Molecular Design of Electrolyte Additives for High-Voltage Fast-Charging Lithium Metal Batteries

Abstract

The incorporation of lithium metal as an anode material in lithium metal batteries (LMBs) offers a transformative pathway to surpass the energy density limits of conventional lithium-ion batteries (LIBs). However, the integration of lithium metal with traditional carbonate-based electrolytes is plagued by challenges, such as the instability of the solid electrolyte interphase (SEI) and the cathode-electrolyte interphase (CEI) at high voltages and high rates. To address these issues, we designed and tested a novel bifunctional additive, vinyl sulfonyl fluoride (VSF), that demonstrates the ability to stabilize both the SEI and CEI under fast-charging and high-voltage conditions. Through a combination of density functional theory (DFT), molecular dynamics (MD) simulations, and electrochemical evaluations, we show that VSF promotes the formation of thin, uniform, and inorganic-rich interfacial layers, which enhance lithium-ion transport and mitigate the degradation typically observed in high-energy LMBs. Full-cell and pouch-cell cycling experiments reveal that VSF significantly improves cycling stability and rate performance, particularly under extreme conditions. The findings highlight VSF as a promising additive for advancing the commercialization of high-performance LMBs.