Performance degradation and failure characteristics of lithium-ion batteries under impact loading

To address performance degradation and safety challenges in lithium-ion batteries under impact, this study aims to investigate the damage and failure characteristics of batteries under various collision forms. For NCR18650BD cylindrical lithium-ion batteries, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) methods, and the multi-physics in-situ monitoring platform were employed, the capacity decay, cycling ageing, and impedance degradation patterns of batteries under ball, cylindrical, and plane punch were analyzed, and the influence of collision form on failure and thermal behavior was revealed. Results show that at an impact energy of 5 J, only the plane punch causes capacity degradation due to lithium inventory loss in the battery at C/20 rate. At 3C rate, the smaller punch means the faster cycle ageing. Furthermore, the larger the punch size, the increased electrochemical impedance of the battery. At an impact energy of 20 J, the smaller punch results in the lower force peak, the more severe battery failure, and the higher probability of thermal runaway. As the impact velocity increases, the overall stiffness of the battery increases, leading to a worsening of force-electric failure. This research provides the theoretical foundation and technical support for the optimized design and safety assessment of lithium-ion batteries.