Stability,electrochemical behaviors and electronic structures of iron hydroxyl-phosphate

Iron hydroxyl-phosphate with a uniform spherical particle size of around 1 μm, a compound of the type Fe_2−y□_y(PO₄)(OH)_3−3y(H₂O)_3y−2 (where □ represents a vacancy), has been synthesized by hydrothermal methods. The particles are composed of spheres of diameter <100 nm. The compound exhibits good electrochemical performance, with reversible capacities of around 150 mAh g⁻¹ and 120 mAh g⁻¹ at current densities of 170 mA g⁻¹ and 680 mA g⁻¹, respectively. The stability of crystal structure of this material was studied by TGA and XRD which show that the material remains stable at least up to the temperature 200 °C. Investigation of the electronic structure of the iron hydroxyl-phosphate by GGA + U calculation has indicated that it has a better electronic conductivity than LiFePO₄.