Pouch cells and cylindrical are both lithium-ion batteries. These two battery formats have a lot in common but there are also some key differences. Cylindrical cells can be one of several chemistries while pouch cells are typically NMC.
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Pouch cells come in all kinds of shapes and sizes. This makes them ideal for small, portable electronics. This is in contrast to cylindrical cells which are only available in a few sizes. Pouch cells can run higher discharge currents than cylindrical cells, but they also don’t have the hard, protective casing that cylindrical cells. Choosing to use pouch or cylindrical cells really depends on your application. Generally speaking, it's best to use cylindrical cells until it's not viable to do so. If cylindrical cells cannot meet your project's needs, then consider using a pouch cell.
In this article, we will compare and contrast pouch and cylinder lithium-ion battery cells. We will also go over some of the advantages and disadvantages of each battery format.
A cylindrical battery is unsurprisingly a battery in the shape of a cylinder. Cylindrical batteries have a strong, metal case that encloses the anodes, cathodes, and separators. The cylinder shape makes this type of cell low-cost to manufacture while providing a great deal of strength. The most common cylindrical cell sizes are 18mm x 65mm and 21mm x 70mm also known as and cells.
Pouch cells are a lithium-ion battery that has the cell chemistry contained in an aluminum foil pouch. Inside a pouch cell, the positive and negative sides are separated with a polymer film. This type of cell has no metal casing, so they are lighter than canister cells. Pouch cells are widely used in portable, small electronic devices.
Yes. Often in conversation and on social media posts, you will see people make a distinction between the two. For example, someone will say, “I’ve been using lipos on my ebike but I’m planning on switching to lithium-ion.”
The reality is that pouch cells, also commonly referred to as lipo cells are a subset of lithium-ion battery technology. So, a lipo cell is a lithium-ion cell, but in a pouch instead of a metal canister.
Cylindrical cells are low cost and their insides are relatively safe due to the metal outer casing. Cylindrical cells are used in e-bike batteries, electric cars, and off-grid batteries. You can also find cylindrical cells in flashlights, remote controls, power tools, medical devices, drones, and much more.
● Low cost is the main advantage of cylindrical cells
● Cylindrical cell production is reliable, consistent, and fast.
● High-temperature resistance
● High strength
● Lower energy density due to gaps between cells
● The steel casing makes them heavier
● Lower discharge current.
Pouch cells definitely have their place in society. They can often produce far higher currents than canister cells and they can be made to fit odd spaces more easily and are more energy dense.
● The polymer separator and aluminum foil casing makes them light
● Pouch cells can deliver more current than a cylindrical cell of the same size
● Lower internal resistance
● Can be made in many sizes and shapes
● Higher energy density
● Complicated to manufacture
● Easy to puncture
● Under heavy use they swell a lot
● Under normal use they swell somewhat
Pouch cells can deliver more current and can be made to fit just about any shape or size. Cylindrical cells, on the other hand, are strong and have good heat dissipation characteristics.
Pouch cells will expand over the life of the battery pack whereas cylindrical cells stay the same size. The phenomenon plays a key role in properly designing a system to use pouch cells. When you are using pouch cells much more care has to be taken in terms of where the battery will go and the room inside that cavity.
Cylindrical cells, on the other hand, always stay the same size. This is because they have a hard metal case and are designed in such a way that they do not expand under normal operation. Personally, I feel like this is the key attribute that makes cylindrical cells the better option in most cases.
Yes. Pouch cells have a higher internal energy density and can be packed very efficiently. Cylinder cells have a packing efficiency of about 90 percent. This is in contrast to pouch cells that can have packing efficiencies as high as 99 percent. So in a given space with a cylindrical cell, you will have about 9% dead space compared to pouch cells.
No matter how much effort you put in, you won’t be able to fill all of the space with cylindrical cells because they have a circular footprint. Circle packing is a highly complicated science and it can get really overwhelming, really quick, but I will tell you this: The hexagonal pattern is the most efficient packing format you can use for cylindrical cells.
