A lithium-ion battery or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. Compared to other types of rechargeable batteries, they generally have higher specific energy, energy density, and energy efficiency and a longer cycle life and calendar life. In the three decades after Li-ion batteries were first sold in 1991, their volumetric energy density increased threefold while their cost dropped tenfold. In late 2024, global demand passed 1 terawatt-hour per year, while production capacity was more than twice that.