A rechargeable battery technology introduced in 1991 that provides greater charge per pound than nickel metal hydride. In 1993, Toshiba introduced the first notebook in the U.S. with a Li-ion battery. Since then, it has become the most popular battery technology for notebooks, cellphones and other handheld devices. In contrast to nickel-based batteries that require full discharges to keep the battery healthy, lithium ion batteries are better with frequent, shallow discharges before charging again. See lithium polymer, lithium iron phosphate and batteries.