Connections are made to pouch cells through the terminal tabs that extend through the seals. These tabs can be used to either make connections with the other pouch cells or to the load. Simply solder the connections together and make sure they are properly insulated from other connections. Some do choose to spot-weld these connections together.
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When it comes to pouch cells vs cylinder cells, this is a major win for pouch cells. Unlike pouch cells, cylindrical cells are not easy to make an electrical connection to. To connect to cylindrical cells (and therefore to connect cylindrical cells together to form battery packs) requires special equipment and experience.
Generally speaking, cylindrical cells will be the best for power walls. More often than not, a powerwall battery does not need to be as small as possible. Also, powerwall batteries are relatively large, especially when you build a DIY powerwall. This means you will have to buy a lot of cells to make one and cylinder cells are way cheaper.
When choosing between pouch cells or cylindrical cells for your project, it can be a tough decision. Once you know each type of battery’s strengths and weaknesses it makes the process a lot easier
Cylindrical lithium battery is a kind of lithium ion battery, its shape is cylindrical, so it is called cylindrical lithium battery. The structure of a typical cylindrical battery includes: casing, cap, cathode, anode, separator, electrolyte, PTC element, gasket, safety valve, etc. Generally, the battery shell is the anode of the battery, the cap is the cathode of the battery, and the battery shell is made of nickel-plated steel plate.
Since Tesla's battery day in September proposed large cylindrical cells, large cylindrical cells have once again become the focus of the battery industry in the market. In addition to Tesla, China's leading cell factories have also begun to invest in the mass industrialization of large cylindrical cells.
According to the data shown by Tesla, the large cylindrical lithium battery will increase the energy by 5 times on the basis of the cylindrical cells, increase the mileage by 16%, and reduce the cost by 14%. Its technical temptation is very significant. However, during the period of rapid development of China's new energy vehicles in the past, first-line brands including CATL and BYD all focused on the technical route of square cells. At present, the industrialization of power batteries is basically based on square batteries, and even Tesla has purchased square batteries with a capacity of about 161Ah in China for use in one of its models.
From a technical perspective, both technical routes have their own value and advantages. In a complex battery system, although batteries account for the highest cost, in terms of safety and cost performance, we cannot only focus on one dimension of batteries. For example, Tesla has industrialized and applied the cylinder and to electric vehicles with energy exceeding 70KWH through advanced management system design. In fact, it is using advanced management to optimize the performance of the battery system.
● Advantages of small capacity flexibility
Due to size and process limitations of cylindrical cells, the capacity of a single cell is usually small. For example, ternary battery 3.5Ah, iron-lithium battery 6Ah, iron-lithium battery 15Ah, iron-lithium battery 20Ah, etc. Aside from electric vehicles and large-scale energy storage markets, in other fields, such as AGV, portable energy storage, and home energy storage, the capacity of single-module batteries is usually not very large. In practical applications, the large-capacity square cells positioned for automobiles and large-scale energy storage do not necessarily exactly match the market demand, including size and capacity.
The small-capacity cylindrical lithium battery can be connected in parallel to meet the battery module capacity needs of certain market demands. For example, the two types of lithium batteries 24V60Ah and 48V30Ah used in AGV cars are relatively common needs. Three types of cylinders, , and , can be combined in parallel to form the required 60Ah or 30Ah modules. At the same time, there are more flexible operation possibilities in the space structure to meet the design requirements of different models.
● Cost advantage
In the production and manufacture of all lithium-ion batteries in lithium battery companies in the world, the process standardization of cylindrical lithium battery is the highest, and it is also the earliest commercialized battery. The assembly efficiency is significantly higher than that of square batteries and pouch batteries. The winding process of cylindrical batteries has reached the level of 200PPM with the gradual improvement of automation. Even though the efficiency of large cylindrical lithium batteries is slightly lower than that of traditional / cylindrical cells, it is much higher than the efficiency of stacking or winding processes of square cells and pouch cells (usually around 10PPM).
