Synergetic effect of high Ni ratio and low oxygen defect interface zone of single crystals on the capacity retention of lithium rich layered oxides

Li-rich layered oxides (LLOs) are promising cathode materials for Li-ion batteries owing to their high capacities (>250 mAh g−1), however, they suffered from severe capacity and voltage fading caused by irreversible oxygen loss and phase changes. Herein, the structural stability of single crystalline and polycrystalline Li1.14Ni0.32Mn0.44Co0.04O2 was compared in detail. It was found that the stability of oxidized oxygen ions on the near surface was improved in single crystals, which retarded oxygen loss from surface and surficial phase changes, possibly owing to the facet regulating and low surface curvature. In addition, the formation-migration of Mn3+, one of the crucial factors that caused capacity fading of LLOs, can be mitigated by increasing Ni3+ ratio. Under the synergistic effect of low oxygen defects on the near surface and high Ni3+ ratio, stable cycling performances and higher thermal stability were obtained.