Electrochemical properties of high-voltage LiNi0.5Mn1.5O4 synthesized by a solid-state method

LiNi0.5Mn1.5O4 cathode material has been synthesized by a solid-state reaction designedly using industrial raw materials (Li2CO3, NiO and electrolytic MnO2) in bulk scale, which are all used without further purification. The aim is to find the optimal preparation process of LiNi0.5Mn1.5O4 material for commercial application. The synthesis temperatures are adjusted to form a disordered Fd(3) over bar m structure at 800-950 degrees C for 12 h and then at 600 degrees C for 6 h. Meanwhile, some powders have also been calcined at 850 degrees C for 8-14 h and next annealed at 600 degrees C for 6 h. XRD patterns, SEM micrographs and distribution curves of particle size shows that the LiNi0.5Mn1.5O4 cathode material calcined at 850 degrees C for 12 h and then annealed at 600 degrees C for 6 h exhibits the best crystallinity, crystal shape as well as the best normal distribution. Electrochemical tests show that the LiNi0.5Mn1.5O4 material synthesized at 850 degrees C for 12 h and then annealed at 600 degrees C for 6 h has the highest capacity and excellent rate capability. After 200 cycles, the capacity retentions of the sample at 1, 2 and 5 C are as high as 97.8%, 98.5% and 98.0% of its initial capacities (120.8, 118.1 and 111.2 mA h g(-1)), respectively. The fundamental findings in this work can be applied to guide the synthesis of spinel LiNi0.5Mn1.5O4 as high performance electrode materials for lithium ion batteries, especially for industry.