1. Overheating of the battery: Overheating of the battery will cause thermal runaway, which is most likely to occur during the charging and discharging of the battery. Because the lithium-ion battery has a certain internal resistance, it will generate a certain amount of heat while outputting electric energy to supply power for pure electric vehicles, which will make its own temperature higher. When its own temperature exceeds its normal working temperature range, it will damage the life and safety of the whole battery.

2. External force impact: Under the application of external force, the lithium-ion battery monomer and battery pack are deformed, and different parts of the lithium-ion battery are relatively displaced, resulting in the tearing of the battery diaphragm and internal short circuit, and the leakage of flammable electrolyte eventually leads to a fire. In the impact of external force, the puncture injury is the most serious, and it may be directly inserted into the battery body, resulting in a direct short circuit between the positive and negative electrodes.

3. Improper use of electricity: When the external short circuit occurs and the heat generated by the battery cannot be dissipated well, the battery temperature will also rise, and the high temperature will trigger the thermal runaway.

4. Overdischarge is one of the least harmful behaviors in using lithium-ion battery pack, but the rise of lithium dendrites caused by overdischarge will reduce the safety of the battery and increase the probability of thermal runaway.

5. Using lithium-ion battery pack during overcharge is one of the most harmful misconduct. Due to excessive lithium intercalation, lithium dendrites grow on the anode surface. Secondly, excessive lithium deintercalation leads to the collapse of cathode structure due to heat generation and oxygen release (oxygen release of NCA cathode). The release of oxygen accelerates the decomposition of electrolyte and produces a lot of gas. Due to the increase of internal pressure, the exhaust valve opened and the battery began to exhaust. After the active substance in the battery cell comes into contact with air, it reacts violently, releasing a lot of heat, which leads to the combustion and fire of lithium-ion battery.

6. Thermal runaway: When the external environment temperature is high or the temperature control system is useless, the battery heat is too high, resulting in short circuit of the lithium-ion battery, which leads to thermal runaway. In fact, the collision and damage of lithium-ion battery, the internal structure and performance of the battery may lead to the situation that heat is out of control.