Composites Li[Li x Ni0.34−x Mn0.47Co0.19]O2 (0.18≤ x ≤0.21) were prepared by a solid state reaction method assisted with co-precipitating. The chemical composition, structure, morphology, and specific surface area of as-prepared composites were systematically characterized by ICP, XRD, SEM, and BET, respectively. The electrochemical performances of the composites were evaluated as high-voltage cathode for lithium-ion batteries. Among all the composites, sample SN exhibited a best electrochemical performance. Except for the initial decay, no obvious capacity fading was observed after cycling 30 cycles at different rates. The discharge capacities were maintained steadily as the current density increased up to 500mAg−1. The improved electrochemical performance of sample SN was attributed to the compromise effect between the increased Li2MnO3 phase and the enhanced Li/Ni disorder.