The objective of the research project was the further development of the PSI membrane technology for redox flow batteries with a view to a commercial implementation. The PhD thesis project comprised a continued development of the membrane chemistry by changing the composition of the graft component for improved oxidative stability. A patent application describing this new chemistry has been filed. Furthermore, the vanadium transport properties across different membrane types has been studied in detail. The amphoteric ion-exchange membrane from PSI hereby showed a clear advantage over commercial membranes. A work package on method development was devoted to the study and implementation of an accelerated stress test (AST) to characterize oxidative stability of membranes. By exposing membranes to a solution of cerium(IV) at elevated temperature (up to 80°C), an acceleration factor for degradation of up to 200 could be attained. This method can greatly help to screen membranes and assess their suitability for vanadium redox flow battery applications. In parallel to this project, technology implementation efforts continued, and in March 2019 the PSI spin-off ‘Gaia Membranes’ was founded. The CTO is Fabio J. Oldenburg, who was the PhD student behind this project. The ‘demonstrator’ work package of this project supported the scale-up efforts of Gaia Membranes to allow supply of first batches of membranes to customers for evaluation and demonstration purposes. Future work is aimed, on the one hand, at further research in the framework of a follow-up PhD study, and, on the other hand, at continuing the implementation of PSI membrane technology and collaboration with the Gaia Membranes.