The most common traditional dry cell is the standard zinc-carbon battery. Many scientists also call this the Leclanche cell after its original inventor. The outer casing of the battery is made of solid zinc metal.
This zinc shell acts as the anode, which is the negative terminal of the battery. A carbon graphite rod sits directly in the center to act as the positive cathode. A thick chemical paste fills all the empty space between the central rod and the zinc shell.
This active paste typically contains a mix of manganese dioxide, ammonium chloride, and zinc chloride. The damp paste lets charged ions move back and forth to maintain an electric current. As you use the battery to power a device, the chemical reactions slowly eat away the zinc casing.
A common student mistake is thinking the battery is completely bone dry inside. It actually must contain enough moisture for the chemical ions to move around. However, the chemical reactions in a standard zinc-carbon dry cell only flow in one direction. Once the internal chemicals completely run out, you cannot safely reverse the process to recharge the battery.