(506a) Molecular Insights into Metal-Free Polymer Batteries

Sociopolitical pressure towards elemental cobalt drives the demand for new energy storage materials. This is challenged by the low recycling rate of Li-ion batteries coupled with anticipated growth in the market. One solution toward this challenge is development of organic or metal-free electrodes to replace cobalt-containing cathodes. Here, macromolecular radicals as redox-active electrodes for metal-free batteries are presented. These polymers generally contain redox-active nitroxide radical groups that reversibly exchange electrons at rates much higher that of current metal oxide cathodes. This manifests as a higher power or a high charging rate. In this talk, insight into the polymer’s redox mechanism is provided using electrochemical quartz crystal microbalance with dissipation monitoring, in which mixed electron-ion-solvent transfer is quantified. This knowledge reveals why certain metal-free electrolytes are well-suited to this polymer class. Specifically, favorable electrolyte-polymer interactions can accelerate the electron transfer kinetics, but, simultaneously, excessive swelling caused by those same interactions can lower the accessible capacity. This effect presents itself in one extreme case for aqueous electrolytes, in which capacity can vary by as much as 1000 % depending on the relative chaotropic/kosmotropic nature of the anions and cations. Last, efforts toward degradable polypeptide radical batteries are presented.