Electrolyte engineering-controlled interfacial chemistries on both lithium metal anode (LMA) and high-voltage cathode are key to stable lithium-metal batteries (LMBs). Here, we demonstrate that a kind of local high concentrated electrolyte (LHCE) by introducing an active difluoroethylene carbonate (DFEC) co-solvent can contribute to excellent interfacial chemistries. Unlike the conventional LHCEs, DFEC with lower LUMO energy serves as both additive and diluent, and reinforces the anion-solvation-derived interfacial layers, leading to the suppression of side reactions/dendrite lithium growth and the acceleration of Li⁺ desolvation/transfer kinetics. Consequently, the assembled high-capacity Li||LiCoO₂ full cell (1.836 mAh cm⁻²) holds a high retention of > 80% over 1000 cycles at 0.3 C under a high cut-off voltage of 4.5 V. More impressively, the addition of DFEC leads to a significant improvement of cycle stability for ∼265 mAh Li||LiCoO₂ pouch cells. Designing functional diluent with a synergistic effect that heightens interfacial chemistries to control anion-solvation is very promising and paves a bright way to develop rechargeable LMBs.