Alumunium Air batteries are primary cells, i.e, non-rechargeable. These batteries are mostly used by military organizations and government. These batteries are catching attention because of their high energy density at much lower weight compared to lithium-ion batteries. The electrodes used in this battery are oxygen and aluminum metal and the electrolyte is water. They all go under chemical reaction which in result produces power.
Theoretically, Al-Air battery can achieve specific energy of 8.1 kWh/kg but practically they could get is 1.3 kWh/kg
The working of an aluminum-air battery is simple just like any electrolytic battery works. The anode here is aluminum metal and the cathode is oxygen and the electrolyte is water mixed with potassium hydroxide.
The aluminum anode gets oxidized to produce aluminum hydroxide and electrons while the cathode oxygen combines with water and electrons to form hydroxide.
The anode oxidation half-reaction is Al + 3OH− → Al(OH)3 + 3e− −2.31 V.
The cathode reduction half-reaction is O2 + 2H2O + 4e− → 4OH− +0.40 V.
The balanced equation is 4Al + 3O2 + 6H2O → 4Al(OH)3 + 2.71 V.
Aluminum is found in the earth in the form of ores one of them is called Gibbsite. The product obtained from the electromechanical reaction going in the battery produces aluminum hydroxide(Gibbsite) which is an ore of aluminum. The energy of this battery is produced from refining the ores of aluminum.
Drawbacks of Aluminum Air Battery
As stated earlier this battery is a primary cell that is it can’t b charged. Aluminum Hydroxide obtained in the electrochemical reaction of the battery cant be converted back to aluminum by supplying it electricity via recharging process as we do in conventional batteries.
To refine the Gibbsite back to Aluminum it requires the whole industry level of reffing process, it can’t be done in the battery itself.
Aluminum Air battery is a use and throw type of battery when the whole anode aluminum gets converted to aluminum hydroxide it requires aluminum top-up in the battery.
When the battery is not in use, the user must drain out the electrolyte otherwise the remaining aluminum will react with oxygen and will get oxidized which will render the battery useless.
This will create a lot of e-waste if not recycled immediately. And if there is mass adoption of Al-Air batteries it will require more infrastructure to refine and recycle aluminum which will be way more costly than setting up chargers for electric cars.
To refine 1kg of aluminum it requires 15 kWh of electricity on average.
Although there is an advantage of greater energy density in Aluminum Air battery it can not be used in a consumer’s car who has to drive regularly, the battery will deplete very soon. And the recycling process of aluminum hydroxide will be very costly.
An EV running on lithium-ion batteries runs for 10-15 years easily and after this period the battery can still be used for light purpose.
The total efficiency of the aluminum-air battery from the refining process till it makes to your vehicle comes out to be near 20% which is too less.
IMO this battery can be used in trucks which have to go for a long-distance in one trip.