Lithium ion rechargeable batteries
have a three-layer structure consisting of an insulative porous
separator sandwiched between sheet-like cathode and anode materials,
which, in the case of a prismatic cell, are wrapped around in
an elliptical form. These materials are impregnated in an electrolyte
and sealed in a metal case. This metal case forms the anode
pin (or cathode pin in the case of an aluminum case). The top
of the battery includes the cathode pin (or anode pin in the
case of an aluminum case) as well as a safety vent to protect
the battery by releasing gas externally if the pressure inside
the cell builds up to extreme levels.
