Metal–air electrochemical cell

The types of metal–air batteries have different capacities

A metal–air electrochemical cell is an electrochemical cell of which the anode is a made from pure metal and the cathode connects to an inexhaustible supply of air.

Types

• Iron–air electrochemical cell
• Zinc–air electrochemical cell
• Sodium–air electrochemical cell
• Magnesium–air electrochemical cell
• Titanium–air electrochemical cell
• Aluminium–air electrochemical cell
• Lithium–air electrochemical cell
• Berylium–air electrochemical cell

Properties of metal–air batteries

Of the various metal–air battery chemical couples (Table 1), the Li–air battery is the most attractive since the cell discharge reaction between Li and oxygen to yield Li₂O, according to 4Li + O₂ → 2Li₂O, has an open-circuit voltage of 2.91 V and a theoretical specific energy of 5210 Wh/kg. In practice, oxygen is not stored in the battery, and the theoretical specific energy excluding oxygen is 11140 Wh/kg (40.1 MJ/kg). Compare this to the figure of 44 MJ/kg for gasoline (see petrol energy content).

Metal–air battery	Calculated open-circuit voltage, V	Theoretical specific energy, Wh/kg (including oxygen)	Theoretical specific energy, Wh/kg (excluding oxygen)
Li–O2	2.91	5210	11140
Na–O2	1.94	1677	2260
Ca–O2	3.12	2990	4180
Mg–O2	2.93	2789	6462
Zn–O2	1.65	1090	1350

Advantages

• The possibility of having a large energy density is only design limited.^{[citation needed]}
• Some metal air electrochemical cells as lithium have a very high energy density.^{[citation needed]}