Synthesis of high-charge capacity triarylamine–thiophene redox electrodes using electrochemical copolymerization

Abstract

Growing interest in electric transportation and renewable energy generation places a high burden on the development of new materials and devices capable of storing and delivering energy at high rates. We have previously shown that efficient, reversible redox couples can be incorporated in conventional conducting polymers to increase the energy and power density of redox electrodes; and furthermore, that molecular variations can be used to influence the molecular structure thereby enhancing Faradaic charge storage capacity. Here, we show that the energy storage capacity of these conducting polymer electrodes can be increased using electrochemical polymerization of multiple monomers with similar oxidation potentials. Low-cost thiophene monomers are incorporated with triarylamine-derivatives to vary the number of thiophenes and conjugation length between redox-centers. The composition of each monomer is systematically varied to identify the optimal composition that provides the highest charge capacity with reduced cost. Compared to the pure homopolymers, a factor of 2 increase in charge capacity is achieved for copolymers prepared with 10 mol% triarylamine groups using simple electrochemical synthesis. These results indicate that a simple building block approach to conducting polymer electrode design can be achieved when proper consideration is given to the polymer precursors.