A new rechargeable zinc battery retains its performance over many cycles thanks to a gel designed to prevent the reactions that typically degrade this type of cell.
Researchers are interested in zinc for electricity storage. It is abundant, relatively inexpensive and can operate with water-based electrolytes. These characteristics make it an appealing candidate for stationary batteries, where weight matters less than it does in a car or phone.
Pixabay illustration
One obstacle nevertheless remains. During charging and discharging, metallic zinc can react with water and form unwanted products. Zinc can also deposit unevenly. These phenomena gradually consume the active materials and reduce the battery's lifespan.
The researchers developed an electrolyte in the form of a hydrogel to better control this environment. A hydrogel is a network of solid molecules capable of retaining a large amount of water. Here, its chemical composition was adjusted to modify the interactions between water, zinc ions and the electrode surface.
The material combines, in particular, groups carrying positive and negative charges with fluorinated components. This architecture reorganizes the molecules around the zinc ions and limits the amount of water able to participate in side reactions. Zinc deposition also becomes more uniform over the course of the cycles.
The performance was first studied using different laboratory assemblies. The team then built cells reaching a capacity on the order of an ampere-hour. This change in scale is important because many promising materials work in very small cells but lose their advantages as the amount of material increases.
Tests show that these cells can retain a significant share of their capacity after many cycles. The researchers also report good charging and discharging efficiency. These results indicate that the electrolyte continues to limit unwanted reactions in a format closer to a usable battery.
This technology will not immediately replace lithium-ion batteries. Energy density, manufacturing cost, lifespan under real-world conditions and large-scale production will still need to be compared. For electricity grid storage, however, a heavier system may remain attractive if it is durable, safe and economical.
The next step will be to manufacture cells with an even greater capacity and test them under different temperature and power conditions. These tests will determine whether the hydrogel retains its properties over several years, a decisive criterion for the daily storage of renewable electricity.