Mobile electronics have developed so rapidly that battery technology has hardly been able to keep pace. The increasing desire for lighter and thinner Li-ion batteries with higher capacities is a continuing and constant goal for in research. Achieving higher energy densities, which is mainly dependent on cathode materials, has become a critical issue in the development of new Li-ion batteries. In this review, we will outline the progress on nanostructured 4 V cathode materials of Li-ion batteries for mobile electronics, covering LiCoO2, LiNixCoyMn1−x−yO2, LiMn2O4, LiNi0.5Mn1.5O4 and Li-rich layered oxide materials. We aim to provide some scientific insights into the development of superior cathode materials by discussing the advantages of nanostructure, surface-coating, and other key properties.