The influence of P-toluenesulfonyl isocyanate on the solvation structure and solid electrolyte interphase formation on graphite anode under high temperatures

Abstract

The formation and stability of the solid electrolyte interphase (SEI) play a crucial role in determining the performance and lifespan of lithium-ion batteries (LIBs) at evaluated temperatures. Electrolyte additives have emerged as promising candidates for modulating the formation kinetics and stability of the SEI layer. In this study, molecular dynamics (MD) and ab initio molecular dynamics (AIMD) simulations were employed to investigate the influences of P-toluenesulfonyl isocyanate (PTSI) as an electrolyte additive in the LiPF₆/EC/DMC electrolyte on the SEI formation process on the graphite anode under high temperatures. MD simulations revealed that PTSI induces modifications in the solvation structure, resulting in two ethylene carbonate (EC) and two dimethyl carbonate (DMC) molecules in the first solvation shell of Li⁺. Furthermore, the PTSI additive suppressed the decomposition of solvent molecules and PF6 anions in the LiPF₆/EC/DMC/PTSI electrolyte under high temperatures according to the AIMD simulations, contributing to a more stable SEI layer. Moreover, this suppression can be attributed to the reduced reactivity of solvent molecules and salt anions, as evidenced by the enhanced bond strength and decreased bond length. These microscopic insights provide a multi-faceted understanding of the functionality of PTSI additives, facilitating the rational design of novel additives.