Relationship between Molecular Structure and Electron Transfer in a Polymeric Nitroxyl-Radical Energy Storage Material

Thomas Gennett, Ross Larsen, Travis Kemper

Research output: Contribution to journalArticlepeer-review

63 Scopus Citations

Abstract

In recent years, stable organic radical functional groups have been incorporated into a variety of polymeric materials for use as electrodes within energy storage devices, for example, batteries and capacitors. With the complex nature of the charge-transfer processes in a polymer matrix, the morphologies of the polymer films can have a significant impact on the redox behavior of the organic-based radical. To elucidate possible effects of packing on electron-transport mechanisms, theoretical modeling of the well-characterized cathode material poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA) was conducted. Polymer morphologies were modeled using classical molecular dynamics simulations, and subsequently, the electronic-coupling matrix element between each radical site was calculated. Building on a previously derived treatment of diffusion in inhomogeneous materials, an expression for an effective electron diffusion length and an effective electron diffusion rate was derived in terms of an electronic-coupling-weighted radial distribution function. Two primary distances were found to contribute to the effective electron transfer length of 5.5 Å with a majority of the electron transfer, nearly 85%, occurring between radical sites on different polymer chains. Finally, we point out that this analysis of charge transfer using an electronic-coupling-weighted radial distribution function has application beyond the specific system addressed here and that it may prove useful more generally for simulating electron-transfer processes in disordered molecular materials.

Original languageAmerican English
Pages (from-to)17213-17220
Number of pages8
JournalJournal of Physical Chemistry C
Volume118
Issue number31
DOIs
StatePublished - 7 Aug 2014

NREL Publication Number

  • NREL/JA-5900-61284

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