What is the cause of the explosion and fire of the lithium ion battery?

Lithium-ion battery is a small, light-weight battery with sufficient power, which can still run well under continuous charge and discharge conditions. Although accidents rarely occur, all accidents that occur are significant, or cause fires and explosions. How do lithium-ion batteries burn? For example, when an internal or external short circuit occurs in a lithium-ion battery, a large amount of heat will be released within a short period of time, and the temperature will rise sharply, causing the heat to run out of control. Then, this flammable electrolyte will be ignited, eventually causing the battery to catch fire or explode. Lithium-ion batteries usually contain a metal coil and flammable lithium liquid. Tiny metal fragments are floating in the liquid. The contents of the battery are under pressure, so if a piece of metal pierces the separator that keeps the objects separated, or the battery is pierced, the high temperature caused by the violent reaction of lithium ions with water in the air can sometimes lead to The lithium ion battery catches fire. Lithium-ion batteries provide high power output with minimal weight. The design of the battery pack is mainly lightweight, which means that there is a thin partition between the battery and the thin case. 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 reactive lithium ions. Another possibility is that lithium-ion batteries may be heated to the point of thermal runaway. Here, the heat of the contents puts pressure on the battery, which may cause the lithium-ion battery to explode. To prevent the fire or explosion of lithium-ion batteries, the first step is to find the thermal explosion mechanism of lithium-ion batteries. The thermal explosion mechanism of lithium-ion batteries is: when the battery is subjected to thermal shock, overcharge, overdischarge, short circuit, vibration, extrusion Under such abuse 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 appear, causing the battery to heat up. If the heat generation rate inside the lithium ion battery is greater than the heat loss rate , 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 battery to burn or explode. The charging and discharging of the lithium ion dendritic growth battery is the transfer of lithium back and forth. During the charging process, the lithium is reduced to metal lithium ions and inserted into the negative electrode. Generally, the lithium ions are inserted into the interlayer structure. However, due to the uncertainty of growth, lithium ions may grow on the surface of the electrode, and the growth layer is like a thorn-like structure like a tree branch. It will destroy the diaphragm inside the battery, causing an internal short circuit and an explosion of the battery. The growth of dendrites and the formation of spikes are also defects in the battery itself. If the battery has defects during processing, the metal lithium ion particles pass through the insulating layer in the battery to connect the positive and negative electrodes, changing the direction of the current. There will be a lot of heat, which will degrade the internal materials, make the chemical reaction out of control, release more heat, and ignite the battery package. Battery overcharge Our current batteries have a protection system. The system will feed back the battery voltage at any time to prevent overcharge. When the protection system in the battery or the battery charger is damaged, it will cause overcharge. When overcharge occurs, the lithium remaining in the positive electrode material will continue to be extracted and inserted into the negative electrode material. If the maximum limit of the carbon negative electrode for inserting lithium ions is reached, the excess lithium ions will be deposited in the form of metal lithium ions On the negative electrode material, the stability of the battery is greatly reduced. It may even cause an explosion under certain circumstances. 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 post: Highly intelligent power management of lithium-ion battery UPS is the general trend of the development of power technology