Sustainable solid electrolyte interphase enables high-energy-density lithium metal batteries under practical conditions.

Secondary lithium metal batteries afford great promises for future energy storage applications. However, high-energy-density Li metal batteries suffer from short lifespan under practical conditions including limited lithium, high cathode loading, and lean electrolyte due to the absence of appropriate solid electrolyte interphase (SEI). Herein, a sustainable SEI was designed rationally by combining fluorinated co-solvents with sustained-release additives in response to challenges from practical conditions. The intrinsically uniform SEI and the constant supplements of building blocks of SEI jointly afford to sustainable SEI. Particularly, specific spatial distributions and abundant heterogeneous grain boundaries of LiF, LiNxOy, and Li2O in SEI effectively regulate uniformity of Li deposition, becoming the foundation of sustainable SEI. In a lithium metal battery with ultrathin Li anode (33 μm), high loading LiNi0.5Co0.2Mn0.3O2 cathode (4.4 mAh cm-2), and lean electrolyte (4.4 g Ah-1), 83% of initial capacity retains after 150 cycles with sustainable SEI compared to 4 cycles with pristine SEI. Furthermore, a pouch cell (3.5 Ah) demonstrated a specific energy of 340 Wh kg-1 for 60 cycles with lean electrolyte (2.3 g Ah-1) based on sustainable SEI. This work affords a fresh guidance to the design principles of SEI in practical Li metal batteries.