Aluminium battery

Aluminium battery

Aluminium batteries or aluminum batteries are commonly known as aluminium-air batteries or Al-air batteries, since they produce electricity from the reaction of oxygen in the air with aluminium. They have one of the highest energy densities of all batteries, but they are not widely used because of previous problems with cost, shelf-life, start-up time and byproduct removal, which have restricted their use to mainly military applications. An electric vehicle with aluminium batteries could have potentially ten to fifteen times the range of lead-acid batteries with a far smaller total weight[1], at the cost of substantially increased system complexity.
Al-air are primary batteries, i.e. non-rechargeable. Once the aluminium anode is consumed by its reaction with atmospheric oxygen at a cathode immersed in a water-based electrolyte to form hydrated aluminium oxide, the battery will no longer produce electricity. However, it may be possible to mechanically recharge the battery with new aluminium anodes made from recycling the hydrated aluminium oxide. Such recycling will be essential if aluminium-air batteries are to be widely adopted.

Electrochemistry

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 total reaction is

4Al + 3O2 + 6H2O → 4Al(OH)3 + 2.71 V.

About 1.2 volts potential difference is created by these reactions, and is achievable in practice when potassium hydroxide is used as the electrolyte. Saltwater electrolyte achieves approximately 0.7 volts per cell.

Aluminum based batteries

Different types of aluminium batteries had been investigated:
Aluminium-chlorine battery was patented by United States Air Force in the 1970s and designed mostly for military applications. They use aluminium anodes and chlorine on graphite substrate cathodes. Required elevated temperatures to be operational.
Aluminium-iodine secondary cell has been investigated by some Chinese researchers.
Aluminium-sulfur batteries worked on by American researchers with great claims, although it seems that they are still far from mass production. It's unknown if they are rechargeable.
Al-Fe-O, Al-Cu-O and Al-Fe-OH batteries were proposed by some researchers for military hybrid vehicles. Corresponding practical energy densities claimed are 455, 440, and 380 Wh/kg