Unraveling Degradation Mechanisms in Polymer-Based Dual-Ion Batteries and Development of Countermeasures for Performance Optimization

• Applicants: Dr. Tobias Placke; Professor Dr. Ulrich S. Schubert
• Subject Area: Polymer Materials ; Solid State and Surface Chemistry, Material Synthesis ; Synthesis and Properties of Functional Materials ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 441233025

Polymer-based batteries are considered as future candidates for sustainable energy storage, motivated by low-energy consuming processes during production of polymers, easy recyclability of the battery cells as well as the utilization of more abundant materials and replacement of critical metals. However, up to date, polymer-based batteries still suffer from various challenges in terms of their electrochemical performance, including poor energy density or cycling stability. In particular, there is still a significant lack of fundamental understanding of the capacity fading mechanisms and aging mechanisms at the electrode/electrolyte interfaces, i.e., of the three-dimensional “interphases” formed at the positive and negative electrodes.In this project, a special type of polymer-based battery will be systematically investigated, i.e., a so-called polymer-based dual-ion battery (DIB) using n- and p-type organic materials for simultaneous storage of cations and anions, respectively. The DIB system differs from the classical cation or anion rocking-chair-type polymer batteries, as both charge carriers, cations and anions, are involved in the dual-ion storage mechanism. This offers various advantages such as a high versatility of possible cation-anion combinations as well as typically a high cell voltage, which might be achieved by suitable host polymer materials. Different strategies will be pursued within this project in order to develop polymer-based DIB systems having an improved energy density and stability. These approaches include (I) the design of new polymeric materials featuring a higher positive electrode potential (“voltage tuning”), (II) the development of hybrid systems such as graphite || polymer systems offering a high cell voltage, (III) all-polymer DIB systems, focusing on different concepts including ambipolar polymers and a “reverse all-polymer DIB system”. The different polymer DIB systems will be comprehensively studied in terms of their electrochemical performance, with particular focus on the impact of the electrolyte and interphases on the reversible capacity and stability during prolonged charge/discharge cycling. For this purpose, the electrolyte will be specifically designed for each polymer system following different strategies such as the use of highly concentrated electrolyte or the addition of electrolyte additives for interphase design and stability enhancement. Furthermore, different ex-situ and in-situ analyses will be applied to gain sig¬nificant and comprehensive insights into mechanistic properties of cation/anion storage, stability of the polymer materials and the role of the interphase formation.It is expected that the fundamental insights gained in this project will be of high importance for the development of improved polymer active materials and optimized electrolytes for polymer-based DIB cells with high energy density and cycling stability.

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