Electronics

Rechargeable zinc-air batteries zero in on lithium

A researcher holds up a rechargeable zinc-air battery
A researcher holds up a rechargeable zinc-air battery
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A researcher holds up a rechargeable zinc-air battery
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A researcher holds up a rechargeable zinc-air battery

Zinc-air batteries are an enticing prospect thanks to their high energy density and the fact they're made with some of the most common materials on Earth. Unfortunately, those advantages are countered by how difficult it is to recharge these cells. Now, a team at the University of Sydney has created new catalysts out of abundant elements that could see rechargeable zinc-air batteries vying with lithium-ion batteries in mobile devices.

The chemical reaction that drives zinc-air batteries to produce electricity comes from the air around the cell. They essentially breathe in oxygen that interacts with a carbon cathode to produce hydroxyl, which in turn interacts with a zinc anode to generate an electric current. Using air as a reactant allows the battery to cram in more zinc, increasing the energy density and making the battery fairly lightweight and safe.

But the problem is that once the zinc anode has been oxidized, it isn't much use. These batteries can be mechanically "recharged" by replacing the zinc component completely, or by using electrocatalysts made from rare-earth minerals that reduce oxygen while discharging the battery, and generate it while recharging.

"Up until now, rechargeable zinc-air batteries have been made with expensive precious metal catalysts, such as platinum and iridium oxide," says Yuan Chen, lead author of the study. "In contrast, our method produces a family of new high-performance and low-cost catalysts."

To create their new electrocatalysts, the researchers made metal oxides out of common elements like iron, cobalt and nickel. Their production method ups the efficiency by very carefully controlling the composition, size and crystallinity of these metal oxides, and the end result can be used to build more easily-rechargeable zinc-air batteries.

To test their new batteries, the team charged and discharged them for 60 cycles of 120 hours, and found that the cells lost less than 10 percent of their efficacy. That means they aren't quite as effective yet as their lithium-air cousins, but they should be cheaper and easier to produce.

The research was published in the journal Advanced Materials.

Source: University of Sydney

3 comments
highlandboy
60 cycles loose 10%. By extrapolation 600 cycles loose 100% or zero charge. So in usable capasity (roughly assumed to be 75% for most applications) is less than 150 cycles. Definately will not work for mobile phones.
jerryd
Why not just reform them instead? Alum, Zinc Air are so dense you can have 100-200kwh in just 50 lbs, swapped at the corner store for either home, business, EV charging, very long range extender. It was done that way with Zinc in a fleet for 2 yrs but couldn't get anyone to build vans, etc for them. And made from offpeak, RE power
chase
They have a battery currently that works similarly.. one from the 50's maybe earlier. You can still get them. I have an older camera that uses them for the light meter. There's a little hole in the top. You pull the cover off to activate it. There was another battery activated by a drop of water. Once the water dried. You added another drop to reactivate it. Again, used in cameras from years gone by.
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