Scientists at Germany's Friedrich Schiller University in Jena have now demonstrated how a finely tuned carbon membrane can prevent these types of batteries from failure, and enable them to be safely charged over hundreds of cycles.The major problem holding back the development of lithium metal batteries, which could store as much as 10 times the energy of today's lithium-ion batteries, is the formation of needle-like structures called dendrites. During charging, as the lithium ions move between the battery's two electrodes, lithium atoms build up on the negative electrode, known as the anode. This accumulation leads to spiky dendrites that can pierce the separator between the electrodes and cause the battery to short circuit and fail.