Unlike conventional batteries, supercapacitors store electricity statically on their surface which means they can charge and deliver energy rapidly. But supercapacitors have a major shortcoming: they need large surface areas in order to hold lots of energy. To overcome the problem, the researchers developed supercapacitors built with millions of nano-wires and shells made from two-dimensional materials only a few atoms thick, which allows for super-fast charging. Their prototype is only about the size of a fingernail. “For small electronic devices, our materials are surpassing the conventional ones worldwide in terms of energy density, power density and cyclic stability,” Choudhary said. Cyclic stability refers to how many times a battery can be charged, drained and recharged before it starts to degrade. For lithium-ion batteries, this is typically fewer than 1,500 times. Supercapacitors with two-dimensional materials can be recharged a few thousand times.