(335d) First-Principles Modeling of Anode/Electrolyte Interfaces in Beyond Li-Ion Batteries
AIChE Annual Meeting
2018
2018 AIChE Annual Meeting
Engineering Sciences and Fundamentals
Electrochemical Fundamentals: Faculty Candidate Session
Tuesday, October 30, 2018 - 1:15pm to 1:30pm
Magnesium batteries suffer from the formation of a passivation layer on the anode, hindering the transport of Mg2+ across the anode/electrolyte interface. One possible explanation for this behavior is the decomposition of species present in the electrolyte upon interaction with the anode surface. Using density functional theory, we assessed the energetics for decomposition of a common solvent, dimethoxyethane (DME), on plausible surface compositions of a Mg anode. The energetics of solvent decomposition were found to strongly depend on the composition of the anode surface. On the metallic surface, DME was found to readily decompose into ethylene gas and adsorbed fragments. Surface compositions consisting of films comprised of oxides and chlorides were predicted to be less susceptible to solvent decomposition, supporting previous literature advocating the presence of a Mg-Cl âenhancement layerâ that improves battery performance.
In Li batteries, a solid-electrolyte interphase (SEI) layer is formed between the anode and the electrolyte in early charge cycles. Any battery employing a metallic Li anode will be limited by the properties of the SEI. Experimental studies on Li anodes have revealed that the native oxide that forms on Li metal is likely to constitute the most inner layer of this SEI. In this study, we modeled the metallic Li/native oxide interface by oxidizing a metallic Li slab with ab initio molecular dynamics (AIMD) and compared the resulting structure to a Li/Li2O crystalline slab model. The AIMD procedure generated a physically realistic, oxidized slab, which showed many similarities with the crystalline model. Our results provide a more realistic picture of the atomistic structure of the interface between metallic Li and its native oxide, and demonstrate some of the fundamental constraints when constructing a battery with a metallic Li anode.