As for the conversion-type iron fluoride (FeF3) cathode material with multielectron reactions for lithium-ion batteries (LIBs), sluggish reaction kinetics and low electrical conductivity pose certain limitations for the long-lasting reversible conversion processes. Herein, the three-dimensional porous nitrogen-doped carbon matrix in situ anchoring FeF3 nanocavities coated by graphitized carbon (FeF3/GC) are rationally prepared. Through the Kirkendall effect, the low-temperature fluorination of NF3 enables the resultant hollow FeF3 nanoparticles to possess a large number of lithium storage cavities and outer graphitized carbon structure, further effectively buffering the expansion of volume. The FeF3/GC cathode delivers a superior discharge capacity of 504.2 mAh g-1 after 1200 cycles at 1000 mA g-1, with a capacity decay rate of only 0.01% per cycle. Even at a rate of 5000 mA g-1, the composite cathode still delivers a discharge capacity of 309.6 mAh g-1. Impressively, the existence of graphitized carbon and the short Li+ diffusion length ensure fast electron/ion transfer, which significantly enhances the conversion reaction kinetics. This study aims to provide a promising strategy for the efficiency enhancement of multielectron cathode conversion reactions for LIBs.
Keywords: FeF3 cathode; Kirkendall diffusion; conversion reaction; graphitized carbon; hollow structure; lithium-ion batteries.