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In this study, the use of a closo-borate salt as an electrolyte for lithium-ion batteries (LIB) was evaluated in a series of solvent systems. The lithium closo-borate salts are a unique class of halogen-free salts that have the potential to offer some advantages over the halogenated salts currently employed in commercially available LIB due to their chemical and thermal stability. To evaluate this concept, three different solvent systems were prepared with a lithium closo-borate salt to make a liquid electrolyte (propylene carbonate, ethylene carbonate:dimethyl carbonate, and 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide). The closo-borate containing electrolytes were then compared by utilizing them with three different electroactive electrode materials. Their cycle stability and performance at various charge/discharge rates was also investigated. Based on the symmetrical cell and galvanostaic cycling studies it was determined that the carbonate based liquid electrolytes performed better than the ionic liquid electrolyte. This work demonstrates that halogen free closo-borate salts are interesting candidates and worthy of further investigation as lithium salts for LIB.
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This content will become publicly available on December 25, 2025
Revealing Lithium Ion Transport Mechanisms and Solvation Structures in Carbonate Electrolytes
Optimizing lithium-ion battery (LIB) electrolytes is essential for high-current applications such as electric vehicles, yet experimental techniques to characterize the complex structural dynamics within these electrolytes are limited. These dynamics are responsible for Li+ transport. In this study, we used ultrafast infrared spectroscopy to measure chemical exchange, spectral diffusion, and solvation structures across a wide range of lithium concentrations in propylene carbonate-based LiTFSI (lithium bis(trifluoromethanesulfonimide) electrolytes, with the CN stretch of phenyl selenocyanate as the long-lived vibrational probe. Phenyl selenocyanate is shown to be an excellent dynamical surrogate for propylene carbonate in Li+ solvation clusters. A strong correlation between exchange times and ionic conductivity was observed. This correlation and other observations suggest structural diffusion as the primary transport mechanism rather than vehicular diffusion. Additionally, spectral diffusion observables measured by the probe were directly linked to the de-solvation dynamics of the Li+ clusters, as supported by density functional theory and molecular dynamics simulations. These findings provide detailed molecular-level insights into LIB electrolytes’ transport dynamics and solvation structures, offering rational design pathways to advanced electrolytes for next-generation LIBs.
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- Award ID(s):
- 2319637
- PAR ID:
- 10590988
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Journal of the American Chemical Society
- Volume:
- 146
- Issue:
- 51
- ISSN:
- 0002-7863
- Page Range / eLocation ID:
- 35329 to 35338
- Subject(s) / Keyword(s):
- Lithium batteries, electrolytes, transport mechanisms, ultrafast infrared spectroscopy
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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