A Rechargeable Zinc-Air Battery Could Transform Energy Use

Deriving much of their power from air, zinc-air batteries have been a promising source of energy due to their large energy densities, relatively inexpensive production costs, and long shelf lives. The problem is that they are often only single-use under specific ambient conditions and with short active lives. However, a new development in producing a rechargeable zinc-air battery could lead to its use in a wider variety of devices.

Like most batteries, zinc-air cells produce electrical power from chemical reactions. They receive one of the reactants—oxygen—from the air, which then reacts with the cathode inside the cell. Water in the cathode reacts with oxygen, forming hydroxide that migrates to the anode. The hydroxide and the zinc from the anode react, producing water and zinc oxide. In this reaction, electrons are released and travel through a circuit to power the connected device. However, since zinc-air batteries rely on the outside environment for one of their reactants, excessive exposure to air or humidity can cause the zinc gel to dry up or flood the cell with water vapor. This reaction is also irreversible because the caustic electrolyte—the liquid that surrounds the cathode and anode—can break down the electrodes.

A new design could solve this issue, leading to longer-lasting zinc-air batteries. Researchers led by Dr. Wei Sun, a materials scientist at the University of Muenster in Germany, created a prototype of a zinc-air battery that could be recharged hundreds of times. They developed a battery using a new electrolyte made from zinc trifluoromethanesulfonate salt instead of the strong alkaline electrolytes traditionally used. The new electrolyte is hydrophobic, keeping water molecules away from the surface of the cathode. This new design improves the reversibility of the reaction, allowing the battery to be recharged. After testing the battery, the team found that their batteries operated for 320 cycles in 1600 hours and had greater chemical stability and energy density than single-use zinc-air batteries.

A rechargeable zinc-air battery would be especially useful in powering electric cars, which have become increasingly popular due to lower emissions compared to those of traditional gasoline-powered cars. Electric cars currently use lithium ion batteries, which are susceptible to explosions, and more expensive to produce than zinc-air batteries. As development continues, zinc-air batteries will become cheaper, lighter, and safer. Their recharging capabilities make them a strong competitor against lithium ion batteries. By using zinc-air batteries, electric cars can become more affordable and environmentally friendly than before. While electric vehicles are only one step closer toward cleaner energy consumption, zinc-air batteries could one day be used for long-term renewable energy storage—an important stride toward mitigating fossil fuel emissions.