LAUSR

The solid electrolyte interphase (SEI) on the graphite particles of lithium‐ion battery anodes passivates the anode against electrolyte reduction due to electron transfer reactions, and a stable and well‐passivating SEI is an important prerequisite for a long cycle life of batteries. Despite the importance of the SEI for fast battery cycling and for battery aging, the transport of ions, electrons, and molecules across the SEI is poorly understood. This prevents the development of improved SEI formation protocols for reducing the SEI formation time during battery manufacturing as well as for slowing down SEI aging. In this perspective article, possible transport mechanisms inside the SEI are considered, and an overview of the results of transport studies on SEIs formed on carbon‐based electrodes is given. The conclusions that can be drawn from these results are discussed as well as the most important open questions, which should be addressed in future work.