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

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 lithium bis(fluorosulfonyl)imide (LiFSI)/1,2-dimethoxyethane (DME) for stable Li metal batteries. 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 ultrahigh specific energy of 503.7 Wh kg-1 with impressive cycling stability of 84.1% capacity retention after 100 cycles.电解液工程对锂金属电池的实用化起到关键支撑作用。然而，通过溶剂化结构设计，同时实现电解液的富阴离子溶剂化结构与高离子电导率仍颇具挑战。本文报道了一种低成本非氟电解液：通过将两亲性正丁基甲基醚（MNBE）引入双(氟磺酰)亚胺锂（LiFSI）/1,2-二甲氧基乙烷（DME）体系，构建了类胶束溶剂化结构。MNBE可通过空间位阻效应有效促进Li⁺与FSI⁻的配位；同时，其惰性烷基链因疏锂特性，可缓解电解液与金属锂之间的副反应。具体而言，该类胶束非氟电解液的离子电导率高达12.55 mS·cm⁻¹，其富阴离子溶剂化结构可促进富含LiF的固体电解质界面（solid-electrolyte-interphase）的形成。基于该电解液，我们构建了7.3 Ah的锂||NMC811软包电池，在严苛工况下展现出503.7 Wh·kg⁻¹的超高比能量，且循环稳定性优异：100次循环后容量保持率达84.1%。