Lithium battery fires have high combustion intensity, burning speed, and will escape a large amount of toxic fumes, which is extremely dangerous. The development of lithium battery fire early detection and alarm technology can effectively reduce the harm caused by such fires. Lithium batteries are on fire in a jet-type gas fire. The higher pressure of the flame itself makes it difficult for the fire extinguishing agent to reach the root of the flame, which greatly reduces the effectiveness of the fire extinguishing agent. Therefore, it is only effective to suppress or delay the lithium battery fire by spraying the fire extinguishing agent before the open flame.
In the process of thermal runaway of lithium battery under thermal overload condition, the surface temperature of the battery rises to different degrees, but its rising rate and rising range are not large, and there is no sudden change characteristics, such as when the ternary lithium battery is deformed. The surface temperature is only 41.3 ° C, and the temperature at the time of ignition is only 56.3 ° C. Therefore, temperature parameters should not be used as the main indicator of lithium battery fire detection.
In the early stage of thermal runaway of lithium batteries, they generally experience a smoking process, which escapes small molecular characteristic gases such as CO, H2, and CH4. These characteristic gases can often mutate from 0 to hundreds or even thousands of millimeters per cubic meter in a few seconds. It is one of the most important features of lithium battery thermal runaway. These characteristic gases are almost non-existent in conventional environments, and gas detection can be used as one of the main indicators for lithium battery fire detection. At the same time, it should be pointed out that there may be differences in the types and contents of the heat out of control of lithium batteries of different types or systems. When using gas detection as the main detection and alarm method for lithium battery fires, specific battery analysis is required.