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10. Evaluating the Polymer Backbone – Vinylene versus Styrene – of Anisyl‐substituted Phenothiazines as Battery Electrode Materials.

Author

Desmaizieres, Gauthier, Perner, Verena, Wassy, Daniel, Kolek, Martin, Bieker, Peter, Winter, Martin, and Esser, Birgit

Subjects
REDOX polymers, STYRENE, ELECTRODES, SPINE, POLYMERS
Abstract

Organic electrode materials are capable candidates for next‐generation greener energy storage solutions. One advantage is that their electrochemical performance can be tuned by structural modification. We herein investigate anisyl‐substituted poly(vinyl‐) and poly(styrylphenothiazines) as positive electrode materials for dual‐ion batteries. π‐Interactions – characteristic to phenothiazine redox polymers – are facilitated in the poly(styrene) derivatives PSAPT and PSAPT‐X‐DVB due to the longer spacing between phenothiazine units and polymer backbone and lead to high cycling stabilities, but reduce their specific capacities. In the poly(vinylenes), the linear PVAPT shows high cycling stability but a dissolution/redeposition mechanism, diminishing its capacity, while the cross‐linked X‐PVAPT demonstrates high cycling stabilities at specific capacities up to 81 mAh g−1 paired with an excellent rate performance, where 10,000 cycles at 100 C rate proceed with 86 % capacity retention. [ABSTRACT FROM AUTHOR]

Published
2023
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22. Lithium Powder Synthesis and Preparation of Powder‐Based Composite Electrodes for Application in Lithium Metal Batteries.

Author

Kolesnikov, Aleksei, Wulfers, Tristan, Kolek, Martin, Bieker, Peter, Stan, Marian Cristian, and Winter, Martin

Subjects
LITHIUM cells, ALLOY powders, METAL powders, POWDERS, NEGATIVE electrode, ELECTRODES, LITHIUM cell electrodes, SCIENTIFIC method
Abstract

The electrochemical performance of lithium metal batteries is affected by many factors, among which the negative electrode is crucial. Although much of the research is focused on lithium metal electrodes from metallic foils, lithium metal powder can also provide several advantages. Herein, the synthesis of lithium metal powder (Lip) using a droplet emulsion technique is described in detail and the scientific background of the method is provided. Furthermore, the electrochemical performance of the composite Lip‐based electrodes prepared with conductive carbon additive (Super C65) via the electrode paste‐casting method is reported. The results indicate that under the same material loading, the composite Lip‐based electrodes can provide at least twice the practical electrode capacity of pure Lip electrodes and with lower overpotentials, as shown in symmetric Li||Li cells. Full cells assembled with an NMC622 cathode and a composite Lip‐based electrode are cycled at least for 100 cycles and show improved cycling performance as compared with the full cells assembled with pure Lip electrodes. In addition, the results also conclude that there are four different types of charge storage mechanisms in these composite Lip‐based electrodes. These occurring mechanisms should be considered when engineering lithium metal electrodes with various designs. [ABSTRACT FROM AUTHOR]

Published
2022
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27. Side by Side Battery Technologies with Lithium‐Ion Based Batteries

Author

Durmus, Yasin Emre, primary, Zhang, Huang, additional, Baakes, Florian, additional, Desmaizieres, Gauthier, additional, Hayun, Hagay, additional, Yang, Liangtao, additional, Kolek, Martin, additional, Küpers, Verena, additional, Janek, Jürgen, additional, Mandler, Daniel, additional, Passerini, Stefano, additional, and Ein‐Eli, Yair, additional

Published
2020
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34. Dibenzo[a,e]Cyclooctatetraene‐Functionalized Polymers as Potential Battery Electrode Materials.

Author

Desmaizieres, Gauthier, Speer, Martin E., Thiede, Inna, Gaiser, Philipp, Perner, Verena, Kolek, Martin, Bieker, Peter, Winter, Martin, and Esser, Birgit

Subjects
ELECTRODE potential, REDOX polymers, POLYMERS, NEGATIVE electrode, CYCLIC voltammetry, THIN films, ELECTRIC batteries
Abstract

Organic redox polymers are attractive electrode materials for more sustainable rechargeable batteries. To obtain full‐organic cells with high operating voltages, redox polymers with low potentials (<2 V versus Li|Li+) are required for the negative electrode. Dibenzo[a,e]cyclooctatetraene (DBCOT) is a promising redox‐active group in this respect, since it can be reversibly reduced in a two‐electron process at potentials below 1 V versus Li|Li+. Upon reduction, its conformation changes from tub‐shaped to planar, rendering DBCOT‐based polymers also of interest to molecular actuators. Here, the syntheses of three aliphatic DBCOT‐polymers and their electrochemical properties are presented. For this, a viable three‐step synthetic route to 2‐bromo‐functionalized DBCOT as polymer precursor is developed. Cyclic voltammetry (CV) measurements in solution and of thin films of the DBCOT‐polymers demonstrate their potential as battery electrode materials. Half‐cell measurements in batteries show pseudo capacitive behavior with Faradaic contributions, which demonstrate that electrode composition and fabrication will play an important role in the future to release the full redox activity of the DBCOT polymers. [ABSTRACT FROM AUTHOR]

