The safety of power batteries is a hot spot in the development of new energy vehicles. Figure 1 is TUV's test project on power battery safety, which is roughly divided into Safety Testing and Abuse Testing. Among them, the crush test and the nail penetration test are abuse tests. These two tests are very damaging to the battery. Extrusion is the direct application of external mechanical force to the battery, forcing the battery to deform, resulting in mechanical deformation of various parts inside the battery, resulting in external / internal structural damage (such as diaphragm breakage, puncture), resulting in internal short circuit, triggering possible The heat is out of control. Acupuncture is the external metal foreign body directly piercing the inside of the battery, piercing the internal components of the battery, also causing internal short circuit, and triggering possible thermal runaway. Here are some examples to look at these two tests.
Figure 1 Battery Safety and Abuse Test Project
Let's take a look at the test of the LFP/C battery. LFP materials have a relatively high thermal stability and help to suppress or delay the occurrence of thermal space and time in abuse testing. Here is a case of ELIIY Power's 50Ah (106Wh/kg) battery, acupuncture test by TUV. The position of the needle piercing is at the center of the battery surface. From the point of view of the penetration of the steel needle, the battery did not observe any anomalies and showed high safety (Fig. 2a-2c).
Figure 2 Acupuncture test of LFP 50Ah battery
Regarding the acupuncture test, EC Power used the simulation technique to study the effect of the thickness of the steel needle on the acupuncture test results of the NCM battery (5Ah, 120Wh/kg). There is a set of data for reference: 20mm steel needle, 150 seconds for acupuncture position temperature to reach 150 degrees Celsius; 10mm steel needle, 75 seconds for acupuncture position temperature to reach 150 degrees Celsius; 5mm steel needle, acupuncture position temperature reaches 150 degrees Celsius only It takes 2 seconds (Figure 3). It shows that the thinner steel needle has a relatively faster local temperature rise at the acupuncture position, which is more likely to cause thermal runaway of the battery.
Figure 3 Effect of the thickness of steel needle on the results of acupuncture
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