Preparation of LiNi0.5Mn1.5O4 Cathode Materials of Lithium-Ion Batteries by Drip Pyrolysis in Fluidized Bed Reactor Followed by Heat Treatment and Their Electrochemical Properties

Abstract

LiNi0.5Mn1.5O4 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 5 h. 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 LiNi0.5Mn1.5O4 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|LiNi0.5Mn1.5O4 at various charge-discharge rates. As a result, the LiNi0.5Mn1.5O4 sample, which was synthesized at 600°C and a fluidization number of Uo/Umf = 5 followed by heat treatment at 800°C for 5 h, delivered a first discharge capacity of 127 mAh g−1 at 0.1 C rate. Furthermore, it also showed excellent capacity retention at 1 C of more than 92% after 100 cycles.