Restraining Planar Gliding in Single-Crystalline LiNi_0.9Co_0.05Mn_0.05O₂ Cathodes by Combining Bulk and Surface Modification Strategies

The delamination cracking from planar gliding along the (003) facets and anisotropic lattice strain perpendicular to the (003) facets inevitable lead to degradation of Ni-rich single-crystal cathode materials, adversely affecting their cyclability. Herein, we rationally design a single-crystal LiNi_0.9Co_0.05Mn_0.05O₂ (SC90) cathode with robust chemo-mechanical properties, in which coherently grown MgO₆ octahedra and BO₄ tetrahedra are incorporated into the lattice, and a stabilizing Mg₃(BO₃)₂ layer is concurrently formed on the particle surface. Multiscale in/ex situ characterizations and theoretical calculations indicate that introducing the MgO₆ and BO₄ units leads to a “pinning effect” within the layered structure. This in turn strongly mitigates mechanical degradation by reducing planar gliding and delamination cracking over extended cycling. Moreover, the Mg₃(BO₃)₂ coating maintains fast lithium diffusion by suppressing parasitic reactions at the cathode|electrolyte interface. The tailored SC90 cathode exhibits a capacity retention of ~88 % after 300 cycles at 5 C rate, significantly outperforming the pristine counterpart (~60 %). Additionally, a pouch-type full cell with a graphite anode sustains a specific discharge capacity of 177 mAh g⁻¹ after 500 cycles, with 90 % capacity retention. This work highlights the “pining effect” in preventing unfavorable slab sliding and structural deterioration, offering new insights for designing advanced ultrahigh Ni single-crystal cathodes.