Morphology-Dependent Battery Performance of Ni-Rich Layered Cathodes: Single-Crystal versus Refined Polycrystal

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.

Zero-Strain Cathodes for Lithium-Based Rechargeable Batteries: A Comprehensive Review

“…97,98 A CAM with specially designed microstructure called core−shell with composition gradient (CSG) showed suppressed crack formation during cycling. Ryu et al 99 compared single crystalline NCM90 and the refined polycrystalline NCM90 with CSG structure (CSG-NCM90). The CSG-NCM90 cathode was composed of elongated, radially oriented primary particles.…”

“…Electrodes consisting of 1D micro- and nanostructured materials demonstrated notably improved electrochemical performances owing to an optimized contact area between active materials and electrolyte, the shortened diffusion paths for Li + ions and electrons, and their ability to accommodate strain. , A CAM with specially designed microstructure called core–shell with composition gradient (CSG) showed suppressed crack formation during cycling. Ryu et al compared single crystalline NCM90 and the refined polycrystalline NCM90 with CSG structure (CSG-NCM90). The CSG-NCM90 cathode was composed of elongated, radially oriented primary particles.…”

Electrochemical Performances of Nickel‐Rich Single‐Crystal LiNi0.83Co0.12Mn0.05O2 Cathode Material for Lithium‐Ion Batteries Synthesized by Tuning Li+/Ni2+ Mixing

“…As for PC-NCM cathodes, liquid electrolyte could penetrate into active materials along grain gaps, lowing the charge transfer resistance and thus enhancing the Li-ion diffusion coefficient and rate performance. [20] However, the reason that affects the rate performance of cathode materials is not only the electrolyte penetration. Due to the fast kinetics of Li + transport induced by low cation disorder (The migration of Li + is relatively easy with little obstruction from Ni 2 + ), SC83 shows superior rate performance.…”

Molten Salt‐Assisted Synthesis of Single‐Crystalline Nonstoichiometric Li1+xNi1–xO2 with Improved Structural Stability

“…[11,12] In addition, LiNiO 2 -based cathode materials generally experience anisotropic lattice expansion/contraction and mechanical stress during cycling, which cause the formation and propagation of intergranular microcracks that consequently induce the spalling of primary particles and pulverization of secondary particles. [2,13,14] The crack generation and particle pulverization not only result in a severe loss of electrical contact, but also aggravate the electrolyte penetration in intergranular microcracks and parasitic interfacial reactions. Furthermore, PC LiNiO 2 particles are vulnerable to cracking and crushing during electrode pressing, which limits the compact density of the electrode and the volumetric energy density.…”