Abstract:

In order to investigate the thermal runaway characteristics of lithium-ion batteries following short-term exposure to high or low temperatures shocks during transport and usage, thermal runaway tests were conducted on fully charged lithium-ion batteries. These batteries were subjected to temperature shocks at -40 to 60 ℃ for 24, 48, and 96 hours before external heating was applied. Analyses were performed on thermal runaway characteristic parameters to explore change rules in thermal runaway characteristics after short-term high- or low-temperature shocks. The results indicate that the overall severity of thermal runaway and the intensity of ejected flames were attenuated by the shock factor. With rising shock temperature, the time difference (Δt₁) between the onset of thermal runaway and the rupture of the battery safety valve shows slight fluctuations overall, while both the time difference (Δt₂) between peak temperature and the onset of thermal runaway and the initial thermal runaway temperature tends to increase. In contrast, peak thermal runaway temperature and flame heat flux decrease relatively. When the impact temperature decreases, Δt₁ gradually shortens, while Δt₂ initially increases and then decreases with lower temperatures. Both the onset and peak temperatures of thermal runaway drop significantly, with reductions of 15.2 and 175.4 ℃, respectively, observed at -40 ℃, along with a reduction in flame heat flux. Additionally, with extended shock durations, Δt₁, initial and peak temperatures of thermal runaway, and flame heat flux all decrease.

Key words: high temperature shock, low temperature shock, lithium-ion batteries, thermal runaway, thermal hazards