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Title: Molecular Dynamics Simulation Study of Solvent and State of Charge Effects on Solid-Phase Structure and Counterion Binding in a Nitroxide Radical Containing Polymer Energy Storage Material

Here we performed molecular dynamics simulations to understand the effects of solvent swelling and state of charge (SOC) on the redox active, organic radical cathode material poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA). We show that the polar solvent acetonitrile primarily solvates the nitroxide radical without disrupting the packing of the (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) pendant groups of PTMA. We also simulated bulk PTMA in different SOC, 25%, 50%, 75%, and 100%, by converting the appropriate number of TEMPO groups to the cation charge state and adding BF 4 - counterions to the simulation. At each SOC the packing of PTMA, the solvent, and the counterions were examined. The binding of the anion to the nitroxide cation site was examined using the potential of mean force and found to be on the order of tens of meV, with a binding energy that decreased with increasing SOC. Additionally, we found that the cation state is stabilized by the presence of a nearby anion by more than 1 eV, and the implications of this stabilization on charge transport are discussed. Finally, we describe the implications of our results for how the SOC of an organic electrode affects electron and anion charge transport during the charging and discharging processes.
Authors:
 [1] ;  [2] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States). Computational Science Center
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States). Chemical and Nanoscience Center
Publication Date:
Report Number(s):
NREL/JA-2C00-67429
Journal ID: ISSN 1932-7447
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 120; Journal Issue: 45; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; molecular dynamics; cathode materials
OSTI Identifier:
1333406

Kemper, Travis W., Gennett, Thomas, and Larsen, Ross E.. Molecular Dynamics Simulation Study of Solvent and State of Charge Effects on Solid-Phase Structure and Counterion Binding in a Nitroxide Radical Containing Polymer Energy Storage Material. United States: N. p., Web. doi:10.1021/acs.jpcc.6b07118.
Kemper, Travis W., Gennett, Thomas, & Larsen, Ross E.. Molecular Dynamics Simulation Study of Solvent and State of Charge Effects on Solid-Phase Structure and Counterion Binding in a Nitroxide Radical Containing Polymer Energy Storage Material. United States. doi:10.1021/acs.jpcc.6b07118.
Kemper, Travis W., Gennett, Thomas, and Larsen, Ross E.. 2016. "Molecular Dynamics Simulation Study of Solvent and State of Charge Effects on Solid-Phase Structure and Counterion Binding in a Nitroxide Radical Containing Polymer Energy Storage Material". United States. doi:10.1021/acs.jpcc.6b07118. https://www.osti.gov/servlets/purl/1333406.
@article{osti_1333406,
title = {Molecular Dynamics Simulation Study of Solvent and State of Charge Effects on Solid-Phase Structure and Counterion Binding in a Nitroxide Radical Containing Polymer Energy Storage Material},
author = {Kemper, Travis W. and Gennett, Thomas and Larsen, Ross E.},
abstractNote = {Here we performed molecular dynamics simulations to understand the effects of solvent swelling and state of charge (SOC) on the redox active, organic radical cathode material poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA). We show that the polar solvent acetonitrile primarily solvates the nitroxide radical without disrupting the packing of the (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) pendant groups of PTMA. We also simulated bulk PTMA in different SOC, 25%, 50%, 75%, and 100%, by converting the appropriate number of TEMPO groups to the cation charge state and adding BF4- counterions to the simulation. At each SOC the packing of PTMA, the solvent, and the counterions were examined. The binding of the anion to the nitroxide cation site was examined using the potential of mean force and found to be on the order of tens of meV, with a binding energy that decreased with increasing SOC. Additionally, we found that the cation state is stabilized by the presence of a nearby anion by more than 1 eV, and the implications of this stabilization on charge transport are discussed. Finally, we describe the implications of our results for how the SOC of an organic electrode affects electron and anion charge transport during the charging and discharging processes.},
doi = {10.1021/acs.jpcc.6b07118},
journal = {Journal of Physical Chemistry. C},
number = 45,
volume = 120,
place = {United States},
year = {2016},
month = {10}
}