Text/Peach Lee
As the power source of electric vehicles, batteries play the role of the "heart" of electric vehicles, providing energy for the operation of electric vehicles at all times. I believe that friends who pay attention to new energy vehicles will have a very in-depth understanding of the battery, many people will pay attention to the performance and safety of the electric vehicle battery, after all, the performance of the battery determines the endurance of the electric vehicle, and the battery safety issue is related to life and health, but do you know that the shape design of the battery is actually different? Today we will tell you how the battery is encapsulated.
At present, according to the packaging method and shape of the battery, it can be divided into square, cylindrical, soft package and other forms, so what are these different shape designs for? And what's the use?
First of all, whether it is a hard shell battery or a soft pack battery, the difference in its internal structure (positive electrode, negative electrode, separator, electrolyte) is still not large, the most important difference is the battery shell, the soft pack battery uses aluminum-plastic composite film as the shell material, and the square and cylindrical batteries use metal materials as the shell, also known as hard shell batteries.
First of all, let's talk about the soft pack battery, which is actually a battery that uses aluminum-plastic film as the packaging material, and needs to use thermal packaging. The basic structure of the soft-pack lithium battery is similar to the cylinder and the square, but the soft-pack lithium battery is a liquid lithium-ion battery covered with a layer of polymer shell, which is packaged in an aluminum-plastic film in the structure, which generally has three layers, the nylon layer is to ensure the shape of the aluminum-plastic film, the Al layer prevents the infiltration of water, and the PP (polypropylene) layer can effectively prevent the internal electrolyte from contacting the Al layer and avoiding the Al layer from being corroded.
The packaging material and structure of the soft pack battery make it have a series of advantages, for example, the safety performance is good, the soft pack battery is packaged in aluminum-plastic film in the structure, and when a safety problem occurs, the soft pack battery will generally burst and crack, and it does not explode like the steel shell or aluminum shell battery cell; the weight is light, which can reduce the burden on the car; the design is flexible, and the shape of the shape can be changed at will.
The disadvantage is that the consistency is poor, the cost is high, it is easy to leak, and the aluminum-plastic film looks very simple, but how to combine the three layers of materials uniformly and firmly is not so easy, and now the good quality of the aluminum-plastic film is basically dependent on imports, and the quality of domestic products needs to be improved.
Cylindrical lithium battery is a round type lithium battery, we usually refer to the cylindrical 18560 lithium battery here, cylindrical lithium battery is more studied and analyzed, the most comprehensive technical discussion of battery varieties. The single is mainly composed of a positive electrode, a negative electrode, a diaphragm, a positive negative collector, a valve, an overcurrent protection device, an insulator and a housing. The early shell material chose more steel shells, and the current stage is dominated by aluminum shells.
Cylindrical lithium batteries have a unified standard, so it can be manufactured and processed in large quantities, and the maturity and perfection of battery manufacturers' technology can make the production speed of cylindrical lithium batteries higher; at the same time, its use range is also wider, in addition to the field of new energy vehicles, it is also widely used in various electronic instruments and meters, and its technology is more mature.
Square lithium-ion batteries usually refer to aluminum shell or steel shell square batteries, the popularity of square batteries in the country is very high, with the rise of automotive power lithium batteries in recent years, the contradiction between automobile mileage and battery capacity is becoming increasingly prominent, domestic power lithium battery manufacturers use aluminum shell square batteries with higher battery energy density, because the structure of square batteries is relatively simple, unlike cylindrical batteries using stainless steel with higher strength as shells and other accessories with explosion-proof safety valves, so the overall accessory weight is lighter, Relative energy density is high.
The square battery will be more malleable and can be customized according to the specific needs of the product on board, but this also leads to its different sizes and no clear standards for manufacturing. Whether it is a manufacturing process or an application standard, there is no clear standard division like cylindrical batteries.
summary:
Although the appearance of different forms, the use of different scenes, but there is no difference in essence, the appearance of the battery design is mainly to meet the needs of major car companies, good or not to use in fact, it is difficult for consumers to say what is the difference, we are more concerned about the battery life and safety performance.