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Rechargeable Li metal batteries (LMBs) have attracted wide attention as promising candidates for the next generation of energystorage systems. However, limited Coulombic efficiency and unregulated dendrite growth restrict its application. Here, we report a kind of electrolyte by introducing fluorinated aromatic diluents into highconcentration electrolytes (HCEs). Unlike other localized HCEs, the fluorinated aromatic diluents pairing with anions promote the formation of a homogeneous and robust solid−electrolyte interphase (SEI), which endows Li metal with an ultrahigh Coulombic efficiency of ∼99.8%. The Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 battery holds a capacity retention of >80% over 260 cycles even with a thin Li anode (20 μm) and a high cathode loading (3.5 mAh cm −2 ). A 1.8 Ah Li||NMC811 pouch cell with a lean electrolyte delivers an energy density of 340 Wh kg −1 and a stable cycling life over 200 cycles. The designed electrolytes, which benefit from the synergetic effects of anions and diluents on the SEI, pave the way for the next-generation LMBs.

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