PNNL

Abstract

Liquid electrolytes in batteries are typically treated as macroscopically homogeneous ionic transport media despite having complex chemical composition and atomistic solvation structures, leaving a knowledge gap of microstructural characteristics. Here, we reveal a unique micelle-like structure in a localized high-concentration electrolyte (LHCE), in which the solvent acts as a surfactant between immiscible salt and diluent. The miscibility of the solvent with both the salt and the diluent results in a micelle-like structure with a smeared interface and an increased salt concentration at the centre of the salt-solvent clusters that extends the salt solubility. These intermingling miscibility effects have temperature dependencies, wherein the localized cluster salt concentration peaks at 25°C and is utilised to form a stable solid-electrolyte interphase (SEI) for optimized performance of Li-metal anode. These findings serve as a guide to connecting the electrolyte microstructure with SEI formation protocols to realise Li-metal batteries.