Designing polymer-based organic thin-film batteries towards IoT applications.

• Applicants: Privatdozent Dr. Gunther Brunklaus; Professor Dr. Rüdiger-A. Eichel; Professor Dr. Andreas Heuer
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Experimental and Theoretical Physics of Polymers ; Polymer Materials
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 441255373

Internet of things (IoT) appliances require batteries that are not only long lasting, environmentally friendly, save and cheap, but they also need to be capable of providing intermittent high current bursts during data transmission. Organic radical batteries potentially meet all these requirements. The goals of this project include optimization of multilayered polymeric organic batteries operating with lithium metal anodes towards higher power densities to accommodate short charge and discharge pulses required for IoT applications. To understand the underlying electron and ion transport mechanisms, a holistic approach comprising synthesis of organic cathode materials and specifically matched polymer electrolytes, in-depth electrochemical characterization, multimodal electron paramagnetic resonance (EPR) analyses and computational modeling will be employed. While a wide range of electro- and physicochemical measurements will be utilized to assess achievable performance of both materials and cell systems, especially with respect to charge/discharge at high C-rates and long-term cycling stability, tailored EPR techniques, including in operando spectro-electrochemical measurements, will play a central role to unravel distributions of radical species and their interaction within the cathode composite as a function of the state of charge. In this way, the relation between cell capacity and state of health on the one hand, and the radical density and electron mobility on the other hand will be established, which will be exploited to further optimize actual cell chemistries. To gain additional insight at the molecular level, molecular dynamics (MD) simulations will be applied to derive ionic diffusivities and conductivities both within the cathode composite and at cathode|electrolyte interfaces. These efforts will be helpful to interpret EPR, PFG-NMR and impedance data, as well as to design novel cathode and electrolyte materials with desired interfacial properties, thereby boosting charge transfer across electrodes within the cells. Molecular structures sampled from MD simulations will be subjected to quantum chemical calculations to obtain key parameters relevant for electron transport as well as EPR observables. Combined with the electrochemical data, these efforts will be utilized to enhance electronic transport in the cathodes experimentally. The gained knowledge will be exploited to develop a prototype of an all-polymeric ORB, thereby validating the synergistic approach for the design of cells and enabling IoT applications.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2248: Polymer-based batteries
• Co-Investigator: Professor Dr. Josef Granwehr