A lithium-ion battery is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types. Unlike lithium primary batteries (which are disposable), lithium-ion cells use an intercalated lithium compound as the electrode material instead of metallic lithium.
Energy to weight loss ratio, slow loss of charge when not in use, durability, safety and cost had made it widely used in consumer electronics. But due to high energy density it has become popular in military to be used electric vehicle and aerospace applications.
Technology
Lithium-ion polymer batteries pack in a higher power density than nickel-based batteries. This gives you a longer battery life in a lighter package, as lithium is the lightest metal. You can also recharge a lithium-ion polymer battery whenever convenient, without the full charge or discharge cycle necessary to keep nickel-based batteries at peak performance.
Charging
Most lithium-ion polymer batteries use a fast charge to charge your device to 80% battery capacity, then switch to trickle charging. That’s about two hours of charge time to power an iPod to 80% capacity, then another two hours to fully charge it, if you are not using the iPod while charging. You can charge all lithium-ion batteries a large but finite number of times, as defined by charge cycle.
A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could use your device for a few hours one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, so you may take several days to complete a cycle. Each time you complete a charge cycle, it diminishes battery capacity slightly.
Source: Wikipedia, Apple.com
