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Selected results from the lab
March 2020The commercialization of pure metals as anode material is often called the "Holy Grail" in battery research. This statement is based on the fact that the energy density of batteries can be increased significantly by the use of pure metals. However, several challenges still need to be overcome before metal anodes can be commercialized. One of the main challenges is to prevent the growth of so-called dendrites during battery charging. Within the scope of several study projects, the WG Schröder works on the analysis and prevention of dendrites. In her bachelor thesis, Ronja Haas reduced the growth of dendrites by the use of different sodium metal alloys. For this purpose, she used liquid sodium-potassium alloys as an anode and sodium-tin alloys as protective layer. Julian Kreissl's master thesis also dealt with the prevention of dendrites in sodium-oxygen batteries. In cooperation with the group of Prof. Dr. Peter R. Schreiner, he used functionalized diamondoids as an additive in the electrolyte. These "molecular diamonds" are incorporated into the anode during charging and ensure planar metal deposition (Figure a; 10.1002/cssc.201903499). Both theses were awarded first place in the categories "Best Bachelor Thesis" and "Best Master Thesis" as part of the Students Program for Electric Mobility of the German Federal Ministry of Education and Research (BMBF) and the Fraunhofer-Gesellschaft – DRIVE-E (Figure b; https://www.uni-giessen.de/ueber-uns/pressestelle/pm/pm188-19driveepreisfuerwissenschaftlichennachwuchs; https://www.iisb.fraunhofer.de/en/press_media/press_releases/pressearchiv/archiv_2019/drive-e_2019_studienpreise.html).https://www.uni-giessen.de/en/faculties/f08/departments/physchem/schroder/picsquarter/BdQ0120/viewhttps://www.uni-giessen.de/@@site-logo/logo.png
The commercialization of pure metals as anode material is often called the "Holy Grail" in battery research. This statement is based on the fact that the energy density of batteries can be increased significantly by the use of pure metals. However, several challenges still need to be overcome before metal anodes can be commercialized. One of the main challenges is to prevent the growth of so-called dendrites during battery charging. Within the scope of several study projects, the WG Schröder works on the analysis and prevention of dendrites. In her bachelor thesis, Ronja Haas reduced the growth of dendrites by the use of different sodium metal alloys. For this purpose, she used liquid sodium-potassium alloys as an anode and sodium-tin alloys as protective layer. Julian Kreissl's master thesis also dealt with the prevention of dendrites in sodium-oxygen batteries. In cooperation with the group of Prof. Dr. Peter R. Schreiner, he used functionalized diamondoids as an additive in the electrolyte. These "molecular diamonds" are incorporated into the anode during charging and ensure planar metal deposition (Figure a; 10.1002/cssc.201903499). Both theses were awarded first place in the categories "Best Bachelor Thesis" and "Best Master Thesis" as part of the Students Program for Electric Mobility of the German Federal Ministry of Education and Research (BMBF) and the Fraunhofer-Gesellschaft – DRIVE-E (Figure b; https://www.uni-giessen.de/ueber-uns/pressestelle/pm/pm188-19driveepreisfuerwissenschaftlichennachwuchs; https://www.iisb.fraunhofer.de/en/press_media/press_releases/pressearchiv/archiv_2019/drive-e_2019_studienpreise.html).
