Ion mobility is a critical performance parameter not only in electrochemical energy storage and conversion but also in other electrochemical devices. It is of particular importance in solid electrolytes and electrode materials. A thorough understanding of the basic principles underlying the ion mobility in crystalline materials is not only interesting from a fundamental, but also from a applied point of view , as for example the reduced performance of batteries at low temperatures is supposed to be related to low ion mobility. In recent years, significant progress has been made in our conceptual understanding of ion mobility in crystalline electrode materials, especially concerning the role of non-ionic interaction between the migrating ion and the host lattice . In this review, we will discuss the materials properties that correlate with ionic conductivity, in particular with the height of the activation barrier, using the descriptor concept. Both experimental and theoretical studies will be addressed in order to establish strategies to identify solid electrolytes and electrodes with improved mobility mobility. This review is concerned with the ion mobility in crystalline battery materials, including both, electrolytes and electrodes. There is a fundamental difference between electrolytes and electrodes: electrolytes are ion conductors, but they should be electronic insulators, otherwise no electrons would flow through an outer circuit upon battery operation. Electrodes, on the other hand, should be both ion-as well as electron-conductors, otherwise the recombination of ions and electrons upon entering electrodes would not be possible. Still, from a quantum chemical perspective, there is no fundamental difference in the determination of migration properties which crucially depend on the minimum energy path connecting two equivalent intercalation sites and the maximum activation barrier along this path.