Fluorinated N,P co-doped biomass carbon with high-rate performance as cathode material for lithium/fluorinated carbon battery

Lithium/fluorinated carbon (Li/CF_x) batteries are greatly limited in their applications mostly due to poor rate performances. In this study, N,P co-doped biomass carbon was synthesized using melamine and phytic acid as doping sources, and the resulting product was then utilized as a precursor for CF_x. The resulting fluorinated biomass carbon has a high degree of fluorination, exceeding the specific capacity of commercial fluorinated graphite while also demonstrating exceptional performance at high discharge rates. During the fluorination process, N,P-containing functional groups were removed from the crystalline lattice in the basal plane. This facilitates the formation of a defect-rich carbon matrix, enhancing the F/C ratio by improving the fluorinated active sites and obtaining more highly active semi-ionic bonds. Additionally, the abundant defects and porous structure promote Li⁺ diffusion. Density functional theory calculations indicated that doping modification effectively reduces the energy barrier for Li⁺ migration, enhancing Li⁺ transport efficiency. The prepared CF_x delivers material with a maximum specific capacity of 919 mAh·g⁻¹, while maintaining a specific capacity of 702 mAh·g⁻¹ at a high discharge current density of 20C (with a capacity retention rate of 76.4%). In this study, fluorinated N,P co-doped biomass carbon, exhibiting ultrahigh capacity and high-rate performance, was prepared for the first time, which can potentially advance the commercialization of CF_x.