(177a) Catalytic Synthesis of CO?-Based Bmec for Safer Lithium Battery Electrolytes: In Situ FTIR Study of Thermal Behavior

The flammability of conventional carbonate-based electrolytes remains a significant barrier to the thermal safety of lithium-ion batteries. As a promising alternative, bis(2-methoxyethyl) carbonate (BMEC), a CO₂-derived linear carbonate, exhibits a high flash point (121 °C) and favorable Li-ion solvation properties [1]. Building on our previous synthesis of BMEC via transesterification, we developed an improved route based on the catalytic alcoholysis of ethylene carbonate (EC) with 2-methoxyethanol under reactive distillation, allowing high-yield production of BMEC with simplified separation.

Given the high Li⁺ transference observed in BMEC-based electrolytes (t₊ = 0.56), compared to 0.27 for conventional EC/DEC systems, we conducted temperature-dependent in situ Fourier transform infrared (FTIR) spectroscopy to examine the underlying solvation structure. In situ FTIR was used to probe the thermal coordination of Li⁺ in BMEC-based electrolytes. Sustained interactions between Li⁺ and the carbonate and ether groups at elevated temperatures would support a strong solvation environment, potentially explaining the high Li⁺ transference number observed. This work demonstrates a simple and efficient catalytic route for producing functional battery solvents from CO₂-based feedstocks while addressing critical safety and transport challenges in lithium-ion batteries.

References

[1] Lee, J.; Jeon, A.-R.; Lee, H. J.; Shin, U.; Yoo, Y.; Lim, H.-D.; Han, C.; Lee, H.; Kim, Y. J.; Baek, J.; Seo, D.-H.; Lee, M. Molecularly Engineered Linear Organic Carbonates as Practically Viable Nonflammable Electrolytes for Safe Li-Ion Batteries. Energy Environ. Sci. 2023, 16, 2924–2933. https://doi.org/10.1039/d3ee00157a.