The accelerated development of materials for utilization in electrical energy storage systems will hinge critically upon our understanding of how interfaces (particularly electrode-electrolyte solid liquid interfaces) control the physical and electrochemical energy conversion processes in energy storage systems. A prime example is found in Lt ion-based battery systems, where a passive multiphase layer grows at the electrode/electrolyte interface due to the decomposition of the liquid electrolyte [ l]. Once formed, this solid electrolyte interphase (SEI) protects the active electrode materials from degradation and also regulates the transport and intercalation of Lt ions during battery charge/discharge cycling [2]. Due to the dynamically evolving nature of this nm-scaled interface, it has proven difficult to design experiments that will not only elucidate the fundamental mechanisms controlling SEI nucleation and growth, but will enable the SEI microstructural and chemical evolution as a function of charge/discharge cycling to be monitored in real time.