The main advantage of lithium-ion batteries is that they can be recharged without losing their capacity over time, which means they are not subject to the “memory effect” that is common in nickel-metal hydride and nickel-cadmium batteries. These batteries are also more energy-efficient and have a longer lifespan than other types of lithium batteries. Lithium metal batteries, for example, can be recharged only a few times before they start to degrade; their high power density requires large amounts of materials and manufacturing processes that make them less environmentally friendly than other types of batteries.