Briefly describe the safety of lithium iron phosphate batteries

The chemical properties of lithium iron phosphate materials are very stable, especially the high temperature stability is very good, even at very high temperatures can not analyze the released oxygen, so the safety performance of lithium iron phosphate batteries is very good, not prone to dangers such as combustion and explosion. Coupled with a reasonable structural design, its safety has been further improved, so the battery will not burn or explode under impact, needle stick, short circuit, etc. Figure 4 shows that after a 20Ah lithium iron phosphate battery is overcharged, a steel nail with a diameter of 8mm is quickly pierced through the battery, and the voltage and temperature changes of the battery are recorded at the same time. In the initial stage of steel nail piercing, due to the internal short circuit, the battery voltage drops rapidly, and a certain amount of heat is released, and the temperature of the battery rises. However, after being pierced, the internal vacuum of the battery drops significantly, causing the short-circuit contact part to deform and poor contact. At this time, no more heat is released, so the voltage tends to stabilize, and the battery temperature only rises slightly. Weight energy density is an important indicator of battery performance. Figure 5 shows that a 20Ah lithium iron phosphate battery is discharged to 2.0V at a rate of 0.3c after being overcharged. The energy released by the battery can be obtained by integrating the discharge curve. After integral calculation, the 20Ah lithium iron phosphate battery released 70.7Wh of energy, and the weight of the battery is 580g, so the weight energy density of the lithium iron phosphate battery can be calculated to be 121.90Wh/kg. Due to the large geographical differences in the use of electric vehicles, there are cold weather conditions in winter in the north, and the lower temperature will inevitably have a certain impact on the performance of the battery. Therefore, in order to know the low-temperature discharge performance of the lithium iron phosphate battery, the 20Ah lithium iron phosphate power lithium-ion battery was stored at -20℃, -10℃, 0℃, 25℃ and 55℃ for 20h in the detection, and then stored here. Discharge at a rate of 0.3c in a low temperature environment (with a discharge capacity of 0-3c at room temperature as 100%), the results are shown in Figure 6. It can be seen that the lithium iron magnetic acid battery can only release about 55% of the capacity at room temperature at a temperature of 20°C, so it may have an adverse effect on the electric vehicle during use. But in fact, it is very clear that the discharge capacity of a single battery decreases more with the decrease of temperature. For electric vehicles, hundreds of batteries are usually packed together, and a certain amount of heat will be released when the battery is working. At this time, the temperature of the battery will inevitably rise, so for battery packs in practical applications, the problem of low-temperature discharge is not very serious. During detection, a single battery has a large exposed specific surface area, so the temperature during the entire detection process is basically the same as the environment, so the discharge capacity is greatly affected. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Do you know how to use lithium batteries correctly?