POUCH CELL PREPARATION

In 1995 the pouch cell surprised the battery world with a radical new design. Rather than using a metallic cylinder and glass-to-metal electrical feed-through, conductive foil-tabs are welded to the electrodes and brought to the outside in a fully sealed way.

The pouch cell makes the most efficient use of space and achieves a 90–95 percent packaging efficiency, the highest among battery packs. Eliminating the metal enclosure reduces weight but the cell needs some support in the battery compartment. The pouch pack finds applications in consumer, military and automotive applications. No standardized pouch cells exist; each manufacturer designs its own.

Pouch packs are commonly Li-polymer and serve well as Power Cells by delivery high current. The capacity is lower than Li-ion in the cylindrical package and the flat-cell may be less durable. Expect some swelling; 8–10 percent over 500 cycles is normal. Provision must be made in the battery compartment for expansion. It is best not to stack pouch cells on top of each other but to lay them flat side by side. Prevent sharp edges that can stress the pouch as they expand.

The prismatic and pouch cells have the potential for greater energy than the cylindrical format but the technology to produce large formats is not yet mature. The cost per kWh is still higher than the 18650. As a comparison, the cost for the Nissan Leaf with Pouch/Prismatic cells is $455/kWh and best practice (DoE/AABC) with pouch/prismatic is $350/kWh. The lowest price per kWh is the Tesla EV with the 18650 cells. The Tesla Gen III battery goes for $290/kWh (Estimations by Greenwich Strategy).

RotaLab provides a wide range of instruments and products for pouch cell research and manufacturing. Some of our products in this line are:

   · Pouch Cell Case/Cup Forming Machine
   · Die Cutter
   · Heating Sealer
   · Vacuum Sealer
   · Slitting Machine
   · Stacking Machine
   · Winding Machine
   · Electrolyte Diffusion and Degassing Chamber
   · Ultrasonic Metal Welder
   · Roll-to-Roll Battery Electrode Coating System