July 2020Lithium-ion batteries have received considerable attention due to the increasing demand for electrochemical energy storage. However, commercial lithium-ion batteries suffer from severe safety concerns stemming from the organic liquid electrolyte (e.g., they are flammable). Solid-state batteries (SSBs) are expected to be a promising candidate complementing batteries with organic liquid electrolyte. Nevertheless, the development of SSBs still faces considerable challenges hindering their full-scale commercialization. One of the major issues is the high charge-transfer resistance between the electrode materials and the solid electrolyte due side reactions at the electrode/electrolyte interface. Therefore, the WG Schröder and the WG Janek investigate the underlying degradation processes in SSBs. In detail, we examine the degradation reactions at the interface of various composite cathode materials and ceramic solid electrolytes within the GER-JPN-joint BMBF-project InCa. The SEM image displays the interface between composite cathode and solid electrolyte, and the graphic schematically illustrates the degradation process. Impedance measurements were carried out to monitor the evolution of the degradation layer between the compounds. A characteristic frequency (~200 – 500 Hz), which can be ascribed to the degradation processes at the interface, is indicated in the Nyquist plot. Thereby, the gradually increasing resistance between composite cathode and solid electrolyte are mainly caused by the growing degradation layer. (Picture submitted by TongTong Zuo and Daniel Schröder).https://www.uni-giessen.de/en/faculties/f08/departments/physchem/schroder/picsquarter/july-2020/viewhttps://www.uni-giessen.de/@@site-logo/logo.png
Lithium-ion batteries have received considerable attention due to the increasing demand for electrochemical energy storage. However, commercial lithium-ion batteries suffer from severe safety concerns stemming from the organic liquid electrolyte (e.g., they are flammable). Solid-state batteries (SSBs) are expected to be a promising candidate complementing batteries with organic liquid electrolyte. Nevertheless, the development of SSBs still faces considerable challenges hindering their full-scale commercialization. One of the major issues is the high charge-transfer resistance between the electrode materials and the solid electrolyte due side reactions at the electrode/electrolyte interface. Therefore, the WG Schröder and the WG Janek investigate the underlying degradation processes in SSBs. In detail, we examine the degradation reactions at the interface of various composite cathode materials and ceramic solid electrolytes within the GER-JPN-joint BMBF-project InCa. The SEM image displays the interface between composite cathode and solid electrolyte, and the graphic schematically illustrates the degradation process. Impedance measurements were carried out to monitor the evolution of the degradation layer between the compounds. A characteristic frequency (~200 – 500 Hz), which can be ascribed to the degradation processes at the interface, is indicated in the Nyquist plot. Thereby, the gradually increasing resistance between composite cathode and solid electrolyte are mainly caused by the growing degradation layer. (Picture submitted by TongTong Zuo and Daniel Schröder).
October 2020Due to their high theoretical storage capacity, lithium-oxygen batteries are regarded as possible energy storage systems of the future, both for mobile and stationary applications. In them, metallic lithium (anodic reaction) is converted with oxygen (cathode reaction) to lithium peroxide. The lithium peroxide formed is stored in the battery and converted back into oxygen and metallic lithium when charged. Despite intensive research in recent years, this type of battery is not yet able to achieve high cycle numbers for electrical recharging. This is due to various side reactions during the charging and discharging process, the origin of which has not yet been fully understood. A possible source of the unintentionally generated by-products is singlet oxygen (¹O₂) formed during operation. ¹O₂ is an excited, short-lived variant of molecular oxygen. It is a strong oxidant and reacts with the other components of the battery such as the electrolyte and the electrode materials. However, since ¹O₂ is not long-term stable and reacts after only a few milliseconds, detection is difficult. One possibility for detection is the so-called trapping in which ¹O₂ is reacted with other molecules, which can then be detected later. At the AG Schröder, the molecule 9,10-dimethylanthracene (DMA) shown in the figure is currently being investigated as an agent for detecting 1O2 in lithium-oxygen batteries, since it reacts specifically with singlet oxygen to form 9,10-dimethyl-9,10-epidioxyanthracene (DMA-O₂). Little is known about its stability and its influence on the chemistry of lithium-oxygen batteries. The DMA-O₂ required for this is produced photochemically in the AG Schröder (see picture) and then purified before it is further investigated. (Image by: Adrian Schürmann)https://www.uni-giessen.de/en/faculties/f08/departments/physchem/schroder/picsquarter/PoQ0320/viewhttps://www.uni-giessen.de/@@site-logo/logo.png
