Abstract Mechanical fracture is commonly regarded as one of key ingredients affecting the reliability of Li-ion battery electrode. In order to avoid the rapid mechanical collapse of electrode, attempts have been made to work on obtaining the accurate critical fracture condition for electrode particle with initial cracks under diffusion-induced stress produced in Li-ion intercalation and deintercalation process. However, considering the integrated fracture process on pristine particle, it is crucial to assess crack initiation phase in fracture analysis so as to obtain the comprehensive failure margins of three-dimensional primary particle. This paper evaluates the diffusion induced stress for NCM primary particle morphology under lithiation–delithiation condition, where the coevolving process of diffusion and stress generation is implemented with both diffusion driven approach and chemical potential driven approach by developing finite element subroutines. Based on the coupled diffusion-stress analyses, crack onset and growth of ternary cathode particle are studied by using ABAQUS extended finite element method (XFEM) with appropriate mesh density and verified by experimental observation. The integrated crack initiation and fracture margins with various current densities and particle dimensions are plotted. The innovative equations to acquire critical particle dimension for crack initiation and fracture under applied electrochemical load are established, which are significant for evaluating particle status. Associating the critical failure diagram with the size distribution of particles in NCM electrode samples, the failure proportion is presented for electrode in microscale. The impact of diffusion on active material property is also investigated comprehensively in stress evolution and fracture analysis.

中文翻译：

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锂离子电池电极初级粒子的扩散致应力及开裂行为

摘要 机械断裂通常被认为是影响锂离子电池电极可靠性的关键因素之一。为了避免电极的快速机械塌陷，人们试图在锂离子嵌入和脱嵌过程中产生的扩散诱导应力下获得具有初始裂纹的电极颗粒的准确临界断裂条件。然而，考虑到原始颗粒的整体断裂过程，在断裂分析中评估裂纹萌生阶段对于获得三维初级颗粒的综合失效裕度至关重要。本文评估了在锂化-脱锂条件下 NCM 初级粒子形态的扩散诱导应力，其中，通过开发有限元子程序，使用扩散驱动方法和化学势驱动方法来实现扩散和应力生成的共同演化过程。在扩散-应力耦合分析的基础上，采用合适的网格密度的ABAQUS扩展有限元法(XFEM)对三元阴极粒子的裂纹萌生和生长进行了研究，并通过实验观察进行了验证。绘制了具有各种电流密度和颗粒尺寸的综合裂纹萌生和断裂边缘。建立了获得外加电化学载荷下裂纹萌生和断裂临界粒子尺寸的创新方程，对评价粒子状态具有重要意义。将临界失效图与 NCM 电极样品中颗粒的尺寸分布相关联，以微尺度呈现电极的失效比例。在应力演化和断裂分析中，还全面研究了扩散对活性材料性能的影响。