Lithium-Ion Battery Electrolyte Miscibility Studied By Spectroscopy

Abstract

Interfaces, interphases, and surfaces are of immense interest to the battery research community since the key reactions and much of the kinetics that determine the performance of the cell occur there. While solid/liquid and solid/solid interfaces have been thoroughly studied, liquid/liquid interfaces have attracted much less attention.Here we target the liquid/liquid interfaces between two liquid electrolytes, employed to create dual electrolyte batteries. The grand idea is that based on two either chemically or mechanically immiscible electrolytes we can expand the overall electrochemical stability window to achieve both high electrolyte oxidation stability on the positive electrode and efficient and stable solid electrolyte interphase (SEI) formation on the negative electrode [1][2].To understand the dual electrolyte systems created we study diffusion across the liquid/liquid interfaces, the formation of any emulsion layers, and if there are chemical reactions occurring. We use confocal Raman spectroscopy focusing on the interface between two porous separators soaked with two different electrolytes as well as in situ Raman depth profiling with micrometer resolution, including the role of pressure to the stack of separators (both glass fibre and polymer based).The observations of for example diffusion and mixing are subsequently correlated with the physicochemical properties of the two electrolytes in order to pave the way for rational design of a dual electrolyte cell.[1] S. He, S. Huang, Y. Zhao, H. Qin, Y. Shan and X. Hou. “Design of a Dual-Electrolyte Battery System Based on a High-Energy NCM811-Si/C Full Battery Electrode-Compatible Electrolyte”. ACS Applied Materials & Interfaces 2021 13 (45), 54069-54078. DOI: 10.1021/acsami.1c17841[2] Ren, Y., Manthiram, A., “A Dual-Phase Electrolyte for High-Energy Lithium–Sulfur Batteries. Adv. Energy Mater”. 2022, 12, 2202566. https://doi.org/10.1002/aenm.202202566