Ian Connellan
Zinc-air (Zn-air) batteries aren’t new – they were first commercially produced in the 1930s – and they have a lot of advantages: good performance, relatively light, safe to use and they can be made at a reasonable cost.
They’re most familiar as commonly available alkaline batteries – made in a huge variety of sizes and used to power devices as diverse as hearing aids and portable music systems.
Trouble is, until now most of them have ended life in landfill.
Now, an international research team reports that they’ve discovered how to create rechargeable zinc-based batteries. They’ve published their results in the journal Science.
Led by Wei Sun of the University of Münster, Germany, the China/Germany/US team’s new system is based on an aqueous electrolyte that solves the old-style batteries’ technical shortcomings.
“Our innovative, non-alkaline electrolyte brings a previously unknown reversible zinc peroxide (ZnO2)/O2 chemistry into the zinc-air battery,” explains Sun.
Compared with conventional alkaline electrolytes, the new non-alkaline electrolyte has some decisive advantages. Foremost among them is that the zinc anode performs more efficiently with a higher chemical stability and electrochemical reversibility – longhand for “it can be recharged”.
According to the team, the new zinc-air batteries offer long-term, stable operation: up to 320 cycles and 1600 hours under normal conditions. This standard of performance offers the potential to compete with the rechargeable lithium-ion batteries currently dominating the market.
“The zinc-air battery provides a potential alternative battery technology with advantages such as environmental friendliness, high safety and low costs,” says Sun, who emphasises that the technology “still requires further, intensive research and optimisation before its practical application”.
The most notable disadvantage of the battery is its rate of charge: a charge/discharge cycle took approximately 20 hours.
While the researchers note that this could be improved by a catalyst, it may not be a huge problem – a fast discharge rate is not necessarily required for storage for the electrical grid.
Using zinc-based batteries for some purposes may free up lithium-ion batteries for uses where performance really matters, which may be important when shifting to renewables.