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 dendrite growth of lithium metal anode (LMA). Herein, copper 2,4,5-trifluorophenylacetate (CuTFPAA) is synthesized and used to stabilize LMA by in-situ constructing a dense and mixed-conductive interfacial protective layer. The in-situ formed passivated layer not only significantly inhibits interfacial side reactions by avoiding direct contact between LMA and electrolyte but also effectively suppresses lithium dendrite growth due to its high mechanical strength. As a result, the CuTFPAA-treated LMAs show greatly improved cycle stability under both high current density and high areal deposition capacity. Notably, the assembled liquid symmetrical cells with CuTFPAA-treated LMAs 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 LiFePO4 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 LiNi0.6Co0.2Mn0.2O2 loading (~ 5.0 mg cm‒2) also exhibits improved cycle stability. These findings underline that the CuTFPAA-treated LMAs show great promise for high-performance lithium metal batteries.