Sb-anchoring single-crystal engineering enables ultra-high-Ni layered oxides with high-voltage tolerance and long-cycle stability

Abstract

Ni-rich layered oxides are promising cathodes for Li-ion batteries, but the inherent structural defects result in severe surface/bulk degradation during long cycling, especially at high cutoff voltage. Herein we propose a Sb-anchoring single-crystalline engineering to enhance the microstructural and electrochemical stability of ultra-high-Ni layered oxides, where the surface-enriched Sb doping inhibits Li-Ni mixing, suppressing the undesired layered to mixed/rock-salt phase transformation; the bulk-doped Sb rivets into Ni sites, reinforcing the bulk phase stability; the single-crystal endows enhanced crack resistance and reduced surface area, preventing surface parasitic reactions and the subsequent proliferation of cathode electrolyte interfaces. In-situ XRD reveals an essential correlation between cycle stability and phase reversibility, whereas Sb doping into both surface and bulk structures showcases a continuous anchoring effect, largely enhancing the phase transformation reversibility. DFT calculations prove a high oxidation tolerance, as Ni²⁺ diffusion barrier is higher than the pure cathode. A representative Li(Ni_0.9Co_0.05Mn_0.05)_0.99Sb_0.01O₂ cathode exhibits a high-voltage up to 4.6 V, and a Li(Ni_0.9Co_0.05Mn_0.05)_0.99Sb_0.01O₂//graphite full-cell demonstrates an ultra-high capacity retention of 93.4 % after 1000 cycles at 1 C in 3.0−4.2 V. This simple and efficient cathode engineering will promote the promising application of Ni-rich layered oxides in high-energy Li-ion batteries.