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Abstract
Understanding the interfacial reactivity of aqueous electrolytes is crucial for their use in future batteries. We investigate the reactivity of the bis(trifluoromethane)sulfonimide (TFSI) anion when exposed to a strong alkaline medium, by means of ab initio molecular dynamics and enhanced sampling techniques. In particular, we study the nucleophilic attack by the hydroxide anion, which was proposed as a mechanism for the formation of the solid electrolyte interphase at the negative electrode with water-in-salt electrolytes. While in the gas phase we recover a stable gaseous product, namely fluoroform, we observe the formation of trifluoromethanol in strong basic conditions, which then rapidly deprotonates to form CF3O-. This anion was suggested recently as a key compound leading to the formation of a solid electrolyte interphase on an Si-C anode. Such an approach could be leveraged to discover convenient additives leading to the formation of a stable interphase.
Content
Supplementary material
Supporting Information
Technical details about the molecular dynamics simulations.
Gas phase reaction
Reaction mechanism in gas phase from the products state (fluoroform and the N(SO$_2$CF$_3$)SO$_3$ anion) to the reactants state (TFSI and OH$^-$)
Liquid phase reaction
Reaction mechanism under basic aqueous conditions from the reactants state (TFSI and OH$^-$) to the unexpected products state (trifluoromethanol and the N(SO$_2$CF$_3$)SO$_2$ anion)
