Batteries come in two types - Li-Polymer (Lithium Polymer) and Li-Ion (Lithium Ion). Li-Polymer has evolved technologically from Lithium-Ion batteries. Current lithium-polymer batteries are actually Lithium-Ion Polymer and perform similarly to Lithium-Ion batteries. The advantage however of Li-Polymer batteries is that they can be made much thinner. Li-Ion are much lighter than earlier battery types (NiCd and NiMH) and have a long life cycle. They are one of the most popular types of rechargeable battery for portable electronics, with one of the best energy densities, no memory effect, and a slow loss of charge when not in use.