Optimization of synthesis conditions of high–tap density FeVO₄ hollow microspheres via spray pyrolysis for lithium–ion batteries

Iron orthovanadate (FeVO₄) hollow microspheres were synthesized by a continuous, one–step, scalable process without the addition of a template material using the ultrasonic spray pyrolysis method. The synthesis conditions were optimized by changing the synthesis temperature in order to synthesize hollow microspheres of FeVO₄ under the constant N₂ gas atmosphere by means of a tubular furnace. The pure crystalline phase of hollow microspheres was achieved at 800 °C, and investigated using XRD, RAMAN, SEM, TEM. The electrochemical performance of hollow microspheres was considered with initial specific discharge/charge capacities of 1373.82 mA h g^{− 1}, 1107.28 mA h g^{− 1}, and an initial columbic efficiency of 80.59% at 0.1 C up to 100 cycles. Superior rate capability and cycle retention performance were due to the FeVO₄ hollow microsphere morphology and high tap density, which improved the electrical contact between the electrolyte, active material, and current collector and shortened the diffusion length of Li⁺ ions during the intercalation/de–intercalation process. Moreover, electrical impedance spectroscopic measurements explained that the enhanced ionic conductivity was due to the morphology and porosity which improved the electrochemical performance of FeVO₄ hollow microspheres and proved it as an auspicious anode material for LIBs.