Preparation of LiNi_0.5Mn_1.5O₄Cathode materials of lithium-ion batteries by drip pyrolysis in fluidized bed reactor followed by heat treatment and their electrochemical properties

LiNi_0.5Mn_1.5O₄ with a spinel structure was prepared by drip pyrolysis in a fluidized bed reactor followed by a short heat treatment from a precursor solution; in which Li(CH₃COO)·2H₂O, Ni(CH₃COO)₂ ·4H₂O and Mn(CH₃COO)₂ ·4H₂O were stoichiometrically dissolved into distilled water. The effect of process parameters such as reactor temperature, superficial gas velocity and annealing temperature on the physical and electrochemical properties of samples were intensively investigated through analysis by X-ray diffraction, thermal gravimetric-differential thermal-mass analysis, Bruneaur-Emment-Teller method and scanning electron microscopy.The samples prepared by the drip pyrolysis showed a spinel structure with low crystallinity and poor electrochemical activity.Thus, the as-prepared samples were then annealed at different temperatures ranging from 700 to 900°C for 5h. Complex analysis showed that the annealing at 700°C leads to the formation of a pure ordered P4₃32 phase, while the annealing at 800 and 900°C leads to the formation of both spinel Fd3m (disordered) and simple cubic P4₃32 (ordered) phases.The final LiNi_0.5Mn_1.5O₄ samples were used as cathode active materials for lithium batteries, and electrochemical tests were carried out for the cell Li|1M LiPF₆ in EC:DEC 1:1| LiNi_0.5Mn_1.5O₄ at various charge-discharge rates. As a result, the LiNi_0.5Mn_1.5O₄ sample, which was synthesized at 600°C and a fluidization number of U_o /U_mf= 5 followed by heat treatment at 800°C for 5h, delivered a first discharge capacity of 127mAhg ^-1 at 0.1 C rate. Furthermore, it also showed excellent capacity retention at 1 C of more than 92% after 100 cycles.