Self-Passivation of a LiNiO2 Cathode for a Lithium-Ion Battery through Zr Doping

A self-passivating Li 2 ZrO 3 layer with a thickness of 5–10 nm, which uniformly encapsulates the surfaces of LiNiO 2 cathode particles, is spontaneously formed by introducing excess Zr (1.4 atom %). A thin layer of Li 2 ZrO 3 on the surface is converted into a stable impedance-lowering solid–electrolyte interphase layer during subsequent cycles. The Zr-doped LiNiO 2 cathode with an initial discharge capacity of 233 mA·h·g –1 exhibited significantly improved capacity retention (86% after 100 cycles) and thermal stability, compared to the undoped LiNiO 2 . While the spontaneously formed Zr-rich coating layer provides surface protection, the Zr ions in the LiNiO 2 lattice delay the detrimental phase transition occurring in the deeply charged state of LiNiO 2 and partially suppress the anisotropic strain emerging from the phase transition. Further optimization of the proposed simultaneous coating and doping strategy can mitigate the inherent structural instability of the LiNiO 2 cathode, making it a promising high-energy-density cathode for electric vehicles.