Silicon-air batteries are viewed as a promising and cost-effective alternative to current energy storage technology. However, they have thus far only achieved relatively short running times. Jülich researchers have now discovered why.In theory, silicon-air batteries have a much higher energy density and are also smaller and lighter than current lithium-ion batteries. They are also environmentally friendly and insensitive to external influences. Their most important advantage, however, is their material. Silicon is the second most abundant element in the Earth's crust after oxygen: it is cheap and its reserves are practically inexhaustible.