Liu Chuanlai, Roters Franz, Raabe Dierk
Max Planck Institute for Sustainable Materials, Max-Planck-Str. 1, Düsseldorf, 40237, Germany.
Nat Commun. 2024 Sep 12;15(1):7970. doi: 10.1038/s41467-024-52123-w.
Solid-state Li-ion batteries, based on Ni-rich oxide cathodes and Li-metal anodes, can theoretically reach a high specific energy of 393 Wh kg and hold promise for electrochemical storage. However, Li intercalation-induced dimensional changes can lead to crystal defect formation in these cathodes, and contact mechanics problems between cathode and solid electrolyte. Understanding the interplay between cathode microstructure, operating conditions, micromechanics of battery materials, and capacity decay remains a challenge. Here, we present a microstructure-sensitive chemo-mechanical model to study the impact of grain-level chemo-mechanics on the degradation of composite cathodes. We reveal that crystalline anisotropy, state-of-charge-dependent Li diffusion rates, and lattice dimension changes drive dislocation formation in cathodes and contact loss at the cathode/electrolyte interface. These dislocations induce large lattice strain and trigger oxygen loss and structural degradation preferentially near the surface area of cathode particles. Moreover, contact loss is caused by the micromechanics resulting from the crystalline anisotropy of cathodes and the mechanical properties of solid electrolytes, not just operating conditions. These findings highlight the significance of grain-level cathode microstructures in causing cracking, formation of crystal defects, and chemo-mechanical degradation of solid-state batteries.
基于富镍氧化物阴极和锂金属阳极的固态锂离子电池理论上可达到393瓦时/千克的高比能量，并有望用于电化学储能。然而，锂嵌入引起的尺寸变化会导致这些阴极中形成晶体缺陷，以及阴极与固体电解质之间的接触力学问题。了解阴极微观结构、运行条件、电池材料的微观力学以及容量衰减之间的相互作用仍然是一个挑战。在此，我们提出了一个对微观结构敏感的化学-力学模型，以研究晶粒级化学-力学对复合阴极降解的影响。我们发现，晶体各向异性、荷电状态依赖的锂扩散速率以及晶格尺寸变化会驱动阴极中的位错形成以及阴极/电解质界面处的接触损失。这些位错会引起大的晶格应变，并优先在阴极颗粒表面区域附近引发氧损失和结构降解。此外，接触损失是由阴极的晶体各向异性和固体电解质的力学性能所导致的微观力学引起的，而不仅仅是运行条件。这些发现凸显了晶粒级阴极微观结构在导致固态电池开裂、晶体缺陷形成以及化学-力学降解方面的重要性。
