Abstract
Primary lithium/carbon monofluoride (Li/CFₓ) batteries are widely recognized for their high theoretical energy density, long shelf life, and low self-discharge, making them ideal for aerospace, medical, and military applications. However, their performance at low temperatures is severely limited due to increased interfacial resistance and reduced lithium-ion transport. In this study, we investigate the effect of electrolyte composition on the ionic conductivity and discharge behavior of Li/CFₓ cells under –20 °C conditions. A series of electrolyte systems was evaluated, including single-salt and dual-salt formulations based on LiDFOB, LiBF₄, LiPF₆, and LiClO₄ in various solvent mixtures (PC:DME, FEC:DME, and PC:DME:EA), with and without additives such as fluoroethylene carbonate (FEC) and lithium nitrate (LiNO₃). Electrochemical impedance spectroscopy revealed that only dual-salt systems and selected additive combinations maintained conductivity above 5 mS/cm at sub-zero temperatures. The best performance was achieved with 0.4 M LiDFOB + 0.6 M LiBF₄ in PC:DME, which exhibited the highest conductivity and a specific discharge capacity of ~220–230 mAh/g. These results demonstrate the critical role of electrolyte optimization in enabling reliable low-temperature performance. Comparative analysis with literature data further confirms the effectiveness of the proposed formulations. This work provides practical guidance for designing advanced electrolytes for primary Li/CFₓ batteries operating in cold environments.