storage kinetics and high capacitance, pseudocapacitive electrodes have been regarded as promising candidates to replace active carbon materials for next-generation supercapacitors. Unfortunately, these materials usually present lower capacitance compared to the Ni/Co-based battery-type materials, and insufficient cycling lifespans due to repeat surface redox reactions. Here, we employ Fe doping and surface coating to construct a high-capacitance robust pseudocapacitive WO3-based electrode (10-Fe-WO3/PANI). Heterovalent doping breaks the octahedral symmetry of WO3 and effectively boosts the reversible capacitance of WO3 due to Jahn-Teller distortion, creating abundant active sites for energy storage. Polyaniline (PANI) coating enhances the structural durability and ion diffusion kinetics of WO3 in the acid electrolyte, promoting long-term cycling performance. As expected, the optimized electrode can deliver a high specific capacitance of 4006 mF cm−2 at 5 mA cm−2, which is about five-fold higher than that of a pure WO3 electrode (733.7 mF cm−2) and can steadily work for 10,000 cycles without apparent capacitance decay. The full device using polypyrrole (PPy) as the cathode exhibits intriguing energy/power density and cycling lifespans, demonstrating the application potential of this material. This work may enlighten the development of cationic doping and advanced pseudocapacitive materials design in electrochemical energy storage fields.