Effects of the particle properties on electrochemical performance of nanocrystalline LiAl_0.1Cu_0.1Mn_1.8O₄ cathode materials prepared by ultrasonic spray pyrolysis

Nanocrystalline LiAl_0.1Cu_0.1Mn_1.8O₄ particles were prepared by the ultrasonic spray pyrolysis using nitrate salts at 800 °C in air atmosphere. The effects of ultrasonic frequency (120 kHz and 2.4 MHz) of the atomizer on the particle properties were investigated by X-ray diffraction, scanning and transmission electron microscopy, and energy dispersive spectroscopy. In addition, cyclic voltammetry and galvanostatic tests were performed to study the influence of the particle structure on the electrochemical behavior in Li-ion battery half-cell. Particle characterization studies reveal that the LiAl_0.1Cu_0.1Mn_1.8O₄ particles have a nanocrystalline spinel structure. The secondary particles have a spherical morphology and the average particle size of the samples decreases with increase in frequency from 3.5 μm to 770 nm. Both samples have porous and partly hollow structure. The initial discharge capacities of LiAl_0.1Cu_0.1Mn_1.8O₄ particles produced using 120 kHz and 2.4 MHz atomizers are 82 and 75 mAh·g^{− 1}, respectively, between 3.0 and 4.8 V at 0.1C rate. Discharge capacities at the 4 V potential region drop to 85% of the initial values for both samples after 110 cycles. Although the micron-sized LiAl_0.1Cu_0.1Mn_1.8O₄ particles exhibit higher capacity at 0.1C than the finer particles, the cathode prepared from the submicron particles has a better rate capability with a retention of the discharge capacity that is 3 times higher at 4C rate.