Such BEP scaling relations have for example recently also been found with respect to the ion mobility in spinel materials . As far as cathode materials in batteries of the rockingchair type are concerned, large binding energies directly translate to high open-circuit voltages and thus to a high energy densities. However, according to these BEP relations, high energy densities and fast ion mobilities cannot be achieved for the same material. Hence a compromise between these two properties has to be made, as the combination of a high energy density and a facile ion migration requires to break these scaling relations.