Influence of the Formation Current Density on the Transport Properties of Galvanostatically Formed Model-Type Solid Electrolyte Interphases

Abstract

During the production of commercial lithium-ion batteries, the solid electrolyte interphase (SEI) on the graphite particles of the negative electrode is typically formed through galvanostatic protocols with low current densities. Consequently, SEI formation is a time-consuming and rather expensive production step. In order to better understand the influence of the formation current density on the transport of ions and molecules across the SEI, we formed model-type SEIs on planar glassy carbon electrodes under galvanostatic control. In accordance with the expectations from electrochemical nucleation and growth theory, we find that the transport of both ions and molecule becomes slower with increasing formation current density. However, it is remarkable that the ion transport is slowed down more strongly than the molecule transport. We show that at high formation current densities of about −71 μA cm−2, our model-type SEIs clearly exceed the area-specific resistance tolerable in commercial lithium-ion cells.