Another Tesla spontaneous combustion happened in Hong Kong. In recent years, the incidents of casualties and property losses caused by lithium battery spontaneous combustion of electric vehicles have emerged in an endless stream, and the safety of lithium batteries is becoming the focus of attention.
The self-ignition of lithium batteries in electric vehicles is more frightening than that in fuel vehicles. On the one hand, whether lithium ternary batteries or lithium iron phosphate batteries, they may spontaneously ignite due to short-circuit after damage to the battery structure. Moreover, compared with the characteristics that fuel must rely on external oxygen combustion, lithium batteries will spontaneously generate oxygen during combustion, which will aggravate combustion.
Therefore, the burning of lithium batteries is often very fast. In general fuel vehicle burning accidents, fire extinguishers can effectively suppress the initial fire, but in the electric vehicle burning accidents caused by battery packs, the burning is very intense, there is almost no time to be suppressed. Moreover, such fires can not be extinguished by water, and in many electric vehicles. In the car burning accident, even if the firefighters have arrived at the scene, they can only watch the lost car burn out.
On the other hand, for the sake of driving stability, most electric vehicles often arrange batteries under the passenger compartment, which can reduce the body gravity, but once the batteries are burned or exploded, it will directly threaten the safety of the passengers in the vehicle.
Because of the danger of lithium batteries, it is very important for any automobile manufacturer to improve the safety of lithium batteries. As we all know, the fuel tank of the fuel truck is usually made of thin steel plate or composite material to ensure its durability. But in the protection of battery packs for electric vehicles, manufacturers often use high-strength steel or aluminum alloy to build a solid shell for batteries, and some also introduce collision energy absorption structures around the battery packs.
In addition, the battery packs of electric vehicles are usually stacked with several batteries or single batteries. Overcharging or overdischarging of each batteries or batteries may cause damage to the battery diaphragm, resulting in short-circuit. Accidents such as Shanghai Tesla spontaneous combustion may be caused by any battery in the battery pack. Short circuit leads to "thermal runaway", which leads to the burning of the whole vehicle.
Even though the reliability of 18650 or 21700 lithium batteries is very high, the accident rate of the whole system will increase sharply when many batteries are stacked. Tesla uses thousands of 18650 or 21700 lithium batteries. To control such batteries, the battery management system must be able to ensure that each battery is not overcharged. And over-discharge, and battery management system is Tesla's core technology.
In addition, because the "thermal runaway" caused by external high temperature is also an important hidden danger of battery pack self-ignition. Panasonic refused to provide 18650 lithium batteries for Tesla in the early days of Tesla's start-up. One important reason is that Tesla did not provide a perfect thermal management solution for the battery pack until Tesla developed electricity. After the liquid cooling system of the pond group, the supply relationship between the two sides was established.
Although comparing with the mature structure of fuel vehicles, there is still a lot of room to improve the safety of battery packs of electric vehicles at present, but behind the self-ignition events of electric vehicles which have received considerable attention together, we must also be clear-headed to realize that the imperfection of electric vehicle products at this stage has brought a lot of complaints from consumers. The propagating volume of spontaneous combustion events can easily be amplified in these negative emotions, because individual events completely deny lithium battery packs are rash.
For the future, how to effectively control the self-ignition and safety of lithium batteries, fluoride can be achieved. Enterprises have begun to study the use of liquid fluoride for cooling and cooling batteries.
Fluoride Solution characteristics:
1. Very moderate boiling point (47 C), evaporation process in the working process, the use of evaporation tropical heat, has a wide range of applicability.
2. Non-dangerous goods or non-explosive, non-flammable flash point
3. It has good electrical insulation and high breakdown voltage greater than 55KV.
4. Good fluidity, lower viscosity than clear water
5. Non-toxic, harmless and non-irritating
6. Environmentally friendly, with 0 ODP value and very low GWP value of 2.2.