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.