The packaging form of battery: cylinder, square and soft bag, who is better?
According to different packaging forms, the battery is divided into cylindrical battery, square battery and soft pack battery. Different structures also mean that they have different characteristics. Today, let's take a look at the advantages and disadvantages of these three structures.
Cylindrical battery: long development time, most mature technology
The development time of cylindrical battery is the longest, technology is also the most mature, and its standardization is high. And because there is a large space between each cell when the cylindrical battery is packaged, this kind of battery has a great advantage in heat dissipation. Many models equipped with the cylindrical battery adopt the air cooling technology with lower cost.
But too many batteries is a more difficult problem. Even for the models with high energy density batteries, thousands of cylindrical batteries need to be put together, which also puts forward higher requirements for the battery management system of vehicles. In addition, the weight of the cylindrical battery is relatively high because the steel shell is needed when it is combined into the battery pack. In theory, the energy density of the cylindrical battery is lower than the other two batteries.
At present, many models on the market use this type of battery. The typical one is Tesla's model 3, which uses the model 21700 (in which 21 represents the diameter of the cylindrical battery 21mm, 70 represents the length of the battery 70mm, and 0 represents the type of the cylindrical battery)
Square battery: simple structure, light weight
Square battery has a high penetration rate in China, because the structure of square battery is relatively simple and the production process is not complex, and because square battery does not use stainless steel with high strength as the shell like cylindrical battery, the energy density of square battery is theoretically higher than that of cylindrical battery. However, the square battery is generally customized design, so it is difficult to unify the production process of square battery, and its standardization degree is low.
Soft pack battery: high energy density, better flexibility of battery layout
Compared with the other two kinds of batteries, the soft pack battery is more thin in volume, so its energy density is the highest in theory. And because of its small size, the flexible battery layout is better than the other two types of batteries.
However, because the interior of the soft pack battery is a superposition design, it needs to add a layer of thin film between each two batteries, which will be filled with liquid, so as to ensure that the battery is at the most appropriate working temperature through heating or cooling, which also means that the soft pack battery needs more complex battery control system.
In the current new energy vehicle market, three kinds of batteries, cylinder, square and soft bag, are all equipped with vehicle models. There is no absolute distinction between good and bad, but each has its own advantages. In terms of the energy density of the cell, the soft battery is the highest in theory, followed by the square battery and the cylinder battery.