Rattling transport of Li+ ions in the cavities of Model Solid Electrolyte Interphases

Aashish, T and Mallik, Bhabani Shankar (2019) Rattling transport of Li+ ions in the cavities of Model Solid Electrolyte Interphases. Masters thesis, Indian institute of technology Hyderabad.

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Abstract

Efficient Energy storage devices have revolutionised 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 our work we focus on one such feature, we probe the diffusion of lithium ion (Li+) in alkyl carbonates as model Solid Electrolyte Interphases (SEI). 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 increasing the chain length of the alkyl group and the temperature. Our research is devoted to three molecules as potential SEI components - lithium methyl carbonate (LMC), lithium ethyl carbonate (LEC) and lithium butyl carbonate (LBC). We elucidate the ionic transport by calculating the Mean squared displacement, Radial distribution curves, Binding energy, 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 demonstrate 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 poor diffusion observed in these SEI constituents.

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