As batteries evolve toward higher cell voltage and capacity, developing detailed knowledge of the electrolyte-electrode interface is critically important. The chemical composition and morphology of interphases dictate not only the reversibility (cycle or calendar life), but also the kinetics of the cell chemistry (power density), and it has been well-recognized that the complicated interplay among electrolyte components (solvent, salt anion, additive) and electrode surfaces affect interphasial properties. Our efforts focus on designing new electrolytes to increase the electrochemical stability window. One way to reach that goal is to modify the SEI through electrolyte composition. To advance these efforts and understand the underlying chemistry at electrolyte-electrode interfaces, we perform in operando EC-AFM and in situ confocal Raman experiments, often supported by XPS and DFT studies.  With these techniques we investigate the dependence on electrolyte composition on SEI formation, composition, and morphology on graphitic anodes and the elusive interphase on graphitic and thin film LNMO cathodes. The results of such investigations aid in the design of electrolytes that advance lithium ion battery technology and expand beyond traditional lithium ion chemistry to emerging energy storage types such as sodium ion and aqueous systems, which interfaces we have begun to study. This presentation will provide an overview of electrolyte-electrode interactions we have studied and their influence on interphases.