Developing superionic polymers for battery and fuel cell applications
18th July 2017, COLLOQUIUM, Hörsaal 2, Hörsaalgebäude II, TU Dortmund
Start: 18th July 2017 04:30 p.m.
End: 18th July 2017 05:30 p.m.
Prof. Dr. Alexei P. Sokolov, Oak Ridge National Laboratory, USA
Prof. Dr. Roland Böhmer, TU Dortmund University
Use of polymer electrolytes in batteries and fuel cells can significantly improve their performance. However, the limiting factor for the broad use of polymer electrolytes remains their relatively low ion and proton conductivity. We present an overview of the relationship between ion and proton transport and structural relaxation in polymer electrolytes, including polymerized ionic liquids (PolyIL). Analysis of the data revealed a significant influence of ion size and chain flexibility on segmental dynamics and ion transport in PolyILs. Based on these studies we proposed a model that can describe the dependence of the glass transition temperature on ion size and chain flexibility. Employing the modified Walden plot analysis we identified ‘superionic’ behavior for many polymer electrolytes and PolyILs, and demonstrate that the decoupling of ionic transport from structural relaxation might be the best way to design polymers with high conductivity. This decoupling increases for smaller ions and for more rigid chains, and we ascribe the decoupling phenomena to frustration in polymer chain packing. Similar ideas can be applied to proton conductivity. We demonstrate significant decoupling of proton mobility from structural relaxation and/or viscosity in a series of protic ionic liquids.