Which polymer and lithium battery are good, what is the difference?

Lithium battery refers to lithium ion secondary rechargeable battery. From the appearance, there are three kinds of cylindrical steel shell, square aluminum shell and soft bag. The soft bag is the polymer in the title. It can be seen that the polymer is actually lithium polymer. The battery is a kind of lithium battery. In this context, lithium batteries are specifically referred to as cylindrical lithium batteries. So polymer and lithium battery which is good, the actual discussion is polymer and cylindrical lithium battery which is better.
We compare each of them in the following ways to try to find out the answer.
1, material
The lithium battery uses a liquid electrolyte, and the inside of the polymer battery uses a gel electrolyte and a solid electrolyte. In fact, domestic polymers are not really called polymers, they can't be real solids, and it's more accurate to call them no flowable liquids. This is a digression, and I will not talk about it here.
2, packaging and appearance
The polymer is packaged in an aluminum plastic film, and the shape can be customized at will. It can be thick or thin, and can be large or small.
The lithium battery is packaged in a steel case and has the most cylindrical shape. The most common one is 18650, which is 18 mm in diameter and 65 mm in height. The shape is fixed. Can't change at will.

 

 


3, security
The polymer has no flowing liquid inside and does not leak. When the internal temperature is high, the aluminum plastic film casing is only flatulent or bulging, and will not explode. Safety is higher than lithium batteries. Of course, this is not absolute. If the instantaneous current of the polymer battery is large enough to cause a short circuit, the battery may spontaneously ignite or explode. The explosion of Samsung's mobile phone battery that occurred a few years ago, and the recall of Lenovo this year due to battery defects, are the same problem.
4, energy density
The average 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.
5, cell voltage
Since the polymer battery is made of a polymer material, it can be made into a multi-layer combination in the battery cell to achieve a high voltage, and the lithium battery cell has a nominal capacity of 3.6V. To achieve a high voltage in practical use, multiple The cells are connected in series to form the ideal high voltage working platform.
Which polymer and lithium battery is good?
It can be seen that the polymer and the lithium battery are good, and it seems that the polymer has an advantage. But what exists is reasonable. They certainly have different aspects that cannot be replaced by each other.
Let's look at the last one:
6, the price
Polymers of generally the same energy are more expensive than lithium batteries. But it cannot be said that this is a disadvantage of polymers.
At present, in the field of consumer electronics, such as notebooks, mobile power supplies, etc., more and more polymers are used instead of lithium batteries.
In a small battery compartment, to achieve the maximum energy density in a limited space, it is still necessary to use a polymer. Because of the fixed shape of the lithium battery, it cannot be customized with the customer's design.
However, polymer batteries do not have a uniform standard size, which in turn has become a disadvantage in some respects. Tesla cars, the battery is composed of more than 7000 18650 series and parallel, plus power control system.
It seems that polymers and lithium batteries are better, better or worse, depending on the specific situation, can not give a single conclusion.

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