Preparation and electrochemical properties of spinel LiFe _xCu_yMn_1.2O₄ by ultrasonic spray pyrolysis

Nanocrystalline LiFe_xCu_yMn_1.2O₄ (x and y=0.2, 0.4 and 0.6) particles were prepared by the ultrasonic spray pyrolysis method using nitrate salts at 800 C in air atmosphere. Particle properties were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Also, cyclic voltammetry and galvanostatic tests were performed to investigate the effects of the double substituent and doping amounts on electrochemical behavior. Results show that the aggregation of nanocrystallites around 90 nm size formed submicron spherical cathode particles. Transition metal ratios in particles exhibited a perfect fit with desired amounts. Although the change of iron and copper amounts do not show significant differences in the particle size and shape morphology, they modify the 4 V and 3 V potential plateaus of spinel LiMn₂O ₄. The discharge capacities of LiFe_0.2Cu _0.6Mn_1.2O₄ particles are 39 and 23 mAh g ^-1 for 4 and 2.6 V potential regions, respectively. 4 V discharge capacity disappeared with increasing of iron and decreasing of copper contents due to random occupation of iron and copper ions in the spinel lattice.