Home » Mobile power battery | The difference between polymer lithium battery and 18650 lithium battery

Mobile power battery | The difference between polymer lithium battery and 18650 lithium battery

by nadlia
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LAt present, the mobile power supply on the market is nothing more than two kinds of batteries, one is a polymer lithium battery, and the other is an 18650 lithium battery.

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concept

polymer battery

Refers to a battery containing a polymer or gel electrolyte inside, while the electrolyte of a traditional lithium-ion battery is dissolved in a liquid electrolyte. Compared with ordinary lithium batteries, polymer batteries have more freedom of shape and do not require high-strength containers. Polymer batteries can be divided into “semi-polymer” and “full polymer”. “Semi-polymer” refers to coating a layer of polymer (usually PVDF) on the separator, so that the adhesion of the cell is stronger, the battery is harder, and the electrolyte is still a liquid electrolyte. The “full polymer” refers to the use of polymers 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 smaller, which greatly improves the safety performance of lithium-ion batteries. But currently only SONY is mass-producing “all polymer” lithium-ion batteries.

On the other hand, polymer batteries refer to lithium-ion batteries that use aluminum-plastic packaging film as the outer packaging, which is commonly known as soft-pack batteries. This packaging film is composed of PP layer, Al layer and nylon layer. Since PP and nylon are polymers, this battery cell is called a polymer battery.

The 18650 lithium battery is just a packaging specification of a lithium battery, indicating that the shape of the battery is a cylinder with a diameter of 18mm and a height of 65mm. It can be an ordinary lithium cobalt oxide battery, a lithium iron phosphate battery, or a lithium-ion polymer battery. In the early days, there were nickel-metal hydride and nickel-cadmium batteries. At present, the common ones are lithium cobalt oxide battery and lithium iron phosphate battery.

General mobile power will use multiple 18650 lithium batteries combined to form a large-capacity battery pack.

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Compared

As far as the two types of batteries currently used in mobile power on the market are concerned, it is difficult to say which battery cell is better, and each has its own advantages. The specific comparison is as follows:

Both batteries are dangerous to some extent.

18650 lithium batteries have the risk of explosion, but due to the development history of more than 30 years, regular manufacturers have designed protection circuits to prevent overcharging and overdischarging, vent holes to prevent excessive internal pressure of the battery, and diaphragms to prevent internal short circuits of the battery. protection mechanism.

Although the polymer lithium battery will not explode, if the protection is insufficient, there is a risk of spontaneous combustion when encountering a violent impact.

As far as the current development level of the two batteries is concerned, the 18650 lithium battery technology is the most mature and stable, and its safety is higher than that of polymer lithium batteries. Tesla electric vehicles also use 18650 lithium batteries.

② The price of 18650 lithium battery is lower, so the price of power bank using 18650 lithium battery is cheaper.

③ Since the standard diameter of the 18650 lithium battery is 18mm, the thickness of the power bank using the 18650 lithium battery must be greater than 18mm and longer than 65mm.

④ Polymer lithium battery has high energy density. Simply put, the polymer lithium battery with the same weight has higher energy than the 18650 battery, but it is not necessarily relative to the volume.

⑤ The internal resistance of polymer lithium batteries with the same capacity is higher than that of 18650 lithium batteries.

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how to choose

Knowing about batteries, you still don’t know how to choose a mobile power supply, right? In fact, it is very simple. If you want a cheap one, you can choose a mobile power bank with a 18650 lithium battery, and if you want a thinner one, you can choose a mobile power bank with a lithium polymer battery.

Although many merchants of mobile power supplies bad-mouth 18650 lithium batteries on the grounds of safety, the reason for the real “unsafe impression” is that many mobile power supplies use fake and inferior 18650 lithium batteries, and battery manufacturers reduce the cost of 18650 lithium batteries in order to save costs. Multiple protection mechanisms.

So no matter what kind of mobile power supply you choose, you should choose a regular big brand and buy it through reliable channels.

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