Battery technology is the key to many new developments: from cell phones to electric vehicles, and therefore it is very likely that there will be spillovers into power banks. Both technologies currently in use have slightly different properties. different:
Lithium-ion: Lithium-ion batteries have a higher energy density, meaning they can store more electrical charge in a given size or volume, and are cheaper to manufacture, but they can have aging problems.
Lithium-polymer: Lithium-polymer power banks do not suffer from the same aging and are therefore a better choice.
However, they are more expensive to manufacture and therefore may not suit all budgets. Sometimes it may be better to spend less, especially if they might be accidentally lost or left in certain places.