(106c) Polymer Batteries and Capacitors: Challenges and Opportunities

Polymer electrodes present unique opportunites for electrochemical energy storage.  By themselves or as active components in composites, polymer electrodes can provide several properties that conventional metal oxide electrodes cannot; polymer electrodes are potentially mechanically flexible, mechanically tough, and can even coat unconventional materials such as textiles. For such materials to be viable, several challenges should first be addressed: oxidative stability and mass transport. For the former, an oxidatively stable polymer allows for a polymer electrode to attain high voltages, and consequently high capacity and high energy density. For the latter, fast mass transport allows a polymer electrode to attain a high power density.

Storing charge through doping and dedoping, conjugated polymers are essential materials for polymer electrodes. This presentation will focus on two types of conjugated polymers which offer exceptional control over oxidative stability and mass transport, polyaniline and poly(dithienopyrrole). Two approaches towards the oxidative stabilization of polyanline will be presented. In the first, aniline monomer is polymerized in the presence of a polyanion to yield a water-dispersible polyaniline:polyanion colloid that is stable up to 4.5 V. In the second, polyaniline is thermally treated in the presence of a polyanion to achieve a similar effect. We will also present side-chain functionalized poly(dithienopyrroles) that are stable up to 4.0 V, and that reversibly switch for 100s of cycles. To address the latter challenge, polyaniline nanofiber electrodes yield a highly porous morphology, yielding higher capacities and energy densities. These approaches could, presumably, be applied to other conjugated polymers.

The future for polymer electrodes is quite promising. New materials, synthetic approaches, and nanomaterials allow can potentially open new doors for this growing and expanding field.