Li Ion Migration at the Interfaces

During the past decade, the electrochemical properties (energy density, power capability, and cycling stability) of practical lithium (Li) batteries have been enormously improved. Surprisingly, although the knowledge exists of how to prepare excellent batteries, a detailed understanding of how they actually work is still lacking. In particular, the impact of interfaces in electrode composites is poorly understood. Here, we collect the most advanced mechanistic studies performed in our laboratory or published in recent literature and try to embed this knowledge into the well-established concepts used in solid-state ionics for many decades. In particular, we focus on the so-called perpendicular and parallel interfacial effects. We show that much of the old wisdom can be applied to batteries, although there are several important differences. We discuss, in some detail, the effects of charge incorporation, electronic interphase contacting, electrode porosity, and heterogeneous doping in selected advanced electrode materials and emphasize the future perspectives.