By replacing the hazardous chemical electrolytes used in commercial batteries, scientists develop a recyclable 'water battery' and solved key issues with the emerging technology, which could be a safer and greener alternative.
"Water batteries" are officially known as aqueous metal ion batteries. These devices use metals such as magnesium or ton zinc, which are cheaper to assemble and less toxic than materials currently used in other types of batteries.
Batteries store energy by creating a flow of electrons that move from the positive end of the battery (the cathode) to the negative end (the anode), and expend energy when the electrons move in the opposite direction. The liquid in the battery is there to transfer electrons back and forth between the two terminals. In a water battery, the electrolyte is water with a few added salts, rather than sulfuric acid or some lithium salt.
Most importantly, the team behind this latest technology has discovered a way to prevent water batteries from short-circuiting. The short circuit can occur when tiny sharp metal growths called dendrites form on the metal anode, and penetrate the battery compartments.
To prevent this, the researchers coated the battery's zinc anode with bismuth metal, which oxidizes to form rust. This creates a protective layer that prevents the formation of dendrites.
The feature also helps prototype water batteries last longer, retaining more than 85 percent of their capacity after 500 charge cycles, the researchers' experiments showed. According to Royce Kurmelovs in The Guardian, the team has so far developed prototypes of coin-sized batteries used in watches, as well as cylindrical batteries similar to AA or AAA. The team is working to improve the energy density of their batteries to make them comparable to the compact lithium-ion batteries found inside pocket-sized devices.
Magnesium is their preferred material because it is lighter than zinc with a higher dynamic energy density. If magnesium-ion batteries can be commercialized, the technology could replace bulky lead-acid batteries within a few years.
The study was published in the journal Advanced materials.
