Despite numerous experimental and theoretical investigations of the mechanical behavior of high-capacity Si and Ge Li-ion battery anodes, our basic understanding of swelling-driven fracture in these materials remains limited. Existing theoretical studies have provided insights into elasto-plastic deformations caused by large volume change phase transformations, but have not modeled fracture explicitly beyond Griffith’s criterion. Here, we use a multi-physics phase-field approach to model self-consistently anisotropic phase transformation, elasto-plastic deformation, and crack initiation and propagation during lithiation of Si nanopillars. Our computational results reveal that fracture occurs within a “vulnerable window” inside the two-dimensional parameter space of yield strength and fracture energy and highlight the importance of taking into account the surface localization of plastic deformation to accurately predict the magnitude of tensile stresses at the onset of fracture. They further demonstrate how the increased robustness of hollow nanopillars can be understood as a direct effect of anode geometry on the size of this vulnerable window. Those insights provide an improved theoretical basis for designing next-generation mechanically stable phase-transforming battery materials undergoing large volume changes.

尽管对高容量Si和Ge锂离子电池阳极的机械行为进行了大量实验和理论研究，但我们对这些材料中溶胀驱动断裂的基本理解仍然有限。现有的理论研究提供了由大的体积变化相变引起的弹塑性变形的见解，但是还没有明确地建立超出格里菲斯准则的断裂模型。在这里，我们使用多物理场相场方法对硅纳米柱的锂化过程中的自洽各向异性相变，弹塑性变形以及裂纹萌生和扩展进行建模。我们的计算结果表明，断裂发生在屈服强度和断裂能的二维参数空间内的“易受伤害的窗口”内，并突出了考虑塑性变形的表面局部以准确预测拉伸应力大小的重要性。骨折发作。他们进一步证明了中空纳米柱的增强的坚固性如何被理解为阳极几何形状对该脆弱窗口尺寸的直接影响。这些见解为设计经受大体积变化的下一代机械稳定的相变电池材料提供了改进的理论基础。他们进一步证明了中空纳米柱的增强的坚固性如何被理解为阳极几何形状对该脆弱窗口尺寸的直接影响。这些见解为设计经受大体积变化的下一代机械稳定的相变电池材料提供了改进的理论基础。他们进一步证明了中空纳米柱的增强的坚固性如何被理解为阳极几何形状对该脆弱窗口尺寸的直接影响。这些见解为设计经受大体积变化的下一代机械稳定的相变电池材料提供了改进的理论基础。