With high energy density and long cycle life, lithium-ion batteries (LIBs) are
currently the most promising electrochemical devices for electric vehicles and
energy storage. However, the safety and reliability of LIBs can be significantly
compromised in low-temperature cyclic due to anode lithium plating and other
factors which are still unclear. Therefore, it is essential to reveal the
thermal-gas stability of LIBs under low-temperature cyclic. This study
investigates the thermal runaway (TR) characteristics and gas production
characteristics after TR of 18650-type NCA LIBs across four states of health
(SOH), from 100% to 70%. Using Glove box, Electrochemical impedance
spectroscopy, Scanning electron microscope, X-ray photoelectron spectroscopy,
Accelerating rate calorimetry, and Gas chromatography, the research identifies
critical trends in temperature rate, gas composition and explosion risk. After
around 150 cycles, there is a significant and rapid decline in capacity. The
internal resistance of batteries continues to increase, lithium is precipitated
on the anode, and the cathode experiences particle fragmentation. Comparing the
70% SOH batteries with the 100% SOH, it is observed that more Li2O,
Li2CO3 and LiF appeared on the anode. The triggering
time of TR was 41.38% earlier, and the maximum temperature during TR decreased
by 7.89%. The mass loss of the 70% SOH batteries were 11.85% higher than that of
the 100% SOH. The gas production volume of the 80% SOH is the lowest, while that
of the 70% SOH is the highest. Compared with the 100% SOH batteries, the upper
limit (UEL) of gas production explosion for 70% SOH decreases by 3.67%, while
the lower limit (LEL) increases by 24.46%. This indicates that the gas
production of fresh batteries has a wider range of explosion limits. These
research findings provide crucial insights for enhancing the safety and
reliability of LIBs during operation, storage, and recycling processes.