To identify the impact of fast-charging aging factors on the operation and thermal safety performance of lithium-ion

batteries, this study first conducts cyclic aging tests on commercial 18650 lithium-ion batteries using 1C/2C charging rate to characterize capacity decay, electrochemical impedance, operating temperature rise, and other characteristics of the battery. Secondly, on the self built thermal runaway platform, compare the differences in thermal runaway behavior and temperature characteristics between fresh and fast-charging aged lithium-ion batteries are compared. The results show that the aging process of lithium-ion battery is nonlinear, and presents three stages corresponding to different aging mechanisms. Increasing the fast-charging rate leads to a significant magnify in charge

transfer impedance and ohmic impedance. The cycle life of lithium-ion batteries with 2C charging rate aging shortens rapidly, and abnormal heat release behavior occurs during the cycle, and the maximum surface temperature reaches 75 ℃ during the charging phase, which not only accelerates the capacity decay of the battery, but also increases the risk of thermal runaway. The results of the thermal runaway test show that the thermal runaway of aged

lithium-ion batteries is delayed and the temperature of thermal runaway is higher. Lithium-ion batteries affected

by fast-charging aging factors have better thermal stability, but the process of thermal runaway is more dangerous.

lithium-ion battery safety, fast-charging, thermal runaway, aging degradation, cyclic life