Batteries without critical raw materials
With operando techniques, it is possible to observe how solvated ions embed themselves in batterie electrodes. This might help to develop alternative batteries. © G. A. Ferrero
The market for rechargeable batteries is growing rapidly, but the necessary raw materials are limited. Sodium-ion batteries, for example, could offer an alternative. A joint research group from HZB and Humboldt-Universität zu Berlin has investigated new combinations of electrolyte solutions and electrode materials for this purpose.
"In contrast to lithium-ion batteries, which are based on the storage of lithium ions in the positive and negative electrodes of the battery, we are working on the one hand with sodium ions, as they also occur in cheap table salt. On the other hand, we store the sodium ions together with their solvate shell, i.e. solvent molecules from the electrolyte solution that separate the two electrodes. This makes it possible to realise completely new storage reactions," explains Prof. Philipp Adelhelm, who heads the research group "operando battery analysis", which was jointly founded by Humboldt University and Helmholtz-Zentrum Berlin in 2020.
The storage of ions when accompanied by their solvation shell in a crystal lattice is referred to as co-intercalation. Up to this point, this concept was limited to the negative electrode of the sodium-ion battery. Now the researchers around Adelhelm have succeeded in extending the concept to the positive electrode of the battery. Dr. Guillermo A. Ferrero, first author of the publication, explains: "With titanium disulphide and graphite, we have for the first time combined two materials that absorb and release the same solvent during charging and discharging of the battery”. The scientists could observe changes in the material during charging and discharging via operando measurements performed in the X-Ray Core Lab at HZB on the LIMAX 160. This helped them to assign the co-intercalation mechanism inside the battery. They could then use this new knowledge to realise a battery with two electrodes that both rely on reversible co-intercalation of solvent molecules.
“We are still in the early stages of understanding the implications of the co-intercalation batteries. But there are a few possible advantages we can envision”, Dr. Katherine A. Mazzio, HZB, explains: The process of co-intercalation could improve upon efficiency by enabling better low temperature performance. It could also be utilised to improve upon alternative cell concepts such as using multi-valent ions instead of Li+ or Na+ storage that are particularly sensitive to the solvation shell.”
Note: This project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. [864698], SEED).
- Electrocatalysts: New model for charge separation at the solid-liquid interfaceHydrogen is at the heart of the transition to carbon neutrality, as both an energy carrier and a reagent for green chemistry. However, large-scale production of hydrogen via electrolysis, as well as the production of many other chemical products, requires significantly cheaper and more efficient catalysts. A precise understanding of the electrochemical processes that take place at the interface between the solid catalyst and the liquid medium is highly useful for developing better electrocatalysts. In the journal Nature Communications, an European team has now presented a powerful model that determines charge separation at the interface, the formation of the electric double layer and local electric potential variations, and the resulting influence on the catalytic activity.
- Environmental Chemistry at BESSY II: Radicals in waterwaysHow do radicals form in aqueous solutions when exposed to UV light? This question is important for health research and environmental protection, for example with regard to the overfertilisation of water bodies by intensive agriculture. A team at BESSY II has now developed a new method of investigating hydroxyl radicals in solution. By using a clever trick, the scientists gained surprising insights into the reaction pathway.
- Theory meets practice – We’re heading back to HTW Berlin!The HZB’s BIPV consultancy office (BAIP) is once again coordinating and delivering the lecture series “Building-Integrated Photovoltaics”.