Influence of Inversion on Mg Mobility and Electrochemistry in Spinels

Tuesday, 3 October 2017: 10:20
Maryland A (Gaylord National Resort and Convention Center)
G. S. Gautam, P. Canepa (Lawrence Berkeley National Laboratory), A. Urban (University of California, Berkeley), S. H. Bo (Lawrence Berkeley National Laboratory), and G. Ceder (University of California, Berkeley)
Spinels are an important class of compounds in energy-dense multivalent batteries with potential cathode (MgMn2O4) and solid electrolyte (MgIn2S4) applications. Both MgMn2O4 and MgIn2S4 are susceptible to inversion, which is the exchange of Mg and metal (Mn/In) sites in the spinel framework. Using first-principles calculations, we evaluate the impact of spinel Inversion, which can directly lead to several distinct local cation environments, on Mg2+ mobility. While activation barriers for various cation decorations determine the active Mg2+ diffusion channels on the atomic scale, the macroscopic migration of Mg2+ is essential for (dis)charge of cathodes or ionic conduction in solid electrolytes. Subsequently, we perform Monte-Carlo simulations to estimate the minimum Mg concentration required to ensure Mg2+ percolation through the spinel structure. Finally, we analyze the influence of inversion on the electrochemical properties of the MgMn2O4 cathode by investigating the phase behavior, average voltages and extractable capacities at various degrees of inversion.