Pros and Cons of Lithium Prismatic Cells Vs Cylindrical Cells

Battery cells come in various shapes to accommodate the diverse designs and functions of electronic devices and battery-powered applications. Two prevalent shapes are prismatic cells and cylindrical cells. Each shape offers distinct advantages depending on the application’s requirements, whether you need cost-effective, mass-producible batteries or those with a higher capacity range.

However, it's crucial to understand the functional differences between these two types. The choice of battery cell can significantly impact your product's design, power availability, and the potential consequences in case of a cell failure. Selecting the appropriate cell type ensures optimal performance and safety for your specific application.

Battery Cell Shapes and Sizes

Battery cells are engineered in various shapes to suit different devices and applications. The most common types are cylindrical and prismatic cells, each with unique characteristics and advantages.

Cylindrical Cells

Cylindrical cells are long and round, resembling the familiar batteries found in toys, remote controls, and many other devices. They are constructed by tightly winding electrodes and placing them inside a specially designed metal can. This shape is particularly advantageous for several reasons:

- Universal Sizes: Cylindrical cells come in standardized sizes like 14650, 18650, 21700, and 26500, making them compatible with various applications and ensuring interchangeability between manufacturers.

- Structural Strength: The round shape allows for even distribution of internal pressure and electrolytes, minimizing the risk of leaks or cell bloating.

- Mass Production: Their straightforward design and widespread use make them easy and cost-effective to mass-produce.

Prismatic Cells

Prismatic Lifepo4 cells are flat and rectangular, designed to maximize space efficiency. They are typically constructed with layers of electrodes encased in steel or aluminum, covered with an insulated film. This design offers several benefits:

- Space-Saving: Their compact shape allows for better space utilization within devices, making them ideal for applications where size and shape are critical, such as in electric and hybrid vehicles.

- Custom Shapes: Unlike cylindrical cells, prismatic cells don't adhere to universal size standards. This flexibility allows manufacturers to design custom shapes tailored to specific applications, though it often requires attention to minimum order quantities and necessary certifications.

However, prismatic cells also present some challenges:

- Stress Points: The flat, rectangular shape, especially at the corners, can be more susceptible to stress from shocks and vibrations. If not adequately protected, these points may weaken over time.

- Electrolyte Distribution: The pointed corners can hinder the even distribution of electrolytes, potentially leading to cell bloating and deformation.

Prismatic cells come in various sizes, and their non-standardized formats mean they are often custom-built. This customization can lead to higher costs and the need for careful consideration of production and certification requirements.

Voltages And Capacities

When it comes to voltages and capacities, there are key advantages and disadvantages to both cell forms. Prismatic cells are larger in size than cylindrical cells and have fewer connections in the application. So prismatic cells allow for larger capacities. For example, one lithium phosphate battery (LifePO4) in prismatic cell form has 3.2 volts 100ah.

On the other hand, cylindrical cells have more connections in the application and come in smaller sizes that allow for less energy storage. Cylindrical cells, despite having lower capacity compared to prismatic cells, excel in voltage power and offer faster discharge rates per amp hour (Ah) because of their design which necessitates more connections.

To achieve the same amp hour rating as a single prismatic cell, approximately 18 cylindrical cells are required. When aiming for a voltage of 48 volts, you would need either 18 prismatic cells or 16 sets of 18 cylindrical cells.

Although cylindrical cells require more units to match the capacity of prismatic cells, they provide better energy efficiency. This characteristic makes cylindrical cells preferable for high-performance applications, such as in toys and consumer electronics, where prolonged battery life is crucial. Conversely, prismatic cells are more suitable for applications with high energy demands, like energy storage systems, medical devices, and electric vehicles.

Lifepo4 Prismatic Cells Vs Cylindrical Cells: Which Is Better?

When comparing LiFePO4 prismatic cells to cylindrical cells, several factors come into play:

Prismatic cells boast a theoretically higher energy density than cylindrical cells. Their simpler structure and less complicated production process contribute to this advantage, as they do not require high-strength stainless steel shells like cylindrical batteries. This makes prismatic batteries increasingly popular in electric vehicle applications.

Prismatic cells also exhibit excellent thermal characteristics, requiring less cooling per energy unit compared to cylindrical cells. They offer superior cycle life even under high and varied loads, which typically degrade other lithium cell formats. With a cycle life up to four times greater than cylindrical lithium cells, prismatic cells can significantly lower operational and ownership costs.

On the other hand, cylindrical batteries have undergone extensive development, making their technology highly mature and standardized. Their assembly allows for more space between individual cells, enhancing heat dissipation. Many models using cylindrical cells leverage cost-effective air cooling technologies.

When choosing between prismatic and cylindrical cells, consider your specific lithium application requirements:

- High Power and Long Service Life: Cylindrical cells are ideal due to their mature technology, standardized design, and effective heat dissipation.

- Limited Space and Cost Considerations: Prismatic cells, despite their higher initial cost, offer compact designs that suit constrained spaces and lower long-term operational costs due to their superior energy density and longevity.

Ultimately, your selection should align with your priorities—whether it's maximizing energy density and cycle life with prismatic cells or leveraging the mature technology and heat dissipation advantages of cylindrical cells.