Correlating Morphological and Structural Evolution with the Electrochemical Performance of Nickel-Rich Cathode Materials: From Polycrystal to Single Crystal

Nickel-rich layered oxides (Ni ≥ 90%) have been recognized as a promising cathode material for Lithium-ion batteries (LIBs) owing to their high energy density and low cost. Herein, we prepared 20 LiNi 0.90 Co 0.06 Mn 0.04 O 2 (Ni90) samples with various morphologies by regulating sintering temperature and the lithium to transition metal ratio. The correlation between the synthesis conditions, structural properties, and electrochemical performance of Ni90 materials was thoroughly investigated during the evolution from polycrystal to single crystal. A positive and linear relationship was found between sintering temperature and primary particle size (PPS), which affect the electrochemical performance profoundly. Polycrystals with small PPS show a high discharge capacity and low polarization, while single crystals with large PPS have low discharge capacity but excellent cycling stability. Moreover, the sluggish kinetic properties of Ni90 materials at the end of discharge (a sharp drop in lithium-ion diffusion coefficient at the end of discharge) lead the morphology factors to a critical feature that dominates the total discharge capacity. Taking discharge capacity and cycling stability into integrated consideration, the quasi-single crystal Ni90 materials with moderate PPS and the lowest cation disordering is the first choice. These findings contribute to a better understanding of polycrystalline and single-crystal Nickel-rich cathode materials for LIBs.