Preparation of α-Fe2O3 Electrode Materials via Solution Process and Their Electrochemical Properties in All-Solid-State Lithium Batteries

α-Fe 2 O 3 particles of various sizes were prepared by a solution process and were applied to the electrodes for all-solid-state lithium rechargeable batteries. The prepared α-Fe 2 O 3 was monodispersed particles with sizes controlled from about 250 nm to 3.7 μm. Their electrochemical properties were examined for the all-solid-state cells with highly conductive Li 2 S-P 2 S 5 solid electrolytes and the influences of the particle size of α-Fe 2 O 3 on the electrochemical performance of the cells were investigated. The first discharge capacities increased with decreasing the particle size of α-Fe 2 O 3 and the cell using the smallest α-Fe 2 O 3 particles of 250 nm showed the highest capacity of 1050 mAh g -1 . The charge-discharge reaction mechanism in the all-solid-state cells was investigated by means of X-ray diffraction and was revealed to be similar to that in conventional cells with a liquid electrolyte. The lithium intercalation to α-Fe 2 Ο 3 occurred in the initial stage of the first discharge only in the cases using α-Fe 2 O 3 particles with small crystallite size, large specific surface area and large pore volume. By controlling the cutoff voltage, the all-solid-state cell retained the constant capacity of about 130 mAh g -1 for 15 cycles at the current density of 0.064 mA cm -2 . The rate capability at 25°C and temperature dependence of the first discharge capacity in the all-solid-state cells were also investigated. The cell at 60°C showed the larger first-discharge capacity of 940 mAh g -1 at the current density of 1.27 mA cm -2 .