Electrochemical performance of ternary lithium-ion batteries after thermal runaway at different ambient temperatures

Ternary lithium-ion batteries (LIBs) can experience hazardous temperature excursions even under normal cycling, posing significant safety risks. Herein, the coupled electro-thermal response of 26,650-type ternary LIBs are investigated subjected to oven-induced heating until thermal runaway (TR) under galvanostatic discharge (1C) at ambient temperatures of −25 °C, 0 °C, 25 °C, 50 °C, and 75 °C, respectively. High-speed videography and post-mortem analysis correlate macroscopic venting/flaming behaviors with microstructural changes in both residual electrodes and ejected materials. The heating-to-runaway process are delineated into four distinct stages based on synchronized voltage and surface temperature records. A consistent voltage dip point emerges 89 ± 5 s prior to TR onset across all these conditions, demonstrating its potential as a robust early-warning signature. With increasing ambient temperature, vented flames intensify markedly, producing larger burn areas and more severe casing deformation. Energy-dispersive X-ray spectroscopy reveals C, O, Al, Ni, Co, Mn, and F in both ejecta and residual electrode materials. Notably, the relative carbon content in ejecta increases monotonically with ambient temperature, implying a temperature-dependent carbonization extent. These results provide quantitative benchmarks for optimizing thermal management strategies and defining safe operating envelopes for ternary LIBs across diverse climatic conditions. • Revealed four phases exist in the behavior of ternary batteries during discharge thermal runaway. • Ambient temperature rise enhances thermal runaway flame intensity and casing damage. • Ejecta carbon content rises with the increases of ambient temperature and indicating the carbonization. • Different ambient temperatures affects the microstructure of electrodes and ejected particles during discharge thermal runaway. • Quantified the V dp , T SVO , and T onset of discharge thermal runaway at different temperatures.