Lithium-ion batteries generally contain a metal coil and flammable lithium-ion liquid. Small metal fragments are floating in the liquid. The contents of the battery are under pressure, so if a piece of metal fragments pierce the separator that insists on the separation of objects, or the battery is pierced, the high temperature caused by the violent reaction between lithium and water in the air will sometimes cause lithium The ion battery catches fire.
Lithium-ion batteries provide high power output with minimal weight. The design of the battery pack is based on lightness, which means that there is a thin partition between the battery and the thin casing. The separators and coatings are quite fragile and they can be pierced. If the battery is damaged, a short circuit will occur. A single spark can also ignite highly active lithium. Another possibility is that lithium-ion batteries may be heated to the point of thermal runaway. Here, the heat of the contents presses the battery, which may cause the lithium-ion battery to burst.
The way to prevent lithium-ion batteries from catching fire or blasting is to find the thermal blasting mechanism of lithium-ion batteries. The thermal blasting mechanism of lithium-ion batteries is: when the battery is subjected to thermal shock, overcharge, overdischarge, short circuit, vibration, Under pressure and other conditions, chemical and electrochemical reactions will occur between the active materials and electrolyte components in the battery, and a large amount of heat and gas will be generated, causing the battery to heat up. If the heat generation rate inside the lithium ion battery is greater than the heat loss Speed, the reaction temperature in the system will continue to rise, when the heat and internal pressure accumulate to a certain level, it will cause the burning or explosion of the battery.
Nano-engineers at the University of California, San Diego have developed a safety feature that prevents lithium metal batteries from rapidly heating up and catching fire when an internal short circuit occurs. The team has ingeniously adjusted the part called the barrier in the lithium-ion battery. The barrier is the barrier between the positive and negative electrodes of the lithium-ion battery. In this way, when the lithium-ion battery is short-circuited, the energy accumulated inside the battery (also Is calories) activity will slow down. After repeated charging of lithium metal batteries, the anode will show a needle-like structure of dendrites. Over time, the dendrites grow long enough to penetrate the barrier and build a bridge between the anode and cathode, causing an internal short circuit. When this happens, the electronic activity between the two electrodes loses control, causing the lithium-ion battery to immediately overheat and stop working.
1. Add flame retardant to the existing electrolyte. However, in order to complete the flame retardancy, it is necessary to add a large amount of flame retardant to the electrolyte, which will correspondingly reduce the ionic conductivity of the electrolyte and significantly affect the electrochemical performance and energy density of the lithium ion battery.
2. The maintenance is achieved by adding a dedicated maintenance circuit, such as: to prevent overcharging of the lithium-ion battery, install a PTC polymer switch or explosion-proof safety valve in the battery safety helmet.
3. The thermal stability of lithium-ion batteries is related to the type of cathode material and electrolyte. After optimizing the synthesis conditions and improving the synthesis method, the cathode material with good thermal stability is synthesized.
4. Weakly oxidize the surface of carbon materials, such as: reduction, doping, surface modification, etc.; or use spherical and fibrous carbon anode materials to improve the thermal stability of lithium-ion batteries.
