Additive‐Mediated Anion Sieving Coordination Strategy for Long‐Lifespan Lithium Metal Pouch Cell with Energy Density over 540 Wh Kg⁻¹

Abstract Elevating the charging cut‐off voltage of Ni‐rich cathodes is an effective approach to boost the energy density of Li metal batteries (LMBs), yet their development is restricted by the unstable cathode electrolyte interphase (CEI). Here, an additive‐mediated anion sieving coordination strategy is proposed to construct a robust CEI to enhance the interfacial stability between the cathode and electrolyte under high‐voltage and temperature, as demonstrated utilizing N‐Methyl‐bis(trifluoroacetamide) (MBTFA) additive in a dual‐salt (LiBF₄/LiDFOB) electrolyte. MBTFA can selectively interact with fluorine in DFOB⁻, weakening the electron‐withdrawing effect of fluorine on oxygen, thereby promoting the coordination ability of oxygen in DFOB⁻ with Li⁺. More DFOB⁻ is selectively introduced into the solvation sheath of Li⁺, replacing BF₄⁻ with inferior film‐forming ability, realizing a B/F‐rich CEI with excellent mechanical stability. Consequently, electrolyte decomposition and cathode structure collapse are remarkably alleviated, and the Li||LiNi_0.8Co_0.1Mn_0.1O₂ cell exhibits enhanced cycling stability under a high cut‐off voltage of 4.7 V and high‐temperature of 55 °C. Impressively, this strategy stabilizes the operation of the pouch cell (541 Wh kg⁻¹) with an extremely ultra‐lean electrolyte (0.95 g Ah⁻¹) for 140 cycles. This work provides new insights into the design of electrolytes for high‐voltage LMBs.