The reason for the small capacity of the cylindrical lithium battery is that the strip-shaped continuous pole piece after coating is cut into strip-shaped small pole pieces, and the miniaturization of the pole piece can improve the utilization rate of the entire pole piece material. Usually under the same screening criteria and automation level, the material utilization rate of cylindrical cells is 3-5% higher than that of square cells.
● The heat dissipation effect is obvious
Lithium-ion battery fires are all caused by thermal runaway, and the spread of thermal runaway is also the main concern of battery system safety performance. Cylindrical structure is the most likely solution to thermal runaway, while square and pouch structures are basically unsolvable. The low capacity of a single cell causes thermal runaway to release less energy, which is different from high-energy, large-capacity square cells or pouch cells. At the same time, with the gradual improvement of material safety, the heat release caused by thermal runaway is reduced, which significantly increases the safety of the battery system.
The curved surface structure of the cylindrical lithium battery limits the heat transfer process between the cells to a certain extent, and has a certain positive effect on the spread of thermal runaway. However, square batteries and pouch batteries are basically unsolvable in this regard. Furthermore, with the promotion of the full-tab process, the heat transfer of cylindrical cells is more on the upper and lower end caps of the cells, and the heat transfer on the curved surface will also be reduced.
The above is some analysis and thinking based on different application scenarios of lithium batteries with different structures. Although the focus is on analyzing the advantages of cylindrical lithium battery, it is undeniable that cylindrical cells have shortcomings in certain application fields. At the same time, it is also necessary to objectively understand the own advantages of square cells and pouch cells.
With the development of lithium battery technology, there are more and more types of cylindrical lithium battery. Cylindrical lithium battery are divided into lithium cobalt oxide, lithium manganese oxide, and ternary materials. The three material systems have different advantages. Let's take a look at the models and specifications of cylindrical lithium battery. Cylindrical lithium battery is usually represented by five digits. Counting from the left, the first and second digits refer to the diameter of the battery, the third and fourth digits refer to the height of the battery, and the fifth digit refers to the circle. There are many types of cylindrical lithium battery, the more common ones are , , , , , , and so on.
● battery
The battery is a cylindrical lithium battery with a diameter of 10mm and a height of 44mm. It is the same size as what we often call the 7th battery. This battery capacity is generally small, only a few hundred mAh, and is mainly used in mini electronic products. Such as flashlights, mini stereos, megaphones, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 14mm and a height of 50mm. This is also the size of what we have always called the AA battery. This kind of battery is generally 3.7V or 3.2V. The nominal capacity is relatively small, a little larger than the battery, generally mAh, and the discharge performance is superior. The most important application field is consumer electronics, such as wireless audio, electric toys, digital cameras, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 16mm and a height of 34mm. Due to its shorter height and relatively small capacity, this kind of battery often appears in glare flashlights, LED flashlights, headlights, laser lights, lighting fixtures, etc.
● battery
The battery is a lithium-ion battery with a diameter of 18mm and a height of 65mm. Its biggest feature is that it has a very high energy density, almost reaching 170 Wh/kg, so this battery is a battery with better cost performance. Most of the battery store we often see are batteries, because it is a relatively mature lithium-ion battery, and the system quality is stable in all aspects. It is widely used in occasions with a battery capacity of about 10 kWh, such as mobile phones, notebook computers and other small electrical appliances.
● battery
The battery is a cylindrical lithium battery with a diameter of 21mm and a height of 70mm. Because of its larger volume and greater space utilization, the energy density of the battery cell and the system can be improved, and its volumetric energy density is much higher than that of the battery. Widely used in digital, electric vehicles, balance cars, solar energy lithium-ion battery street lights, LED lights, power tools, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 26mm and a height of 65mm, with a nominal voltage of 3.2V and a nominal capacity of mAh. This kind of cylindrical lithium battery has the characteristics of excellent capacity and high consistency, and has gradually become a trend to replace batteries. Many products in power lithium batteries will also gradually favor it.