FOUR SHAPES

Same chemistry, different packaging

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Coin

Small discs for watches and for testing new materials in the lab

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Cylindrical

A wound roll in a steel can: 18650, 21700, 4680

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Pouch

Flat layers in a soft foil bag

Prismatic A rigid rectangular aluminium can

The format decides how the cell is cooled, packed and made.

WOUND OR STACKED

Roll it up or lay it flat

Cylindrical and many prismatic cells wind long electrode strips into a jelly roll. Pouch cells usually stack cut sheets or Z-fold the separator between them.

Winding is fast; stacking packs the corners better.

THE NAMES

Reading cylindrical sizes

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18650 18 mm across, 65 mm long: laptops and early electric cars

21700 21 × 70 mm: about 50% more energy per cell

4680 46 × 80 mm, often tabless: fewer, bigger cells per car

CR2032 A coin cell 20 mm across and 3.2 mm thick

Bigger cells mean fewer parts per pack, but they are harder to cool.

SPOT IT

Which cell format?

Each format leaves clues: a steel can, a soft bag, a rigid box or a tiny disc.

Coin for the lab, the other three for products.

TABS

Getting current out

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A traditional jelly roll has one or two tabs, so electrons may travel a metre along the foil. Tabless designs fold the whole foil edge into the terminal, cutting resistance and heat for faster charging.

Where the current exits matters as much as what it is stored in.

UNIT 12 STUDY COMPLETE

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Ready for the Fab Challenge?

You've seen the four main cell formats and how electrodes are wound or stacked inside them.