Facile Ball-Milling Synthesis of Pseudo-Single-Crystalline Nickel-Rich Layered Oxide Cathodes Towards Long-Lifespan Lithium-Ion Batteries

Ni-rich layered oxides (LiNi_xCo_yMn_1−x−yO₂, designated as NCM, where x ≥ 0.8 and x + y < 1) are widely favored as cathode materials for lithium-ion batteries due to their high energy density and cost-effectiveness. However, polycrystalline NCM particles with numerous grain boundaries are prone to microcrack formation and propagation during long-term cycling, resulting in structural collapse and capacity degradation. On the contrary, single-crystal NCM particles with small particle size and few grain boundaries can prevent microcrack formation, thereby enhancing the cycling stability. However, the synthetic methods for obtaining single-crystal NCM particles are expensive and intricate. Herein, a facile ball-milling method is applied to transform pristine micron-sized polycrystalline NCM particles into submicron pseudo-single-crystal particles. By virtue of the pseudo-single-crystal structure, the H2–H3 phase transition and microcracks are effectively suppressed. It is demonstrated that polycrystalline NCM particles with 30-min ball-milling treatment (B-NCM-2) exhibit high capacity of 128.3 mA h g⁻¹ with superior capacity retention of 82.5% after 200 cycles at current density of 100 mA g⁻¹. Even after 400 cycles, the B-NCM-2 sample still delivers impressive reversible capacity of 102.2 mA h g⁻¹ that is far superior to the polycrystalline NCM cathode. This study offers a feasible and effective approach to directly obtain pseudo-single-crystal NCM particles for long-lifespan lithium-ion batteries.