Enhanced Electrical Connectivity in High Energy Density Single-Crystal NCA Electrodes via Polycrystalline Blending Design

Single-crystal (SC) Ni-rich cathodes offer superior cycle stability compared to polycrystalline (PC) cathodes but face challenges with lower rate capability, particularly in high-energy-density commercial electrodes with limited conductive additives. It remains unclear whether this limitation stems primarily from insufficient interparticle connectivity or sluggish lithium diffusion within individual SC particles. Moreover, quantitatively visualizing the utilization of electrodes based on electrical connectivity or lithium diffusion remains challenging. In this study, we employed electrochemical analysis, 46-point probe resistance measurements, and synchrotron-based transmission X-ray microscopy (TXM) to reveal that the poor rate capability of SC electrodes is primarily due to inferior interparticle connectivity. Incorporating PC particles significantly reduces electrical contact resistance, while larger particle sizes further enhance electrode connectivity. Based on these insights, blending a minor fraction of large PC particles effectively improves the rate capability of SC electrodes. TXM lithium imaging at high cycling rates reveals that improved electrical contact between SC and PC particles boosts electrical connectivity, ensuring effective particle utilization and enhanced performance across the electrode.