KOH-Induced Surface Defluorination and Hydroxylation of CFX for Ultrahigh Power Density Primary Batteries.

Abstract

Low power capability remains one of the primary challenges for lithium/fluorinated carbon (Li/CF_x) batteries. Surface modification represents a typical strategy for enhancing the intrinsic conductivity and reaction kinetics of CF_x. However, most existing surface modification methods suffer from complex procedures and nonuniform products. To address this problem, this study reports a one-step liquid-phase reaction method, KOH as a defluorination agent, to achieve controlled surface defluorination and -OH grafting on CF_x. The defluorination process reduces edge-inert CF₂/CF₃ groups, exposes CC bonds, and forms an ultrathin, graphene sheet-like conductive coating (≈1 nm thick) on the CF_x surfaces, enhancing lithium-ion and electron transport kinetics during the early discharge stage. Simultaneously, the grafted -OH groups weaken the surrounding CF bonds via hydrogen bonding, increasing the proportion of semi-ionic CF bonds and boosting the electrochemical activity of CF_x. Their synergistic effect significantly improves the reaction kinetics of CF_x during discharge. Relative to pristine CF_x cathodes, batteries using KOH-induced CF_x cathodes achieve a 70C discharge capability, attain 98.42 kW kg^-1 power density, and exhibit near-doubled (95%) improvement in energy density at 50C. This work provides a practical new avenue for large-scale preparation of high-power fluorinated carbon cathodes, facilitating their industrial application.