Journal Article

FZJ-2023-02568

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Multimodal investigation of electronic transport in PTMA and its impact on organic radical battery performance

Daniel, D. T.FZJ*RWTH* ; Oevermann, S.FZJ* ; Mitra, S. ; Rudolf, K. ; Heuer, A.FZJ* ; Eichel, R.-A.FZJ*RWTH* ; Winter, M.FZJ* ; Diddens, D.FZJ* ; Brunklaus, G.FZJ* ; Granwehr, J. (Corresponding author)FZJ*

2023
Macmillan Publishers Limited, part of Springer Nature [London]

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Please use a persistent id in citations: doi:10.1038/s41598-023-37308-5  doi:10.34734/FZJ-2023-02568

Abstract: Organic radical batteries (ORBs) represent a viable pathway to a more sustainable energy storage technology compared toconventional Li-ion batteries. For further materials and cell development towards competitive energy and power densities, adeeper understanding of electron transport and conductivity in organic radical polymer cathodes is required. Such electrontransport is characterised by electron hopping processes, which depend on the presence of closely spaced hopping sites.Using a combination of electrochemical, electron paramagnetic resonance (EPR) spectroscopic, and theoretical moleculardynamics (MD) as well as density functional theory (DFT) modelling techniques, we explored how compositional characteristicsof cross-linked poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA) polymers govern electron hopping andrationalise their impact on ORB performance. Electrochemistry and EPR spectroscopy not only show a correlation betweencapacity and the total number of radicals in an ORB using a PTMA cathode, but also indicates that the state-of-health degradesabout twice as fast if the amount of radical is reduced by 15%. The presence of up to 3% free monomer radicals did not improvefast charging capabilities. Pulsed EPR indicated that these radicals readily dissolve into the electrolyte but a direct effect onbattery degradation could not be shown. However, a qualitative impact cannot be excluded either. The work further illustratesthat nitroxide units have a high affinity to the carbon black conductive additive, indicating the possibility of its participation inelectron hopping. At the same time, the polymers attempt to adopt a compact conformation to increase radical–radical contact.Hence, a kinetic competition exists, which might gradually be altered towards a thermodynamically more stable configuration byrepeated cycling, yet further investigations are required for its characterisation.

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Contributing Institute(s):

1. Helmholtz-Institut Münster Ionenleiter für Energiespeicher (IEK-12)
2. Grundlagen der Elektrochemie (IEK-9)

Research Program(s):

1. 1222 - Components and Cells (POF4-122) (POF4-122)
2. 1223 - Batteries in Application (POF4-122) (POF4-122)
3. DFG project 422726248 - SPP 2248: Polymer-basierte Batterien (422726248) (422726248)
4. HITEC - Helmholtz Interdisciplinary Doctoral Training in Energy and Climate Research (HITEC) (HITEC-20170406) (HITEC-20170406)

Appears in the scientific report 2023

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