Calcination Temperature Effect on Citrate-Capped Iron Oxide Nanoparticles as Lithium-Storage Anode Materials

摘要

In this work, citrate-capped magnetites (cit-Fe_3O_4) are facilely synthesizedaccording to a modified co-precipitation method, and the resulting cit-Fe_3O_4underwent thermal calcination under N2 flow for 2 h. The calcined cit-Fe_3O_4at 500 ℃, so-called C-Fe_3O_4 (500 ℃), exhibits the XRD patterns attributedmainly to the fcc crystalline phases of magnetite (Fe_3O_4). On the other hand,the calcined cit-Fe_3O_4 at 700 ℃, so-called C-Fe2O3 (700 ℃), exhibits the X-raydiffraction (XRD) patterns attributed mostly to hexagonal crystalline phasesof hematite (α-Fe_2O_3). The iron oxides calcined at different temperatures(500, 600, 700 ℃) are employed as active anode materials for Li-ion batteries.After 80 cycles at the current rate of 0.1 C, the C-Fe_2O_3 (700 ℃) exhibits thehigher reversible capacity by ≈200% than that of the C-Fe_3O_4 (500 ℃). Theimproved reversible capacity of the C-Fe_2O_3 (700 ℃) is attributed to thetransformation of magnetite phases into hematite phases with highercrystallinity, which is more beneficial for faster transfer of charge carriers andstructural stability.