Published
2021
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35. In situ 7 Li-NMR analysis of lithium metal surface deposits with varying electrolyte compositions and concentrations

Author

Küpers, Verena, Kolek, Martin, Bieker, Peter, Winter, Martin, and Brunklaus, Gunther

Subjects
ddc:540
Abstract

A major challenge of lithium metal electrodes, in theory a suitable choice for rechargeable high energy density batteries, comprises non-homogeneous lithium deposition and the growth of reactive high surface area lithium, which eventually yields active material losses and safety risks. While it is hard to fully avoid inhomogeneous deposits, the achievable morphology of the occurring lithium deposits critically determines the long-term cycling behaviour of the cells. In this work, we focus on a combined scanning electron microscopy (SEM) and 7Li nuclear magnetic resonance spectroscopy (7Li-NMR) study to unravel the impact of the choice of conducting salts (LiPF6 and LiTFSI), solvents (EC : DEC, 3 : 7, DME : DOL, 1 : 1), as well as their respective concentrations (1 M, 3 M) on the electrodeposition process, demonstrating that lithium deposition morphologies may be controlled to a large extent by proper choice of cycling conditions and electrolyte constituents. In addition, the applicability of 7Li-NMR spectroscopy to assess the resulting morphology is discussed. It was found, that lithium deposition analysis based on the 7Li chemical shift and intensity should be used carefully, as various morphologies can lead to similar results. Still, our case study reveals that the combination of SEM and NMR data is rather advantageous and offers complementary insights that may provide pathways for the future design of tailored electrolytes.

Published
2019

36. Enabling Mg‐Based Ionic Liquid Electrolytes for Hybrid Dual‐Ion Capacitors.

Author

Meister, Paul, Küpers, Verena, Kolek, Martin, Kasnatscheew, Johannes, Pohlmann, Sebastian, Winter, Martin, and Placke, Tobias

Abstract

We report on the reversible (de)intercalation of TFSI− anions from a Mg‐based ionic liquid electrolyte, Mg(TFSI)2 in Pyr14TFSI, in graphite ∥ activated carbon hybrid dual‐ion capacitor (DIC) cells. The role of different pseudo reference electrodes (PREs) including Ag‐wire and Li metal is discussed regarding the comparability of different battery cells. We show that an Ag‐wire PRE is not suitable for the designated purpose, while the use of a Li metal PRE results in high reproducibility. Mg‐based DIC cells are compared with cells based on pure Pyr14TFSI and LiTFSI‐Pyr14TFSI electrolytes, and with graphite ∥ Li metal dual‐ion cells employing LiTFSI‐Pyr14TFSI. At 5.2 V vs. Li|Li+, Mg‐containing DIC cells reveal an improved performance compared to Li‐based cells, i. e. higher capacity (87 vs. 85 mAh g−1) and higher Coulombic efficiency (98 vs. 96 %). These results may pave the way to further studies and performance improvements of Mg‐based batteries and to hybrid DIC chemistries with other cations, especially multi‐valent ones. [ABSTRACT FROM AUTHOR]

Published
2021
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40. Lithium Metal Batteries: Cross Talk between Transition Metal Cathode and Li Metal Anode: Unraveling Its Influence on the Deposition/Dissolution Behavior and Morphology of Lithium (Adv. Energy Mater. 21/2019)

Author

Betz, Johannes, primary, Brinkmann, Jan‐Paul, additional, Nölle, Roman, additional, Lürenbaum, Constantin, additional, Kolek, Martin, additional, Stan, Marian Cristian, additional, Winter, Martin, additional, and Placke, Tobias, additional

Published
2019
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48. In situ7Li-NMR analysis of lithium metal surface deposits with varying electrolyte compositions and concentrations.

Author

Küpers, Verena, Kolek, Martin, Bieker, Peter, Winter, Martin, and Brunklaus, Gunther

Abstract

A major challenge of lithium metal electrodes, in theory a suitable choice for rechargeable high energy density batteries, comprises non-homogeneous lithium deposition and the growth of reactive high surface area lithium, which eventually yields active material losses and safety risks. While it is hard to fully avoid inhomogeneous deposits, the achievable morphology of the occurring lithium deposits critically determines the long-term cycling behaviour of the cells. In this work, we focus on a combined scanning electron microscopy (SEM) and 7Li nuclear magnetic resonance spectroscopy (7Li-NMR) study to unravel the impact of the choice of conducting salts (LiPF6 and LiTFSI), solvents (EC : DEC, 3 : 7, DME : DOL, 1 : 1), as well as their respective concentrations (1 M, 3 M) on the electrodeposition process, demonstrating that lithium deposition morphologies may be controlled to a large extent by proper choice of cycling conditions and electrolyte constituents. In addition, the applicability of 7Li-NMR spectroscopy to assess the resulting morphology is discussed. It was found, that lithium deposition analysis based on the 7Li chemical shift and intensity should be used carefully, as various morphologies can lead to similar results. Still, our case study reveals that the combination of SEM and NMR data is rather advantageous and offers complementary insights that may provide pathways for the future design of tailored electrolytes. [ABSTRACT FROM AUTHOR]

Published
2019
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