Research Group Dr. Reiner Mönig

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Mikroskopie und Mechanische Messungen

Mikroskopie

Materialien hochpräzise zu betrachten und deren Veränderung bei diversen Einflüssen in Echtzeit zu beobachten, ist eine Hauptaufgabe der Mikroskopie. Die Lichtmikroskopie wird verwendet, um Materialien im Inneren des Elektrolyten in Echtzeit zu untersuchen. Sie bietet die einzige Möglichkeit, Prozesse in Echtzeit in realistischen Umgebungen zu beobachten. Diese Technik wird beispielsweise für die Untersuchung der Lithiumabscheidung genutzt – unter vergleichbaren Bedingungen wie in realen Zellen.

Die Rasterelektronenmikroskopie ist ein vielseitiges Werkzeug zur Untersuchung von Materialien mit hoher Auflösung. Bei Batterie-Materialien wird der Fokus auf luftempfindliche Materialien gelegt, die mit einem speziellen Transfersystem übertragen werden.

Mechanische Messungen

Während des Einlagerns und des Herausnehmens von Lithium bilden sich mechanische Spannungen in Elektrodenmaterialien. Diese Belastungen können zu Schäden führen und somit ist eine Messung dieser Spannungen hilfreich für die Beurteilung der Zuverlässigkeit des Materials. Ein effektiver Weg zur Durchführung solcher Experimente ist die Substratkrümmungsmethode, bei der ein dünner Film auf einem Träger – dem Substrat – betrachtet wird. Wenn der Film mechanische Spannungen erfährt, biegt sich der Verbund aus Elektrodenfilm und Substrat geringfügig durch. Durch Messen der Substratkrümmung können die Spannungen im Elektrodenfilm berechnet werden. Am HIU besteht die einzigartige Möglichkeit, solche Messungen auf der Grundlage von Partikelverbundelektroden durchzuführen wie sie in richtigen Batterien verwendet werden.

 

Dr. Dominik KramerScientist Tel: +49 (0721) 608 24894Mail: dominik.kramer(at)kit.edu
ForschungsgruppeResearch Group Dr. Reiner Mönig
Dr. Reiner MönigPrincipal Investigator (PI)Tel: +49 (0721) 608 22487Mail: reiner.moenig(at)kit.edu
ForschungsgruppeResearch Group Dr. Reiner Mönig

(images will be uploaded shortly)

 

Light Microscopy

Light Microscopy is used to investigate materials inside the electrolyte in real time. Although the resolution of light microscopy is limited to about 300nm it offers the unique possibility the observe processes in real time in realistic environments. In our research we strongly rely on this technique for example for investigating lithium plating where the same solid electrolyte interface conditions as in real cells can be established. In this research we observe protrusion growth during lithium deposition and identify the governing mechanisms. In contrast to what is known from the literature we reveal that dendrite growth is controlled by defects and that concentration gradients or electrical fields or diffusion inhomogenities do not strongly affect the growth of dendrites.

 

Scanning Electron Microscopy

SEM is a versatile tool for investigating materials at high resolution. For battery materials care has to be taken about air sensitive materials which are transferred using a special transfer system. In our SEM setups we have two options. We can use a dedicated in situ cell that uses ionic liquid based electrolytes with very low vapor pressure to observer electrode materials in real time. This technique is particularly suitable for conversion or alloying materials where strong changes occur within the first or first few cycles. For higher cycle numbers we hae develop a technique that allows the inspection of an electrode region over the course of several hundred or thousands of cycles. In this experiment the cell is disassembled and reassembled after investigation and transfer to be tested for several weeks or even months. In this experiment we can compare the same electrode regions before during and after the tests.

 

Substrate Curvature Measurements

During insertion and extraction of lithium, mechanical stresses form in electrode materials. These stresses can lead to damage and therefore a measurement of these stresses is useful for assessing the reliability of a material. An effective way for performing such experiments is the substrate curvature technique, where a thin film on a relatively thick substrate is considered. If the film experiences mechanical stresses, the film substrate composite bends. By measuring the curvature of this system, the stresses in the film can be calculated. At HIU we have the unique possibility to perform such measurements on particle based composite electrodes as used in real batteries. In our experiments the electrodes are glued to borosilicate cantilevers and their bending is monitored. Our home-built setup has a very high sensitivity and measures at speeds of up to 30ms. Tracking the mechanical stresses not only helps to assess the mechanics of a material, since stress and electrochemistry are strongly coupled the measurements can also be used to monitor phase transformations or degradation effects.

