Batteries are becoming increasingly important for energy storage as the share of wind and solar power increases in the energy system. A critical parameter for use in, e.g., electric vehicles, is the specific energy – how much energy can be stored per kg of battery. Li-ion batteries have a relatively high specific energy but their cost is also high. For this reason researchers have for some time been looking into alternatives. Zinc-air batteries is a promising option. Zinc is inexpensive, and the theoretical specific energy of zinc-air batteries is significantly higher than that of Li-ion.
Zinc-air batteries have been used for many years as a primary (non-rechargeable) battery. However, to be used as a secondary (rechargeable) battery they need to be able to survive many cycles of charge-discharge. This is still challenging to achieve due to detrimental reactions occurring in the anode of the battery.
Now, researchers at DTU Energy have come up with a new way of studying these reactions as they occur: in situ X-ray diffraction. They built a tiny capillary zinc-air battery which could be mounted in the beamline at the synchrotron at DESY in Germany. By measuring the diffraction patterns while subjecting the battery to several charge-discharge cycles, the researchers could follow the changes in the composition of the anode as they happened. The researchers were able to show that the conversion between zinc (Zn) and zinc oxide (ZnO) does not happen uniformly within the anode and that the composition and morphology changes dramatically after just a single cycle. They also found that ZnO is migrating to other parts of the battery.
Now that the researchers have shown the great promise of their new characterization method they plan to continue their studies to identify ways of counteracting the degradation. The novelty and impact have already been recognised by Journal of Materials Chemistry A which based on input from the peer reviewers has designated the study as a top 20% Hot Article.