To determine if the solid-electrolyte-interphase (SEI) selectively permits reduction of redox shuttles because of specific surface interactions, through-film ferrocenium reduction was studied on the edge and basal planes of highly oriented pyrolytic graphite (HOPG). Monitoring ferrocene kinetics in-situ during SEI formation demonstrated that the SEI formed in LiPF6-based electrolyte is unstable on both graphite orientations, and that introducing just 1.6 mM of PF6- to the electrolyte chemically dissolves the SEI formed in LiClO4-based electrolyte. When PF6- was avoided completely, a 2 V overpotential was sufficient to reduce ferrocenium through the SEI on the basal plane, suggesting through-film tunneling. On the edge plane, more complicated behavior was observed. On both orientations, the shuttle cation can function as an oxidizing agent that corrodes the SEI. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.028212jes] All rights reserved.