Localized high-concentration electrolytes get more localized through micelle-like structures

Corey M. Efaw, Qisheng Wu, Ningshengjie Gao, Yugang Zhang, Haoyu Zhu, Kevin Gering, Michael F. Hurley, Hui Xiong, Enyuan Hu, Xia Cao, Wu Xu, Ji-Guang Zhang, Eric J. Dufek, Jie Xiao, Xiao-Qing Yang, Jun Liu, Yue Qi & Bin Li

November 2023 - Liquid electrolytes in batteries are typically treated as macroscopically homogeneous ionic transport media despite having a complex chemical composition and atomistic solvation structures, leaving a knowledge gap of the microstructural characteristics. Here, we reveal a unique micelle-like structure in a localized high-concentration electrolyte, in which the solvent acts as a surfactant between an insoluble salt in a diluent. The miscibility of the solvent with the diluent and simultaneous solubility of the salt 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 a typical localized high-concentration electrolyte peaks in localized cluster salt concentration near room temperature and is used to form a stable solid–electrolyte interphase on a Li metal anode. These findings serve as a guide to predicting a stable ternary phase diagram and connecting the electrolyte microstructure with electrolyte formulation and formation protocols of solid–electrolyte interphases for enhanced battery cyclability.

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