A comparative investigation of aging effects on thermal runaway behavior of lithium-ion batteries

Thermal runaway is a major concern for the large-scale application of lithium-ion batteries. The thermal runaway performance of lithium-ion batteries not only depends on materials and cell design, but also changes with degradation. This paper presents a comparative investigation of the aging effects on the thermal runaway behavior of a large format lithium-ion battery. The batteries are first degraded under four different aging paths. The aging mechanisms are then investigated through post-mortem analysis on the battery at the end of life, by comparing the electrochemical properties, morphology and composition of the fresh and degraded electrodes. The thermal stabilities of the fresh and degraded electrodes are also evaluated using differential scanning calorimetry. Adiabatic thermal runaway tests are performed on the batteries at different states of health using accelerating rate calorimetry to reveal the evolution of battery thermal runaway performance under the four degradation paths. Finally, the correlations between the aging mechanism and the changes in battery thermal runaway behavior are summarized. The results show that the thermal stability of the anode+electrolyte thermodynamic system exhibits obvious changes, which contribute to the evolution of battery thermal runaway performance, while the thermal stability of the cathode remained unchanged. Lithium plating turns out to be the key reason for the deterioration of battery thermal runaway performance during aging process.