Why did the 18650 lithium battery have an explosion history

Why did the 18650 lithium battery have an explosion history?

More than 300 years ago, Benjamin Franklin began to capture lightning, which opened people's understanding of lightning and electricity. Since then, many people have been considering how to store the captured electricity, so the gradual battery has gradually evolved and emerged as an important invention in history, The emergence of batteries has indeed solved many problems and greatly improved life and work efficiency. The emergence of lithium batteries has deepened people's understanding of. 18650 lithium battery is the first liquid lithium battery invented and used so far. The use of 18650 lithium battery can be seen in many fields. 18650 lithium battery has very obvious advantages over other NIMH and NiCd batteries, And the reliability is relatively good. Now 18650 lithium battery has also been used in industry and large equipment.

It is generally believed that the power is used up when the cut-off voltage of ternary lithium battery is below 3.0V (the specific cut-off voltage depends on the minimum value of the protection board, but also up to 2.8V and 2.75V). Most lithium batteries cannot be discharged lower than the set cut-off voltage, otherwise continuing to discharge will cause excessive discharge and damage the battery (generally, lithium batteries are used with a protective plate, so excessive discharge will also lead to the failure of the protective plate to detect the battery voltage, so the battery cannot be normally charged). 4.2V is the maximum limit voltage of ternary lithium battery. It is generally considered that the lithium battery is full when the voltage of the lithium battery is charged to 4.2V. During the battery charging process, the battery voltage gradually rises from 3.7V to 4.2V. The lithium battery cannot be charged above 4.2V, otherwise the lithium battery will be damaged. This is the special place of lithium battery. Generally speaking, 18650 lithium battery has the following advantages.

1. Wide application range:

Notebook computers, walkie talkies, portable household appliances, instruments, sound equipment, toys, cameras, digital products, electronic equipment;

2. Multi parallel and multi series can be combined into lithium battery pack with different capacity and voltage;

3. Low internal resistance of lithium battery:

The internal resistance of polymer cell is small. The internal resistance of domestic polymer cell can even reach 30 milliohm, which greatly reduces the self power consumption of battery and prolongs the standby time of mobile phone, which can fully reach the level in line with international standards. The polymer that supports high discharge current is lithium

Battery is an ideal choice for remote control model toys, and has become the most promising product to replace Ni MH battery products.

4. Without memory effect, it is not necessary to empty the remaining power before charging, which is convenient to use;

5. The voltage is high. The voltage of 18650 ternary lithium battery is 3.7V nominal voltage, which is much higher than the voltage of 1.2V of Ni MH Ni Cd battery;

6. High safety performance. 18650 lithium battery is non-toxic, environment-friendly, non fire and non explosion. It has been certified by RoHS trademark. It can pass various safety performance tests. It has good high temperature resistance and continuous discharge efficiency of 99.9% at 60 degrees. In order to prevent short circuit of lithium battery, the positive and negative electrodes of lithium battery are separated, so the short circuit accident rate is minimized. There is no self short circuit except man-made damage, A protective plate can be installed to avoid overcharge and discharge of the battery, so as to prolong the service life of the battery.

7. Long service life. The normal cycle service life of 18650 lithium battery can reach more than 600 times (one cycle after full discharge), which is more than twice that of ordinary dry battery.

8. Large capacity. The general capacity of 18650 ternary lithium battery is 1200mah-3350mah. The capacity of imported batteries may be hundreds of milliamps, while the capacity of dry batteries with the same volume is only about that of lithium batteries. If lithium batteries are combined in parallel and in series, 18650 lithium batteries can be combined into high-voltage and high-capacity battery packs.

Why did the 18650 lithium battery have an explosion history?

The vast majority of 18650 lithium batteries are encapsulated in steel shell. Due to the lack of protective plate function protection, the battery with poor quality will increase its internal pressure under overcharge and discharge, and will explode when it exceeds the withstand value. Short circuit, high temperature or battery extrusion deformation or even puncture may cause explosion.

After decades of technological breakthrough and innovation, the preparation process of 18650 lithium battery has been very mature. In addition to excellent performance and great improvement, its safety performance is also more perfect. In order to avoid explosion of sealed metal shell, 18650 lithium battery is now equipped with a part of safety valve in the middle of the positive top cap, which is standard for each battery, This is the most important safety and explosion-proof effective measure for 18650 lithium battery.

When the internal pressure of the battery is too high, the safety valve of the positive cap will be opened due to the internal and external pressure difference for exhaust and pressure reduction to avoid explosion accidents. However, when the safety valve is opened, the electrolyte leaked inside the battery will chemically react with oxygen molecules in the air under high temperature conditions, and smoking may still occur. In addition, 18650 lithium batteries will be equipped with a protective plate when leaving the factory, which is used to prevent over charging and over discharging of the lithium battery, so as to further improve the safety performance of the battery.

Why did 18650 lithium battery explode before? All because unscrupulous manufacturers use substandard low-quality 18650 batteries or even second-hand waste electricity to save costs. At present, the 18650 lithium battery produced by major battery manufacturers such as Panasonic, Sony, hongwell battery and Hongwei energy is actually very safe, and the utilization rate of 18650 battery is very high.

Conclusion: for lithium batteries, it is understandable that there is occasional smoke. In previous years, the stability of lithium battery technology to internal bipolar chemical reaction is not very stable. Decades later, the technology is relatively mature. 18650 lithium battery, as a battery with high cost performance and energy, has a wide range of application fields. 18650 lithium battery is used in industry and life.