Enhancing Thermal and High-Voltage Cycling Stability of Ni-Rich Layered Cathodes through a Ti-Doping-Induced Surface-Disordered Structure

Abstract

Due to the high-energy density and potential cost advantage, Ni-rich layered oxide cathodes have attracted attention in electric vehicles. However, the inferior thermal stability and long-term cycling stability in a deeply charged state seriously restrict their large-scale applications. The oxygen topotactic lattice structure degradation caused by the irreversible anionic redox reaction has been considered one of the main reasons that cause the abovementioned electrochemical issues. Herein, we propose a modification strategy by constructing a surface-disordered structure to improve the thermal and high-voltage oxygen lattice structure stability of Ni-rich layered cathodes. Density functional theory calculations indicate that Ti4+ with a d0 electronic structure can be used as the inducer of surface-disordered structures. We directly demonstrate the successful design of a surface-disordered structure on the LiNi0.8Mn0.1Co0.1O2 model compound through neutron diffraction and scanning transmission electron microscopy measurements. The constructed surface-disordered structure can enhance the thermal and high-voltage cycling stability of LiNi0.8Mn0.1Co0.1O2. Furthermore, in situ X-ray diffraction and surface structure analyses indicate that this surface-disordered structure can improve the reversibility of bulk structure transition and stability of the formed cathode electrolyte interphase. This facile construction method of the surface-disordered structure provides a reference for industry and other layered oxide cathodes.