The Role Electronic Junctions in Artificial Interface Engineering: The Case for Indium Tin Oxide on LiMn2O4 Electrodes

Abstract

Electrode coatings have become an indispensable tool for the commercialization of high voltage cathodes. So far, electronically insulating and ionically conducting surface coatings are typically used to improve the electrochemical stability of battery cells. In this paper, it is shown that not only insulating materials but also highly electronically conductive coatings such as indium tin oxide (ITO) can effectively inhibit electrolyte decomposition through the formation of electronic junctions while preserving ionic and electronic conduction. The exact electrolyte decomposition kinetics are determined through direct measurements utilizing a LiMn2O4 (LMO) thin-film model system and explained by a theoretical exposition on the electronic band structures of the active material, coating material, and redox species in the electrolyte. Junction formation is worked out specifically for ITO coated LMO thin-film electrodes but can be generalized to any material and morphology. Aside from the beneficial effect of well-engineered electronic junctions on electrochemical stability, highly conductive coatings can be exploited to improve the contact between the active material and the current collector through the creation of a shunt conductor, as demonstrated in the final section of the article.