Lee Seok Woo, Lee Hyun-Wook, Ryu Ill, Nix William D, Gao Huajian, Cui Yi
Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.
Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
Nat Commun. 2015 Jun 26;6:7533. doi: 10.1038/ncomms8533.
Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Here, we demonstrate physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. This study will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries.
在对硅作为锂离子电池负极的研究大量涌现之后，锂化单晶硅颗粒的异常体积变化和断裂在包括力学在内的各个领域引起了广泛关注。然而，在实际电池中，锂化是在受限介质中的硅簇中同时发生的。因此，了解单个硅结构在封闭空间中锂化过程中的相互作用是很有必要的。在这里，我们使用定义明确的硅纳米柱对展示了锂化过程中膨胀硅结构的物理和机械相互作用。非原位扫描电子显微镜（SEM）和原位透射电子显微镜（TEM）研究表明，压缩应力会改变反应动力学，使得当柱子被机械夹紧时，优先锂化发生在自由表面。这种机械相互作用通过减轻硅结构中的拉应力集中来提高锂化硅的抗断裂能力。这项研究将有助于在电极层面改进高性能锂离子电池的硅结构设计。
