Synergistic Effect of Mn3+ Formation-Migration and Oxygen Loss on the Near Surface and Bulk Structural Changes in Single Crystalline Lithium-Rich Oxides.

Micron-sized single crystal particles could be used to intensify structural changes between bulk and surface area during the charge-discharge process owing to their long-range order. In this study, the effects of Mn3+ formation-migration and oxygen loss on the structure change from the bulk side to the near surface in single crystalline Li1.2Mn0.54Ni0.13Co0.13O2 were decoupled by regulating the voltage windows of 2-4.5, 3-4.8, and 2-4.8 V because Mn3+ formation-migration and oxygen loss mainly occurred below 3 V and beyond 4.5 V, respectively. It is found that oxygen vacancies and phase transformation can be retarded by suppressing the formation-migration of Mn3+. Finally, we also conducted an important insight that boron ion doping in tetrahedral site could be used to suppress Mn3+ migration from octahedral site to tetrahedral site and disrupt the synergistic effect of Mn3+ migration and oxygen loss.