Battery: A device that stores electrical energy for later use. When energy goes into storage, the battery is charging. When energy leaves the storage materials, the battery is discharging. These are known as electrochemical devices because the electric charge is stored in chemicals. When power is needed, chemical reactions inside the device produce electrons.

Engineers: People who use science to design and build structures, machines and systems. Their work helps build safe roads, bridges and buildings, and to make reliable cars, trains, airplanes, computers and software.

Hybrid: A plant or animal that has parents of different species or varieties. It may also be a machine or device that has two different functions or fuel sources. Some cars are called hybrids because they can use electricity and gasoline to power their motion.

Ion: An atom or group of atoms that has an electric charge — either positive or negative.

Lithium: A silvery white element that is the lightest metal. It’s a component of some energy-storage batteries.