Morphology of the Solid Electrolyte Interphase on Graphite in Dependency on the Formation Current

Abstract

In this study, detailed insights in the solid electrolyte interphase (SEI) properties and its formation kinetics on different graphite types and in electrolyte mixtures based on ethylene carbonate as well as on propylene carbonate are presented. The competing most important reactions of (i) SEI formation and (ii) solvent cointercalation leading to exfoliation could be controlled by adjusting the specific current in the first cycle; in some cases it was possible to suppress the exfoliation completely and the electrode could be stably cycled. Post mortem scanning electron microscopy clearly revealed differences in the SEI film morphology on graphite particles after electrochemical cycling, depending on the formation conditions. By means of differential electrochemical mass spectrometry (DEMS) the solvent cointercalation prevailing over SEI film formation could be detected in propylene carbonate based electrolytes.