Many Faces of Electrochemical Interfaces: Examples from Solid State and Redox Flow Batteries

Electrochemical interfaces are ubiquitous in nature and technology. In this talk I will overview two important electrochemical energy storage technologies, solid state and redox flow batteries, that cover both portable electronics and grid-scale applications. After a brief introduction into the role of various interfaces in these applications, I will focus on just a few aspects of interfacial electrochemistry of both types of batteries based on our recent first-principles based simulation work. For lithium ion batteries (LIBs) I will discuss our results on transition metal dissolution from high-voltage spinel- structured cathodes, an important degradation pathway contributing to the capacity fading and solid electrolyte interface (SEI) formation. In the case of all-vanadium redox flow batteries, I will present the results of ab initio molecular dynamics based modeling to examine mechanistic pathways of vanadium redox transformations occurring in both aqueous solution and at graphite electrodes. Specifically, we find that the edge surface is characterized by the formation of ketonic C=O functional groups in water due to complete water dissociation into H/O/H configuration. The surface O atoms serve as active sites for adsorption of V2+/V3+ redox couple in the anolyte, and VO2+/VO2 + species redox couple in the catholyte. Overall, our results help unveil the reaction mechanisms previously hypothesized experimentally and suggest that the V2+/V3+ redox reaction should be the rate-limiting step rather than VO2+/VO2 +.

Vitaly Alexandrov
Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, NE, USA;