ReVolt and SINTEF group in Norway have developed a new rechargeable zinc-air battery that needs oxygen to generate current. Non-rechargeable zinc-air batteries have been available for sometime now, but development of rechargeable version has been difficult.

The rechargeable zinc-air battery consists of air electrode, a zinc electrode, and an electrolyte all set in a casing that lets in air. To form electric current, air electrode produces hydroxyl ions that oxidizes at the zinc electrode to release electrons. During recharging the process is reversed and oxygen is released to the air. However, after few discharge/recharge cycles air electrolyte becomes deactivated and the reduction and oxidation reactions stops. The water-based electrolyte can also dry up or get absorbed too deeply into the zinc pores.

To change this characteristics the new zinc-air batteries use gelling and binding agents to control the zinc electrode shape and control the humidity inside the battery. Also new catalysts used in the battery improves both the reduction and production of oxygen during discharge/recharge cycles.

Revolt will launch small batteries for use in hearing aids next year, as the new battery can last only about 200 cycles. But the company plans to increase the life of the batteries to about 300-500 cycles for use in cellphone and other electronic.

Revolt is also developing zinc-air batteries for use in electric vehicles. The design of these batteries is slightly different and they resemble fuel cells, with zinc slurry forming a liquid zinc electrode, which is pumped through series of tubes where it reacts with air electrode and produces electricity. Zinc oxide produced from this reaction is stored in another compartment and it flows back through the tubes when the battery is recharged. Recharging releases oxygen and the zinc oxide reverts to zinc.

As air is freely available more zinc slurry can be stored resulting in higher energy density and more electricity compared to other battery technologies. This makes the zinc-air battery technology ideal for use in vehicles. Also use of zinc slurry increases the life of the battery for up to 10,000 discharge/recharge cycles.

Compared to lithium-ion batteries, zinc-air batteries store three times more energy and cost around half. But use in consumer electronic like cellphone might be slightly difficult as the battery requires air vents. Nonetheless the battery technology is perfect for use in electric vehicles and ReVolt believes that they will start mass production of batteries for electric vehicles in few years.
[Via Physorg]