The electrochemical kinetic processes of Li+ ions, including the desolvation of the Li+ ions from the electrolyte to the solid electrolyte interphase (SEI), the transportation of desolvated Li+ ions across the SEI, and the charge transfer at the interface between the SEI and graphite, determine the rate performance and cycling stability of the graphitic anode in lithium-ion batteries (LIBs). In this work, fluorine-terminated self-assembled monolayers were grafted on the surface of spherical graphite particles to regulate the chemical composition and structure of SEI formed on the graphite surface in the presence of conventional ester electrolytes. The comprehensive characterization and first-principles calculation results illustrate that a uniform LiF-dominated SEI film can be generated on the as-functionalized graphite anode due to the carbon-fluorine bonds' cleavage of fluorine-terminated self-assembled monolayers. The LiF-dominated SEI film is particularly beneficial for desolvated lithium-ion transport across the SEI, affording LiCoO2//graphite full cells with substantially enhanced fast-charging capability and cycle stability. This strategy should be potentially useful for modifying other anode materials to regulate the interfacial chemistry between the anode and electrolyte in lithium-ion batteries.
Keywords: SEI; graphite; interfacial chemistry; lithium-ion batteries; self-assembled monolayers.