- Aluminum Air Battery Definition: An aluminum air battery is defined as a type of battery that uses aluminum as the anode and oxygen from the air as the cathode to generate electricity.
- Working Principle: The aluminum air battery working principle involves the reaction of aluminum with oxygen in the presence of an electrolyte, producing electrons that flow through an external circuit.
- High Energy Density: Aluminum air batteries have a high energy density, making them suitable for applications where weight and energy capacity are critical.
- DIY Guide: You can create a simple aluminum air battery at home using household materials like aluminum foil, salt solution, bloating paper, charcoal dust, and wires.
- Commercial Limitations: Despite their potential, aluminum air batteries are not widely used due to high production costs and corrosion issues caused by carbon dioxide.
An aluminum-air battery is a metal-air cell: aluminum metal is the anode and oxygen from air is the cathode reactant. Unlike sealed Batteries that store both reactants, this cell takes the oxidizer from the atmosphere, so most of the stored mass is the aluminum.
Aluminum air batteries therefore reach a high energy per unit mass compared with many packed cells, but they are primary batteries. You do not plug them in to recharge. You replace the spent aluminum.
In an aluminum air battery, aluminum is the anode and oxygen in air is reduced at the cathode. Specific energy (watt-hours per unit mass) can be high because the pack does not have to carry the oxidizer.
Production stays limited. Anode-grade aluminum is costly once recycling is incomplete, and alkaline cells suffer parasitic corrosion plus carbonate from air. Military, backup and a few vehicle range-extender demos are the usual homes for the technology.
That high specific energy is why developers have shown aluminum-air packs as electric-vehicle range extenders, not as everyday plug-in traction batteries.
A classroom aluminum-air cell can be made from household goods. The steps below light a small LED. They are not a copy of a commercial KOH cell.
Aluminum Air Battery Experiment
For this demonstration you need:
- Aluminum foil.
- Saturated solution of water and salt
- Blotting paper
- Fine charcoal dust.
- Two small pieces of electric wires and
- One light emitting diode.
Procedure of Making Simple Aluminum Air Battery
Spread a piece of aluminum foil on a table. In a pot, make a saturated salt-water solution. Soak a piece of blotting paper in that solution.
Lay the wet blotting paper on the foil. Sprinkle fine charcoal dust on the paper. Place a bare wire lead in the dust, then cover it with a second salt-soaked blotting sheet of the same size. Roll the stack tightly so charcoal never touches the foil and the insulated part of that lead exits one end. Fix a second bare wire to the foil. Connect a low-rated light emitting diode (LED) between the charcoal lead and the foil lead, then press the roll. The LED should glow. That is a home aluminum-air demonstration cell.
Working Principle of Aluminum Air Battery
As in the figure, an aluminum-air cell has an air cathode. A silver-based catalyst is one commercial choice. That electrode limits CO2 while admitting O2 into the electrolyte. Oxygen then reacts with H2O in a KOH solution and takes electrons to form OH– ions. Those ions oxidize the aluminum anode to Al(OH)3 and release electrons. The electrons leave the aluminum anode and travel through the external circuit to the air cathode, where the reduction reaction consumes them.
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, develops metal-air cells, including aluminum-air and zinc-air. Those cells take oxygen from the air. Reviews put the theoretical specific energy of aluminum fuel near 8 kWh per kilogram of metal. Practical cells are lower, and the figure changes if the mass is aluminum only or the whole battery.
This type of battery cannot be charged from a socket. It is a primary battery. Mechanical recharge means replacing the spent aluminum electrode and handling the hydroxide product, which returns the stack to a charged state.
High specific energy plus that swap process are why some teams have shown aluminum-air as an EV range extender, not as a drop-in petroleum tank. Aluminum smelting uses a large amount of electricity. The discharge product can be recycled back to metal.
A practical limit is the reaction of CO2 with the alkaline electrolyte, plus corrosion of the aluminum anode. Carbonate and parasitic loss both get worse in the presence of CO2 from air. A selective air electrode can prevent CO2 from reaching the electrolyte. Phinergy describes a silver-based air electrode that lets O2 in and prevents CO2 from entering.
These electrons then flow to the air anode from aluminum cathode
(Air anode & AL cathode – correct ???)
That is correct Kumar.
The electrons flow to the air anode from the aluminum cathode through the external circuit.
Also, remember that conventional current flow is in the opposite direction to electron flow. So conventional current flows to the aluminum cathode from air anode through the external circuit.
What is the financial viability of such batteries vis a vis conventional ones?
Has Elon Musk shown interest in these batteries?
They are actually quite economically feasible. Although currently, the issue is a technical one. Aluminum is usually alloyed with tin or other elements as pure aluminum will be corroded by the electrolyte. The hydrated alumina that is created by the cell reaction forms a gel-like substance at the anode subsequently reducing the electricity output. This is one issue being addressed in research into Aluminum–air cells.
Funnily enough, Elon Musk has commented on them. In 2015 when an article on the Standford scientists breakthrough went viral, he tweeted that “Battery “breakthroughs” need to state power *and* energy density (not the same thing), plus how long they last. They usually fail on energy.” (https://twitter.com/elonmusk/status/585185843649716225).
Although I’m sure he is keeping a keen eye on current research and development.