Lithium-ion batteries face insufficient capacity at low temperatures. The lithium-ion desolvation process in the vicinity of a solid electrolyte interphase (SEI) layer is considered the major problem. Thus, an accurate determination of lithium-ion solvation structures is a prerequisite for understanding this process. Here, using a cryostat combined with an FTIR spectrometer, we found that as the temperature decreased, the number of coordinating carbonates in the first solvation shell of the lithium ion increased with a decreased population of the contact ion pair (CIP). More specifically, we found that two or more carbonate molecules replace a single PF6- anion upon CIP dissociation. This experimental finding shows that the prevailing notion that four carbonate molecules coordinate each lithium ion to form a tetrahedral structure is invalid for describing lithium-ion solvation structures. We anticipate that the present work will elucidate one of the molecular origins behind the low performance of lithium-ion batteries at low temperatures.
Bibliographical noteFunding Information:
This work was supported by the Institute for Basic Science (IBS-R023-D1) (M.C.) and the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (NRF-2020R1A2C2010675, NRF-2020R1A5A1019141) (K.K.).
© 2022 American Chemical Society.
ASJC Scopus subject areas
- Materials Science(all)
- Physical and Theoretical Chemistry