Jelly roll (battery)

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The inside of a Nickel-metal hydride battery, showing the jelly roll design

The jelly roll or Swiss roll design is the design used in the majority of cylindrical rechargeable batteries, including nickel-cadmium (NiCd), nickel-metal hydride (NiMH) and lithium-ion (Li-ion).

In this design, an insulating sheet is laid down, then a thin layer of an anode material is laid down, a separator layer is applied, and a cathode material is layered on top. This sandwich is then rolled up and inserted into a hollow cylinder casing. The battery is sealed, metal contacts are attached, and an optional button top is applied if the battery is intended to replace an AAA/AA/C/D alkaline battery. A label with the brand name is then applied, or a blank protective label, often green (NiMh) or blue (NiCd), for a generic or OEM battery.

The design gets its name because the cross section of the battery looks like a Swiss roll cake. Occasionally the design is also used for primary (non-rechargeable) batteries, although most primary batteries use the conventional rod-paste-tube design.