Cylindrical cells are a popular and less expensive option for electric vehicles, largely because their construction was born out of the consumer battery space, says Joe LoGrasso, a director of the U.S. Advanced Battery Consortium and senior manager of energy storage & high voltage systems at FCA US. “It probably offers the greatest ease in terms of capability,” says LoGrasso. “The negative is that it requires a lot more interconnects and complexity in terms of designs, but I think it can be made to be manufactured competitively as well.”
Prismatic cells, as described by NHTSA, are constructed in a wound or flat plate configuration. NHTSA writes: “Wound prismatic cells are generally constructed by wrapping the layers around a bobbin or mandrel, similar to that of a cylindrical cell. In a flat plate cell, discrete layers are stacked side by side and pressed together or folded. Prismatic cells that are designed for automotive applications can have much larger capacities than cylindrical cells.”
Pouch cells are fundamentally prismatic cells with flexible polymer coated aluminum packaging instead of a metal can, NHTSA says. The individual layers are stacked or folded, packed under vacuum and held together by the pouch. Most of the pouch designs use a gel electrolyte technology, while typical lithium ion cells used by manufacturers use liquid. A pouch’s gel electrolyte has higher resistance but doesn’t have the risk of spilling that a liquid electrolyte does.