Aerobic batteries are a type of battery that uses oxygen from the surrounding air as a reactant (typically at the cathode) to generate electricity. They are often referred to as metal-air batteries and include types like zinc-air, aluminum-air, and lithium-air batteries. They are known for their high energy density but require access to air to function. Anaerobic batteries are batteries that do not require oxygen from the surrounding air to operate. All the necessary reactants for the electrochemical reaction are contained within a sealed system. Most common battery types, such as lithium-ion, lead-acid, nickel-cadmium, and nickel-metal hydride batteries, are anaerobic. They can operate independently of the external environment.