Unraveling the Effects of Al Doping on the Electrochemical Properties of LiNi0.5Co0.2Mn0.3O2 Using First Principles

One of the prevailing approaches to tune properties of materials is lattice doping with metal cations. Aluminum is a common choice, and numerous studies have demonstrated the ability of Al3+ doping to stabilize different positive electrode materials, such as Li[Ni-Co-Mn]O-2 (NCMs). Currently, an atomic level understanding of the stabilizing effect of Al doping in NCMs is limited. In this work, we investigate the effect of Al doping on Ni-rich-NCM-523 (LiNi0.5Co0.2Mn0.3O2). Our results suggest that Al stabilizes the structure of the cathode material via strong Al-O iono-covalent bonding due to a significant Al(s)-O(p) overlap, as well as significant charge transfer capabilities of Al. The calculated formation energies suggest that Al doping results in stabilization of partially lithiated states of NCM-523. On the other hand, calculated voltages indicate only a minor change in the voltage profiles as a function of the state-of-charge due to Al doping, and a modest increase in the Li diffusion barrier was observed. We note that high doping concentrations might mitigate the Li diffusion rates. (C) The Author(s) 2017. Published by ECS. All rights reserved.