21700 battery is a type of cylindrical battery, with 21 specifically referring to the outer diameter of the cylindrical battery being 21mm; 700 refers to the height of the cylindrical battery being 70.0mm.

    The 18650 battery and 21700 battery are both developed to meet the demand for longer driving range of electric vehicles and improve the effective utilization of vehicle battery space, but the battery size is different.

    So, under the same data, the 18650 cylindrical lithium battery, which is more common in 21700, may have a capacity that is more than 35% higher.

The new 21700 has four obvious advantages:

    (1) The battery cell capacity has increased by 35%. Taking Tesla's 21700 battery as an example, after switching from the 18650 model to the 21700 model, the individual battery capacity may reach 3-4.8Ah, a significant increase of 35%.

    (2) The energy density of the battery system has increased by about 20%. According to the data exposed by Tesla, the energy density of the 18650 battery system used in the early stages was about 250Wh/kg, while the energy density of the 21700 battery system produced later was around 300Wh/kg. The volumetric energy density of the 21700 battery was nearly 20% higher than that of the original 18650.

    (3) The cost of the system is expected to decrease by about 9%. According to the analysis of battery price information exposed by Tesla, the energy lithium battery system of 21700 battery is priced at $170/Wh, while the price of 18650 battery system is $185/Wh. After using 21700 battery on Model 3, the cost of battery system alone may decrease by about 9%.

    (4) The component of the system is expected to decrease by about 10%. The overall volume of 21700 is greater than 18650. With the increase of unit capacity, the energy density of each unit is higher. Therefore, the number of battery cells required for the same energy can be reduced by about one-third. While reducing the difficulty of system management, it will also reduce the number of metal structural components and electrical accessories used in the battery pack, which further reduces the weight of the battery. After Samsung SDI switched to a new set of 21700 batteries, the invention system reduced the weight by 10% compared to current batteries.

    (5) Adhering to the high durability and strong performance of the 18650 battery, the 21700 battery has greatly improved its performance in all aspects compared to the 18650. In addition, compared to other battery models, 21700 is comparable to the 18650 battery class in terms of battery raw material selection, manufacturing process, and technical flow, which have more mature skills

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