ReVolt makes zinc air batteries rechargeable

One of the more promising new battery technologies being researched are zinc-air batteries. These batteries are cheaper and have a significantly larger capacity for storing energy than existing lithium-ion batteries. The average lithium-ion battery stores only a third of the energy that zinc-air batteries are capable of storing and cost about twice as much as the zinc-air counterpart.

A Swiss company called ReVolt plans to release a zinc-air battery next year. At first, the batteries will be small units that will be used in hearing aids. Later the batteries will come in larger forms for mobile phones and much later, the zinc-air battery will find its way into electric vehicles.

The zinc-air battery was developed by a firm called SINTEF in Norway and ReVolt was formed to market the battery. In a zinc-air battery, oxygen from room air is used to generate current. The air is used as an electrode and the battery contains an electrolyte and a zinc electrode in a casing that is porous and allows air inside. The zinc-air battery is much safer than lithium-ion batteries because there are no volatile materials inside the battery that could possibly catch fire.

The zinc-air battery produces electricity when the air electrode is discharged with the help of catalysts producing hydroxyl ions in the aqueous electrode. The zinc electrode then gets oxidized and releases electrons to form an electric current. When the battery is recharged, the process happens in reverse and oxygen is released into the air electrode.

The challenge for the researchers was to devise a method where the air electrolyte wasn’t deactivated in the recharging cycle to the point where the oxidation reaction slowed or stopped. The slowing or stopping of the oxidation reaction reduced the number of times that the zinc-air battery could be recharged.

The zinc-air batteries ReVolt is working on are also being developed for future use in electric vehicles. Before that point can be reached the batteries have to reach the point of being able to withstand up to 10,000 charge cycles.

These claims would be remarkable for any battery. What makes the company even more unique is that ReVolt is developing larger-scale and more reliable batteries using zinc-air technology, which has been abandoned by most energy storage companies for being too fickle for long-term recharging.

Typically, zinc-air cells give out after a couple months, making them fit only for button-cell applications like watches and hearing aids. ReVolt is hoping to turn this around, making them work through 500 and 2,000 recharge cycles. If it can, it will scale them up for electric vehicle and grid storage capacities, and offer them at a more affordable price than competing battery makers.

By combining hypercapacitors and lithium-ion batteries, ReVolt supplies the fast-discharge “peak” power in an automotive system — that “oomph” you feel when you stomp on the gas. Then it uses zinc-air cells as the general motive force that a Tesla Motors’ Roadster could use to travel over 600 miles on one charge.

If zinc-air batteries become a reality, cell phones could go unplugged for days at a time. Laptops would become more portable that ever. Black & Decker cordless blenders could be used in true wilderness conditions without backup batteries. With three times the storage potential of lithium-ion batteries of similar size, zinc air batteries could make almost any appliance imaginable more useful and reliable. On top of that, the cells use less exotic and more stable materials, making them cheaper.

When ReVolt announced that they were developing a zinc slurry pumping device inside its batteries to prevent clogging, people took notice. The technology is still in the midst of being scaled for electric vehicles and grid applications, and refined for long-term durability. In order to make them suitable for electric cars use, the cells will have to be flattened for easy packaging and installation.

Given the progress the company has made so far, the question isn’t “if” it can make zinc-air a rechargeable energy source, it’s “when.” With an estimated two to five years left in the development phase before electric car batteries and grid storage solutions become viable, there is plenty of time for competitors to release their own batteries.