Aromatic polyaroxydiazole pseudocapacitive anode materials with tunable electrochemical performance through side group engineering

Abstract

Conductive polymers (CPs) are promising electrode materials for pseudocapacitors due to their high electronic conductivity and outstanding pseudocapacitive charge storage capability. Herein, aromatic polyaroxydiazole (POD) with high electron deficient oxadiazole rings were synthesized to develop n-type CPs by side group engineering. Electron-withdrawing side groups (i.e., –F, –Br, –NO₂) were imported to phenylenes to tune the main chain's electronic structure, making the oxadiazole rings more electron-deficient. The lowest unoccupied molecular orbital (LUMO) and energy gap of the resulting POD can be achieved using the side group of –NO₂, which has the LUMO energy level of −4.16 eV with the onset doping potential of −0.46 V (vs. Ag/AgCl). Meanwhile, its energy gap and electronic conductivity are 2.98 eV and 4.07 × 10⁻⁴ S cm⁻¹, respectively, indicating good electronic conductivity. A binder-free anode composed of poly(1,4-phenylene-1,3,4-oxadiazole) (p-POD) and commercial activated carbon (YP80F) was prepared and used to construct an asymmetric supercapacitor, which could deliver a high operating voltage of 2.35 V, a maximum energy density of 20 W h kg⁻¹ with a power density of 6832.2 W kg⁻¹. Therefore, POD is a promising pseudocapacitive anode material with a tunable chemical structure, high capacitance, and high conductivity for pseudocapacitors.