Brief introduction to the design of the internal structure of a safe lithium battery

The panic of the explosion of mobile phones caused by lithium batteries has always left people with a lingering after the past, including global brands such as Dell and Apple. This makes people have to consider a question: Is the explosion of lithium batteries inevitable?

Lithium-ion batteries are used in mobile phones and notebooks. The so-called lithium-ion batteries are devices that rely on the movement of lithium ions between the positive and negative electrodes to supply and release electricity. It requires that lithium ions cannot be attached during the shuttle between the positive and negative electrodes. Other influencing factors are clean movement. In theory, this design is completely achievable, but in practice, because lithium-ion batteries are extremely sensitive products, any abnormal situation may cause problems in the battery.

All lithium battery explosions are caused by short circuits. The phenomenon of short circuit are overcharge, over discharge, overcurrent, and overheat, they are short-circuited by the internal structure of the lithium battery. The so-called internal factors determine the external cause, lithium battery. The structure itself is a process manufacturing process, and the process manufacturing process is difficult to 100% avoid.

The positive and negative electrodes of the lithium ion stay should be clean, and the electrolyte and separator in the shuttle should be free of impurities. However, in the manufacturing process, it is difficult to completely avoid the adhesion of metal dust, copper foil or aluminum foil to the electrolyte and the separator. When people use improperly (overcharge, over discharge, overcurrent) or put the lithium battery in extreme environment (excessive temperature), the lithium battery will overheat, and the debris will be broken at room temperature, which will be broken, thermal movement in the hot electrolyte space. Next, if the debris is close to the diaphragm, the hot debris will affect the isolation of the diaphragm and cause a short circuit.

It can be seen that the short circuit is caused by two reasons: one is that there is impurities in the battery body, and the other is that the impurities will move, and the intermediary between the two is heat. Therefore, the short circuit must be accompanied by heat, and the heat is not necessarily short-circuited. In the third step, the short circuit will spark, and the electrolyte is a flammable liquid. It is easy to understand that the spark will cause the battery to burn and explode in a closed space. Therefore, there is now a polymer lithium battery that replaces the liquid electrolyte with a colloidal electrolyte, which can reduce the probability of short circuit. But it cannot be completely avoided.

Once the battery is short-circuited, depending on the structure of the battery and the degree of temperature, in general, the battery body will leak, burn and explode, and the safety problem caused by combustion is the most serious.

The page contains the contents of the machine translation.