Research on overcharge mitigations and thermal runaway risk of 18650 lithium-ion batteries

Abstract

The safety issues of lithium-ion batteries are becoming increasingly severe, and overcharging is one of the primary abuse conditions that can lead to safety incidents in lithium batteries. Overcharging can cause the internal heat of the battery to rise uncontrollably, potentially resulting in thermal runaway under extreme conditions. To thoroughly analyze the impact of protection devices on the overcharging behavior of lithium batteries under different charging rates, this study selected eight types of commercial 18650 ternary lithium batteries. The study systematically evaluated the thermal runaway risk of these batteries under overcharge conditions of 10 V-3 A low current and 10 V-6 A high current. After the overcharge experiments, the batteries were disassembled to analyze the performance of their thermal runaway protection mechanisms during overcharging. The results indicate that under the 10 V-3 A low-current overcharge conditions, the overcharge protection mechanisms of the batteries were effective in preventing thermal runaway. However, under the 10 V-6 A high-current overcharge conditions, the overcharge protection mechanisms failed to effectively curb the occurrence of thermal runaway. Furthermore, the study analyzed the thermal runaway risk of multiple parallel cells and assessed the impact of two typical faults, short charging and interrupted charging, on the thermal runaway risk of the battery pack. These findings provide a scientific basis for further enhancing the safety of lithium-ion batteries.