Al & Ti Synergy enhancing ionic diffusion and stabilizing lattice oxygen for the high voltage single crystal Ni-rich layered oxide cathode materials

Single crystal Ni-rich layered oxide cathode materials enjoy better stability compared to polycrystalline materials, exhibiting good prospects in high energy density lithium-ion batteries. However, the poorer structure stability and rate performance are faced for the future large-scale application of single crystal Ni-rich layered oxide cathode material. The synergistic effect of Al and Ti is studied by in-situ differential electrochemical mass spectrometry (DEMS) and in-situ X-ray diffraction (XRD) combination with density functional theory (DFT) calculations to reveal the phase stabilization mechanism, improving the cycling stability of high voltage Ni-rich single crystal Li(Ni_0·83Co_0·12Mn_0.05)O₂ cathode material. It is indicated that bonding energy between the transition metal and oxygen atoms in the layered oxide are increased by introduction of Al and Ti elements, enhancing the stability of lattice oxygen and increasing the diffusion rate of Li⁺. The Al³⁺ can inhibit cation mixing, while Ti⁴⁺ can optimize the layered structure, which reduces structural failure caused by reaction heterogeneity, enhancing the cycling and rate performance of the cathode material in 4.5 V high voltage. The outstanding stably 500 cycles are obtained with capacity retention rate of 71.8%, compared to the unmodified sample with only 35.1% capacity.