Conjugated topologically confined composite electrolytes for robust high-voltage and high-temperature semi-solid-state lithium metal batteries

Abstract

High-voltage lithium metal batteries (LMBs) face severe cathode-electrolyte interfacial degradation at elevated temperatures. To address this issue, we develop a conjugated topologically confined composite electrolytes (M-FGPE) by in situ incorporating π-conjugated metal-organic frameworks (MOFs) into a fluorinated polymer matrix, using an imidazolium‑based ionic liquid ([BMIM][TFSI]) as a safe yet dynamic platform for active solvation‑structure engineering. The densely distributed π-conjugated electrons in MOFs strongly couple with TFSI− anions via orbital coupling, creating a nanoconfined environment that restricts anion migration. Concurrently, the C−F groups of the fluorinated polymer establish ion-dipole interactions with [BMIM]+ cations. This dual-interaction mechanism effectively disrupts the intrinsic Coulombic ordering of the ionic liquid, fostering an anion-dominated solvation structure and enhancing stability under high-voltage and high-temperature conditions. Furthermore, the unique electrolyte architecture facilitates the formation of a robust LiF/Li3N-rich electrode-electrolyte interface, which simultaneously suppresses lithium dendrites, transition metal dissolution, and lattice oxygen release. As a result of these synergistic effects, Li‖LiCoO2 cells deliver 76.2% capacity retention after 250 cycles at 4.60 V and 60 °C, while 5.4 Ah pouch cells (435 Wh kg−1) maintain 95.1% capacity retention after 30 cycles with a lean electrolyte dosage of 2.0 g Ah−1. This work pioneers a conjugated topological confinement strategy for high-energy LMBs.