(Invited) Tailoring Polymer Structure and Composition for High-Power and High-Charge Capacity Redox Electrodes

Conventional batteries are efficient at delivering a continuous supply of power; however, limited discharge rates prevent their use in high power applications. Many energy systems require sources that can repetitively supply high power bursts, which include electric transportation, utilization of renewable energy sources, and portable electronics. This demand can be addressed using advanced Li-ion batteries and supercapacitors, devices that combine the high power, rapid switching, and exceptional cycle life of a capacitor with the high energy density of a battery. Electroactive conducting polymers are suitable candidates for high-power energy storage, but they are currently limited by i) the lack of nano/micro-structure control over large areas, ii) relatively low charge-capacity, and iii) material stability.

In this presentation, we will discuss our group’s recent progress on engineering high-energy and high-power electrode materials for energy storage, including scalable synthesis of nano/micro-structured polymer electrodes and integrating high-charge capacity redox polymers. To increase power, redox polymer microtubes with nanometer thickness are synthesized on large area substrates by controlling gas nucleation density, which guides to formation of nanostructured electrodes. Nanostructured electrodes exhibit superior performance at high charge/discharge rates relative to planar electrodes. To increase electrode charge capacity, redox molecules and polymer are incorporated into conducting polymer electrodes during electrochemical synthesis. The capacitance of polypyrrole electrodes can be increased from 249 F/g to 550 F/g using hydroquinone dopants, and up to 400 F/g using naturally abundant Alkali lignin. We show that the conditions for electrode synthesis, along with the type (and molecular composition) of lignin, exhibit strong correlations with electrode performance.