Simulation of First-Charge Oxygen-Dimerization and Mn-Migration in Li-Rich Layered Oxides xLi(2)MnO(3 center dot)(1-x)LiMO2 and Implications for Voltage Fade

摘要

The instabilities of Li-rich layered oxide xLi(2)MnO(3)center dot(1 - x)LiMO2 (lithium-ion-battery cathode materials) during the first charge are investigated using first-principles dynamical simulation. To complement our earlier simulations for (x = 0.4, M = Ni0.5Mn0.5), we address here: pure Li2MnO3; small x; M compositions that include Co; a composite with Co spinel, Li2MnO3 center dot Li2M2O4; a Li2MnO3 slab. We discuss how the threshold fraction f of Li2(1-f)MnO3 delithiation at which instabilities occur at the surface, f(th)(surface), differs from that in the bulk, f(th)(bulk). Approaches to inhibit voltage fade are discussed.