The success of lithium-ion batteries in small-scale applications translates to large-scale applications, with an important impact in the future of the environment by improving energy efficiency and reduction of pollution. In this review, we present the progress that allows lithium-insertion compounds with the spinel structure to become the active cathode element of a new generation of Li-ion batteries, namely the 5 V cathodes, which promise to improve the technologies of energy storage and electric transportation, thereby addressing the replacement of the gasoline engine and the increasing demand for green energy power sources. The compounds considered here include the spinel LiNi0.5Mn1.5O4 and its related Cr-doped structure. Emphasis is placed on the control of physical properties that is needed to guarantee the reliability and the optimum electrochemical performance of these materials as the active cathode element of Li-ion batteries. We also report the structural evolution of the spinel phase in both charge (Li extraction) and discharge (Li insertion) reactions.
