A Systematic Study on the Effects of Solvating Solvents and Additives in Localized High‐Concentration Electrolytes over Electrochemical Performance of Lithium‐Ion Batteries

Abstract

Localized high‐concentration electrolytes (LHCEs) based on five different types of solvents were systematically studied and compared in lithium (Li)‐ion batteries (LIBs). The unique solvation structure of LHCEs promotes the participation of Li salt in forming solid electrolyte interphase (SEI) on graphite (Gr) anode, which enables solvents previously considered incompatible with Gr to achieve reversible lithiation/delithiation. However, the long cyclability of LIBs is still subject to the intrinsic properties of the solvent species in LHCEs. Such issue can be readily resolved by introducing a small amount of additive into LHCEs. The synergetic decompositions of Li salt, solvating solvent and additive yield effective SEIs and cathode electrolyte interphases (CEIs) in most of the studied LHCEs. This study reveals that both the structure and the composition of solvation sheaths in LHCEs have significant effect on SEI and CEI, and consequently, the cycle life of energetically dense LIBs.

Unveiling the Role of Fluorination in Hexacyclic Coordinated Ether Electrolytes for High-Voltage Lithium Metal Batteries

“…The solvation ability of fluorinated ethers ranks as EMP > F1EMP > F2EMP > F3EMP. On the one hand, the increased AGG and CIP solvation structures due to weaker solvation of highly fluorinated ethers are beneficial for generating passivation layers on Al current collector and Ni-rich cathodes. ,, On the other hand, decreased SSIP shall seriously hinder the ionic diffusion. , Thus, the electrochemical properties of electrolytes and ultimately the cycling performances of LMBs still need rigorous evaluation.…”

“…16,21,22 On the other hand, decreased SSIP shall seriously hinder the ionic diffusion. 46,47 Thus, the electrochemical properties of electrolytes and ultimately the cycling performances of LMBs still need rigorous evaluation.…”

Ion Transport in (Localized) High Concentration Electrolytes for Li-Based Batteries

“…High concentration electrolytes (HCEs) have gained significant attention over the past decade for their lower flammability, advantageous interfacial properties, and promise of enabling lithium metal anodes and high-voltage cathodes. − While promising from an interfacial standpoint, HCEs are more expensive and have lower conductivity and have significantly higher viscosity than traditional ∼1 M electrolytes. Recently, localized high concentration electrolytes (LHCEs), where an inert nonsolvating but miscible diluent is added to high concentration electrolytes, have been proposed as a lower cost alternative to HCEs that still possesses favorable interfacial properties. − …”

“…As expected from the increase in viscosity with increasing molality (i.e., decreasing solvent to salt ratio), D i self decreases for all species as molality increases. In both LCHE systems, the TTE self-diffusion coefficient is significantly higher than that of either ion or the DMC, an indication that the TTE is not part of the primary ion solvation sheath . This is in agreement with solvent structures obtained from ab initio molecular dynamics and Raman measurements. , Examining the product of self-diffusion coefficients and viscosity, ηD i self is relatively constant for DMC molecules across the entire studied range of salt concentration, suggesting solvent self-diffusion can largely be explained by changes in solution viscosity (see Figure b).…”

“…Recently, localized high concentration electrolytes (LHCEs), where an inert nonsolvating but miscible diluent is added to high concentration electrolytes, have been proposed as a lower cost alternative to HCEs that still possesses favorable interfacial properties. 6 − 8 …”