Ion Mobility in Crystalline Battery Materials

Ion mobility in electrolytes and electrodes is an important performance parameter in electrochemical devices, particularly in batteries. In this review, the authors concentrate on the charge carrier mobility in crystalline battery materials where the diffusion basically corresponds to hopping processes between lattice sites. However, in spite of the seeming simplicity of the migration process in crystalline materials, the factors governing mobility in these materials are still debated. There are well‐accepted factors contributing to the ion mobility such as the size and the charge of the ions, but they are not sufficient to yield a complete picture of ion mobility. In this review, possible factors influencing ion mobility in crystalline battery materials are critically discussed. To gain insights into these factors, chemical trends in batteries, both as far as the charge carriers as well as the host materials are concerned, are discussed. Furthermore, fundamental questions, for example, about the nature of the migrating charge carriers, are also addressed. Ion mobility is a critical performance parameter in electrochemical devices. In crystalline materials, ion migration typically occurs via hopping between two local minima. In this review, chemical trends in the ion mobility in crystals and the nature of the migrating species are discussed, resulting in the identification of descriptors for the height of the activation barrier for migration.