1-Ethyl-3-methylimidazolium tetrafluoroborate is an ionic liquid used in the recycling of osmium in the dihydroxylation of olefins with osmium (VIII) oxide. Studies show 1-Ethyl-3-methylimidazolium tetrafluoroborate can affect lysozyme amyloid fibrillization and has a more prominent effect on morphology and thermal stability.

1-ethyl-3-methylimidazolium tetrafluoroborate as an electrolyte additive

A 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI–BF4) ionic liquid is introduced into an electrolyte as a functional additive to enhance the low-temperature performance of LiNi0.5Co0.2Mn0.3O2 (NCM523)/graphite batteries. Linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) tests show that EMI–BF4 can be oxidized in advance and produce low impedance solid-electrolyte interphase (SEI) films on the electrode surfaces. Compared with the batteries without the EMI–BF4 additive, the capacity retention of the NCM523/graphite batteries with 1% 1-Ethyl-3-methylimidazolium tetrafluoroborate additive is enhanced from 82.3% to 93.8% after 150 cycles at a low temperature of ?10?°C. In addition, at ?30?°C, the discharge capacity of the batteries with 1% EMI–BF4 additive is nearly doubled. And at the room temperature of 25?°C and after 400 cycles, the capacity retention also increases from 80.3% to 85.9%, and the coulomb efficiency remains at approximately 100%. These results demonstrate that 1-Ethyl-3-methylimidazolium tetrafluoroborate used as a functional electrolyte additive has promising prospects for application to improve the low-temperature performance of NCM523-based lithium-ion batteries.[1]

To investigate the effect of the 1-Ethyl-3-methylimidazolium tetrafluoroborate addition on the ionic conductivity, the ionic conductivities of the electrolytes containing 0, 0.5, 1, 2, and 5% EMI–BF4 were measured at different temperatures. Overall, it can be seen that the ionic conductivity is related to the temperature, and the drop in the temperature will lead to a decrease in the ionic conductivity. Above 0?°C, 1-Ethyl-3-methylimidazolium tetrafluoroborate has almost no observable effect on the ionic conductivity of the electrolyte due to the limited addition amount. By contrast, the addition of EMI–BF4 has a positive influence on the ionic conductivity when the temperature drops to between 0?°C and ?40?°C. In summary, an ionic liquid EMI–BF4 was developed as an electrolyte additive to participate in the construction of a stable low-impedance SEI on the cathode and anode surfaces of the NCM532/graphite batteries. While improving the cycle performance of the NCM532/graphite full cells at low temperatures, it also improves the cycle stability of the cells at room temperature. The addition of EMI–BF4 additives in the electrolyte with a mass ratio of 1% significantly improved the electrochemical performance characteristics of the NCM532/graphite batteries and proved the feasibility of using ionic liquids in LIBs. In addition, it is possible to screen out a large number of groups that contribute to the performance improvement of NCM532/graphite batteries and then use the expected adjustability of the ionic liquids to design a series of new additives and functional electrolytes to match the requirements of LIBs.

Effect of 1-Ethyl-3-methylimidazolium Tetrafluoroborate on Lysozyme

The effect of 1-Ethyl-3-methylimidazolium tetrafluoroborate is more prominent than EMIM-ac due to the different specific interactions of the anionic part with the protein surface. Although both ILs induced formation of amyloid fibrils with typical needle-like morphology, a higher variability of fibril morphology consisting of a different number of intertwining protofilaments was identified for EMIM-BF4.. The effect of 1-Ethyl-3-methylimidazolium tetrafluoroborate and EMIM-ac on the kinetics of lysozyme amyloid fibrillization was studied by Thioflavin T (ThT) fluorescence assay. The restriction of free rotations of benzylamine and benzothiazole rings of ThT upon binding with amyloid fibrils leads to the increase of its fluorescence signal that is used to quantify the amount of fibrils. The thermal stability of lysozyme decreases dose-dependently in the presence of studied ILs. With increasing EMIM-BF4 concentration the transition temperatures Td are shifted to lower values. The DSC measurements support these suggestions. In the presence of EMIM-BF4, a lower ΔH was found compared to the ILs-free conditions or EMIM-ac at given concentrations, showing that less energy is required for the protein thermal denaturation in the presence of EMIM-BF4. In the case of EMIM-ac, the acetate ion interacts locally with the protein β-domain loop and C-helix via hydrogen bonding and van der Waals interactions, which may be responsible for the slightly weaker effect of EMIM-ac in comparison with 1-Ethyl-3-methylimidazolium tetrafluoroborate on the thermal stability of lysozyme.[2]

We distinguished several fibril types consisting of a various number of protofilaments and protofibrils intertwining into mature fibrils. The secondary structure of fibrils formed in different ILs varies only within the 3–4% range for particular secondary structure motifs. The fibrils prepared in 1% EMIM-ac have slightly higher content of β-sheet conformations and unordered structure and lower content of α-helix and β-turns than 1-Ethyl-3-methylimidazolium tetrafluoroborate. We assume that EMIM-BF4 induces formation of fibrils with more complex architecture by affecting the protein hydration and facilitating the hydrophobic interactions. In the presence of EMIM-BF4, a lower ΔH was found compared to the ILs-free conditions or EMIM-ac at given concentrations, showing that less energy is required for the protein thermal denaturation in the presence of 1-Ethyl-3-methylimidazolium tetrafluoroborate In the case of EMIM-ac, the acetate ion interacts locally with the protein β-domain loop and C-helix via hydrogen bonding and van der Waals interactions, which may be responsible for the slightly weaker effect of EMIM-ac in comparison with EMIM-BF4 on the thermal stability of lysozyme.

References

[1]Wang, W., Yang, T., Li, S., Fan, W., Zhao, X., Fan, C., Yu, L., Zhou, S., Zuo, X., Zeng, R., & Nan, J. (2019, September 10). 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF?) as an ionic liquid - type electrolyte additive to enhance the low - temperature performance of LiNi?.?Co?.?Mn?.?O?/graphite batteries. Electrochimica Acta, 317, 146 - 154.

[2]Fedunova D, Antosova A, Marek J, Vanik V, Demjen E, Bednarikova Z, Gazova Z. Effect of 1-Ethyl-3-methylimidazolium Tetrafluoroborate and Acetate Ionic Liquids on Stability and Amyloid Aggregation of Lysozyme. Int J Mol Sci. 2022 Jan 11;23(2):783. doi: 10.3390/ijms23020783. PMID: 35054967; PMCID: PMC8775716.