Spinel-structured lithium manganese oxide LiMn2O4 (LMO) along with its derivative LiNi0.5Mn1.5O4 (LNMO) are one of the most extensively studied class of cathode materials for rechargeable lithium ion batteries (LIBs). However, it is well established that the dissolution of transition metals (TMs) from the LMO and LNMO surfaces leads to a substantial capacity fading of LIBs. Therefore, the fundamental understanding of the surface properties of spinel oxide, including the mechanism and kinetics of the dissolution process is essential to minimize TMs dissolution and hence to prolong the lifetime of LIBs. By employing a series of DFT calculations augmented by ab initio molecular dynamics (AIMD) simulations, we investigate the evolution of surface TMs (Ni and Mn) oxidation states for the (001) and (111) spinel surfaces as a function of lithium content, surface protonation, and the presence of oxygen vacancies. Subsequently, we explore the interactions between organic electrolyte species (diethyl carbonate) and spinel surfaces. We specifically employ enhanced free-energy sampling techniques to simulate TMs dissolutions with explicit treatment of organic electrolyte. We examine dissolution kinetics and mechanisms and propose plausible dissolution scenarios.

Computational study of LiNi0.5Mn1.5O4 spinel surface properties including transition metals dissolution

256th National Meeting (2018)

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