“We Can Influence Which Materials Are Used”

Interview for Battery Day, 18 February 2025

18 February 2025 – Johannes Thienenkamp is a doctoral candidate at the Department of Physical Chemistry at the University of Münster and a research associate at Helmholtz Institute Münster (HI MS; IMD-4) of Forschungszentrum Jülich. On the occasion of the International Battery Day on 18 February 2025, he talks about new research methods and sustainable materials.

What are your main areas of work?

I work in the Methodology group, which, together with the Electrolytes department, is headed by Dr Gunther Brunklaus. Our work focuses on polymer electrolyte and method development for lithium-ion and next-generation batteries.

At Helmholtz Institute Münster, you are responsible for the large-scale facility ‘Dynamic Nuclear Polarization (DNP) Nuclear Magnetic Resonance (NMR)’. What is special about this method?

In terms of methodology, I mainly work with NMR spectroscopy. Thanks to its versatility, the method is a standard method for chemists to elucidate chemical structures and reaction mechanisms, for example, and we have also used it in the past to study battery materials and entire batteries. Dynamic nuclear polarisation, on the other hand, is a special feature or extension of NMR spectroscopy. With its help, the detected signal intensity can be amplified by a factor of up to 1000 during an NMR experiment. This is particularly important in battery research, as we are particularly interested in the layer between the electrode and the electrolyte.

When the electrolyte of a battery comes into contact with the anode or cathode, so-called solid-liquid interphases (SEI) are formed, which essentially consist of reaction products of more or less intended chemical reactions of the electrodes with the electrolyte. These interphases or layers are usually only a few nanometres thick and therefore difficult to access. However, their structure and chemical composition have a significant influence on a battery's cycling behaviour, such as charging rate and lifespan. Using the signal amplification of DNP NMR, we can characterise these interphases and thus better explore the effects of degradation, longevity and rapid charging capability of batteries at the cell level.

What results have you already been able to achieve with the method?

We purchased and installed the DNP NMR spectrometer two years ago as part of the “For-Analytik” project funded by the German Federal Ministry of Education and Research (BMBF). During installation and commissioning, we developed and built novel probe heads that we can use to examine batteries during charging and discharging. Furthermore, we were able to determine the components of electrodes and electrolyte interphases in lithium metal batteries as a function of different electrolyte formulations. We are also currently looking at the interphase components of various lithium-ion batteries (LIB). The aim now is to correlate the characterisation of the interphase components with the cycling behaviour of the batteries in order to make suggestions for improved electrolyte formulations or targeted electrode production.

What role does collaboration play in your research?

With its potential to characterise interphase components, DNP NMR is a particularly special method and thus perfectly complements the portfolio of methods used in battery research. Since there are currently only a few research groups in the world that use DNP NMR in the field of battery research, which is mainly due to the costs and complexity of the method, we are happy to examine electrodes and electrolyte formulations from project partners in a wide range of international collaborations and share our findings with them. This allows for the continuous development of individual cell concepts. In addition, we are in contact with the manufacturing company to develop new hardware that will enable us to make even better use of DNP amplification for battery research.

You have already worked with different cell systems. What advantages have emerged in each case?

In scientific literature, the lithium metal battery is often referred to as the holy grail in terms of energy density, which is due to the high theoretical capacity of lithium metal. At comparable electrode potential, lithium metal has a theoretical capacity about ten times higher than graphite, which is the standard anode material for lithium-ion batteries. The big challenge for lithium metal batteries, however, is their shorter lifespan compared to the well-established lithium-ion technology. Nevertheless, the first companies are already producing lithium metal batteries, and in France, for example, the first buses are running with them. These are solid-state batteries based on polymers, which we also investigate at Helmholtz Institute Münster.

In addition to research into solid-state lithium metal batteries, I am working on the BMBF project “KaFeBar” with partners from Humboldt University Berlin, Justus-Liebig University Giessen, the University of Bayreuth, Wolfram Chemie and the group of Prof. Dr Wolfgang Zeier at Helmholtz Institute Münster on the development of potassium solid-state batteries. This technology is still at the very beginning, but offers great potential when it comes to the availability of raw materials and short supply chains in Europe. With potassium-ion batteries, as with sodium-ion batteries, the focus is less on energy density and more on using potassium, a resource that is readily available in Germany. Even though global lithium reserves are not currently a bottleneck, Europe and thus Germany are dependent on imports, since lithium is mainly mined in South America, China and Australia. Potash salts, on the other hand, are already mined in Germany on a scale of millions of tonnes. However, the role that potassium solid-state batteries will play in the future depends on the application scenarios in industry and the continued availability of raw materials.

What role does sustainability play in your research?

As battery researchers, we always consider the energy transition. In our research, we cannot influence how electricity is generated, but we can influence which materials are used to store it. Resource availability, supply chains and production locations have a direct influence on the sustainability of a technology. For me, this is particularly reflected in the work on potassium-ion batteries.

Where do you currently see particular challenges for German battery research?

In its funding. Since the drastic decline in the number of new funding projects announced by the federal government, the future training of young battery researchers and the associated research has been deprived of an important cornerstone. This jeopardises the future operation of research infrastructure built up over years. Therefore, I would like to join the appeal of many battery researchers in Germany to resume state project funding by the federal government as it was before 2023.