Lithium batteries can be classified into cylindrical batteries, prismatic batteries, and pouch batteries based on their packaging. Although prismatic batteries are currently the mainstream power batteries on the market, each of the three types has its own advantages and disadvantages.
In the realm of cylindrical batteries, Tesla stands out as a leader in the power battery industry. From the 18650 to the 21700, and now to the soon-to-be-mass-produced 46800 battery, Tesla has consistently set the trend.
Taking the 18650 battery as an example, 18 represents the diameter of the battery, 65 represents the height of the battery, and 0 represents that it is a cylindrical battery. The same applies to 27100 and 46800 batteries.
The 18650 battery was the earliest developed lithium battery packaging form. By 1992, cylindrical batteries had already seen significant development. Initially, 18650 batteries were mostly used in digital products.
Due to its first-mover advantage, cylindrical cells are the most mature packaging technology. Specifically, 18650 cells have a higher yield rate, and the cost of the battery pack can be effectively controlled.
Compared to prismatic hard-shell batteries, cylindrical batteries have less space utilization. However, cylindrical batteries can utilize the gap in the middle of the cylinder to allow coolant to flow, which can also be considered a form of space utilization.
On the downside, the disadvantages of the 18650 cannot be ignored. First, the 18650 battery uses a metal casing and has a relatively small single cell capacity. In order to meet the capacity requirements, it can only be compensated by a significant increase in the number of cells. Therefore, a larger number of cells places higher demands on the BMS battery management system.
Square batteries are currently the most widely used type of battery in the lithium battery field. Major domestic new energy vehicle manufacturers such as BYD, Geely, and NIO all use square hard-shell batteries, while international traditional manufacturers such as Audi and BMW also employ square battery solutions.
One of the most important reasons for the wide application of prismatic batteries is the abundance of suppliers and the relatively lower technical difficulty. The vast majority of battery suppliers in China have chosen to develop prismatic batteries. For example, well-known companies such as CATL, BYD, and Guoxuan High-Tech are major suppliers of prismatic hard-shell batteries.
Besides the abundance of suppliers, square batteries also offer greater customization options and higher space utilization compared to cylindrical batteries. However, the problem lies in the fact that the outer hard protective shell significantly increases the overall weight of the battery pack. Therefore, domestic manufacturers like Li Auto's ONE have begun to use aluminum as the outer protective shell to effectively ensure lightweight design and thus improve battery energy density.
Meanwhile, square batteries have larger individual cell capacity and volume, naturally reducing the number of cells required, thus lowering the requirements for the battery management system (BMS). Currently, the most representative square hard-shell motor battery is the NCM811 battery launched by CATL.
The disadvantage of prismatic batteries lies in their high degree of customization, leading to inconsistent manufacturing processes and noticeable differences between each battery. Compared to cylindrical batteries, prismatic hard-case batteries have more stringent requirements for cooling system layout. However, with the introduction of national battery standards policies, the differences between prismatic batteries will decrease in the future.
Although pouch batteries are being used more and more in the automotive market, they are not unfamiliar to us because lithium batteries in mobile phones are mostly packaged in pouch form.
The outer casing of pouch batteries is made of aluminum-plastic film, making them lighter than square and cylindrical batteries that use aluminum casings. For the same capacity, pouch batteries are 20% lighter, while for the same weight, they offer 50% more capacity than aluminum-cased batteries.
Therefore, the theoretical energy density of pouch batteries is higher than that of prismatic and cylindrical batteries. As for disadvantages, pouch batteries currently need to address issues such as high standardization and cost, heavy reliance on imported high-end aluminum-plastic film, and poor consistency.
The market believes that pouch batteries have great potential and will become the mainstream in the future.
