Thermal runaway-induced short-circuit arc in highly integrated lithium-ion battery systems: mechanisms, thresholds, and mitigation strategies

Thermal runaway-induced short-circuit arc in battery cell blocks or modules pose severe risks to electric vehicle safety; Despite this risk, however, their failure mechanisms, path and safety thresholds remain insufficiently understood. This study addresses these gaps by investigating short-circuit arc in commercial battery systems. Three short-circuit arc modes (case-to-case, case-to-busbar, and busbar-to-busbar) and corresponding failure paths were identified, with the case-to-case mode confirmed as the most hazardous. Experimental characterization reveals three phenomena during the case-to-case mode: weak Joule heating, intrinsic breakdown, and thermal breakdown with temperatures exceeding 1400 °C under 117 V and 7.2 mm, capable of triggering adjacent cell thermal runaway. A quadratic correlation between the critical breakdown voltage and electrode spacing was established, and a risk map was proposed. This study clarifies the mechanisms of thermal runaway-induced short-circuit arc, providing a quantitative safety design tool for highly integrated/high-voltage battery systems.