80% of accidents of lithium-ion battery are caused by short circuit. After short circuit, battery fire and explosion accidents occur frequently. The safety problem of power lithium battery is pushed to the forefront of public opinion again. The reason why short circuit causes more serious consequences is related to the phenomenon of "thermal runaway".

The thermal stability of battery material has always been an important factor in the safety of power lithium battery. Compared with the negative material, the energy density and power density of the positive material are lower. The thermal reaction between battery material and electrolyte is also considered as the main inducement for the development of thermal runaway battery. Therefore, the key to power lithium battery is to find the cathode material with good thermal stability.

In essence, "thermal runaway" is a positive energy feedback cycle process: the increased temperature will cause the system to become hot, and the system will become hot and raise the temperature, which in turn will make the system hotter. Thermal runaway is a very common phenomenon, from concrete curing to star explosion, there may be thermal runaway.

The causes of thermal runaway of lithium-ion battery are as follows:

1. Often overcharge.

2. Unauthorized modification of shell.

3. The ambient temperature is over 60 ° C.

4. The tear of the diaphragm separating the negative electrode and the positive electrode of lithium-ion battery will lead to short circuit, which often causes thermal collapse.