Prismatic Cells vs. Cylindrical Cells: What is the Difference?

Prismatic Cells vs. Cylindrical Cells: What is the Difference?

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 cylindrical battery formats have dominated in recent years, several factors suggest that prismatic cells may soon take the lead.

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Because Laserax provides laser solutions for battery manufacturing, we are watching these developments closely. Before diving into upcoming trends, let's review the two types of batteries.

What Are Prismatic Cells

A prismatic cell is a cell housed in a rigid rectangular casing. This shape allows for efficient stacking of multiple units in a battery module. There are two types of prismatic cells: those with electrode sheets stacked inside the casing, and those with electrodes that are rolled and then flattened.

For the same volume, stacked prismatic cells can release more energy at once, offering better performance, whereas flattened prismatic cells contain more energy, providing greater durability. Prismatic cells are primarily used in energy storage systems and electric vehicles due to their larger size, making them unsuitable for smaller devices like e-bikes and cellphones. Therefore, they suit energy-intensive applications best.

What Are Cylindrical Cells?

A cylindrical cell is enclosed in a rigid cylinder. Their small, round shape makes them adaptable to devices of various sizes. Unlike other formats, their design prevents swelling, an issue where gases accumulate within the casing.

Cylindrical cells first gained prominence in laptops. Tesla further popularized them by using them in its early electric vehicles, such as the Roadster and Model S, which contained between 6,000 and 9,000 cells. They are also used in e-bikes, medical devices, and satellites. Their robustness makes them ideal for space exploration; for example, NASA’s Mars rover operates on cylindrical cells. Even the high-performance electric race cars in Formula E use the same cells.

Main Differences Between Prismatic and Cylindrical Cells

Several key differences set prismatic cells apart from cylindrical ones, including their shape, size, number of electrical connections, and power output.

Size

Prismatic cells are significantly larger than cylindrical cells, containing more energy per cell. A single prismatic cell can hold the same amount of energy as 20 to 100 cylindrical cells. This larger size limits their applications to energy-intensive uses, whereas the versatility of cylindrical cells allows them to fit a broader range of applications.

Connections

Given their larger size, fewer prismatic cells are needed for the same energy output, resulting in fewer electrical connections. This minimizes the chances of manufacturing defects, an advantage over cylindrical cells that require more connections.

Power

While cylindrical cells store less energy compared to prismatic cells, they can discharge energy more rapidly. Their numerous connections per amp-hour (Ah) make them ideal for high-performance applications. Examples include Formula E race cars and the Mars Ingenuity helicopter, both requiring extreme performance in demanding conditions.

Why Prismatic Cells Might Be Taking Over

The EV industry is evolving rapidly, making it unclear whether prismatic cells will outpace cylindrical ones. Currently, cylindrical cells are more prevalent in EVs, but there are compelling reasons to believe that prismatic cells will rise in popularity.

First, the format of prismatic cells allows manufacturers to produce larger cells, reducing the number of electrical connections and manufacturing steps. This drives down costs. Prismatic batteries are also well-suited for the lithium-iron phosphate (LFP) chemistry, which uses more abundant and less expensive materials compared to other chemistries.

There are strong signals that LFP prismatic cells are gaining traction. For instance, many Asian EV manufacturers already use LiFePO4 batteries, a type of LFP battery in prismatic format. Tesla has also begun using prismatic batteries for the standard-range versions of its cars manufactured in China.

However, LFP chemistry has its downsides, including lower energy content and challenges in accurately predicting battery charge levels via Battery Management Systems (BMS).

You can watch this video to learn more about the LFP chemistry and its rising popularity.

Prismatic Cells in Energy Storage Systems

When it comes to battery pack production demand, energy storage systems (ESS) are as crucial as electric vehicles. ESSs already employ prismatic cells and are likely to continue doing so. Prismatic cells offer a longer cycle life, lower danger, and reduced costs compared to cylindrical cells.

The Switch to Prismatic Batteries

Tesla’s 4680 cylindrical cell, known for its tabless design, high energy density, and low manufacturing cost, is highly notable. Still, Elon Musk has spoken about prismatic cells' advantages, leading Tesla to use them in certain car models.

Though the 4680 cylindrical cells haven't yet been replaced, Tesla's future choices will be telling. Will they switch from Nickel-Cobalt-Aluminum oxide (NCA) chemistry to LFP and opt for prismatic cells? Given the rising costs of raw materials, this seems a strong possibility.

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