Analysis of failure behavior and safety performance on sodium-ion batteries under dynamic loads

Sodium-ion batteries (SIBs) have emerged as a promising candidate for energy storage applications owing to their material abundance and cost-effectiveness; however, safety issues under mechanical abuse conditions remain insufficiently understood. This study systematically investigates the failure mechanisms of commercial 18650 sodium-ion batteries subjected to radial compression by integrating experimental and numerical approaches. Experiments were conducted using an electronic universal testing machine to characterize the mechanical-electrical-thermal responses at different compression speeds and states of charge (SOC), with synchronous measurements of load, voltage, and temperature. A homogenized finite element model was established to simulate the dynamic crushing behavior at impact velocities ranging from 1 m/s to 35 m/s. The failure mechanisms were interpreted based on stress wave theory, and the failure criteria were calibrated using the experimental results. The results indicate that under quasi-static loading, the battery exhibits a four-stage deformation process, in which the peak load coincides with the onset of failure. With increasing compression velocity, both the peak load and the failure displacement increase, while the temperature rise of batteries at 0% SOC is only weakly affected. In contrast, higher SOC significantly intensifies the temperature rise and advances the occurrence of failure. Under dynamic impact conditions, the failure displacement decreases with increasing impact velocity and shows a pronounced reduction beyond 20 m/s, whereas the load-displacement curve exhibits a distinct plateau at high velocities. The crack initiation location displays a strong dependence on impact velocity: it originates in the central region at low velocities (<15 m/s), shifts to the bottom at approximately 20 m/s, and moves to the impact end when the velocity exceeds 30 m/s. This transition is mainly governed by the propagation, reflection, and superposition of stress waves. Overall, the results indicate that failure of sodium-ion batteries is triggered by structural instability leading to internal short circuits. The SOC primarily controls the thermal response under low-speed compression, whereas stress wave effects dominate the failure behavior at high impact velocities. The proposed model demonstrates good predictive capability for the macroscopic mechanical response and provides valuable insights for the safety design of sodium-ion batteries.