Morphology-Dependent Battery Performance of Ni-Rich Layered Cathodes: Single-Crystal versus Refined Polycrystal
Hoon‐Hee Ryu, Soo-Been Lee, Chong Seung Yoon, Yang‐Kook Sun
Abstract
Single-crystal, conventional, and refined polycrystalline (Li[Ni0.9Co0.05Mn0.05]O2) cathodes were prepared, and their performances and capacity fading behaviors in half cells were compared. The rate capability and cycling stability of polycrystalline cathodes are better than those of single-crystal cathodes. Furthermore, the performance of the refined polycrystalline cathode is markedly improved owing to the elongated, radially oriented primary particles of the cathode, which effectively suppresses severe intergranular microcracking during cycling. The rapid capacity fading behavior of single-crystal cathode stems from kinetically hindered Li+ intercalation, resulting from its long Li+ diffusion paths and microstructural damage caused by repeated cycling. The accumulation of internal stress in large single-crystal particles during cycling leads to fracturing and the development of an extensive network of regularly spaced slip bands. Structural damage concentrated in these slip bands causes inhomogeneities in the distribution of Li+ within particles and hinders Li+ diffusion, leading to poor electrochemical performance.