Surface-to-bulk engineering with high-valence W6+ enabling stabilized single-crystal LiNi0.9Co0.05Mn0.05O2 cathode

Single-crystal Nickel-rich layered oxides has been recognized as one of the promising cathodes for next-generation lithium batteries on account of their high capacity, while its practical application was hindered by structural instability and slow Li+ transfer kinetics. Herein, a surface-to-bulk engineered single-crystal LiNi0.9Co0.05Mn0.05O2 (Ni90) cathode, which features W-doped bulk and Li2WO4 surface layer, was successfully achieved by a one-step high-valence W6+ modification. The as-obtained W-modified Ni90 delivers excellent cycling stability (89.8% capacity retention after 300 cycles at 0.5 C) and rate capability. The enhanced electrochemical performance was ascribed to the doped-W induced stabilized lattice oxygen, reduced Li+/Ni2+ mixing and inhibited H2-H3 phase transition in the bulk, and Li2WO4 layer generated stabilized cathode/electrolyte interface. In addition, the thinner LiF-rich cathode electrolyte interphase (CEI) on surface and smaller grain size for W-modified Ni90 benefit to its Li+ diffusion dynamics. The effect of high-valence W6+ on single-crystal Ni-rich cathode was firstly revealed in detail, which deepens the understanding of electrochemical behavior of Ni-rich cathode with high-valence cations modification, and provides clues for design of high-performance layered cathodes.