How is a Li-polymer battery different from a Li-ion battery?
The major difference is that the lithium-salt electrolyte is not held in an organic solvent as in the Li-ion design, but in a solid polymer composite such as polyethylene oxide or polyacrylonitrile. This allows a semi rigid form factor and very thin cells. Li-polymer cells can be encased in aluminum foil laminate pouches that are just 0.1 mm thick, rather than the 0.25- to 0.4-mm thick aluminum or steel cans traditionally used with Li-ion cells. Li-polymer cells are constructed by stacking electrode and electrolyte materials in a flat sandwich, rather than winding them in a jellyroll fashion as is done with Li-ion cells.