Work

Enhanced stability of high energy aqueous capacitor based on redox-active nanomaterials and electrolyte

Year: 2025

Type: article

Abstract: In order to develop high energy density aqueous electrochemical capacitors, it is necessary to employ redox-active species able to increase capacitance and voltage range. Based on our previously reported double-redox capacitor using Kuraray YP50F porous carbon functionalized with Bi2S3 nanoparticles (NPs) as negative electrode, 1M NaI aqueous solution as electrolyte, and YP50F as positive electrode, in this work we study the benefits of reducing the Bi2S3 size, and increasing the loading of Bi2S3 NPs. The use of smaller nanoparticles and a loading of 15% wt. Bi2S3 NPs to the carbon surface results in a device with higher capacitance values at all currents (from 0.5 A g-1 to 10 A g-1). This optimized device shows stability issues that can be solved by electrolyte buffering or pre-iodination treatment of the YP50F carbon used in the positive electrode. Moreover, the combination of both treatments delivers an excellent capacity retention after 1000 cycles. A post-mortem ex-situ XPS analysis shows that the absence of iodates and periodates, along with the remarkable preservation of Bi-S species and minimal formation of sulfates, significantly enhances the overall performance of the double-redox aqueous supercapacitor.

Source: Journal of Power Sources

DOI: 10.1016/j.jpowsour.2025.238098