(a) The battery with oval safety valve; (b) the battery with round safety valve; (c) the battery with cavity safety valve; (d) error analysis of the expansion force. Similarly, the safety valve type had a large influence on the gas venting behavior of the batteries.
When the internal pressure value of the battery reached the opening pressure of the safety valve, the safety valve opened. At stage II, the safety venting can be seen in the recording image in Fig. 3, a large amount of electrolyte was ejected from the inside of the battery.
The cavity safety valve of Sample battery 3 # has a top cap, which impedes the instantaneous venting behavior and leads to a higher maximum expansion force during TR. Fig. 5. The expansion force and gas pressure variations of the LFP batteries with three types of safety valves.
The expansion force and gas pressure variations of the LFP batteries with three types of safety valves. (a) The battery with oval safety valve; (b) the battery with round safety valve; (c) the battery with cavity safety valve; (d) error analysis of the expansion force.
During the safety venting, the gas venting pressures of Sample batteries 1 #, 2 # and 3 # were 181 ± 21, 3220 ± 325, and 132 ± 11 Pa. Due to the surface temperature and opening time being similar for three batteries, the safety valve type dominates over gas venting pressure of battery during safety venting.
The safety valve is an important component to ensure the safe operation of lithium-ion batteries (LIBs). However, the effect of safety valve type on the thermal runaway (TR) and gas venting behavior of LIBs, as well as the TR hazard severity of LIBs, are not known.