Researchers at the University of Adelaide are exploring the possibilities of rechargeable aqueous zinc batteries as a replacement for the traditional lithium-ion batteries in EVs.
While lithium-ion batteries are currently the favoured option by industry, the limitations associated with supply of the resource and environmental drawbacks are driving the search for more resilient alternatives.
"An AZB will use water-based liquid, usually water with dissolved zinc salts as the electrolyte and zinc metal as the anode,” said Zaiping Guo, a professor at the university’s School of Chemical Engineering. “The liquid is water-based so it is not flammable which makes it much safer than other batteries. They are also a promising alternative because of the abundance of zinc as a resource, its low environmental impact and the battery's high volumetric capacity."
However, AZBs have limited life cycles due to their narrow working temperature range. Also, reactions between the zinc and electrolytes in AZBs are uncontrollable which can cause hydrogen gas release and corrosion within the battery.
The research team has developed what they call decoupled dual-salt electrolyte, DDSE, which uses two different zinc salts to enhance the performance of a liquid to control the behaviour of ions.
A report on the research was recently published in the journal Nature Sustainability.
"One type of salt helps the battery work well in different temperatures and improves how fast the battery can charge, while the other type helps protect the zinc metal inside the battery, so it lasts much longer," says report author Guanjie Li, also from the School of Chemical Engineering. "Together, they give the battery very good performance. It can charge quickly and work for many cycles over a wide range of temperatures and with very little energy loss when sitting unused.
"In our DDSE, the first salt-like zinc perchlorate, Zn(ClO4)2, stays mostly in the liquid and controls how the battery handles freezing and how fast ions move,” explained Li. "The second salt-like zinc sulfate, ZnSO4, sticks to the zinc metal surface and protects it from damage. Because each salt stays in its own area and does its own job, the battery works much better overall. We used lots of advanced tools to see this special distribution and to understand the deeper science behind how it works."
Senior research fellow and co-author Shilin Zhang said the cells kept 93% of their capacity even after 900 charge-discharge cycles and worked from temperatures as cold as -40°C to as warm as +40°C.
"This is the first time such a well-balanced performance has been achieved in our field," said Zhang. "Unlike conventional ‘lean-water’ designs of high-concentration or organic-aqueous hybrid electrolytes, our decoupling strategy results in a non-flammable, affordable and sustainable electrolyte formula, retaining the intrinsic merits of aqueous systems.”
Zhang said that this approach provides for the practical deployment of AZBs in smart grids and electric vehicles, which in turn, offers nations safer and more sustainable energy. "Our next step is to try this electrolyte in more practical battery systems. We want to fine-tune the recipe and also improve other battery parts, so we can build a real battery prototype that has a long-life, high-energy density, and low cost."
More information is available on the website of the University of Adelaide.
