PNNL

Abstract

Graphite stands out as the preferred anode material in commercial lithium-ion batteries (LIBs). However, its limited compatibility with diverse organic molecules poses a significant challenge in selecting electrolyte solvents for LIBs. The issue arises from the co-intercalation of solvent molecules into the graphite layer alongside Li ions, resulting in layer exfoliation. This constraint has left few choices for electrolyte solvents, primarily relying on ethylene carbonate (EC)-based mixed solvents. Consequently, the translation of electrolyte advancements from the past three decades into practical LIBs has been hindered. In this study, we present electrolytes exhibiting a micelle-like structure designed to impede the liquid-phase exfoliation of the graphite layer. The micelle-like electrolyte structure, derived from concentrated long-chain lithium salts, effectively segregates Li ions from free diethylene carbonate (DOL) solvent molecules. This segregation mitigates interactions between graphite particles and free solvent molecules during Li intercalation. Our proposed mechanism provides valuable insights, elucidating the exceptional stability of graphite in numerous unstable solvents with concentrated long-chain lithium salts, such as LiTFSI. These findings offer a pivotal guideline for enhancing LIB performance by overcoming electrolyte limitations on graphite anodes.