Due to their high theoretical storage capacity, lithium-oxygen batteries are regarded as possible energy storage systems of the future, both for mobile and stationary applications. In them, metallic lithium (anodic reaction) is converted with oxygen (cathode reaction) to lithium peroxide. The lithium peroxide formed is stored in the battery and converted back into oxygen and metallic lithium when charged. Despite intensive research in recent years, this type of battery is not yet able to achieve high cycle numbers for electrical recharging. This is due to various side reactions during the charging and discharging process, the origin of which has not yet been fully understood. A possible source of the unintentionally generated by-products is singlet oxygen (¹O₂) formed during operation. ¹O₂ is an excited, short-lived variant of molecular oxygen. It is a strong oxidant and reacts with the other components of the battery such as the electrolyte and the electrode materials. However, since ¹O₂ is not long-term stable and reacts after only a few milliseconds, detection is difficult. One possibility for detection is the so-called trapping in which ¹O₂ is reacted with other molecules, which can then be detected later. At the AG Schröder, the molecule 9,10-dimethylanthracene (DMA) shown in the figure is currently being investigated as an agent for detecting 1O2 in lithium-oxygen batteries, since it reacts specifically with singlet oxygen to form 9,10-dimethyl-9,10-epidioxyanthracene (DMA-O₂). Little is known about its stability and its influence on the chemistry of lithium-oxygen batteries. The DMA-O₂ required for this is produced photochemically in the AG Schröder (see picture) and then purified before it is further investigated. (Image by: Adrian Schürmann)
December 2020In recent years, organic redox flow batteries (RFB) have increasingly become the focus of attention as large-scale energy storage systems, since they do not contain toxic and rare metal ions compared to the established vanadium RFB. Due to this, the demand for new organic active materials, which are used as catholyte or anolyte in organic RFB, is increasing. The long-term stability of the organic active materials is crucial for a possible commercial success of RFB. Our research group is focusing on the characterization of the performance and stability of organic active materials for RFB in operation. The picture shows an example of the results obtained with a diazanaphthoquinone (synthesized by AG Wegner at the JLU; cooperation within a project funded by the BMEL). The diazanaphthoquinone (top) was measured using an operando UV/Vis cell (left), while electrochemical measurements (right) were performed simultaneously. The UV/Vis measurements are used to identify products and degradation products, whereas long-term electrochemical measurements allow to determine the kinetics of the occurring degradation reactions. Overall, our group always relies on a powerful combination of analytics (operando, in-situ and ex-situ) and theoretical considerations to advance the understanding of organic active materials for RFB. (Image by: Dominik Emmel and Simon Kunz)https://www.uni-giessen.de/en/faculties/f08/departments/physchem/schroder/picsquarter/copy_of_PoQ0320/viewhttps://www.uni-giessen.de/@@site-logo/logo.png
In recent years, organic redox flow batteries (RFB) have increasingly become the focus of attention as large-scale energy storage systems, since they do not contain toxic and rare metal ions compared to the established vanadium RFB. Due to this, the demand for new organic active materials, which are used as catholyte or anolyte in organic RFB, is increasing. The long-term stability of the organic active materials is crucial for a possible commercial success of RFB. Our research group is focusing on the characterization of the performance and stability of organic active materials for RFB in operation. The picture shows an example of the results obtained with a diazanaphthoquinone (synthesized by AG Wegner at the JLU; cooperation within a project funded by the BMEL). The diazanaphthoquinone (top) was measured using an operando UV/Vis cell (left), while electrochemical measurements (right) were performed simultaneously. The UV/Vis measurements are used to identify products and degradation products, whereas long-term electrochemical measurements allow to determine the kinetics of the occurring degradation reactions. Overall, our group always relies on a powerful combination of analytics (operando, in-situ and ex-situ) and theoretical considerations to advance the understanding of organic active materials for RFB. (Image by: Dominik Emmel and Simon Kunz)
