Vibrational spectroscopic and density functional studies on ion solvation and ion association of lithium tetrafluoroborate in 4-methoxymethyl-ethylene carbonate

Concentration Effects on the Entropy of Electrochemical Lithium Deposition: Implications for Li+ Solvation

“…Qiao et al studied the ion contact pair formation of LiBF 4 in 4-methoxymethyl-ethylene carbonate (MEC) at different temperatures. 27 They report a Raman band corresponding to ion contact pair interactions even for their measurement with the lowest concentration (0.26 mol·L −1 ). The intensity of the band increased with concentration.…”

Solvation Structure and Dynamics of the Lithium Ion in Organic Carbonate-Based Electrolytes: A Time-Dependent Infrared Spectroscopy Study

“…Previous studies reported a Li + solvation shell consisting of 2 to 6 carbonates in the first coordination sphere. − ,− Since the interaction energy between Li + and carbonates is 45–60 kcal/mol, ,, it is expected that Li + will have a stable solvation shell with specific signatures in the IR spectrum. The FTIR spectra (Figure ) show only two peaks for both electrolytes at X (Li + ) > 0.…”

“…While Li + favors tetrahedral coordination in many solvents, − the coordination number of Li + in organic carbonates has been postulated to be between 2 and 6. − ,− Considering all Li + –carbonate complexes with a Li + coordination in this range, only solvation complexes with 2, 3, 4, and 6 coordinated molecules should have a single IR active vibrational transition, which discards 5 as a possible coordination number. In addition, a solvation structure containing 6 carbonates should have two Raman active transitions besides the single IR active mode, while those containing 2, 3, or 4 carbonates should only have one additional Raman active transition .…”

“…Numerous experimental − and theoretical methodologies ,− have been used to investigate the lithium ion (Li + ) solvation shell structure or the organic carbonate-based electrolytes. However, simple molecular structural characteristics remain controversial.…”

“…However, simple molecular structural characteristics remain controversial. For example, the coordination number of Li + has been proposed to be between 2 and 6 in organic carbonates, with most studies suggesting a coordination number of either 4 or 6. − ,− Presently, there is still no definitive answer to the nature of the Li + coordination in carbonate-based electrolytes. Moreover, there is also not a clear understanding of how the structure of the carbonate affects the conductivity and viscosity of the electrolyte …”