Efficient energy storage devices have revolutionized the way we use modern technology. Over two decades of research enabled the creation of lithium-ion cells with high recyclability, specific energy, and stability. Despite extensive research, certain aspects of lithium-ion cells continue to pose a challenge. In the current study, we focus on one such feature; we probe the diffusion of lithium ion (Li+) in alkyl carbonates as model solid electrolyte interphases (SEIs). These interphases have a complex composition, offer high resistance, and yet are an indispensable part of the cell. In this study, we unveil the effects of an increasing number of carbon atoms in the chain length of the alkyl group and the temperature. Our research is devoted to three chemical entities as potential SEI components: Lithium methyl carbonate, lithium ethyl carbonate, and lithium butyl carbonate. We elucidate the ionic transport by calculating the mean squared displacement, radial distribution curves, binding energy, and van Hove functions and by applying electric fields. Our findings on structure factor plots reveal similarities with ionic liquids; calculation of Young's modulus from a series of isothermal-isobaric simulations demonstrates a decreasing trend in mechanical strength for systems with extended alkyl groups. Based on the evidence from these properties, we propose that increasing the chain length does not enhance the diffusion observed in these SEI constituents. Copyright © 2019 American Chemical Society.