Chemical reaction studies of N-methyl-N-propyl-pyrrolidinium-bis(fluorosulfonyl)imide-based ionic liquid with the lithium metal surface were performed using ab initio molecular dynamics (aMD) simulations and X-ray Photoelectron Spectroscopy (XPS). The molecular dynamics simulations showed rapid and spontaneous decomposition of the ionic liquid anion, with subsequent formation of long-lived species such as lithium fluoride. The simulations also revealed the cation to retain its structure by generally moving away from the lithium surface. The XPS experiments showed evidence of decomposition of the anion, consistent with the aMD simulations and also of cation decomposition and it is envisaged that this is due to the longer time scale for the XPS experiment compared to the time scale of the aMD simulation. Overall experimental results confirm the majority of species suggested by the simulation. The rapid chemical decomposition of the ionic liquid was shown to form a solid electrolyte interphase composed of the breakdown products of the ionic liquid components in the absence of an applied voltage.

Study of the initial stage of solid electrolyte interphase formation upon chemical reaction of lithium metal and N-Methyl-N-Propyl-Pyrrolidinium-Bis (Fluorosulfonyl) Imide

Critical effects of electrolyte recipes for Li and Na metal batteries

Thermally Stable and Nonflammable Electrolytes for Lithium Metal Batteries: Progress and Perspectives

The solid-electrolyte interphase (SEI) is known to dictate the performance of a Li metal anode, where its inorganic compositions are primarily responsible for Li+ conduction, electron insulation, a...

Tailoring Electrolyte Solvation Chemistry toward an Inorganic-Rich Solid-Electrolyte Interphase at a Li Metal Anode

Perspective on solid-electrolyte interphase regulation for lithium metal batteries

Safe, Stable Cycling of Lithium Metal Batteries with Low‐Viscosity, Fire‐Retardant Locally Concentrated Ionic Liquid Electrolytes

Wide temperature cycling of Li-metal batteries with hydrofluoroether dilution of high-concentration electrolyte

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adfm.202070234

Ionic Liquid Electrolytes: Safe, Stable Cycling of Lithium Metal Batteries with Low-Viscosity, Fire-Retardant Locally Concentrated Ionic Liquid Electrolytes (Adv. Funct. Mater. 35/2020)

High-power Li-ion batteries (LIBs) are widely used in electric vehicles and grid storage applications and are therefore in high demand; however, their realization requires a fundamental understanding of electrochemical polarization arising during charge/discharge reactions. To date, electrochemical polarization is poorly understood because of the complexity of experimental measurements and the lack of a proper theory of the microscopic structure of the electrolyte solution and complicated interactions among solution species. The present work comprehensively reviews the components of this polarization and discusses their physicochemical nature, focusing on those due to (i) Ohmic polarization in the electrolyte, (ii) interfacial charge transfer, (iii) concentration gradients in solid and electrolyte phases, (iv) ion transport within the electrode pores, and (v) the electronic resistance of the composite electrode and current collector interface. We also briefly touch on today's understanding of the microscopic structure of LIB electrolytes and the experimental analysis of polarization sources, subsequently addressing the relative contributions of polarization components and their dependence on diverse parameters, for example, electrode/electrolyte materials and the dimensional factors of composite electrodes (thickness/porosity/tortuosity). Thus, this review is expected to assist the setting of correct battery R&D targets and aid the identification of delusive studies that lack a comprehensive understanding of the physicochemical nature of electrochemical polarization and therefore report unrealistic high-power performances.

Bonhyeop Koo

Papers

Safe, Stable Cycling of Lithium Metal Batteries with Low‐Viscosity, Fire‐Retardant Locally Concentrated Ionic Liquid Electrolytes

Wide temperature cycling of Li-metal batteries with hydrofluoroether dilution of high-concentration electrolyte

Ionic Liquid Electrolytes: Safe, Stable Cycling of Lithium Metal Batteries with Low-Viscosity, Fire-Retardant Locally Concentrated Ionic Liquid Electrolytes (Adv. Funct. Mater. 35/2020)

Physicochemical nature of polarization components limiting the fast operation of Li-ion batteries

A crystalline organic electrolyte for safe, room-temperature operable all-solid-state sodium batteries