(information will be uploaded shortly)

 

The research group uses the equipment below

  • Electron microscope Zeiss Merlin with EBSD und EDX and transfer system
  • three substrate curvature device with thermostatization
  • Raman Microscope and diffractometer

(images will be uploaded shortly)

 

The electron microscopy and spectroscopy group is partner in a number of national and international collaborations and projects. Battery related projects are pursued as part of the following projects.

MIT – Department of Materials Science and Engineering

There is a close cooperation with the research group of Prof. Carl V. Thompson, Department of Materials Science and Engineering, MIT.

Further information

A specific filter for this group’s publications is not yet available. Please take a look at „publications“ in the website’s header for now.

Mitglieder
Dr. Dominik KramerScientist Tel: +49 (0721) 608 24894Mail: dominik.kramer(at)kit.edu
ForschungsgruppeResearch Group Dr. Reiner Mönig
Dr. Reiner MönigPrincipal Investigator (PI)Tel: +49 (0721) 608 22487Mail: reiner.moenig(at)kit.edu
ForschungsgruppeResearch Group Dr. Reiner Mönig
Forschung

(images will be uploaded shortly)

 

Light Microscopy

Light Microscopy is used to investigate materials inside the electrolyte in real time. Although the resolution of light microscopy is limited to about 300nm it offers the unique possibility the observe processes in real time in realistic environments. In our research we strongly rely on this technique for example for investigating lithium plating where the same solid electrolyte interface conditions as in real cells can be established. In this research we observe protrusion growth during lithium deposition and identify the governing mechanisms. In contrast to what is known from the literature we reveal that dendrite growth is controlled by defects and that concentration gradients or electrical fields or diffusion inhomogenities do not strongly affect the growth of dendrites.

 

Scanning Electron Microscopy

SEM is a versatile tool for investigating materials at high resolution. For battery materials care has to be taken about air sensitive materials which are transferred using a special transfer system. In our SEM setups we have two options. We can use a dedicated in situ cell that uses ionic liquid based electrolytes with very low vapor pressure to observer electrode materials in real time. This technique is particularly suitable for conversion or alloying materials where strong changes occur within the first or first few cycles. For higher cycle numbers we hae develop a technique that allows the inspection of an electrode region over the course of several hundred or thousands of cycles. In this experiment the cell is disassembled and reassembled after investigation and transfer to be tested for several weeks or even months. In this experiment we can compare the same electrode regions before during and after the tests.

 

Substrate Curvature Measurements

During insertion and extraction of lithium, mechanical stresses form in electrode materials. These stresses can lead to damage and therefore a measurement of these stresses is useful for assessing the reliability of a material. An effective way for performing such experiments is the substrate curvature technique, where a thin film on a relatively thick substrate is considered. If the film experiences mechanical stresses, the film substrate composite bends. By measuring the curvature of this system, the stresses in the film can be calculated. At HIU we have the unique possibility to perform such measurements on particle based composite electrodes as used in real batteries. In our experiments the electrodes are glued to borosilicate cantilevers and their bending is monitored. Our home-built setup has a very high sensitivity and measures at speeds of up to 30ms. Tracking the mechanical stresses not only helps to assess the mechanics of a material, since stress and electrochemistry are strongly coupled the measurements can also be used to monitor phase transformations or degradation effects.

Equipment

(information will be uploaded shortly)

 

The research group uses the equipment below

  • Electron microscope Zeiss Merlin with EBSD und EDX and transfer system
  • three substrate curvature device with thermostatization
  • Raman Microscope and diffractometer
Zusammenarbeit

(images will be uploaded shortly)

 

The electron microscopy and spectroscopy group is partner in a number of national and international collaborations and projects. Battery related projects are pursued as part of the following projects.

MIT – Department of Materials Science and Engineering

There is a close cooperation with the research group of Prof. Carl V. Thompson, Department of Materials Science and Engineering, MIT.

Further information

Publikationen

A specific filter for this group’s publications is not yet available. Please take a look at „publications“ in the website’s header for now.

Fakten zur Gruppe