The Synergic Effects of Zr Doping and Li₂TiO₃ Coating on the Crystal Structure and Electrochemical Performances of Li-Rich Li1.2Ni0.2Mn0.6O₂

Lithium-rich manganese-based layered oxides (LLOs) cathodes attract great attention due to their high specific capacity. But the low rate capability, inferior cycling stability, voltage decay and the poor low-temperature performances hinder their application. Herein, we propose a synergistic strategy of Zr doping and Li2TiO3 coating to mitigate the drawbacks of Li1.2Ni0.2Mn0.6O2, and the cooperative modification mechanism is unraveled. In addition to the pre-doping of Zr in the precursor, a little fraction of Ti is also doped in the host during the coating process. This combines the advantages of Zr/Ti dual doping and Li+-conductor Li2TiO3 coating, which cooperatively enhances the rate capability, cycling stability and the poor low-temperature performances as well as mitigate the voltage decay. Neutron diffraction analysis indicates that the interslab spacing and the bond length of O-O and TM-O are enlarged which lowers the Li+ diffusion energy barrier and the repulsive interaction between Li-ions and TM cations, and facilitate Li+ diffusion and rate capability. The Li+/Ni2+ intermixing is also mitigated which further enhances Li+ diffusion and the layered structure stability. Furthermore, the tightly bound Li+-conducting Li2TiO3 layer not only avoids the electrode side reaction but also enhances the Li+ diffusivity.