Employment of Chitosan–linked Iron Oxides as Mesoporous Anode Materials for Improved Lithium–ion Batteries

This study investigates the concentration effect of chitosan on the formation of iron oxide composites and their electrochemical performance as anode materials in Li–ion batteries. The molecular bridging effect of chitosan chains induces the clustered aggregation of citrate–capped Fe3O4 (C–Fe3O4) through the electrostatic interactions between carboxylate groups of C–Fe3O4 and amine groups of chitosan. The thermal calcination of chitosan–linked Fe3O4 leads to carbon–coated Fe2O3 (Fe2O3@carbon) with the mesopore range of porosity (20–30 nm). The mesoporous Fe2O3@carbon exhibits an improved electrochemical performance as anode materials in Li–ion batteries. The capacity retention of Fe2O3@carbon is twice that of bare Fe2O3 after the 50th cycle at 0.1 C. During the charge–discharge process, the Fe2O3@carbon (3 ml of chitosan) exhibits the highest retention capacity among as–prepared samples, whereas Fe2O3@carbon (1 ml of chitosan) exhibits the lowest retention capacity owing to the weakly cross–linked iron oxides. The improved performance of Fe2O3@carbon as anode materials is mainly attributed to the optimal cross–linking effect and structural integrity of mesoporous composite which is beneficial for the effective transport of electrolytes and/or Li–ons, suggesting a useful guideline for preparing porous electrode materials using metal oxide particles.