Why are 18650 lithium batteries made into cylindrical shape?

The definition rule of cylindrical lithium battery: such as 18650 type, which refers to a cylindrical battery with a diameter of 18mm and a length of 65mm.

In fact, cylindrical steel shell cells are not only 18650, but also 26650 and other sizes.

In the early days, lithium batteries were steel-shell cells, and the shell material was steel. Since the metal expansion coefficient of steel materials is not as good as that of aluminum shell materials, when the battery is short-circuited, the probability of explosion is higher than that of aluminum shells. Early lithium batteries were mainly used in the field of consumer electronics. Used in notebooks and mobile phones, 18650 is used on notebooks.

And mobile phones are the first to use square aluminum shell cells to replace steel shell cells (in the past, mobile phone batteries would bulge after using for a long time). Due to the development of ultra-thin smart phones, mobile phone lithium batteries have now developed to the third generation. of polymer batteries.

The rounded sides can distribute the pressure, which can improve the safety performance of the battery in the case of strong squeeze. Another advantage of cylindrical batteries is that mass production is simpler. When the winding machine winds the separator and the positive and negative electrodes, it can be automated. A single size such as 18650 can be used to make batteries of the same size and different capacity formulas. cost.

As the technology of cylindrical batteries is becoming more and more mature, for example, different types of lithium-ion batteries can be used on 18650 (lithium iron phosphate, lithium cobalt oxide, lithium titanate).

The above is the article sharing of Keheng lithium battery new energy manufacturers on why 18650 lithium batteries are made into cylindrical shape.