Synergistic\nEffect of Mn<sup>3+</sup> Formation–Migration\nand Oxygen Loss on the Near Surface and Bulk Structural Changes in\nSingle Crystalline Lithium-Rich Oxides

Micron-sized\nsingle crystal particles could be used to intensify\nstructural changes between bulk and surface area during the charge–discharge\nprocess owing to their long-range order. In this study, the effects\nof Mn³⁺ formation–migration and oxygen loss on the\nstructure change from the bulk side to the near surface in single\ncrystalline Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ were decoupled by regulating the voltage\nwindows of 2–4.5, 3–4.8, and 2–4.8 V because\nMn³⁺ formation–migration and oxygen loss mainly\noccurred below 3 V and beyond 4.5 V, respectively. It is found that\noxygen vacancies and phase transformation can be retarded by suppressing\nthe formation–migration of Mn³⁺. Finally, we also\nconducted an important insight that boron ion doping in tetrahedral\nsite could be used to suppress Mn³⁺ migration from octahedral\nsite to tetrahedral site and disrupt the synergistic effect of Mn³⁺ migration and oxygen loss.