BF3-based Electrolyte Additives Promote Electrochemical Reactions to Boost the Energy Density of Li/CFx Primary Batteries

Lithium/fluorinated carbon (Li/CFx) batteries have attracted wide attention due to their high theoretical energy density. However, the reaction product of LiF is an insulator in their discharge process, which seriously hinders the Li+ migration, leading to the inferior capacity of CFx (x ≈ 1) cathodes. Herein, a low-cost and facile electrolyte additive containing the BF3 functional group has been proposed to effectively alleviate the voltage lag phenomenon and improve the energy density of Li/CFx batteries. In particular, the discharge voltage platform and energy density of CFx are significantly increased to 2.62 V (vs 2.51 V in the electrolyte without additives) and 2018 Wh Kg−1 (vs 1863 Wh Kg−1 in the electrolyte without additives) when the electrolyte contains 1 wt % pyrazine di-boron trifluoride (PRZ), respectively. This significant improvement can be attributed to the BF3-based additives effectively dissolving the insulation discharge product LiF, thereby increasing the Li+ migration rate and allowing more CFx to participate in the reaction and release capacity. This work provides a low-cost additive method to maintain high energy density for Li/CFx batteries, which has great potential for practical applications.