A Lithium-polymer (Li-Po) is quite an old technology that you can find in your old, bar phones or laptops. These batteries have a similar structure like Li-ion batteries, but is made of a gel-like (Silicon-Graphene) material which is quite light in weight. Due to its light and flexible characteristics, these batteries are used in laptops and most of the high-capacity powerbanks. http://www.candovip.com/battery-and-energy-storage/li-ion-cylindrical-battery/