What appear to be lovely autumn leaves are actually the dendritic sprawl of lithium growing inside a battery. Brookhaven scientists use a technique called transmission electron microscopy to study the emergence of the atomic structures that cause batteries to age so poorly. Mapping what goes wrong on this fundamental scale helps us design new and improved nanotechnology for everything from smartphones to electric vehicles. A lithium-ion battery (sometimes Li-ion battery or LIB) is a member of a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging. A nanowire is a nanostructure, with the diameter of the order of a nanometer. It can also be defined as the ratio of the length to width being greater than 1000. Alternatively, nanowires can be defined as structures that have a thickness or diameter constrained to tens of nanometers or less and an unconstrained length. Nanotechnology (nanotech) is the manipulation of matter on an atomic, molecular, and supramolecular scale.