What is the difference between 18650 battery cells and polymer battery cells used in power banks?
What is 18650 battery cell
At present, there are generally two types of battery cells in the mobile power market: 18650 battery cells and polymer battery cells. These two types of battery cells dominate the vast market share in the lithium battery industry. Here is an explanation of the two common types of battery cells in mobile power supplies.
18650 battery cell
18650 is a standard lithium-ion battery model established by Sony Corporation in Japan to save costs, where 18 represents a diameter of 18mm, 65 represents a length of 65mm, and 0 represents a cylindrical battery. Common 18650 batteries are divided into lithium-ion batteries and lithium iron phosphate batteries.
18650 Capacity Regular Size
There are generally 2200mAh, 2400mAh, and 2600mAh capacity standards. According to industry insiders, the 18650 has currently achieved a maximum single cell capacity of 3400mAh. If the mobile power bank uses 18650 as the battery cell, it is basically connected together with the above specifications.
18650 packaging
18650 is generally packaged in a steel shell, meaning that the lithium ions in 18650 are in liquid form, like a cup filled with water, similar to this understanding. So 18650 can only be cylindrical. If you see thick and large mobile power banks when buying them, they are basically 18650 battery cells.
18650 Security
Due to the special nature of 18650 packaging (using steel shells), if the quality of the produced products is not up to standard, the biggest danger is explosion. The explosion incidents that occurred in laptops a few years ago were caused by quality control issues with Sony's laptop batteries (usually using 18650).
Lithium polymer battery cell
Lithium polymer battery cells are generally made by mixing lithium cobalt oxide, lithium manganese oxide, and ternary lithium as raw materials. Made through a certain proportion of a mixture of the three and a certain process, the outer packaging is mainly made of aluminum-plastic film, and the lithium substance in the middle is a paste. So the shape can be customized arbitrarily. At the same time, ultra-thin batteries such as 0.33mm and 0.50mm can be produced.
Lithium polymer battery cell capacity
Due to the fact that polymer batteries can be of any size, they do not have a standard shape. Generally, the body area is marked as length * width * thickness. In addition, the battery cell has a positive and negative tolerance, with a positive tolerance of 0.5mm for length and width and a negative tolerance of 0.55mm for thickness (these two positive and negative tolerances). Therefore, it indicates that the capacity of polymers is determined by the size of their volume and is also related to the ratio of lithium raw materials used.
Lithium polymer battery cell safety
The polymer battery is covered with a layer of aluminum-plastic film on the outside, and then wrapped with a layer of high-temperature adhesive tape. The biggest safety of the polymer is leakage, short circuit, causing swelling, and in the worst case, combustion and flames. Therefore, compared to 18650, polymer battery cells are safer. However, burning can also pose safety hazards, so it is recommended that users of portable power banks avoid placing them on pillows or beds as much as possible.
At present, the mobile power bank market still has a relatively large shipment volume of
18650, and the vast majority of mobile power banks use 18650.
At present, in the high-end mobile power market, the vast majority of them use polymer cells to make mobile power supplies. To a certain extent, it is recommended that users buy mobile power supplies with polymer cells, especially those with large capacity, such as 8000mA or more. If a safety accident occurs, the consequences will be more serious, while polymer cell mobile power supplies will only emit small sparks at most and are unlikely to explode.
