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.