Material-structure-property relations in bifunctional electrodes for metal oxygen batteries revealed with homogenous material synthesis and advanced operando analysis

• Applicant: Professor Dr.-Ing. Daniel Schröder
• Subject Area: Synthesis and Properties of Functional Materials ; Energy Process Engineering
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 514804331

For full utilization of renewable energy, large-scale batteries with high energy efficiency and high reversibility are strongly required for balancing the renewable energy production and society’s energy consumption. Metal–oxygen (or metal–air) batteries are promising for this purpose, with their low-cost, abundant, recyclable and highly safe constituents. However, they are suffering from poor performance of the electrode materials, both in activity and durability, due to low catalytic activity of bifunctional catalysts used for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during discharging and charging at the cathode, respectively. For solving this problem, the Japanese side applicants have proposed an innovative bilayer design for the oxygen electrodes that allows the use of optimized single-functional instead of bifunctional catalysts, and proved that the activity and durability can be improved. Further efforts are needed to develop highly active catalysts. Nitrogen-doped carbon and layered double hydroxides are known as promising ORR and OER catalysts, but their optimization has been challenging due to compositional inhomogeneity caused by the conventional synthetic methods. Here, the Japanese-side applicants propose novel synthetic methods based on material science to minimize the inhomogeneity. On the other hand, even if improved catalysts are developed, the bilayer design needs further development to match each optimized catalyst. To do so, it is necessary to establish experimental and model-based methods to exactly comprehend what reactions might occurs in the electrodes. While the Japanese side applicants have only limited experience in these areas, the German side applicants can offer broad experience to understand such phenomena, including nonlinear electrochemical impedance spectroscopy (NEIS), hydrodynamic linear sweep voltammetry (HLSV) with rotating ring disk electrodes (RRDE), time of flight acoustic measurements (AE), X-ray tomography and operando X-ray diffraction. Furthermore, the German side is capable to conduct physico-chemical modeling to gain better insight into the occurring processes. Accordingly, the collaboration between the Japanese and German applicants can achieve the goal of establishing highly active and durable oxygen electrode technology for metal–oxygen batteries. In addition, both Japanese and German sides are planning to exchange young faculty members and students to share knowledge with the counterpart and obtain feedback for further improvement in their tasks. The obtained results within the project will be transferred into teaching modules for bachelor and master course students in both countries. The derived understanding on the technology and methodology can potentially be transferred to the technological level for not only metal–oxygen batteries but also application in fuel cells and water electrolysis.

• DFG Programme: Research Grants
• International Connection: Japan
• Cooperation Partners: Professor Hajime Arai; Professor Atsunori Ikezawa; Professor Keiko Waki
• Co-Investigator: Dr. Katja Kretschmer