Aluminum Air Battery: How Do They Work? (Plus DIY)

Batteries are often heavy, which limits their use in applications where lightweight energy sources are essential.

Aluminum air batteries solve this problem by using air as the cathode, making them much lighter.

In an aluminum air battery, aluminum is used as an anode, and air (the oxygen in the air) is used as cathode. This results in the energy density – i.e. energy produced per unit weight of the battery – very high compared to other conventional batteries.

However, aluminum air batteries are not widely produced due to the high cost of the anode and corrosion from carbon dioxide in the air. Therefore, they are mainly used in military applications.

The high energy density of aluminum air batteries gives them great potential for use in electric vehicles.

Making an aluminum air battery is quite simple – and can be done using simple household goods. We’ll go over a DIY (Do It Yourself) guide to making an aluminum air battery.

Aluminum Air Battery Experiment

For creating this experimentally we require,

1. Aluminum foil.
2. Saturated solution of water and salt
3. Bloating papers
4. Fine charcoal dust.
5. Two small pieces of electric wires and
6. One light emitting diode.

Procedure of Making Simple Aluminum Air Battery

Just take a piece of aluminum foil and spread it on a table. In a pot make a saturated solution of water and salt. Take a piece of bloating paper. Get the piece of bloating paper soaked by saturated salt solution.
Then get the soaked piece of bloating paper spread over the aluminum foil. Now put some fine dust of charcoal over the bloating paper. After keeping a non-insulated wire lead in the charcoal dust, cover it with another piece of salt solution soaked bloating paper of same size. Now tightly roll the total thing in such a way that, no charcoal dust can touch directly the aluminum foil and insulated portion of the lead wire comes out from one end of the roll. Now take another wire and fix the non insulated portion of the wire to the aluminum foil. Now if we connect a low rated light emitting diode (LED) with these two leads (one from charcoal and other from aluminum foil) and press the roll with our fingers, the LED will glow. This is how an aluminum air battery can be created in our home.

Working Principle of Aluminum Air Battery

As in the figure right, an aluminum air battery has air cathode which may be made of silver based catalyst and it helps to block CO₂ to enter in the battery but it allows O₂ to enter in the electrolyte. Then this oxygen reacts with H₂O in KOH electrolyte solution takes electrons from solution and creates OH^– ions. These ions then associate with Al anode and create Al(OH)₃ and release electrons. These electrons then flow to the air anode from aluminum cathode through the external circuit for compensating lack of electrons in the electrolyte solution due to cathode reduction reaction.

Chemical Reaction of Aluminum Air Battery

Four aluminum atoms react with 3 oxygen molecules and 6 water molecules and produce 4 aluminium hydroxides

Aluminum Air Battery Equation

The anode oxidation (half-reaction),

The cathode reduction (half-reaction),

Total reaction,

Phinergy, an Israeli company, specializes in metal air batteries like aluminum and zinc air batteries. These batteries take oxygen from the air. Aluminum air batteries have a high energy density of 300 Wh per pound of aluminum and a power density of 30 Watts per pound.

This type of battery cannot be electrically recharged. Basically this is a primary battery. But the difficulty of recharging can be overcame by mechanical recharging process. Mechanical recharging of aluminum air cell is done by replacing aluminum electrode. In this process, the battery can be turned to its fully charged condition from discharged battery cell stack.
Because of its high energy and power densities, facilities of mechanical recharging, aluminum air battery is may be the most suitable alternative of petroleum fuel for automobile in near future. These battery also have very low environmental impact.

The main disadvantage of this technology is, the reaction of CO₂ with aluminum. Aluminum gets very easily affected by corrosion due to the presence of CO₂ in the air. This problem can be overcame by introducing special air electrode which can prevent CO₂ to reach to the aluminum sheet. Phynergy has developed an air electrode with silver based catalyst and this structure lets O₂ enter into aluminum sheet and prevents CO₂ to enter.