The energy density of Li ion batteries (LIBs) needs to be improved for the requirement of electric vehicles, hybrid electric vehicles and smart grids. Developing high-voltage LIBs is an important trend. In recent years, high-voltage cathode materials, such as LiCoPO4, Li3V2(PO4)3, Li2CoPO4F, LiNi0.5Mn1.5O4, and lithium-rich layered oxides, and matched electrolytes including stable solvents and functional additives, have been investigated extensively. In this review, we summarize the recent progress in high-voltage cathode materials and matched electrolytes, as well as the optimization of other cell components such as conductive agents, binders, positive cans, separators and current collectors. The problems and prospects of high-voltage LIBs are also discussed.