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| Hauptseite > Publikationsdatenbank > EPR spectroscopic investigation of Lithium-organic batteries |
| Hauptseite > Publikationsdatenbank > EPR spectroscopic investigation of Lithium-organic batteries |
| Conference Presentation (After Call) | FZJ-2022-04763 |
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2022
Abstract: Electrochemical energy storage is of key importance to meet future energy demands sustainably. The most used battery technology utilizes lithium metal as the anode and transition metal oxides or phosphates (LiCoO2, LiFePO4 etc.) as cathode material. Owing to the toxicity of the metals, production costs and poor recyclability, transition metal oxides as cathode materials have a negative environmental impact. Organic radical polymers are a promising alternative, as they feature tuneable redox properties, fast kinetics and are more environmentally sustainable.[1]EPR is well suited to study these systems as the polymers comprise of paramagnetic species as redox units. A common radical polymer, bearing TEMPO radicals as redox units is PTMA (poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate)).[2] Herein, we report EPR spectroscopic characterization of PTMA polymers using cw-EPR and pulsed-EPR techniques and study charge/discharge characteristics of a Li-PTMA cell using in operando EPR spectroscopy. Cw-EPR is primarily used for radical quantification and to distinguish between nitroxide radicals undergoing exchange and isolated nitroxides by lineshape fitting. Laplace inverted pulsed-EPR relaxation offers insight into electronic contact between the active material (PTMA) and SuperP conductive carbon present in the composite cathode. The redox state of the active material was monitored by acquiring cw-EPR spectra during battery cycling using an in operando EPR cell [3] with lithium metal as the anode and a PTMA composite cathode(65 wt% PTMA, 30 wt% SuperP, 5 wt% CMC(Carboxymethyl cellulose)). The Li-PTMA in operando cell shows good electrochemical reversibility of the active material for over60 cycles and an irreversible accumulation of mossy (microstructured) lithium is indicated by the linewidth of the lithium resonance. In the electrochemically oxidized state of the radical polymer, EPR spectrum shows the presence of immobilised nitroxide radicals arising from electrochemically inactive regions of the cathode film. EPR serves as an optimal spectroscopic technique for gaining insights into structural and mechanistic features of organic radical batteries (ORB). Comparative studies using pulsed-EPR techniques on pristine and post-cycled battery materials would also reveal degradation pathways and changes in the radical environment, further aiding the optimization of the ORB setup. Literature:[1] Muench, S. et al. Chem. Rev. 116, 9438–9484 (2016). [2] Nakahara, K. et al. Chem.Phys. Lett. 359, 351–354 (2002). [3] Niemöller, A. et al. J. Chem. Phys. 148, 014705(2018).
Keyword(s): Energy (1st) ; Materials Science (2nd) ; Chemistry (2nd)
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