Synthesis and characterization of nanoflaky maghemite (γ-Fe2O3) as a versatile anode for Li-ion batteries

• Published in: Ceramics international 2019-01, Vol.45 (1), p.131-136
• Main Authors: Golmohammad, M., Shahraki, M. Maleki, Golestanifard, F., Mirhabibi, A., Yang, G.
• Format: Article
• Language: English
• Subjects: Anode; Lepidocrocite(γ-FeO(OH)); Li-ion battery; Maghemite(γ-Fe2O3); Nanoflaky
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2018.09.143

In this study, nanoflaky maghemite (γ-Fe2O3) was successfully prepared by heating of synthesized lepidocrocite (γ-FeO(OH)). Once maghemite obtained, the electrochemical performance of nanoflaky maghemite, as an anode for Li-ion batteries, was investigated. Synthesis of lepidocrocite was optimized by adjusting the heating time and ratio of ethylene glycol (EG) to water in solution. The results revealed that with equal ratio of EG to water, the obtained phase was crystalline lepidocrocite whereas in other ratios lepidocrocite was not the only emerged phase. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) results revealed that increasing heating time has no effect on morphology. This increment only led to the slight crystallite growth and agglomeration of precipitation. The optimized lepidocrocite were heated at 230 °C for 2 h to form maghemite, which was confirmed by using XRD. FESEM, high-resolution transmission electron microscopy, and nitrogen adsorption-desorption results disclosed that the particles have flaky morphology with thickness of less than 10 nm and surface area of 105 m2 g−1. Cyclic voltammetry results of anode body (prepared using nanoflaky maghemite) demonstrated reversible formation pathway of iron and lithium oxide through discharging and charging. Moreover, galvanostatic charge–discharge cycling showed a reversible capacity of about 480 mAh g−1 after 50 cycles at current density of 500 mA g−1. Good cyclability, and capacity retention of the anode is due to the nananometric size and flaky shape of the maghemite particles. These particles’ shape made it easier for them to expand and contract in thickness direction with minimized destructions imposed.