Comparative Thermal Runaway Behavior Analysis of High-Nickel Lithium-Ion Batteries with Different Specifications 2022-01-0706

High-nickel lithium-ion batteries extend the driving mileage of electric vehicles (EVs) to 600km without much cost increment. However, thermal accidents commonly occur due to their poor thermal stability, such as thermal runaway. To address the issue, a comprehensive analysis of the thermal runaway behavior of high-nickel lithium-ion batteries with different specifications is conducted. The thermal runaway process is divided into five stages based on self-heating generation, voltage drop, safety valve rupture, and thermal runaway triggering for the three tested cells. The three tested cells demonstrate similar behaviors during each stage of the thermal runaway process. However, there are still apparent differences between their characteristics. This study analyses the thermal runaway features from the following aspects: (i) characteristic temperature; (ii) the relationship between sudden voltage drop and characteristic temperatures; (iii) temperature recovery; (iv) thermodynamics. Although Cell 01 has the highest T1, its T2 is the lowest. In contrast, Cell 03 has the lowest T1, but its T2 is the highest. After the self-heating generation, the sudden voltage drop occurs only after a rise of 1°C for Cell 02. While Cell 03 has a sudden voltage drop after a temperature rise of 28.9°C compared to its T1. From the perspective of the energy barrier, the activation energy barrier of side reactions inside the cell increases due to the happening of venting taking away active substances. Thus, the cell temperature recovery rate is slower for Cell 01 and Cell 02. In contrast, even if safety venting has happened for Cell 03, its energy barrier still drops to a large extent. Therefore, the cell temperature recovers quickly after venting. This study provides guidance for the thermal safety design of EVs, especially for thermal runaway detection and prevention in real applications.