To achieve higher energy density batteries while maintaining battery safety, better understanding is needed of processes such as solid-electrolyte interphase (SEI) formation due to electrolyte decomposition at the electrode surface. Research has historically been hindered by a lack of methods to directly probe electrochemical processes during battery cycling; more recently, several approaches have been developed to address this. We have developed a small-angle neutron scattering (SANS) based approach to observe electrochemical processes utilizing an ordered mesoporous hard carbon electrode with a high surface area that is of interest for high capacity, high power applications. The talk will present work on several electrolytes and modified electrodes examined by SANS - what has been learned about how the SEI forms and the microstructure of hard carbon electrodes changes during cycling, and what the implications are for battery design.