What are the differences between 21700 and 18650 ?

Energy density and battery life In terms of energy density, if 21700 and 18650 are batteries manufactured with the same chemical raw materials, their energy density is the same. On the contrary, if 21700 and 18650 are not manufactured with the same chemical raw materials, their energy density will be different. For example, the unit volume energy density of lithium iron phosphate batteries is lower than that of ternary lithium batteries. In terms of battery life, if 21700 and 18650 are batteries of the same type, then 21700 batteries have a larger volume and higher capacity than 18650 batteries, and 21700 batteries can provide longer battery life. If 21700 and 18650 are different types of batteries, their battery life is likely to be close to the same, that is, 18650 batteries use high-energy-density batteries, and the battery capacity of their production can become larger, which is likely to be close to the capacity of 21700 lithium iron phosphate batteries.

Application scenarios and uses 21700 batteries are usually used in devices that require higher energy storage and longer battery life, such as emergency backup UPS power supplies for electric vehicles and large electronic devices. 18650 batteries are mostly used in smaller devices such as flashlights, small electronic devices and some electric vehicles.

Cost and procurement difficulty For a single battery cell (single battery), since the production scale of 21700 batteries may be smaller than that of 18650 batteries, and in the case of the same type of batteries, 21700 batteries have more capacity and use more basic raw materials than 18650 batteries, so their production costs will be higher, which may lead to slightly greater procurement difficulty and slightly higher prices.

The difference between the number of cells and the number of cells Since the diameter of 21700 battery is larger and can accommodate more capacity, the shell required per m2 of 21700 battery is 33% less than that of 18650 battery, so the shell cost of 21700 battery is lower than that of 18650. At the same time, since the number of batteries with the same Wh is reduced by 33%, the demand for liquid injection and sealing process is also reduced. In the case of forming a large battery pack, the cost is reduced.

Formation equipment and efficiency. As the overall number of batteries decreases, the demand for formation equipment is also greatly reduced, which improves efficiency and reduces costs. In summary, the differences between 21700 and 18650 batteries mainly lie in size, capacity, energy density, application scenarios, cost procurement difficulty, battery housing and battery quantity, formation equipment and efficiency, etc. It is necessary to choose the appropriate battery type according to specific application requirements.