Feb. 18, 2025
The cylindrical lithium iron battery is one of the earliest industrialized lithium battery products. After more than 20 years of development, its production process has become highly refined, resulting in high manufacturing efficiency and relatively low costs. This also contributes to a lower overall PACK cost. Additionally, cylindrical lithium batteries have a higher yield rate compared to prismatic and pouch lithium batteries. They also offer excellent consistency and safety, making them a reliable choice for various applications.
Because the cylindrical iron-lithium battery is generally packaged in a steel shell, although the safety is relatively high, the weight will also be heavier, which will also make the specific energy of the lithium battery pack relatively low.
Prismatic iron-lithium batteries typically feature aluminum alloy or stainless steel casings, providing strong structural support. Inside, they utilize either winding or laminated technology, which offers better protection for the battery cells compared to soft-packed lithium batteries. Additionally, their safety performance is significantly improved compared to cylindrical lithium batteries.
While prismatic lithium iron battery packs can be customized to fit specific product sizes, this flexibility leads to a wide variety of battery types in the market. The lack of standardization makes it challenging to unify manufacturing processes, resulting in lower automation levels and inconsistencies between individual cells. Moreover, the lifespan of a prismatic lithium battery pack may be considerably shorter than that of a single battery cell due to these variations.
Prismatic, pouch, and cylindrical lithium-ion battery cells are three widely used form factors, each offering distinct advantages and disadvantages. The choice of form factor depends on the specific needs of the application. Here's a concise comparison:
- Prismatic cells feature a flat design, making them highly space-efficient.
- Pouch cells are adaptable to various shapes and sizes, offering flexibility in design.
- Cylindrical cells are compact and stackable, making them ideal for certain applications where space utilization is key.
- Prismatic cells are rigid, offering less flexibility in fitting unconventional spaces.
- Pouch cells are highly flexible, able to adapt to irregular and unconventional spaces.
- Cylindrical cells offer moderate flexibility, though they are less versatile when it comes to fitting irregular spaces.
- Prismatic cells generally have a moderate weight, which varies depending on the materials used.
- Pouch cells are lightweight due to their flexible packaging.
- Cylindrical cells also have a moderate weight, influenced by the metal casing surrounding the cell.
- Prismatic cells may incur higher manufacturing costs due to their complex design.
- Pouch cells are often more cost-effective because of their simpler manufacturing process.
- Cylindrical cells benefit from economies of scale and widespread use, making them a cost-effective option.
Different battery cell shapes are designed to accommodate various devices and applications. The three primary types—cylindrical, prismatic, and pouch cells—each have unique structural characteristics that influence their performance and suitability for different uses.
Cylindrical cells are round and elongated, similar to the batteries commonly found in toys, remote controls, and other consumer electronics. These cells are constructed by tightly winding electrodes and encasing them in a metal can, which allows for efficient manufacturing and robust structural integrity.
As the most widely used battery shape, cylindrical cells offer excellent durability. Their round design ensures uniform distribution of the electrolyte and internal pressure, reducing the risk of leaks and cell bloating. Additionally, they follow standardized size formats such as 14650, 18650, 21700, and 26500, making them easily interchangeable across different devices.
Prismatic cells have a flat, rectangular shape with internal components arranged in stacked layers and enclosed in a steel or aluminum casing. A protective insulated film covers the exterior of the can. This design maximizes space efficiency within a device, making prismatic cells a popular choice for electric and hybrid vehicles, where optimal space utilization is crucial.
However, prismatic cells come with certain structural challenges. The pointed corners of their rectangular design may experience increased stress from shocks and vibrations, making them more susceptible to damage if not properly enclosed. Additionally, the corners may hinder uniform electrolyte distribution, increasing the risk of cell bloating and deformation over time.
Unlike cylindrical cells, prismatic cells lack universal size standards, meaning manufacturers create custom sizes tailored to specific applications. As a result, buyers must consider factors such as minimum order quantities and necessary certifications when sourcing these batteries.
When comparing voltages and capacities, both prismatic and cylindrical cells have their own advantages and drawbacks.
Prismatic cells are larger in size and require fewer connections within an application, allowing for higher capacity storage. For example, a single Lithium Iron Phosphate (LiFePO4) prismatic cell can have a capacity of 3.2V and 100Ah. This makes them ideal for applications that require high energy storage with minimal wiring complexity.
Cylindrical cells, in contrast, are smaller in size and require more connections in an application. While they have a lower capacity per cell, they offer higher voltage power and faster discharge rates per amp-hour (Ah) due to their increased number of connections.
To achieve the same amp-hour capacity as a single prismatic cell, approximately 18 cylindrical cells would be required. Similarly, to reach a 48V system, you would need 18 prismatic cells compared to 16 groups of 18 cylindrical cells.
Although more cylindrical cells are needed to match the capacity of prismatic cells, they provide better energy efficiency and higher discharge performance, making them advantageous for applications requiring quick power delivery. It's due to this reason that cylindrical cells are used more often in high-performance applications such as toys and electronics for longer-lasting battery life. Prismatic cell shapes are better suited for energy-intensive applications such as storage systems, medical devices, and vehicles.
When assembling a battery pack, the alignment depends on the cell shape. Cylindrical cells are arranged in series and parallel configurations, typically in three rows of four or four rows of three, depending on available space. Their round shape allows optimal airflow for temperature control, enabling efficient heat dissipation and performance.
Prismatic cells are generally stacked in series. Due to their rectangular shape, they make direct contact with each other, limiting airflow and reducing heat dissipation efficiency. Instead, heat transfers between adjacent cell walls.
Prismatic cells typically last around 2,000 cycles, whereas cylindrical cells have a shorter lifespan of 300 to 500 cycles. A critical aspect of battery cell lifecycles is how a single faulty cell affects the pack. In cylindrical packs, a failing cell has minimal impact due to multiple connections, allowing continued power delivery. However, in prismatic packs, one defective cell can compromise the entire battery pack's performance.
All battery packs, regardless of shape, must undergo testing based on their cell chemistry, industry standards, and customer specifications. Testing and certification are common requirements for lithium battery chemistries in both cylindrical and prismatic cells.
Cylindrical cells are easier to manufacture due to well-established technologies, making them more cost-effective. Prismatic cells, while typically more expensive, are priced based on cell size and order volume. Customers should also consider that certain battery chemistries, such as lithium, may incur higher costs due to the required testing and certification compared to nickel-based chemistries.
Choosing the best battery shape for your budget depends on the application's power needs, lifecycle, and desired cost. Neither type of battery is inherently better; prismatic cells offer greater long-term capacity but come at a higher price. Cylindrical cells are cheaper, provide better thermal management, and are less prone to issues like bloating or leakage, though they have lower capacities and may require larger volumes to match the capacity of prismatic cells.
As lithium-ion battery technology continues to advance, the selection between prismatic, pouch, and cylindrical cells is influenced by the specific needs of the application. Each cell design presents its own set of advantages, and manufacturers must evaluate factors like space constraints, flexibility, weight, and cost to choose the most appropriate cell type for the intended purpose.
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