Explosion-proof battery
The type of explosion of battery core can be classified into three types: external short circuit, internal short circuit and overcharge. The outer part of this system refers to the external surface of the core, which includes short circuit caused by poor insulation design inside the battery pack. When the electric core is short circuited and the electronic component fails to cut off the circuit, high heat will be produced inside the core, resulting in the gasification of some electrolyte and the support of the shell of the battery. When the internal temperature of the battery is high to 135 degrees centigrade, the fine diaphragm will close the hole, the electrochemical reaction terminates or nearly terminates, the current drops and the temperature drops slowly, thus avoiding the explosion. However, the closing rate of the hole is too bad, or the diaphragm is not closed at all. The battery temperature continues to rise, more electrolyte vaporizes, the battery shell is finally broken, and the battery temperature is even raised to the material to burn and explode. The internal short circuit is mainly caused by burrs of copper foil and aluminum foil, or the dendrites of lithium atoms penetrating through the diaphragm.
These tiny needled metals can cause short circuit. Because the needle is very thin and has a certain resistance value, the current will not be very large. The burr of copper foil is caused by the production process. It can be observed that the battery leakage is too fast, most of which can be screened by the electric core plant or the assembly plant. Moreover, because the burr is fine, sometimes it will be burned, so that the battery will return to normal. Therefore, the probability of burglings caused by short circuit burr is not high. Such a statement, from the core plant can often have a low voltage on the low battery, but few explosion events, and get statistical support. Therefore, the explosion caused by internal short circuit is mainly caused by overcharge.
Because after charging, the polar plates are filled with needle like lithium metal crystals, puncturing everywhere, and short circuiting everywhere. Therefore, the battery temperature will gradually increase, and finally the high temperature will be the electrolyte gas. In this case, whether the temperature is too high and the material is burning and exploding, or the shell is brace first, so that the air goes in with the lithium metal to oxidize fiercely, it is the explosion. But the explosion caused by overcharging caused by internal short circuit does not necessarily happen at the time of charging. It is possible that the battery temperature is not high enough to allow the combustion of the material and the gas generated is not enough to break the battery shell. Consumers will stop charging and take the mobile phone out. At this time, the heat generated by many short-circuit short-circuit increases the temperature of the battery slowly, and detonation takes place only after a period of time. The common description of consumers is that when picking up a cell phone, the cell phone is found to be very hot and exploded after being thrown away.
Based on the above types of explosion, we can focus on the three aspects of overcharge prevention, external short-circuit prevention, and upgrading the safety of electric cores. Overcharge prevention and external short circuit protection are electronic protection, which is related to battery system design and battery assembly. The emphasis of the core safety enhancement is chemical and mechanical protection, which is related to the battery core manufacturer.
