Synthesis and performance of LiNi0.5Mn1.5O4 cathode materials with different particle morphologies and sizes for lithium-ion battery

Hollow hierarchical structured LiNi0.5Mn1.5O4 materials with tunable morphology and size have been successfully prepared through a urea-assisted hydrothermal route accompanied with high-temperature calcination process. The physical and electrochemical properties of the materials were characterized by XRD, FT-IR, SEM, CV, EIS, GITT and galvanostatic charge/discharge tests. The effects of H2O/ethylene glycol (EG) volume ratio in the solvent on the structure, morphology, and electrochemical properties of carbonate precursor and LiNi0.5Mn1.5O4 products were systematically investigated. XRD results show that varying the H2O/EG volume ratio exerts no obvious effect on the cubic spinel structure of LiNi0.5Mn1.5O4, while the Mn3+ and impurity contents gradually decrease with the increasing volume ratio of EG in solvent. SEM observation illustrates that by increasing the volume ratio of EG, the morphology of carbonate precursor can be tailored from olive-like to peanut-like then further to sphere-like, and the particle size shows a gradual decreasing trend. The LiNi0.5Mn1.5O4 products generally maintain their respective precursor's morphology and exhibit hollow hierarchical structure after high-temperature calcination, except for that synthesized at H2O/EG volume ratio of 1:3. The electrochemical results show that the use of less EG during hydrothemral process is advantageous to the electrochemical properties of LiNi0.5Mn1.5O4 material. Among them, the LiNi0.5Mn1.5O4 product synthesized at H2O/EG volume ratio of 3:1 exhibits optimal electrochemical performance, with discharge capacity of 128.4 mAh/g at 10 C and capacity retention rate of 99.2% after 100 cycles at 1 C.