The solid electrolyte interphase (SEI) film plays a significant role in the capacity and storage performance of lithium primary batteries. The electrolyte additives are essential in controlling the morphology, composition and structure of the SEI film. Herein, fluoroethylene carbonate (FEC) is chosen as the additive, its effects on the lithium primary battery performance are investigated, and the relevant formation mechanism of SEI film is analyzed. By comparing the electrochemical performance of the Li/AlF₃ primary batteries and the microstructure of the Li anode surface under different conditions, the evolution model of the SEI film is established. The FEC additive can decrease the electrolyte decomposition and protect the lithium metal anode effectively. When an optimal 5% FEC is added, the discharge specific capacity of the Li/AlF₃ primary battery is 212.8 mAh g⁻¹, and the discharge specific capacities are respectively 205.7 and 122.3 mAh g⁻¹ after storage for 7 days at room temperature and 55 °C. Compared to primary electrolytes, the charge transfer resistance of the Li/AlF₃ batteries with FEC additive decreases, indicating that FEC is a promising electrolyte additive to effectively improve the SEI film, increase discharge-specific capacities and promote charge transfer of the lithium primary batteries.

The limited rate performance of Li||CF_x batteries hinders their wide application, owing to the low conductivity of CF_x cathode material and the undesirable solid electrolyte interface (SEI) layer formed on the Li anode surface. Herein, a strategy for constructing a three-dimensional lithium anode (3D-Li anode) with high specific surface area and an in situ formed favorable SEI layer is proposed to enhance the interfacial stability and uniformity of ion transport and realize a Li||CF_x battery with remarkable comprehensive performance. A 3D-Li anode (Li@CuO-Cu foam) is successfully constructed by molten Li infusion of a thermal oxidation processed copper foam. The lithiophilicity of the Cu foam framework is optimized by the formed CuO. The Li@CuO-Cu foam||CF_x battery exhibits a high discharge specific capacity (1149.6 mAh g⁻¹ at 0.1 C) along with a high discharge plateau voltage (2.65 V). At a high rate of 10 C, the 3D-Li anode-based batteries still demonstrate a discharge specific capacity of 463 mAh g⁻¹, which is about 2.5 times that of the conventional Li||CF_x, and exhibit excellent storage performance (620.3 mAh g⁻¹ after storage at 55 °C for 90 days) and a low monthly self-discharge rate (1.28%). This work demonstrates a promising strategy to construct a three-dimensional lithium metal anode and significantly improve the rate and storage performance of Li||CF_x batteries.