1. Overview of three types of batteries 1. Cylindrical battery cell The cylindrical battery cell was first invented by Sony Corporation of Japan in 1992. It has a long history of development and a high degree of standardization. Common models include 18650, 21700, 46800, etc. It adopts a mature winding process, with a high degree of automation, high production efficiency, good consistency and relatively low cost. For example, the 21700 battery used in Tesla Model 3 and Model Y, and the 46800 battery that is about to be mass-produced, once made the cylindrical battery cell popular in the market. However, there are also some problems with cylindrical batteries. Due to the cylindrical shape, the space utilization rate is low, and in the case of modularization, a large space waste will be caused. At the same time, the radial thermal conductivity is not good, the number of windings of the battery cannot be too many, and the single cell capacity is small. When used in electric vehicle...