Oh Yuntaek, Kim Hwiho, Lim Jongbeom, Hwang Yujeong, Jo Sugeun, You Hyunji, Seog Jihyun, Lim Jongwoo
Department of Chemistry, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea.
Samsung SDI, 150-20, Gongse-ro, Giheung-gu, Yongin-si, Gyeonggi-do 17084, Republic of Korea.
ACS Appl Mater Interfaces. 2025 May 14;17(19):28094-28102. doi: 10.1021/acsami.5c01515. Epub 2025 May 5.
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.
与多晶（PC）阴极相比，单晶（SC）富镍阴极具有卓越的循环稳定性，但在倍率性能方面面临挑战，尤其是在具有有限导电添加剂的高能量密度商业电极中。目前尚不清楚这种限制主要是源于颗粒间连接性不足还是单个SC颗粒内锂扩散缓慢。此外，基于电连接性或锂扩散对电极利用率进行定量可视化仍具有挑战性。在本研究中，我们采用电化学分析、46点探针电阻测量和基于同步加速器的透射X射线显微镜（TXM）来揭示SC电极倍率性能差主要是由于颗粒间连接性较差。掺入PC颗粒可显著降低电接触电阻，而较大的颗粒尺寸进一步增强电极连接性。基于这些见解，混合一小部分大尺寸PC颗粒可有效提高SC电极的倍率性能。在高循环速率下进行的TXM锂成像表明，SC和PC颗粒之间改善的电接触增强了电连接性，确保了有效颗粒利用并提高了整个电极的性能。
