Graphitized Carbon-Coated Iron Fluoride Nanocavities for Enhanced Kinetics of Multielectron Cathode Conversion Reactions

Abstract

As for the conversion-type iron fluoride (FeF 3 ) 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 FeF 3 nanocavities coated by graphitized carbon (FeF 3 /GC) are rationally prepared. Through the Kirkendall effect, the low-temperature fluorination of NF 3 enables the resultant hollow FeF 3 nanoparticles to possess a large number of lithium storage cavities and outer graphitized carbon structure, further effectively buffering the expansion of volume. The FeF 3 /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.