In situ electrochemical characterization of poly-3,4-ethylenedioxythiophene/tetraalkylphenylene diamine films and their potential use in electrochemical energy storage devices

There is currently a newfound interest in novel approaches towards the synthesis and design of new materials for electrical energy storage (EES). We present a new breed of materials, based on redox-active substituted (RAS) conducting polymers (CPs) that can provide high energy and power densities, high conductivity, long-term durability, and potentially lower costs. In the work presented, we investigate a model system to illustrate the approach's validity. We have modified PEDOT (3,4-polyethylenedioxythiophene) by covalently binding a small RAS, N1,N1,N4,N4-tetraalkylbenzene-1,4-diamine (TAPD). The addition of this pendant (RAS) gives rise to a dramatic increase in the energy density of the material compared to traditional CPs, due to the increased number of electrons transferred per monomer unit (from 0.6 e(-) to 2.6 e(-)). In situ UV-Vis and Raman spectroelectrochemistry yielded important mechanistic information about the electrochemical reactions of RAS-CP, which directly affect device performance. Electrochemical quartz crystal microbalance (EQCM) studies provided important insights regarding the ion transport in the RAS-CP films during electrochemical cycling. Moreover, device level characterization has been done, and at high charge/discharge rates of 1C the capacity of our materials is ca. 65 mAh/g. Furthermore, the electropolymerized RAS-CP electrodes only contain active material, precluding the need for both binder and conducting additives. (C) 2015 Elsevier B.V. All rights reserved.