Engineering Homogeneous Dopant Distribution via Nano-Sol Infusion: A Strategy for Microcrack Suppression in LiNiO₂

LiNiO₂ (LNO), a promising candidate for the commercialization of high-energy-density lithium-ion batteries, offers high reversible capacity but suffers from limited cycle life due to anisotropic lattice distortion and the resulting chemical and mechanical degradation during repeated cycling. To address these challenges, we propose a nano-sol infusion doping strategy that overcomes the inherent limitations of conventional solid-state doping, namely poor dopant homogeneity throughout secondary particles and particle agglomeration caused by high-temperature calcination. This process enables nanoscale (∼10 nm) dopant precursors to be uniformly infused into the cathode precursor using only a small amount of solvent and simple equipment, facilitating stable dopant incorporation and homogeneous distribution during subsequent calcination. The infusion-doped LNO (ID-LNO) synthesized by this approach delivered a capacity retention of 86.06% after 100 cycles at 1 C, outperforming both undoped and solid-state doped LNO. The results clearly demonstrate that ID-LNO possesses superior structural stability, characterized by the suppression of microcrack formation and mitigation of c-axis contraction during the H2-H3 phase transition. This study demonstrates that nano-sol infusion doping is a novel synthesis strategy capable of fundamentally alleviating the structural degradation of LNO and suggests it as a viable approach with potential applicability to various high-valence dopants and ternary layered oxide compositions (e.g., NCM and NCA) for the development of long-life, high-rate, and high-energy-density lithium-ion batteries.