Polymer–Pendant Interactions in Poly(pyrrol-3-ylhydroquinone): A Solution for the Use of Conducting Polymers at Stable Conditions

Abstract

While various organic molecules have been suggested as environmentally friendly alternatives to inorganic electrode materials for lithium ion batteries, most of them suffer from slow kinetics as well as capacity fading due to dissolution. Herein we present the synthesis of poly(pyrrol-3-ylhydroquinone) (PPyQ), a polypyrrole (PPy) derivative with pending hydroquinone groups, for investigation of the use of a conducting polymer to immobilize redox active quinone units. This strategy eliminates dissolution of the active material while also increasing the conductivity. The quinone pending groups in PPyQ cycle reversibly in the potential region where the polymer backbone is conducting and chemically stable. In situ spectroelectrochemistry on PPyQ films reveals UV/vis transitions inherent to PPy, as well as quinone centered transitions, allowing detailed investigation of the interplay between the polymer doping process and the quinone redox conversion. Intriguingly, it is found that the charging of the PPy backbone halts during the redox reaction of the quinone pending groups. This opens up for the possibility of using PPy at low and constant doping levels while utilizing the charge storage capacity of the quinone pending groups when creating electric energy storage materials based on sustainable and renewable components.