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.
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&#; 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.
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There are three main types of lithium-ion batteries (li-ion): cylindrical cells, prismatic cells, and pouch cells. In the EV industry, the most promising developments revolve around cylindrical and prismatic cells. While the cylindrical battery format has been the most popular in recent years, several factors suggest that prismatic cells may take over.
Because Laserax provides laser solutions for battery manufacturing, we are watching these developments closely. Before we go over what&#;s coming, let&#;s do a quick overview of the two types of batteries.
A prismatic cell is a cell whose chemistry is enclosed in a rigid casing. Its rectangular shape allows efficiently stacking multiple units in a battery module. There are two types of prismatic cells: the electrode sheets inside the casing (anode, separator, cathode) are either stacked or rolled and flattened.
For the same volume, stacked prismatic cells can release more energy at once, offering better performance, whereas flattened prismatic cells contain more energy, offering more durability.
Prismatic cells are mainly used in energy storage systems and electric vehicles. Their larger size makes them bad candidates for smaller devices like e-bikes and cellphones. Therefore, they are better suited for energy-intensive applications.
A cylindrical cell is a cell enclosed in a rigid cylinder can. Cylindrical cells are small and round, making it possible to stack them in devices of all sizes. Unlike other battery formats, their shape prevents swelling, an undesired phenomenon in batteries where gasses accumulate in the casing.
Cylindrical cells were first used in laptops, which contained between three and nine cells. They then gained in popularity when Tesla used them in its first electric vehicles (the Roadster and the Model S), which contained between 6,000 and 9,000 cells.
Cylindrical cells are also used in e-bikes, medical devices, and satellites. They are also essential in space exploration because of their shape; other cell formats would be deformed by the atmospheric pressure. The last Rover sent on Mars, for example, operates using cylindrical cells. The Formula E high-performance electric race cars use the exact same cells as the rover in their battery.
Shape is not the only thing that differentiates prismatic and cylindrical cells. Other important differences include their size, the number of electrical connections, and their power output.
Prismatic cells are much larger than cylindrical cells and hence contain more energy per cell. To give a rough idea of the difference, a single prismatic cell can contain the same amount of energy as 20 to 100 cylindrical cells. The smaller size of cylindrical cells means they can be used for applications that require less power. As a result, they are used for a wider range of applications.
Because prismatic cells are larger than cylindrical cells, fewer cells are needed to achieve the same amount of energy. This means that for the same volume, batteries that use prismatic cells have fewer electrical connections that need to be welded. This is a major advantage for prismatic cells because there are fewer opportunities for manufacturing defects.
Cylindrical cells may store less energy than prismatic cells, but they have more power. This means that cylindrical cells can discharge their energy faster than prismatic cells. The reason is that they have more connections per amp-hour (Ah). As a result, cylindrical cells are ideal for high-performance applications whereas prismatic cells are ideal to optimize energy efficiency.
Example of high-performance battery applications include Formula E race cars and the Ingenuity helicopter on Mars. Both require extreme performances in extreme environments.
The EV industry evolves quickly, and it&#;s uncertain whether prismatic cells or cylindrical cells will prevail. At the moment, cylindrical cells are more widespread in the EV industry, but there are reasons to think prismatic cells will gain in popularity.
First, prismatic cells offer an opportunity to drive down costs by diminishing the number of manufacturing steps. Their format makes it possible to manufacture larger cells, which reduces the number of electrical connections that need to be cleaned and welded.
Prismatic batteries are also the ideal format for the lithium-iron phosphate (LFP) chemistry, a mix of materials that are cheaper and more accessible. Unlike other chemistries, LFP batteries use resources that are everywhere on the planet. They do not require rare and expensive materials like nickel and cobalt that drive the cost of other cell types upward.
There are strong signals that LFP prismatic cells are emerging. In Asia, EV manufacturers already use LiFePO4 batteries, a type of LFP battery in the prismatic format. Tesla also stated that it has begun using prismatic batteries manufactured in China for the standard range versions of its cars.
The LFP chemistry has important downsides, however. For one, it contains less energy than other chemistries currently in use and, as such, can&#;t be used for high-performance vehicles like Formula 1 electric cars. In addition, battery management systems (BMS) have a hard time predicting the battery&#;s charge level.
You can watch this video to learn more about the LFP chemistry and why it is gaining in popularity.
When it comes to battery pack production demand, energy storage systems (ESS) are just as important as electric vehicles. ESSs are already using prismatic cells and it is very likely that they will keep using them. Prismatic cells have a longer cycle life, are less dangerous, and come at a low cost compared to cylindrical cells.
With its tabless cell design, high energy density, and low manufacturing cost, Tesla&#;s cylindrical cell is probably the most noteworthy battery cell at the moment. But recently, Elon Musk has talked about the advantages of prismatic cells, and Tesla has begun using them in certain car models.
The cylindrical cells haven&#;t been replaced by prismatic cells yet, but Tesla&#;s next move will be telling of what the future holds. Will they replace the &#;s Nickel-Cobalt-Aluminum oxide (NCA) chemistry with the LFP chemistry? If so, will they switch to prismatic cells, the preferred format for this chemistry? With the increased cost of raw materials around the world, it is a strong possibility.
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