Which is safer between 18650 lithium battery and polymer lithium battery?

The so-called polymer lithium battery refers to a lithium ion battery using a polymer as an electrolyte, and is specifically classified into two types of "semi-polymer" and "all-polymer". "Semi-polymer" means applying a layer of polymer (typically PVDF) to the separator to make the cell more adhesive, the battery can be made harder, and the electrolyte is still a liquid electrolyte. By "all polymer" is meant the use of a polymer to form a gel network inside the cell and then injecting the electrolyte to form an electrolyte. Although "all-polymer" batteries still use liquid electrolytes, they are used in much smaller quantities, which greatly improve the safety performance of lithium-ion batteries. According to the author's knowledge, only SONY is now mass-produced "all-polymer" lithium-ion batteries.

On the other hand, a polymer battery refers to a lithium ion battery using an aluminum plastic packaging film as an outer package, which is also known as a soft pack battery. The packaging film is composed of three layers, a PP layer, an Al layer and a nylon layer. Since PP and nylon are polymers, such a battery cell is called a polymer battery.

1, the price is lower

The international price of 18650 is about 1USD/pcs, which is about 3RMB/Ah according to 2Ah. The price of polymer lithium battery, the low-end cottage factory is 4RMB/Ah. The middle end is 5~7RMB/Ah, and the middle and high end are above 7RMB/Ah. Like ATL, LiShen, it can usually sell around 10RMB/Ah, and you are not willing to pick up.

2, it can not be customized

SONY has always wanted to make lithium-ion batteries the same as alkaline batteries. There are certain industry standards, like the 5th and 7th batteries, which are basically the same in the world. However, because of the great advantage of lithium-ion battery, it can be designed according to the customer's needs. It is impossible to have a unified standard. So now, the lithium-ion battery industry is basically only a standard model of 18650. Others are based on customers. The requirements are designed.

3, poor security

We know that in extreme cases (such as overcharge, high temperature, etc.), lithium-ion batteries will undergo intense chemical reactions inside and generate a large amount of gas. The 18650 battery uses a metal casing with certain strength. When the internal air pressure reaches a certain level, the steel shell will rupture and explode, causing a terrible safety accident.

This is why rooms that test 18650 batteries generally must be protected by layers, and they must not be tested when testing. 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 rupture and will not explode. The worst case is burning. Therefore, the polymer battery is superior to the 18650 battery in terms of safety.

4, low energy density

In general, the capacity of 18650battery can be about 2200mAh, so the energy density is about 500Wh/L, while the mass production of polymer battery can be close to 600Wh/L.

But polymer batteries also have their own drawbacks. Mainly because of the higher cost, because it can be designed according to customer needs, the research and development costs inside should be counted. Moreover, the variety of shapes and types, resulting in various fixtures in the manufacturing process are non-standard parts, and correspondingly increased costs. The versatility of the polymer battery itself is also due to the flexible design, and often it is necessary to redesign the customer for the difference of 1mm. It seems that the popular public opinion is that polymer lithium batteries are safer and are said to never explode. According to my understanding, the more reliable statement of polymer lithium batteries is mainly from the manufacturers of TaoBao fake mobile power, using polymer lithium batteries as a selling point to attack products using 18650 batteries.

Everyone can use the "battery explosion" as the key word, the main news related to the mobile phone, and now the mobile phone, can not find the non-polymer lithium battery model, so the polymer lithium battery compared the claim that the 18650 lithium battery is safer is untenable, and there is no such thing as an absolute explosion. In addition to individual extreme explosion cases, the bulging phenomenon is almost a common problem of polymer lithium batteries.

18650 lithium battery, polymer lithium battery: Which is safer?

Of course, the polymer lithium battery has its unique and 18650 (cylindrical) lithium battery is completely irreplaceable: square flat, which makes it a big player in thin and light portable electronic devices, in addition to everyone's highly dependent mobile phones, ultra-thin notebooks Polymer lithium batteries are also used. Whether its security is high or low, as long as we can't do without the phone, it's in your hand or in your trouser pocket.

Fortunately, the star models of mainstream mobile phone brands are almost all Japanese and Korean batteries. They are all from international companies. The overall security is very high. You don't have to worry about this for everyday use.

18650 lithium battery, polymer lithium battery: Which is safer?

Turning back to the 18650 lithium battery, this "old" battery, which is often attacked by various cottage mobile power manufacturers, is still widely used in various electronic devices, such as mobile power. In fact, in high-end applications, such as professional imaging equipment, laptop batteries, 18650 has been the main role, the large-scale application of Tesla electric vehicles has improved the high security image of this battery.

The 18650 lithium battery has mature technology, good consistency and high capacity density. It has the advantage that polymer lithium batteries cannot be replaced in large-capacity hybrid applications.

So, what choices should we make when we need to consider the type of battery in our daily lives? Or take mobile power as an example, the personal point of view is: choose a well-known battery supplier's products, such as: Sanyo, Panasonic, Sony, Samsung, LG, domestic lishen, BAK, Changjiang, Zhuoneng, etc. also have a certain scale of strength The brand, security also has a relatively high guarantee. The safety of the battery is mainly controlled by the quality of the manufacturer, not whether it is a polymer or a normal lithium battery.

18650 lithium battery, polymer lithium battery: Which is safer?

By the way, a widely accepted misconception is made that the polymer lithium battery does not mean that it is lighter and thinner. Lightness or thickness has always been closely related to energy density. Whether the battery is cylindrical or square, there is no significant difference in the volumetric weight of the same capacity lithium polymer battery and 18650 lithium battery during the same period.

First of all, the shape of the 18650 battery is cylindrical, and there is liquid inside. Because of the design of the battery and the characteristics of the raw materials, the power type 18650 battery is suitable for large current discharge, so almost all high-power products on the market use 18650 lithium batteries, but ultra-thin notebooks, especially It is a tablet computer, etc., because it requires a thinner appearance, so instead of using a 18650 battery, it uses a polymer lithium battery, but a high-power digital camera is different, because the charge and discharge of the flash requires a large voltage and a large current, so it can only With the 18650 power lithium battery or other models of power batteries, but the volume is slightly smaller, such as 18500 power lithium battery is commonly used in digital camera products; and with the 18650 power lithium battery high energy density and high current discharge advantages, so just now electric cars are designed with 18650 power lithium batteries.

The advantages of polymer lithium battery are small size and large capacity, the shortcoming is that the life is shorter than 18650, because different designs and materials are used, some have liquid inside, some are dry or colloidal, and the performance is not as good as 18650 when discharging at high current. Cylindrical batteries, so the need for large-capacity and small-volume electrical equipment, usually using polymer lithium batteries, the most typical performance is mobile phones, tablets and other equipment.

The page contains the contents of the machine translation.