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, we 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 seem- ing 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, we will critically discuss possible factors influencing ion mobility in crystalline battery materials. To gain insights in these factors, we discuss chemical trends in batteries, both as far as the charge carriers as well as the host materials are concerned. Furthermore, we will also address fundamental questions, for example about the nature of the migrating charge carriers.