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What is the difference between polymer lithium battery and liquid lithium battery?

by:dcfpower     2021-03-22

Lithium batteries are divided into polymer lithium batteries and liquid lithium batteries, how do you distinguish it? What are the differences and advantages of polymer lithium batteries and liquid lithium batteries?

In fact, there are some simpler methods that can be distinguished directly from the appearance. Generally, polymer lithium batteries are not protected by iron-made shells and have a certain degree of softness. Liquid lithium batteries are generally protected by a hard case, such as the 18650 lithium batteries on the market.

There is one thing everyone should pay attention to: 18650 refers to a cylindrical battery with a diameter of 18mm and a length of 65mm. Although most of the 18650s on the market are liquid lithium batteries, any statement that 'polymer lithium batteries are safer than 18650 XX' is wrong.

The working principle of the two is the same. Both charge and discharge are realized through the process of lithium ion insertion and extraction. The insertion of lithium ions into the negative electrode is charging, and the extraction of lithium ions from the negative electrode is discharge.

Lithium batteries contain the three most basic elements of positive electrode, negative electrode and electrolyte (materials filled between the two levels). Of course, there is also a separator that prevents direct contact between the positive and negative electrodes (of course, lithium ions are It can pass smoothly, if the diaphragm is not good, it will short-circuit and cause an explosion); and the main difference between liquid lithium battery pack and polymer lithium battery pack is:

1. The difference in material: polymerization In the lithium battery pack, at least one of the three basic elements mentioned above must be made of polymer materials, for example, the electrolyte solution is replaced by polyacrylic acid, polymethacrylic acid, etc.

2. The difference in electrolyte morphology: liquid lithium-ion batteries mostly use liquid organic solvents + conductive salts, while polymer lithium batteries replace these electrolytes with colloids/solids (see battery model for specific components) .

Simple comparison between polymer lithium battery and liquid lithium battery:

Liquid lithium battery energy density (Wh/L)>300~280 Customizable degree (shape) is flexible and difficult, Heavy weight (requires metal protective shell). The energy density of the polymer lithium battery is customized to be higher, the shape design is more flexible, it can be of any shape, and the weight is lighter.

1. Energy density: The greater the energy density, the more capacity a unit volume can have. The energy density of the polymer lithium battery has now reached 600Wh/L+ through the improvement of materials/thickness of the negative electrode (anode) and separator.

2. Degree of customization: The polymer lithium battery is easier to be thin and light in shape, and there is no need to use a metal protective shell to wrap it, so it is easier to customize into various shapes.

3. Weight: liquid lithium battery is heavier, polymer lithium battery is lighter, the same volume.

4. Safety: Under extreme conditions (such as overcharge/high temperature), a violent chemical reaction will occur inside the lithium battery, generating a large amount of gas. At this time, the liquid lithium battery is wrapped in a metal shell. When the pressure is quite high, the shell will burst and explode, while the polymer lithium battery is only wrapped with packaging aluminum film (or plastic shell), as long as the internal pressure is slightly higher, it will expand or rupture, and will not cause an explosion. However, it should be noted that both liquid lithium batteries and polymer lithium batteries can burn under extreme conditions.

5. Cost: In addition to the higher material cost of polymer lithium batteries than liquid lithium batteries, because polymer lithium batteries can be customized to a higher degree, they will produce more in the process of design and manufacturing. Expenses, such as various custom-made fixtures, test equipment, etc., cause the cost of polymer lithium batteries to be higher than that of liquid lithium batteries with standard/regular shapes.

Related articles:

Flow chart of polymer lithium battery pack manufacturing, why is the lithium battery pack not discharged?

Method for calculating the capacity of polymer lithium battery Injection method for polymer lithium battery pack

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