In‐Situ Constructing a Mixed‐Conductive Interfacial Protective Layer for Ultra‐Stable Lithium Metal Anodes

Lithium metal batteries are the most promising next‐generation energy storage technologies due to their high energy density. However, their practical application is impeded by serious interfacial side reactions and uncontrolled dendrite growth of lithium metal anode. Herein, copper 2,4,5‐trifluorophenylacetate is designed and explored to stabilize lithium metal anode by in‐situ constructing a dense and mixed‐conductive interfacial protective layer. The formed passivated layer not only significantly inhibits interfacial side reactions by avoiding direct contact between lithium metal anode and electrolyte but also effectively suppresses lithium dendrite growth due to the unique inorganic‐rich compositions and mixed‐conductive properties. As a result, the copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes show greatly improved cycle stability under both high current density and high areal deposition capacity. Notably, the assembled liquid symmetrical cells with copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes can stably work for more than 3000, 5000, and 4800 h at 1.0 mA cm −2 –1.0 mAh cm −2 , 2.0 mA cm −2 –5.0 mAh cm −2 , and 10 mA cm −2 –5.0 mAh cm −2 , respectively. Furthermore, the assembled liquid full cell with a high LiFePO 4 loading (~16.9 mg cm −2 ) shows a significantly enhanced cycle life of 250 cycles with stable Coulombic efficiencies (>99.1%). Moreover, the assembled all‐solid‐state lithium metal battery with a high LiNi 0.6 Co 0.2 Mn 0.2 O 2 loading (~5.0 mg cm −2 ) also exhibits improved cycle stability. These findings underline that the copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes show great promise for high‐performance lithium metal batteries.