Batteries that explode？18650 lithium battery or polymer battery safer？

Will the 18650 battery or polymer batteries that explode？ Let’s learn about what is 18650 and Polymer first.

Polymer lithium battery refers to the lithium ion battery that uses polymer as electrolyte. Specifically, it can be divided into “semi polymer” and “all polymer”. “Semi polymer” refers to coating a layer of polymer (generally PVDF) on the isolation membrane to make the adhesion of the cell stronger, the battery can be made harder, and its electrolyte is still a liquid electrolyte. The “all polymer” refers to the use of polymer to form a gel network inside the cell, and then inject electrolyte to form an electrolyte. Although “all polymer” batteries still use liquid electrolyte, the amount is much less, which greatly improves the safety performance of lithium ion batteries. Now only SONY is mass producing “all polymer” lithium-ion batteries.

On the other hand, polymer battery refers to the lithium ion battery with aluminum plastic packaging film as the outer packaging, which is also known as the pouch cell. This packaging film is composed of three layers, namely PP layer, Al layer and nylon layer. Since PP and nylon are polymers, this cell is called polymer battery.

Advantage of 18650 battery

Price lower

The international price of lithium 18650 battery is about 1USD/pcs, which is about 3RMB/Ah based on 2Ah.

The price of polymer lithium battery is 4RMB/Ah for low-end knock-off factories, 5-7RMB/Ah

for middle end factories, and more than 7RMB/Ah for middle and high-end factories

Customize

SONY has always wanted to make lithium-ion batteries look like alkaline batteries and have certain industrial standards, just like No. 5 batteries and No. 7 batteries, which are basically the

same all over the world. However, since one of the advantages of lithium ion battery is that

they can be designed according to customer needs, it is impossible to have a unified standard.

Disadvantage of 18650 battery

Poor safety

The main reason of batteries that explode, We know that under extreme conditions (such as overcharge, high temperature, etc.), lithium ion batteries will undergo violent chemical reactions inside, generating a large amount of gas. The 18,650 battery uses a metal shell with a certain strength. When the internal air pressure reaches a certain value, the steel shell will break and batteries that explode, causing a terrible safety accident.

This is why the room where 18650 batteries are tested must be protected layer by layer, and no one can enter during the test. Polymer batteries do not have this problem. Even in extreme cases, because of the low strength of the packaging film, as long as the air pressure is slightly higher, it will break without batteries that explode. The worst case is combustion. Therefore, polymer battery is superior to 18650 lithium battery in terms of safety.

Low energy density

The average 18650 battery capacity can reach about 2200mAh, so the energy density is about 500Wh/L, while the mass production of polymer batteries can approach 600Wh/L at this stage.

But polymer batteries also have their own shortcomings. The main reason is that the cost is high. Because the design can be based on customer needs, the R&D cost should be included. Moreover, various shapes and types lead to non-standard fixtures in the manufacturing process, which also increases the cost accordingly. The poor versatility of polymer battery itself is also caused by flexible design. It is often necessary to re design a new one for customers for the sake of 1mm difference

How 18650 manufacturer avoid batteries that explode?

Most 18650 batteries are encapsulated in steel shells. Due to the lack of protection function, batteries with poor quality will have a sudden increase in internal pressure when overcharged (overcharged), and will explode when exceeding the withstand value. Problems such as short circuit, high temperature, or the battery being squeezed, deformed or even punctured may cause batteries that explode.

18650 safety valve

After 30 years of development, the 18650 battery preparation process has been very mature. In addition to its performance, its safety is also very perfect. In order to avoid batteries that explode of the sealed metal shell, 18650 batteries are now equipped with a safety valve on the top. The safety valve is the standard configuration of each 18650 battery and the most important explosion-proof barrier.

When the internal pressure of the battery is too high, the safety valve on the top will open for exhaust and decompression to avoid batteries that explode. However, when the safety valve is opened, the chemical substances leaked from the battery will react with the oxygen in the air under high temperature, and fire may still occur. In addition, some 18650 batteries now have their own protective plates, which have the functions of overcharge, overdischarge and short-circuit protection, and have very high safety performance

Use 18650 correctly

The previous explosion of mobile power was all caused by unscrupulous manufacturers using substandard 18650 batteries or even second-hand waste electricity to save costs. At present, the 18650 batteries produced by major battery manufacturers such as Panasonic, Sony, Samsung, etc. are actually very safe, and the usage rate of the 18650 batteries is very high. We can use them correctly in daily use and avoid short circuit, damage or high temperature of the batteries. We don’t need to worry about the battery explosion. We can’t overturn a boat of people with one stick, and judge the safety of 18650 by individual inferior products.

Summary

In fact, for lithium batteries, batteries that explode would be avoid with BMS and proper assembly. In the past, the stability was not so strong. But as a lithium battery with very high performance contrast, the 18650 will certainly be used more and more widely. After all, the 18650 lithium battery is the best choice for this indispensable battery.