Anion Solvation in Carbonate-Based Electrolytes

Abstract

With the correlation between Li + solvation and interphasial chemistry on anodes firmly established in Li-ion batteries, the effect of cation−solvent interaction has gone beyond bulk thermodynamic and transport properties and become an essential element that determines the reversibility of electrochemistry and kinetics of Li-ion intercalation chemistries. As of now, most studies are dedicated to the solvation of Li + , and the solvation of anions in carbonate-based electrolytes and its possible effect on the electrochemical stability of such electrolytes remains little understood. As a mirror effort to prior Li + solvation studies, this work focuses on the interactions between carbonate-based solvents and two anions (hexafluorophosphate, PF 6 − , and tetrafluoroborate, BF 4 −) that are most frequently used in Li-ion batteries. The possible correlation between such interaction and the interphasial chemistry on cathode surface is also explored.

Revealing electrolyte oxidation via carbonate dehydrogenation on Ni-based oxides in Li-ion batteries by in situ Fourier transform infrared spectroscopy

“…Energy & Environmental Science (B1813 cm À1 ) and oligomer (B1820 cm À1 ) features were convoluted between the VC (B1830 cm À1 ) and EC (B1800 cm À1 ) features, and they were less observable than in LP57 (Fig. 2b), possibly because the transformation to VC is faster or greater in LiClO 4 due to the less dissociative LiClO 4 salt 87,88,99,100 and more free solvents in the electrolyte, giving rise to more dominant VC features. DFT calculations show that the solvent molecules are stabilized with Li + interaction, while free solvents have higher energy levels of highest occupied molecular orbital (HOMO) and decreased stability against oxidation, 88,102,103 where here we also show the higher tendency towards dehydrogenation with the less dissociative LiClO 4 salt and less Li + -coordinated solvents.…”

Progress in Aqueous Rechargeable Sodium‐Ion Batteries

“…Due to the coexistence of Lewis basicity of its oxygen site and Lewis acidity of its hydrogen site, water could solvate most salts to form the solvation structure. In the Na + dilute solutions, the primary and secondary solvation shells typically contain an Na‐ion coordinated with six water molecules, due to largely free water molecules available . Traditionally, the dilute Na‐ion solutions are employed as the electrolytes for ASIBs due to their high ionic conductivity and low cost.…”

Properties of Ion Complexes and Their Impact on Charge Transport in Organic Solvent-Based Electrolyte Solutions for Lithium Batteries: Insights from a Theoretical Perspective

“…Whereas the solvation behavior of lithium ions is often studied by various computational approaches (for a recent overview, see Refs. [55,56,82]), it is often assumed that anions reveal only a weak solvation behavior, which is of minor importance for the electrochemical performance of standard LIB or LMB electrolyte solutions [164,165]. The underlying assumption can be related to the abundant usage of high donor number solvents such as EC or PC in combination with the HSAB principle, which both predict a strong coordination of the solvent molecules around the hard cations, whereas the coordination of hard solvents around soft anions is energetically less favorable [38].…”