Abstract:

Lithium metal anodes offer a high theoretical specific capacity (3860 mAh/g) and, when combined with high-voltage cathodes, can significantly boost the energy density of lithium metal batteries (LMBs). However, their practical application is challenged by issues such as lithium dendrite growth, unstable solid-electrolyte interphase (SEI), and poor compatibility with high-voltage cathodes in DME ether-based electrolytes. To address these challenges, this work introduces a siloxane electrolyte as a substitute for DME ether-based electrolytes. The high chemical bond energy of siloxane enhances the oxidation stability of the electrolyte, making it compatible with high-voltage cathodes. Furthermore, the strong interaction between Li⁺ ions and FSI^- anions in the siloxane electrolyte promotes the preferential reduction of FSI^- anions on the lithium anode surface. This process forms a LiF-rich SEI film, effectively inhibiting dendrite growth and improving Li⁺ transport kinetics. Compared to DME ether-based electrolytes, cells utilizing the DMS-1 siloxane electrolyte exhibit superior electrochemical performance. The Li||Cu cycle can be stable for 300 cycles at a current density of 1.0 mA/cm². Full cells with Li||LFP and Li||NCM811 cathodes also show excellent electrochemical performance in the DMS-1 electrolyte. The Li||LFP cell maintains its capacity without significant fading after 400 cycles at 2.0 C. The Li||NCM811 cell achieves 83% capacity retention after 300 cycles at 1.0 C, showing excellent cycle stability. The siloxane electrolyte developed in this work provides a promising strategy for constructing long-cycle, high-voltage LMBs.

Key words: lithium metal battery, electrolyte, high-voltage, electrochemical performance