Elektrospun, ion-conducting polymer membranes as solid electrolytes

• Applicants: Professor Dr. Tom Nilges; Professor Dr. Leo van Wüllen
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 421749423

In the proposed project we intend to synthesize electrospun solid electrolytes composed by different ion-coordinating polymers and conductive salt additives. After determination and optimization of the electrochemical properties we intend to identify the underlying conduction mechanism for the ion transport through the membranes. Four different polymers, selected Li, Na and Mg conductive salts and additives will be used to prepare fiber membranes via electrospinning. Such membranes will be tested concerning their thermal, mechanical and electrochemical properties in order to identify the best performing ion conductive systems. Four different polymers, polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl¬ methacrylate (PMMA), polyvinylidene fluoride (PVdF), and selected dissolved conductive salts will be electrospun to fiber membranes which will be examined by thermal analysis, X-ray diffraction and temperature-dependent impedance spectroscopy according their crystallinity and ion conductivity afterwards. Selected ion conducting systems will be checked by solid state NMR spectroscopy to determine their local ion dynamics. Electrospun Li and Na-based conductive salt@polymer systems showed one to two orders of magnitude enhanced ion conductivity than comparable solution cased or hot-pressed samples with higher conductive salt concentration. The electrochemical stability of the two systems kept comparable. Even PVdF showed a significant enhanced ion conductivity as an electrospun LiBF4@PVdF membrane. After the successful synthesis and characterization of electrospun solid electrolyte membranes we will enhance and optimize the mechanical and electrochemical properties by lubricants and nano-scaled inert materials. Based on the spectroscopic results we will derive the underlying conduction mechanisms of the different membrane systems. Due to the intrinsic anisotropy of the fiber membranes this mechanism will be significantly different than for the state-of-the-art solution-casted of hot-pressed samples. We intend to achieve electrospun solid state electrolyte systems with conductivities > 10−3 S cm−1 at room temperature, thermal stability > 80°C and a sufficient mechanical and electrochemical stability. The aim is to understand the increase of the ion mobility and conductivity of the electrospun membranes compared with conventionally synthesized solution-casted or hot-pressed systems, and to optimize such systems for a potential usage in sild state battery and super capacitor applications.

• DFG Programme: Research Grants