Tailoring Intergranular Interfaces through Zirconium Solubility-Controlled Segregation for Optimized LiNiO₂ Cathodes

Structural instability and interfacial degradation pose critical challenges in the design of Ni-rich layered cathodes for high energy density lithium-ion batteries. Here, an intergranular interface engineering of LiNi_0.996Zr_0.004O₂ (LNO-Zr) cathode is proposed and realized on a kilogram-scale by in situ doping, promoting the preferential growth of electrochemically active facets and inducing the segregation of Zr at intergranular interfaces. The incorporation of Zr⁴⁺ into Ni(OH)₂ precursors effectively modulates surface energy, guiding crystal growth toward preferential {010}/{101} facets and promoting the formation of ultrafine primary particles with enhanced Li⁺ pathways. During calcination, a conformal Li₂ZrO₃ nanolayer forms at intergranular interfaces due to the limited solubility threshold of Zr in the cathode lattice, acting as a grain growth inhibitor to preserve the radially oriented structure. This engineered architecture mitigates lattice strain, suppresses microcrack propagation, and reduces parasitic reactions. Consequently, the LNO-Zr cathode delivers a high specific capacity of 239.1 mAh g^-1, excellent cycling retention of 78.3% after 200 cycles at 1C, and improved Li⁺ diffusion kinetics with suppressed H2-H3 phase transitions. This work introduces a scalable strategy for intergranular interface engineering of LiNiO₂ cathodes, providing valuable insights into defect chemistry and mechanical stabilization in high-performance Ni-rich cathodes.