Lithium-rich layered oxides, xLi2MnO3$(1�x)LiMO2(M 1⁄4 Ni, Mn, Co), have been under intense investi- gation as high-performance cathode materials for lithium ion batteries due to their high discharge ca- pacity, low cost and environmental benignity. Unfortunately, the commercialized application of these cathode materials have so far been hindered by their severe capacity and voltage fading during high voltage cycling (>4.5 V vs. Li/Liþ). In an attempt to overcome these problems, herein, highly crystalline Al2O3 layer from the hydrolysis of aluminum isopropoxide are coated on 0.5Li2M- nO3$0.5LiNi0.5Co0.2Mn0.3O2 with controlling the growth of Al2O3 crystals. The coin cell with bare cathode material delivers a high discharge capacity over 268.2 mAh g�1 between 2.0 V and 4.8 V, while the Al2O3 coated cathode material shows the excellent cycling stability corresponding to 98% capacity retention after 100 cycles at 1C. More importantly, the highly crystalline Al2O3 coated cathode materials exhibit a significantly lower discharge voltage decay compared to the bare cathode materials, which could be ascribed to the suppression of the layered-to-spinel transformation by compact and highly crystalline Al2O3 layer. The results here will shed light on developing cathode materials with special structures and superior electrochemical properties for high-performance lithium ion batteries.