Predicted Operando Polymerization at Lithium Anode via Boron Insertion

Abstract

Concentrated dual-salt/ester systems have been demonstrated as an effective method in regulating the solid electrolyte interphase (SEI) formation that facilitates the long-term cycling stability of lithium metal batteries (LMBs). However, the atomic mechanism of the dual-salt enabling the stable SEI formation remains unclear. In this work, a hybrid scheme, combining ab initio and reactive force field methods (HAIR), is employed to investigate the initial reaction of SEI formation by monitoring 1 ns molecular dynamics (MD) simulation. The simulation results reveal that lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is subject to a sacrificial decomposition to protect lithium difluoro(oxalato)borate (LiDFOB) from being over-reduced by Li metal. The boron (B) released from LiDFOB can initiate a polymerization reaction by cutting the C–O bond. Such unexpected reaction turns dimethoxyethane (DME), a previously considered stable solvent, into a radical that can facilitate the propagation of polymerization. These insights from simulation provide atomic understanding about the complex reaction in SEI.

Group Members

William A. Goddard III

Charles and Mary Ferkel Professor