Synthesis and Lithium Intercalation Properties of Nanocrystalline Lithium Iron Oxides

Lithium iron oxides Li x Fe y O z were synthesized by oxidizing Fe 2 + with lithium peroxide in the presence of lithium hydroxide in aqueous solutions followed by firing the precursors at 200 ≤ T ≤ 800°C. The samples were characterized by X‐ray powder diffraction, transmission electron microscopy, wet‐chemical analyses, and surface‐area measurements. The Li/Fe ratio in the samples depends on the concentrations and volumes of the reactants used in the synthesis. Samples fired at a lower temperature of 200°C with a nanocrystalline microstructure and optimum Li/Fe ratio exhibit a capacity of about 140 mAh/g in the range 1.5-4.3 V with excellent cyclability. On the other hand, samples fired at higher temperatures T ≥ 400°C with well‐defined crystalline phases exhibit much lower capacity (<50 mAh/g).