Effects of Electrolyte Salts on the Electrochemical Performance of Aromatic Polyaroxydiazole Anodes for Pseudocapacitors

Abstract

Poly(4,4′-biophenylene-1,3,4-oxadiazole) (b-POD) is an n-type conductive polymer (CP) with a high specific capacitance and excellent rate performance. However, its practical application in pseudocapacitors is hindered by severe cycling performance decay. Electrolytes, as crucial components, significantly influence the electrochemical performance of pseudocapacitors. Therefore, selecting an appropriate electrolyte is essential for improving the cycling stability of b-POD, as thoroughly investigated in this study. Larger cations with lower surface charge densities require a smaller driving force for injection into the b-POD electrode, resulting in a more positive doping potential. Particularly, Bu₄N⁺ with a well-delocalized electronic structure forms a weaker interaction force with negatively charged polymer polarons, facilitating its dissociation from the polymer polarons, thereby ensuring good reversibility and excellent cycling stability. In the Bu₄NBF₄ electrolyte, b-POD exhibits a capacitance retention of 93.2% after 10 000 cycles, coupled with a Coulombic efficiency close to 100%. Furthermore, it demonstrates outstanding rate performance, maintaining a specific capacitance of 272 F g^–1 even at 20 A g^–1, which is 87.2% of the specific capacitance tested at 1 A g^–1. Finally, a high-performance asymmetric pseudocapacitor with high energy and power densities has been fabricated. This study aims to offer insights into the design of next-generation POD-derived pseudocapacitors.