Fluorination Regulates Heat Generation in Ah-Level Lithium/Fluorinated Carbon Pouch Cells
Lithium/fluorinated carbon (Li/CFx) batteries are among the most promising high-energy-density primary batteries, yet substantial heat generation during discharge poses safety concerns, particularly for high-mass-loaded pouch cells. This study systematically investigates the effects of fluorination temperature on the structure and kinetics of fluorinated porous carbon (FPC) cathodes and on heat generation in Ah-level Li/FPC pouch cells. FPC samples with varying degrees of fluorination were synthesized by adjusting fluorination temperature, which influenced not only the F/C ratio but also the C–F bonding configuration, pore structure, and electronic transport capability. Pouch cells employing more highly fluorinated cathodes generated the most heat during discharge, with heat generation exhibiting clear stage dependence, predominantly in the 0–20% depth of discharge (DOD) range. Post-discharge structural characterization and kinetic analysis revealed that highly fluorinated FPC cathodes (FPC-250) undergo more concentrated LiF accumulation, leading to higher charge-transfer resistance, stronger polarization, lower Li+ diffusivity, and higher nucleation overpotential. These factors collectively intensify early-stage heat generation. The study establishes a correlation between fluorination temperature and cathode structure, discharge-product evolution, discharge kinetics, and heat generation, demonstrating that regulating fluorination temperature is an effective strategy for improving the thermal safety of Li/CFx batteries.