LiNi0.5Mn1.5O4 obtained by sol–gel method often shows low capacity and 4V discharge plateau due to the small amount of Mn3+ and impurity phases. In this study, fluorine-doped spinel with nominal composition of LiNi0.5Mn1.5O3.975F0.05 was prepared using sol–gel technique and re-annealing in oxygen. XRD measurements reveal that fluorine doping can suppress the formation of NiO impurity. The electrochemical performance of LiNi0.5Mn1.5O3.975F0.05 as cathode material for lithium-ion batteries was examined. Comparing with LiNi0.5Mn1.5O4, fluorine doping enhances the initial capacity from about 130mAhg−1 to over 140mAhg−1 between 3.5 and 5.2V and simultaneously reduces the voltage polarization. About 95% capacity is retained after 40 cycles. By followed re-annealing in oxygen, the 4V plateau can be obviously restrained.