Cylindrical batteries are usually packaged in cylindrical steel shells, and the bare cells are made using a winding process. Cylindrical batteries are one of the best practices for lithium batteries and are also standardized and universal products. As early as 1992, Japan’s SONY company developed the 18650 battery. Currently, cylindrical batteries can be divided into 14650, 18650, 21700, 32700, 4680 and other models, which are named after the battery size. 18650 is the most mature technology, while 21700 is the new battery that Tesla has been promoting in recent years. Due to its geometric shape, the gap between cylindrical batteries is larger, which is conducive to air circulation, thereby improving heat dissipation efficiency. There are relatively more cylindrical cells, and higher requirements for thermal management systems. Cylindrical batteries have good consistency, high production efficiency, and strong heat dissipation capabilities at the system level. After the size upgrade, it can improve its original low single energy density, many cells required for the module, and the resulting poor lifespan and complex management. But in general, its low energy density and low product grouping efficiency are still obvious disadvantages.
