Si doping at high voltage spinel LiNi0.5Mn1.5O4 are presented as an effective strategy to greatly increase the electrochemical performance. Well-crystallized LiNi0.5Mn1.5-xSixO4 (x=0.05, 0.10, 0.15, 0.20) with homogeneous Si distribution are successfully synthesized through solid-state reaction. Structural and electrochemical characteristics are investigated through FESEM, XRD, FTIR, Raman spectroscopy, cyclic voltammetry and galvanostatic charge/discharge testing. It can be demonstrated that Si doping significantly improves the electrochemical performance. LiNi0.5Mn1.35Si0.15O4 exhibits reversible capacities of 123 mAh/g after the 100th cycle at 0.5C and LiNi0.5Mn1.35Si0.15O4 as well as LiNi0.5Mn1.3Si0.2O4 show superior electrochemical stability over the pristine LiNi0.5Mn1.5O4 material. Since the Si-O bond exhibits high dissociation energy of 798kJ/mol (298K), which is far beyond of the dissociation energies of the Mn-O or Ni-O bonds, the excellent electrochemical performance might be associated with an increased structural and chemical stability caused by incorporation of Si into the Oxygen-rich crystal lattice.