Engineering Self-Repairing Rechargeable Batteries

Stacking faults that occur in the material Na2RuO3 during charge-discharge cycles can be repaired due to a force known as coulombic attraction.

AsianScientist (Jun. 7, 2019) – Researchers in Japan have developed a self-repairing material that could extend the lifespan of batteries. Their findings are published in the journal Nature Communications.

From smartphones to pacemakers and even cars, batteries are increasingly used to power many modern devices. Scientists are constantly finding ways to increase the longevity of batteries and how much charge they can store, what is known as battery capacity.

Although most gadgets currently run on lithium-ion batteries, technology for sodium-ion batteries is fast catching up. Both types of batteries can store and deliver a large amount of charge, thanks to the way their constituent materials pass electrons around. However, in both lithium and in sodium batteries, repeated cycles of charging and usage can significantly reduce the storage capacity over time.

In the present study, a team of scientists led by Professor Atsuo Yamada at the University of Tokyo, Japan, has invented a self-repairing material—oxygen redox-layered oxide (Na2RuO3)—that could allow rechargeable batteries to last much longer.

As batteries charge and discharge, the metallic layers inside them degrade and develop cracks or flakes—called stacking faults—which reduce the batteries’ ability to store and deliver charge. These stacking faults occur because the material is held together by a weak force called the Van der Waals force, which is easily overwhelmed by the stress put on the materials during charging and use.

In contrast, Na2RuO3 is held together by coulombic attraction, which is far stronger than the Van der Waals force, making it more resistant to degradation than conventional metallic layers. The material is also capable of self-repair, wherein stacking faults are reordered during battery charging.

“This means batteries could have far longer life spans, but also they could be pushed beyond levels that currently damage them,” said Yamada. “Increasing the energy density of batteries is of paramount importance to realize electrified transportation.”

The article can be found at: de Boisse et al. (2019) Coulombic Self-ordering Upon Charging a Large-capacity Layered Cathode Material for Rechargeable Batteries.


Source: University of Tokyo; Photo: Atsuo Yamada/University of Tokyo.
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