During the first cycle of an alkali battery, a passivation layers forms on the electrode surface called the solid electrolyte interphase (SEI), which can grow upon further cycling. This is believed to be related to the significant first-cycle capacity loss observed in disordered carbon electrodes in both alkali ion batteries. We wish to investigate the influence of changing the electrolyte from carbonate-based to ether-based on subsequent SEI formation and growth, providing a real-time verification of various ex situ studies. Understanding the nature of SEI growth is extremely important in the search for better batteries.