The Role of Intergranular Cracks on Fast Charging and Accelerated Degradation in Polycrystalline Layered Oxide Cathodes

Polycrystalline layered oxide cathodes such as Li(Ni_xMn_yCo_z)O₂ (NMC) and Li(Ni_xCo_yAl_z)O₂ (NCA) are some of the most widely used materials for Li-ion batteries. Due to anisotropic volume expansion upon lithium insertion and removal, such particles undergo substantial intergranular cracks. In this article, we presents a perspective on both the positive and negative roles of cracks on the electrochemical performance of these polycrystalline cathode particles based on recent research. Like in many other systems, cracks and fractures result in performance degradation and failure. However, in layered oxide particles, they also play a critical role in faster reaction kinetics by enabling electrolyte penetration, thereby shortening the diffusion length and increasing the reaction area. Acknowledging this dual nature of cracks and electrolyte penetration is critical in understanding how cathode materials are analyzed, modeled, and engineered for future energy storage applications.