The Rise of 21700 Lithium Batteries! | IMREN Battery
At present, the 18650 battery, which is widely used, has been developed for many years. Compared with other types of battery technology, although it is relatively mature, it still faces problems such as high heat production, complex grouping, and inability to realize fast charging. In this context, 21700 cylindrical ternary cells came into being. In January 2017, the new 21700 battery jointly developed by Tesla and Panasonic began mass production, and emphasized that it was the battery with the highest energy density and the lowest cost among the current mass production batteries.
The battery 21700 is the model of cylindrical battery, 21 refers to the outer diameter of cylindrical battery is 21mm; 70 refers to the length of cylindrical battery is 70mm. 21700 is a new model developed to meet the requirements of electric vehicles for longer driving range and improve the effective utilization rate of vehicle battery space. With the same material, the capacity of 21700 cylindrical lithium battery can be more than 35% higher than that of 18650 cylindrical lithium battery.
21700 Four advantages:
1. The capacity of single battery is increased by 35%. Taking the 21700 battery produced by Tesla as an example, after switching from 18650 model to 21700 model, the single battery capacity of the battery can reach 3~4.8Ah, a significant increase of 35%.
2. The energy density of the battery system is increased by about 20%. According to the data released by Tesla, the energy density of the 18650 battery system used in the early stage is about 250Wh/kg. Later, the energy density of the 21700 battery system produced by Tesla is about 300Wh/kg. The volume energy density of the 21700 battery is nearly 20% higher than the original 18650.
3. The cost of the system is expected to decrease by about 9%. According to the analysis of battery price information released by Tesla, the price of 21700 battery power lithium battery system is $170/Wh, while the price of 18650 battery system is $185/Wh. After using 21700 batteries on Model 3, the cost of battery system alone can be reduced by about 9%.
4. The weight of the system is expected to decrease by about 10%. The overall volume of 21700 is larger than 18650. With the increase of monomer capacity, the energy density of monomer is higher, so the number of battery monomers required under the same energy can be reduced by about 1/3. While reducing the difficulty of system management, the number of metal structures and electrical accessories used in the battery package will also be reduced, which further reduces the weight of the battery. After Samsung SDI switched to a new set of 21700 batteries, it found that the weight of the system was reduced by 10% compared with the current battery.
The high reliability and stability of the 18650 battery has been maintained, and the performance of the 21700 battery has been greatly improved compared with the 18650 battery in all aspects. In addition, compared with other battery models, 21700 is similar to the more mature 18650 battery in terms of raw material selection, manufacturing process and technical process. Therefore, most of the production lines of 18650 and 21700 are compatible, and some enterprises are safer to make articles on the production line and close the production line to the compatibility of 21700 and 18650.
The pursuit of high specific energy for power batteries has become an irreversible trend. Many battery companies have begun to turn their attention to the layout of 21700 batteries. The production lines of some enterprises are imported from abroad, but they are assembled by themselves, so they can invest less costs to realize the transformation from 18650 to 21700.