Game Between 21700 and 18650 Batteries | IMREN
According to the latest national standard document GB/T34013-2017 Specification and Dimensions of Power Battery for Electric Vehicles, the IEC naming method for battery size and model is continued, and the "General Requirements for Battery Product Size and Specification", "Dimensional Tolerance Requirements" and "Dimensional Range Requirements" are specified, among which the cylindrical battery size and specification are 18650, 21700, 26650, 26700, 32700 and 32134; The square battery has different sizes from 65mm to 217mm.
At present, in order to improve the energy density of the battery system, reduce the number of cells, and reduce the cost, both square, cylindrical and flexible batteries have a trend of expanding the size of individual cells. It is obvious that the current cylindrical battery field has experienced an upgrade from 18650 to 21700/26650.
18650 and 21700 are two mainstream models at present. The new 21700 has four significant 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 disclosed by Stella, 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 Stella 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 disclosed by Tesla, the price of 21700 battery power lithium battery system is 170 dollars/Wh, while the price of 18650 battery system is 185 dollars/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%. It can be seen from the above that 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 stable performance 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. Some enterprises' production lines are imported from abroad, but they are assembled by themselves, so they can invest less cost to realize the conversion from 18650 to 21700.
