Ti-Based Surface Integrated Layer and Bulk Doping for Stable Voltage and Long Life of Li-Rich Layered Cathodes

High-energy-density lithium-rich layered oxides (LLOs) hold the greatest promise to address the range anxiety of electric vehicles. Their application, however, has been prevented by fast voltage decay and capacity fading for years, which mainly originate from irreversible transition-metal migration and undesirable cathode-electrolyte interfacial reactions. Herein, a Ti-based surface integrated layer and bulk doping, which greatly improve the voltage and capacity stability of LLOs is synchronously constructed. More importantly, STEM and Raman results demonstrate that continuous and uniform surface Ti-based integrated layer is a spinel-like rocksalt structure with Fd-3m space group, which is built through by several the replacement of Li ions in surface several atomic layers by Ti ions. After 500 cycles, Ti-150 sample delivers a capacity retention of 85%, and its voltage decay rate from the 30th to the 500th cycle is only approximate to 0.72 mV/cycle. Spectral results and DFT calculations suggest that bulk Ti-doping mitigates the migration of Mn and Ni ions in the bulk, while Ti-based integrated layer significantly suppresses surface structure evolution and interfacial reactions by impeding the generation of surface Li vacancies during Li extraction as well as preventing direct contact between electrolyte and active materials.