The increasing awareness of the negative impacts humanity has on the global ecosystem resulted in an ever growing demand for a more sustainable energy and material consumption over the past decades. Environmentally benign electricity generation and energy storage represent two of the key technological approaches to address this issue. In this context, organic radical batteries (ORB) and redox flow batteries (RFB) possess significant advantages as energy storage technologies due to the sustainable material basis they rely on and the performance characteristics they offer. However, while material development is continuously advancing in this research field, methods for the proper characterization and performance optimization of ORBs and RFBs still need to keep pace with this development to exploit the full potential of these technologies. This thesis, therefore, aims to contribute with a physical perspective to the investigation and optimization of these novel energy storage systems. In particular, porous electrode morphologies in ORBs and special methods to produce them are investigated. Furthermore, non-conventional cell designs for the electrochemical reactors of RFBs are investigated and their impact on the performance parameters of the RFB are explored. Finally, two methods for the reliable and accurate measurement of the electrolytes' state-of-charge as one of the most important key parameters were developed and characterized.