Rapid microwave assisted hydrothermal synthesis of porous α-Fe2O3 nanostructures as stable and high capacity negative electrode for lithium and sodium ion batteries

Abstract

Hematite porous α-Fe₂O₃ nanostructures were prepared within 60 minutes by a rapid microwave assisted hydrothermal process. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies confirm the phase and structural co-ordination of α-Fe₂O₃, respectively. Scanning electron microscopy (SEM) images reveal the formation of well defined uniform shaped α-Fe₂O₃ nanospheres. The transmission electron microscopy (TEM) image shows the porous nature of the α-Fe₂O₃ nanospheres with an interconnected monocrystallites structure. Swagelok type lithium and sodium batteries were fabricated using the developed porous α-Fe₂O₃ nanostructures as a negative electrode material. As a negative electrode material in Li-ion cells, the porous α-Fe₂O₃ nanostructures deliver a second cycle discharge capacity of 1000 mA h g⁻¹ at a 0.1 C rate. At a higher current density of 5 C, the porous α-Fe₂O₃ nanostructures exhibit a specific capacity of 264 mA h g⁻¹. In the case of Na-ion batteries, the porous α-Fe₂O₃ nanostructures as negative electrode exhibit a reversible capacity of 300 mA h g⁻¹ with excellent cycleability and coulombic efficiency at 0.1 C up to 100 cycles. The observed excellent electrochemical performance is attributed to the porous nature and uniform shape of the α-Fe₂O₃ nanostructures that are composed of interconnected monocrystallites. Importantly, the architecture of α-Fe₂O₃ nanostructures, comprising interconnected monocrystallites could be developed within a short time by a rapid microwave synthesis process and it can be applied to develop different morphological nanostructures for better energy storage device applications.