Lithium ion (Li-ion) batteries pack high energy density in a tiny package, making them the ideal choice for devices such as laptops and cell phones. Commercialized in 1991 by Sony, Lithium ion batteries provided a superior alternative to the prevalent nickel-cadmium (Ni-Cad) batteries of the day.
Lithium has long been desirable for batteries because it is the lightest of all metals, making it a tantalizing choice for a portable energy source. In fact, ever since the 1970s, lithium based batteries have been available in a non-rechargeable form. Watch batteries are one well-known example.
The relative instability of the lithium proved even more apparent during charging, leading to its slow adoption as a rechargeable battery. The end result is a compromise where the name says it all - lithium ion batteries use only the ions rather than the metal itself. The outcome is a much more stable though slightly less powerful energy source ideal for recharging. And even with the decrease in power, lithium ion based batteries still deliver more than double the voltage of nickel-cadmium.
Other than higher power and lower weight, li-ion batteries are user friendly as well. Unlike its predecessor, the nickel-cadmium, lithium-ion batteries do not suffer from the "memory effect." That is, the battery does not have to be fully discharged before being recharged. On the other hand, earlier nickel-cadmium batteries would "remember" where they were recharged, leading them to charge only to that point again. Later developed nickel-metal-hydride batteries also solved this problem.
Though the batteries do not suffer from the memory effect, it is just the opposite that users should be wary of. Lithium ion batteries shouldn't be run all the way down before charging; they respond much better with constant recharges. Battery gauges, on the other hand, are often impacted and display incorrect readings from this practice. This leads some people to believe a memory effect exists, when in fact it's the meter that needs to be reset. Draining the battery all the way down every 30 charges or so can recalibrate the gauge.
Eventually all rechargeable lithium ion batteries will meet their end. After about two to three years, li-ion batteries expire, whether or not they are being used. To prolong the battery when not in use, store it in a cool dry place at approximately 40 percent capacity. Also, avoid exposing a lithium ion battery to extreme temperatures for prolonged periods of time, and recharge constantly when in use. When it's time to eventually dispose, lithium ion batteries are much safer than many other types of rechargeable batteries, allowing them to be safely placed in the trash. As with most other things - if recycling is an option, that is the best one of all.