18650 and 21700 are different specifications of lithium batteries with the same voltage. The size of 21700 is larger than 18650, so its capacity is also larger.
The advantage of 18650 is that its capacity is generally between 1200mAh and 3600mAh, while the capacity of ordinary batteries is usually only about 800mAh. If multiple 18650 batteries are combined, it can easily exceed 5000mAh. However, its disadvantage is that its volume is already fixed, so in some applications, such as laptops, it may not be easy to locate.
The advantage of 21700 is that its single cell capacity can reach 3-4.8Ah. In comparison, the energy density of 18650 battery system is around 300Wh/kg, which is 20% higher than the 250Wh/kg of 18650 battery system. In addition, the power lithium battery system of 21700 is priced at $170/kWh, a decrease of 8.1% compared to the price of $185/kWh of 18650.
In terms of cost, after switching to 21700, the system cost is about $155/KWh, achieving a reduction of about 9%. Overall, the 21700 battery maintains the high reliability and stability of the 18650 battery, and has greater improvements in various aspects compared to the 18650.