Synthesis and Electrochemical Properties of Hexagonal Sliced LiNi0.5Mn0.5O2 as Cathode Materials for Li-ion Batteries

Abstract

Single-phase lithium nickel manganese oxide, LiNi_0.5Mn_0.5O₂, was successfully synthesized from nickel manganese oxide precursor that prepared by co-precipitation step by step. SEM images show the final product LiNi_0.5Mn_0.5O₂ has a uniform morphology composed of hexagonal cubes with the diameter about 300 nm composed of hexagonal slices and smooth crystal surface. The measured cation ratios of Ni: Mn in different sites is nearly 1:1 according to the results of EDAX. X-ray diffraction pattern shows that the product is well crystallized with a high value of I₀₀₃/I₁₀₄ and no diffraction peaks of LiMn₂O₃ can be detected. Electrochemical performance of as-prepared LiNi_0.5Mn_0.5O₂ was examined in the test battery by charge-discharge cycling with different rate. The cycling behavior between 2.5 and 4.4 V at a current rate of 20 mA g^-1 shows a reversible capacity of about 209 mAh g^-1 with little capacity fading after 30 cycles. High-rate capability test shows that even at a rate of 320 mA g^-1, stable capacity about 108 mAh g^-1 is still retained. The favorable electrochemical performance was primarily attributed to regular and stable crustal structure with the uniform morphology.