Testing Chambers Knowledge

  Lithium-ion batteries are widely used in new energy vehicles. In recent years, the explosion accidents of new energy vehicles have caused widespread concern and attention to their safety. Lithium-ion batteries may burn and explode under extreme conditions such as overcharge, collision and high temperature, and it is very difficult to put out.   1.Analysis of buring process and characteristics of lithium-ion battery   Lithium-ion battery is mainly composed of positive electrode, negative electrode, diaphragm, electrolyte, shell and other components. The cathode material is usually lithium intercalated transition metal oxide or polyanion compound; The anode material is mostly graphite. The electrolyte is mainly composed of organic mixed solution and lithium salt. The diaphragm is mainly used to isolate the positive and negative materials, prevent the short circuit caused by the passage of electrons, and let the ions in the electrolyte pass through.  When the battery ...

  1.5 Nail Penetration The nail penetration test evaluates the safety of the battery by penetrating the steel needle through the sample at a certain speed. The steel needle passes through the battery, damaging the integrity of the electrode and diaphragm, resulting in a short circuit in the battery and continuous heat generation.  The severity level of nail penetration test is relatively high, and only three of the standards introduced in this article include this test. According to the difference of the test samples, the test parameters (needle depth, steel needle diameter, needle speed, etc.) of the needle test are quite different. SAEJ2464 200 and GB/T31485-2015 both require the steel needle to remain in the sample for 1h after penetrating the sample, but FreedomCAR does not specify.   1.6 Rollover The rollover test simulates the rollover and overturn that the vehicle may encounter in an accident, which is also called rotation in some standards (UL2580-2013, SAEJ2929 2...

  In recent years, countries around the world have continuously increased policy support for new energy vehicles, and car companies such as Tesla have also launched new models. It has led to the rapid growth of the global electric vehicle market.  However, the fire and explosion accidents of electric vehicles have occurred many times, making the safety issue the focus of consumers. In this context, countries and relevant international organizations have issued standards for the safety testing of power batteries to standardize the safe use of power batteries.   At present, the international technical standards/specifications related to the safety of power batteries are shown in the figure. Among them, the standards issued by ISO (International Organization for Standardization), IEC (International Electrotechnical Commission) and SAE International (Society of Automotive Engineers) are international standards, which have strong reference significance for national standards, ...

  3.Comparison and analysis of nail penetration thermal runaway test Comparing the results of the six groups of tests, the batteries were damaged, but the severity of the tests was different. According to the different experimental characteristics, the experimental characteristics of nail penetration can be divided into three categories.   Category I: For example, the batteries in Group 1 and Group 5 only discharge electrolyte, without smoke and explosion;   Class II: For example, although the battery in Group 3 and Group 6 did not explode, a small amount of smoke and electrolyte were emitted from the pressure relief valve of the battery;   Category III: For example, the battery exploded and produced a large amount of smoke in the test of group 2 and group 3, which caused severe damage. It can be found that the result of thermal runaway caused by nail penetration is more random, but it has caused serious damage to the battery. In the first type of test results, the ...

  In recent years, the global energy crisis and environmental pollution have become increasingly serious. As a clean and pollution-free energy storage, lithium-ion batteries are gradually applied to new energy vehicles, solar energy conversion energy storage equipment, mobile communication equipment and other fields.  At present, new energy vehicles with lithium-ion batteries appear in more and more cities, but some potential safety hazards are gradually exposed. According to the fire investigation report of new energy vehicles, the vast majority of fires are caused by the battery heat out of control. Improper use, accidental damage or defects of lithium-ion batteries may lead to explosion and fire.  Among many reasons that trigger the thermal runaway of the battery, acupuncture is an irreversible destructive behavior that causes the battery damage. When the battery is pierced by sharp objects or subjected to a large impact force, it will cause mechanical damage to the ba...

  1.Safety of lithium-ion battery under overheating condition The safety problems of lithium-ion batteries are mainly manifested by fire and explosion caused by uncontrolled heat. The causes of thermal runaway can be divided into external conditions and internal conditions. The internal temperature of the battery also keeps rising when the external temperature keeps rising.  When the temperature rises to a certain temperature, the diaphragm will be thermally closed and the positive and negative poles will be isolated for safety protection. However, if the diaphragm fails to close effectively, or the diaphragm melts and breaks, or other exothermic reactions occur inside the battery at the same time, so that the battery temperature continues to be high, it may cause safety problems. It can be seen that the safety problems caused by overheating are the result of the comprehensive action of internal and external conditions.   For example, when the temperature of lithium cobal...