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What is the 18650 battery and why is it generally rated low?

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First of all, clarify a concept - polymer lithium batteries. 18650 pack builder From the perspective of the internal materials of the battery, the so-called polymer lithium battery refers to the use of polymer as an electrolyte lithium-ion battery, which is specifically divided into "semi-polymer" and "full polymer" two kinds. "Semi-polymer" means that a layer of polymer (generally PVDF) is coated on the isolation film, so that the adhesion of the cell is stronger, the battery can be made harder, and the electrolyte is still a liquid electrolyte. The "full polymer" means that the polymer is used to form a gel network inside the cell, and then the electrolyte is injected 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. As far as I know, only SONY is currently mass-producing "all-polymer" lithium-ion batteries.

Polymer batteries, on the other hand, are those that use aluminum-plastic packaging for external lithium-ion batteries, battery manufacturing machine often referred to as flexible packaging batteries. This film consists of three layers, PP, Al and nylon. Because polypropylene and nylon are polymers, the battery is called a polymer battery.

From the point of view of the subject, li ion battery construction it should refer to the latter - the so-called lithium-ion battery using polymer packaging materials - and the corresponding 18650 battery uses a steel shell as the outer packaging. And many domestic manufacturers advertise that the batteries they produce are polymer batteries, which is the same meaning, don't be fooled by them

18650 is the originator of lithium-ion batteries - SONY Corporation of Japan, an important standard lithium-ion battery model that we set in order to save time and cost, where 18 indicates a diameter of 10mm, 65 indicates a data length of 65mm, and 0 indicates a cylindrical battery. SONY has always wanted to make lithium-ion batteries like alkaline battery technology, with certain industrial development standards, like No. 5 batteries, No. 7 batteries, basically the same around the world. However, because one of the major advantages of lithium-ion batteries is that students can design the shape structure according to the analysis of customer demand information at the same time, it is impossible to have such a national unified standard, so now the lithium-ion battery industry is basically only 18650 this industry standard model. The others need to be designed according to the target customer service needs.

Compared with 18650 batteries, polymer batteries have the following advantages:

1. High energy density. The general 18650 battery capacity can be about 2200mAh, so the energy density is about 500Wh/L, and the energy density of the polymer battery can be close to 600Wh/L at this stage of mass production.

2. Security is good. We know that lithium-ion batteries under extreme conditions (such as overcharge, high temperature, etc.) will have a violent chemical reaction inside and produce a large amount of gas. The 18650 battery uses a metal housing and has a certain strength. When the internal air pressure reaches a certain degree, the steel shell will explode, causing serious safety accidents. This is why the testing of the 18650 battery chamber generally must use multiple layers of protection, and it is absolutely impossible to enter the test. This is not the case with polymer batteries, even in extreme cases where the strength of the packaging film is lower, rupture without causing an explosion at slightly higher air pressure, and in the worst case, combustion. So polymer batteries are safer than 18650 batteries.

3. Able to design according to customer needs. This has already been said above, so I won't repeat it.

4. the price can be sold relatively high... The international market price of 18650 is about 1USD/pcs, and if we calculate the capacity according to 2Ah, it is about 3RMB/Ah. The price of polymer as a lithium battery, the low-end cottage factory in 4RMB/Ah, the middle end in 5~7RMB/Ah, and the middle and high end in 7RMB/Ah or more. Like ATL, Force God, the average student can directly sell to 10RMB/Ah or so, and your single is small and many people are not willing to pick up.

But polymer batteries also have drawbacks. The main cost is higher because you can design according to the needs of the customer, where the research and development costs will be included. Moreover, the shape is changeable and the variety is wide, resulting in all kinds of fixtures in the manufacturing process are non-standard parts, which also increases the cost correspondingly. The poor versatility of the polymer battery itself is also the result of flexible design, often in order to make a 1mm difference, it needs to be redesigned for the customer, cost, ah, cost. .

Of course, what I said above is not absolute. The 18650 also has high-end applications, such as the recently popular Tesla Model S, which uses the 18650 battery pack supplied by Panasonic. So 18650 does not represent low-end, but some domestic cottage factories make this variety low-end.

What goes into the making and operation of a battery?

A battery is a collection of connected cells that can produce higher voltages and/or currents. The total voltage increases when cells are coupled in erie (polarity assisting). Physical cell size has an effect on cell resistance, which has an effect on the cell's capacity to supply current to a circuit.