关键词: 三元锂离子电池, 热失控, 电热耦合, 过充程度, 加热功率

Abstract:

Lithium-ion batteries are widely used in electrochemical energy storage and new energy vehicles. Thermal runaway-induced fires in these batteries pose significant threats to human life and property, restricting the development of electrochemical energy storage and new energy vehicle industries. Current research on lithium-ion battery thermal runaway mainly focuses on the phenomenon under single-abuse conditions. Studies on thermal runaway events triggered by multiple abuse are relatively scarce. Furthermore, the internal mechanisms of thermal runaway induced by electrothermal coupling are not yet well understood. This study investigated the thermal runaway characteristics of a 58 Ah ternary lithium-ion battery cell under the combined effects of electrical and thermal abuse. The differences in thermal runaway characteristics between electrothermal coupling and single abuse conditions were analyzed. Additionally, the effects of different overcharge levels and heating power on thermal runaway behavior under electrothermal coupling were examined. The results revealed that under electrothermal coupling abuse, thermal runaway progresses more rapidly, with an earlier onset of thermal runaway and valve opening, shorter venting and flame-ejection durations, a lower thermal runaway trigger temperature, and a higher peak thermal runaway temperature. These effects significantly raise the risk level. Batteries with a high state of charge (SOC) exhibit a greater risk of thermal runaway. The SOC boundaries for valve opening and thermal runaway for 100 W heating power under electrothermal coupling conditions were determined to be 120% SOC—125% SOC and 125% SOC—128% SOC, respectively. At 100 W and 200 W heating power, the battery voltage variation was similar to that under single overcharge conditions, while at heating powers exceeding 300 W, the variation resembled single overheating conditions. This result indicates that at low heating powers, the internal reaction mechanism under electrothermal coupling is closer to overcharging, whereas at high heating powers, thermal effects dominate. Under electrothermal coupling, thermal runaway progresses more rapidly at high heating powers, with an earlier valve opening and thermal runaway onset. However, at low heating powers, thermal runaway is more severe, exhibiting more intense ejection behavior and a higher peak thermal runaway temperature. Thus, this study provides valuable insights to enhance the safety performance of large-capacity ternary lithium-ion batteries under multiple abuse conditions.

Key words: ternary lithium-ion battery, thermal runaway, electro-thermal coupling, overcharge level, heating power