Jan 5 2021
New chemistry has created a high-performance and economical zinc-air battery, thus providing an attractive energy-storage solution.
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A research team led by Dr. Wei Sun of MEET Battery Research Center at the University of Muenster has developed a new high-performance, eco-friendly, safe and cost-effective zinc-air battery (ZAB) that could provide the ideal solution to energy storage demands.
The battery builds on novel new chemistry, which should eliminate some of the problems that have historically hindered such technology. The team has devised a non-alkaline, aqueous electrolyte that should make zinc-air batteries more chemically stable by preventing electrochemical irreversibility caused by the use of alkaline electrolytes.
The research team — including scientists from Fudan University, Shanghai, the University of Science and Technology, Wuhan, the University of Maryland, and the US Army Research Laboratory — detail their findings in a paper published in the journal Science¹.
“Our innovative, non-alkaline electrolyte brings a previously unknown reversible zinc peroxide (ZnO2)/O2 chemistry into the zinc-air battery."
Dr. Wei Sun, MEET Battery Research Center, University of Muenster
Metal-Air Batteries: Not Quite Perfect Energy Storage
ZABs are an off-shoot of a wider family of batteries that combine metal and air in which the positive electrode (cathode) is carbon-based with a precious metal covering, whilst the other electrode (anode) is made of another metal. Most commonly, zinc, aluminum, magnesium, or lithium.
Air is allowed to flow freely through the battery, which results in the oxygen it carries, reacting with the metal, forming an oxide, activating the electrolysis process and thus, creating a current.
The fact that the oxygen is brought in from outside the battery means that there is more room within the cell to fill with an electrolyte material. This gives these types of batteries, high capacities and impressive energy densities. For example, a 50 kg lithium-air battery can power a vehicle for about 500 km on a single charge².
ZABs have been a focus of research for a surprisingly long-length of time — stretching right back to the 19th century. During their development, non-chargeable ZABs have found applications in a number of devices including hearing aids and wireless communication devices.
Yet, the true potential of these devices has been hampered by a number of technological hindrances. In particular, the corrosion of anodes in ZABs and the tendency of dendrites to form on the zinc anode has made reversible ZABs unviable. So, improving the chemical stability of ZABs could remove this roadblock and point the way to a chargeable version of these devices.
That’s where Wei Sun’s team comes in.
Stabilizing Zinc-Air Batteries
The team created their non-alkaline aqueous electrolyte based on the zinc trifluoromethanesulfonate salt, discovering that it possessed several advantages over traditional strong alkaline electrolytes.
In particular, the team’s new electrolyte is hydrophobic, meaning that it keeps water created during oxidation away from the surface of the cathode. This means improved chemical stability, and crucially, reversibility. Thus resulting in a ZAB that can be recharged.
The team found that the full zinc-air batteries could operate stably for 320 cycles and 1,600 hours under ambient air atmosphere. The researchers arrived at their conclusion by performing several specially designed electrochemical, analytical techniques and multiscale simulations.
In addition to providing stability and reversibility, the team’s new electrolyte means that their ZAB also has increased energy density. In fact, they believe that this element has been improved so-significantly that ZABs could even one-day compete with the current rechargeable-battery-market leader — lithium-ion batteries.
“The zinc-air battery provides a potential alternative battery technology with advantages such as environmental friendliness, high safety, and low costs. This technology still requires further, intensive research and optimization before its practical application.”
Dr. Wei Sun, MEET Battery Research Center, University of Muenster
References
¹ Sun W, Wang F, Zhang B, Zhang M, Küpers V, Ji X, Theile C, Bieker P, Xu K, Wang C, Winter M, [2021], ‘A rechargeable zinc-air battery based on zinc peroxide chemistry’, Science, DOI: 10.1126/science.abb9554
² Torabi. F., Ahmadi. P., [2019], ‘Simulation of Battery Systems,’ Fundamentals and Applications, [https://www.sciencedirect.com/book/9780128162125/simulation-of-battery-systems]