Suitable Salt for Solid Electrolyte Interphase Formation in Al Anode Dual-Ion Battery

Abstract

Solid electrolyte interphase (SEI) formation upon reaction between electrode and electrolyte is an important phenomenon in metal anode-based batteries. Various components such as the nature of the electrode surface, solvent, additive, and salt contribute toward the SEI formation. In this work, we carried out ab initio molecular dynamics (AIMD) simulations on an electrolyte involving three different salts (LiPF6, LiBF4, and LiTFSI) in contact with the Al and LiAl anodes. We also checked the role played by the concentration of salt along with its nature during SEI formation. Different extents of salt decomposition are identified in different cases, and LiTFSI is found to be the most suitable salt leading to an inorganic-component-rich SEI layer. LiBF4 on the other hand decomposes minimally resulting in a solvent derived organic SEI. We highlight the importance of preferential reduction of salt before solvent to form inorganic-rich SEI which is preferable compared to organic SEI. The higher salt concentration is also found to support preferential salt decomposition. Overall, our work signifies the choice of proper salt along with its concentration to tune the SEI growth process in Al anode dual-ion batteries.