LiF Pre-Nucleation Strategy for Mitigating Heat Generation at the Kinetic Bottleneck in Li/CFx Batteries.

Abstract

Li/fluorinated carbon (Li/CFx) primary batteries offer ultrahigh energy density but are hindered by undesirable and often overlooked exothermic reactions, especially under high current densities. Herein, for the first time, the correlation between CFx structural evolution and heat generation is systematically investigated, identifying LiF nucleation as the kinetic bottleneck. At this stage, the temperature rise rate is 8.6 to 29.8 times higher than during the LiF growth stage in a 20 Ah pouch cell at 0.5 C. Based on these findings, it is proposed a LiF pre-nucleation strategy by chemically introducing LiF nuclei. LiF exhibits stronger adsorption energy on pre-existing LiF nuclei than on CFx substrate, thereby promoting selective LiF growth on these nuclei. As a result, the LiF nucleation overpotential is reduced by 0.32 V, and the temperature rise rate at the kinetic bottleneck step decreases from 0.149 to 0.097 °C s-1, leading to a 13.5 °C reduction at LiF nucleation stage. This study not only deepens the understanding of heat generation mechanisms in Li/CFx batteries but also provides a new strategy for enhancing Li/CFx battery safety.