The current collector in a battery or capacitor is a conductive component that collects electrons from the external circuit and distributes them to the active materials in the electrodes. It's usually made of a metal, such as copper or aluminum, and is designed to maximize conductivity while minimizing resistance and weight. The current collector plays a crucial role in the overall efficiency and performance of the device. For example, in lithium-ion batteries, the current collector facilitates the flow of electrons during charging and discharging, directly impacting the battery's power output and lifespan.