Multifunctional silane additive enhances inorganic-organic compatibility with F-rich nature of interphase to support high-voltage LiNi${}_{0.5}$Mn${}_{1.5}$O${}_4$//graphite pouch cells

A novel electrolyte additive, 3, 3, 3-trifluoropropylmethyldimethoxysilane (TFPMDS), is first proposed to modify both the cathode and the anode of lithium-ion batteries at the same time. Charging/discharging tests demonstrate that the electrolyte with 1 wt% TFPMDS not only greatly improves the capacity retention of LiNi${}_{0.5}$Mn${}_{1.5}$O${}_4$ (LNMO)//Li cell (29.6%→90.8%) and graphite//Li cell (68.1%→98.3%), but also successfully ensures the long-term cycle stability of LNMO//graphite pouch cell at 4.9 V. Further electrochemical measurements combining with spectroscopic characterization and theoretical calculations indicate that TFPMDS additive displays three principal functions: 1) Be preferentially oxidized to build a robust cathode electrolyte interphase (CEI) enriched in F/Si species with F-rich nature of strong oxidation-resistance. 2) Be able to scavenge the hazardous HF, F${}^{-}$, and H${}^{+}$ through its strong binding with these species and thus to protect LNMO at high-voltage. 3) Be preferentially adsorbed on the graphite surface to form a "framework", and to co-construct an elastic solid electrolyte interphase (SEI) after the reduction of ethylene carbonate. Importantly, the Si-O group within TFPMDS is especially important for constructing a "molecular bridge" at the CEI/SEI interphase coupling the inorganic and organic species to improve its compatibility, stability, and elasticity. (© 2024 Wiley‐VCH GmbH)