How powerful is the burning and explosion of 18650 lithium batteries?

by:CTECHi     2021-09-18
How powerful is the burning and explosion of 18650 lithium batteries? The 18650 lithium battery may explode due to improper use during charging and discharging; especially under abusive conditions (such as heat, overcharge, short circuit, vibration, squeezing, etc.), the battery may burn, explode, and even cause personal injury. condition. Therefore, studying the explosion mechanism of lithium batteries is of great significance to improving the safety of lithium ion batteries. How powerful is the burning and explosion of 18650 lithium batteries? 18650 lithium batteries generally contain a protective circuit board inside, mostly to prevent over-discharge. As a conversion device for chemical energy to generate electrical energy, lithium-ion batteries must have great energy. It is safe that this energy can be released slowly. If a violent reaction occurs, it will become extremely unstable. First of all, high temperature and high heat energy appear, and then a large amount of gas generated in a sealed environment will cause excessive internal pressure and expansion. When the internal pressure increases, the reaction speed will be promoted (just like the principle of pressure cooker). Such a vicious cycle will reach the time of expansion. When the shell endurance limit is reached, this balance will be broken and the shell will be torn apart. Once the shell is torn, a large amount of gas will find a way to escape, and it will suddenly vent. At this time, it is actually the most dangerous, just like the rupture of a truck tire. Like the explosion, close range can concuss human internal organs and bleed internally, and there are also examples of broken ribs. There have been reports of deaths on the spot in which Samsung mobile phones were short-circuited when answering the phone. Most of them in China are lithium-ion batteries, which are extremely powerful and should be paid attention to. There have been several cases of lithium battery explosions, and another lithium battery factory in Shenzhen has exploded. The preliminary investigation was that the explosives were semi-finished products of lithium batteries in the aging workshop. The parent company also 'fired and exploded due to spontaneous combustion of stacked battery cells.' Some people said that the suspension was because Shenzhen’s batteries were too hot to stand. In addition, according to investigations, a fire broke out in the warehouse of the factory on March 22, and the fire was not extinguished until the early hours of the next day, causing economic losses of 20 million yuan. The two fire accidents were only less than four months apart. Calculate, a full-charged 2.6AH 18650 ternary lithium battery has an energy of 2.6*3.65*3.6u003d34.164 kilojoules. The energy generated by a general muzzle is about 2.2 kilojoules. 1 joule is equivalent to the work done when a force of 1 Newton moves an object 1 meter in the direction of the force, so within a range of 50 meters, it can be easily Kill the enemy. Think about it, a Tesla needs to use more than 7,000 3.4AH 18650 lithium batteries. As long as it is a lithium battery, there is a risk of explosion, but this is a small risk. But once it explodes, the explosive power of the 18650 lithium battery with the larger capacity is unimaginable. Reasons for burning or explosion of 18650 lithium battery 1. Internal short circuit: structural or process defects lead to the insertion of the tab, the excess of the diaphragm package is too small, burrs, and the diaphragm discount, etc. Interpolation of the tabs often occurs in thick batteries and internal parallel structures. The insulation of the tabs is not in place. Adding a protective plate to the subsequent finished product or during use can easily cause an internal acute short circuit and cause combustion or explosion. However, this situation is almost always Less, unless external factors. 2. External short circuit: Lithium batteries below 1AH are caused by external short circuits to explode after burning. They are usually caused by bulging or simply burning the tabs. Personal analysis is caused by external short circuits of power batteries or large-capacity mobile phone batteries. combustion. This involves improper use by the customer-the tab insulation is not considered when the metal outer box is installed, and abnormal smoke and combustion of the battery occurs at the installation site; the power battery is also often lack of structural fixation measures (not considered properly), and the battery pack is used during the user's use. Shaking can cause damage to the battery's external insulating protective film or damage to the connecting wire, which will eventually lead to short-circuit burning. 3. Overcharge explosion: This is the most dangerous and the one most feared by enterprises, but it still happens occasionally. From what we know, there are two points: a. The user does not use the matching charger as required, which destroys the protection circuit and the user often charges for an unlimited time. In this case, it is difficult to not explode; b. 18650 lithium battery The unreasonable configuration and the failure of the protective plate will cause a mess in this case. The same applies to a single battery. 4. When the 18650 lithium battery is heated, the reactions inside the battery are like a reaction chain, and each reaction promotes each other and proceeds in sequence. The first is that the SEI film releases heat to heat the battery, which promotes the reaction between the negative electrode and the solvent to release more heat, leading to the reaction between the negative electrode and the binder and solvent decomposition, and then the positive electrode begins to undergo thermal decomposition reaction, releasing a large amount of heat and gas. , And finally cause the lithium battery to burn or explode. 5. Manufacturing process. The manufacturing process of the 18650 lithium battery is also an important factor that affects the safety performance of the battery. The three main factors are the positive and negative electrode capacity ratio, slurry uniformity control, and coating quality control. 6. Temperature. There are many factors that affect the safety of lithium batteries. Among them, battery materials have an important impact on the safety of lithium batteries, because battery materials are generally thermally active. When the temperature of the battery continues to rise, many thermal reactions occur inside it. When the heat cannot be dissipated in time, it is easy to cause battery safety accidents, so the choice of lithium battery positive and negative materials has an important impact on battery safety performance. Many people have seen the explosion of 18650 lithium batteries. The power of a lithium battery explosion can cause serious fires and even deaths, and a small one can damage battery products. The power of a lithium battery explosion is like a spark, which can start a prairie fire, so you must not ignore lithium. The battery exploded. Under normal circumstances, lithium batteries will not explode, but once they explode, they will be very dangerous.
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