In this work, Li2SiO3, a layer-structured fast Li+-ion conductor with three-dimensional Li+ paths, has been firstly introduced into LiNi0.5Mn1.5O4 to form novel cathode composites of (1-x)LiNi0.5Mn1.5O4·xLi2SiO3 via a citric acid-assisted sol-gel method. The effects of Li2SiO3 on the phase structure, morphology and electrochemical performance of the materials were investigated. As x increases, the structure and electrochemical properties of the materials are tailored. The cathode material with x=0.10 delivers ultrahigh initial discharge capacity ∼150.3mAhg−1, which is 24.4% larger than that of the pristine LiNi0.5Mn1.5O4 (120.8mAhg−1). The Li2SiO3-composited LiNi0.5Mn1.5O4 materials present an enhanced cycling stability, better rate performance and lower charge transfer resistance. These excellent electrochemical properties indicate that the compositing of fast Li+-ion conductor Li2SiO3 is an effective method to enhance the electrochemical performance of LiNi0.5Mn1.5O4-based cathode materials.