Depending on the package, the battery is divided into cylindrical, square and soft pack batteries. Different structures also mean that they have different characteristics. Today, let's take a look at the advantages and disadvantages of these three types of batteries.
Cylindrical battery: long development time, the most mature technology
Cylindrical batteries have the longest development time, and the technology is the most mature, with a high degree of standardization. Moreover, because the cylindrical battery has a large space between the batteries when it is packaged, such a battery has great advantages in heat dissipation, and many models equipped with a cylindrical battery adopt a lower cost air cooling technology.
However, the excessive number of batteries is a relatively difficult problem. Even if a vehicle with a high energy density battery is used, thousands of cylindrical batteries need to be put together, which puts higher requirements on the vehicle battery management system. In addition, since the cylindrical battery needs to adopt a steel shell when assembled into a battery pack, its weight is relatively high. Theoretically, the energy density of the cylindrical battery is lower than that of the other two batteries.
At present, many types of batteries are used in the market, and the representative one is Tesla's model3, which uses the model number 21700 (21 indicates that the diameter of the cylindrical battery is 21mm, and 70 indicates that the battery length is 70mm. , 0 indicates a cylindrical battery of the type of a cylindrical battery).
Square battery: simple structure and light weight
The popularity of square batteries in China is very high, because the structure of square batteries is relatively simple, the production process is not complicated, and because square batteries do not use high-strength stainless steel as the shell like cylindrical batteries, the energy density of square batteries is theoretically It has a higher energy density than a cylindrical battery. However, since the square batteries are generally designed to be customized, the production process of the square batteries is difficult to unify, and the degree of standardization is low.
Soft pack battery: high energy density, better battery layout flexibility
The soft pack battery adopts a superimposed manufacturing method and is slimmer in volume compared to the other two types of batteries, so its energy density is theoretically the highest among the three types of batteries. And because the soft pack battery is smaller, it is more flexible in battery layout than the other two types of batteries.
However, since the inside of the soft pack battery has a superimposed design, it is necessary to add a thin layer between every two batteries, and the sheet is filled with liquid, and the battery is at an optimum working temperature by heating or cooling, which also means a soft pack. Batteries require more sophisticated battery control systems.
To sum up
In the current market, cylindrical, square, and soft-packed batteries are used, and there is no absolute difference between good and bad. It can only be said that each has its own advantages. In terms of cell energy density, theoretically, the soft pack battery is the highest, the square battery is the second, and the cylindrical battery is the smallest.