We present a simple method for producing SiO2-modified LiNi0.5Mn1.5O4 (LNMO) cathode materials. Manganese carbonate was directly mixed with nickel nitrate and lithium hydroxide, and a spherical structure LNMO cathode material was prepared by two-step calcination, then ethyl orthosilicate and LNMO powder were simply mixed in solid and liquid phases to prepare SiO2-coated LNMO material. The effect of SiO2 coating on the structure of LNMO was studied by diffraction of X-rays, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis and differential scanning calorimetry. An amorphous SiO2 coating layer developed on the surface of the LNMO particles in the modification and this could alleviate the strike of hydrogen fluoride (HF) caused by electrolyte decomposition as well as the development of a solid electrolyte interphase. The electrochemical performance of the coated material was as follows: when the amount of SiO2 was 0 wt%, 1 wt%, 2 wt%, and 3 wt%, the initial discharge capacity of the sample was 98.2, 84.1, 101.3, and 89.8mAh/g, respectively. After 50 charge−discharge cycles, the capacity retention rates are 92.7%, 66.8%, 97.9%, and 93.8%, respectively. The cyclic stability of the samples can be significantly improved when the SiO2 coating amount is 2 wt% and 3 wt%, indicating that SiO2 coating can not only improve the discharge-specific capacity of the material but also improve its cyclic stability.