Integrated electrode-electrolyte Interface engineering strategy using potassium trimethoxy (trifluoromethyl) borate for lithium-metal batteries

Abstract

Lithium (Li) metal is emerging as a promising anode material for next-generation energy storage systems. However, the uncontrolled growth of Li dendrites causes low coulombic efficiency and safety risks, hindering the practical application of Li metal batteries. To surmount these obstacles, potassium trimethoxy(trifluoromethyl)borate (PMFB, K+–MFB−) is used as a multifunctional electrolyte additive in a conventional carbonate-based electrolyte. With a trace addition of 0.01 M (~ 0.16 wt%), K+ cations of the PMFB molecules form a cationic electrostatic shielding layer that promotes homogenous Li deposition. Simultaneously, the MFB− anions with a strong coordination force with Li+ ions (−4.27 eV) adjust the Li+ solvation structure, reducing the number of solvated solvents and constructing Li+–MFB− ion pairs, which possess a lower lowest unoccupied molecular orbital (LUMO) level compared to other solvents in the electrolyte. Consequently, a uniform solid electrolyte interphase (SEI) layer enriched with inorganic species, such as LiF, Bsingle bondO and Bsingle bondF, derived from the reduction of Li+–MFB− ion pairs is formed. A full cell exhibits stable cycling performance, retaining 94.0% of its capacity after 400 cycles at 3C.