The interfacial surface reactivity at the cathode/electrolyte interface of high-voltage Li-ion batteries employing the LiNi0.5Mn1.5O4 (LNMO) spinel as the active cathode material is largely responsible for the severe capacity fade exhibited by LNMO/graphite Li-ion battery systems, where the formation of an unstable passivation layer at the cathode ultimately leads to the surface leaching of transition metal ions. Thus, an enhanced understanding of electrolyte/cathode chemical processes is important for the design of interfacial material components which mitigate capacity fade. In previous simulation work employing a single-molecule/surface model, we showed that various electrolyte molecules undergo spontaneous oxidation decomposition reactions at the LNMO cathode surface similar in mechanism to the stepwise and concerted proton-coupled electron transfer reactions proposed in recent experimental work by Kostecki et al.[1,2] We extend our previous work by going beyond a single-molecule/surface model to including more complex interactions at the surface. We performed Density Functional Theory calculations (PBE+U and HSE06 methods) in implicit solvent on model electrolyte/cathode interfaces consisting of clusters (carbonates, sulfonates, and fluorinated solvents) interacting with the various stable LNMO cathode surfaces to examine the effect of including explicit neighboring molecules on the electrochemical stability of an electrolyte molecule interacting with a surface. Using the metadynamics and the Nudged Elastic Band method, we also examined the bonding properties and energetics of Ni and Mn transition metal ions near the electrolyte/cathode surface reactions to determine if surface reactivity, such as the hydrogen passivation of surface oxygen atoms, facilitates the subsequent removal of transition metal ions from the surface. [1] Borodin O. et al, Nanotechnology 26, 354003, 2015 [2] Kostecki R. et al, J. Am. Chem. Soc. 137, 3533−3539, 2015

Modeling of oxidation decomposition reactions and transition metal dissolution at the electrolyte/cathode interface for the spinel-structured LiNi0.5Mn1.5O4 high-voltage cathode

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.