Electromechanical structural integrity and thermal stability dictate the safety performance of lithium-ion batteries. Progressive deformation and failure across microscopic and macroscopic lengths scales that are responsible for internal short circuit (ISC) in lithium-ion cells under mechanical abuse conditions remains elusive. In this study, a series of indentation tests were conducted on lithium-ion cells with different capacities up to the occurrence of ISC. The external response and internal configuration of these cells were investigated. It is discovered that cells with different capacities and state of charges exhibited different behaviors. Maximum temperature, which is often regarded as the most important parameter related to thermal runaway (TR), varied considerably due to the complicated contact configurations. X-ray computed tomography (XCT) showed that ISC was a collective result of shear band or other strain-localization modes in the electrode assembly, shear offsets in the granular coatings of electrodes, and the accompanying ductile fracture in the metal foils. We believe that the irregular strain-localization modes (kinks, cusps, and buckles), radical mismatches in mechanical properties of different layers, and geometric features of the indenter eventually lead to the tearing/puncture of cell separator at various locations. The results could provide useful guidance for the micromechanical modeling of lithium-ion cells.

机电结构的完整性和热稳定性决定了锂离子电池的安全性能。在机械滥用条件下，导致锂离子电池内部短路（ISC）的微观和宏观尺度的逐渐变形和破坏仍然难以捉摸。在这项研究中，对具有不同容量的锂离子电池进行了一系列压痕测试，直到发生ISC。研究了这些细胞的外部反应和内部结构。发现具有不同容量和电荷状态的电池表现出不同的行为。最高温度通常被认为是与热失控（TR）有关的最重要参数，由于复杂的触点配置，其温度变化很大。X射线计算机断层扫描（XCT）显示，ISC是电极组件中剪切带或其他应变局部化模式，电极颗粒涂层中的剪切偏移以及金属箔中伴随的韧性断裂的共同结果。我们认为，不规则的应变局部化模式（扭结，尖头和弯折），不同层的机械性能的根本失配以及压头的几何特征最终导致细胞分离器在各个位置的撕裂/刺穿。研究结果可为锂离子电池的微机械建模提供有用的指导。我们认为，不规则的应变局部化模式（扭结，尖头和弯折），不同层的机械性能的根本失配以及压头的几何特征最终导致细胞分离器在各个位置的撕裂/刺穿。研究结果可为锂离子电池的微机械建模提供有用的指导。我们认为，不规则的应变局部化模式（扭结，尖头和弯折），不同层的机械性能的根本失配以及压头的几何特征最终导致细胞分离器在各个位置的撕裂/刺穿。研究结果可为锂离子电池的微机械建模提供有用的指导。