Non-fluorinated electrolytes with micelle-like solvation for ultra-high energy density lithium metal batteries

Abstract

Electrolyte engineering plays a critical role in enabling lithium (Li) metal batteries. However, the simultaneous realization of anion-rich solvation structure and high ionic conductivity of electrolytes via solvation structure design remains challenging. Here, we report a low-cost, non-fluorinated electrolyte with a micelle-like solvation structure by introducing amphiphilic n-butyl methyl ether (MNBE) into Li bis(fluorosulfonyl)imide (LiFSI)/1,2-dimethoxyethane (DME) for stable Li metal batteries (LMBs). MNBE can effectively promote Li⁺-FSI⁻ coordination through steric crowding. Meanwhile, the inert alkyl chains of MNBE can mitigate the reaction between electrolyte and Li metal due to their lithiophobicity. Specifically, the micelle-like, non-fluorinated electrolyte exhibits an ionic conductivity as high as 12.55 mS cm⁻¹, and its anion-rich solvation structure promotes the formation of LiF-rich solid-electrolyte interphase. We constructed a 7.3 Ah Li||NMC811 pouch cell employing this electrolyte under harsh conditions, exhibiting ultra-high specific energy of 503.7 Wh kg⁻¹ with impressive cycling stability of 84.1% capacity retention after 100 cycles.