Australasian Science: Australia's authority on science since 1938

Batteries that Store Protons

By Stephen Luntz

A step has been taken towards high efficiency batteries with the creation of a system that holds protons within a metal lattice.

One of the most popular suggestions for storing energy has been to split water into hydrogen and oxygen. When power is needed, the hydrogen can be burned. In theory the system is a closed loop, but applications have been bedeviled with problems since hydrogen is very hard to store.

Now the RMIT School of Aerospace, Mechanical and Manufacturing Engineering has announced an alternative path in the International Journal of Hydrogen Energy. Splitting water produces protons, which then usually combine with electrons to form hydrogen, but A/Prof John Andrews says his team skipped that stage to bind the protons into a metal hydride.

“We’re not producing gas in the charging phase, and don’t have to convert back into protons to release the energy,” Andrews says. “Consequently we should be able to get about the same efficiencies as lithium ion batteries.”

While Andrews describes the work so far as an “exciting indicator of the promise of the concept,” he admits that the team is “nowhere near the efficiencies” needed for commercialisation. He thinks that activated carbon, being cheaper and lighter, may eventually replace the nickel/lanthanum hydride tested as a storage mechanism.

Even at this early stage, however, “the storage is superior for energy per unit mass and volume” than widely used battery technologies. As Andrews notes, “hydrogen is lighter than anything else. The weight is in the storage material.”

Previous attempts at what the team calls a “proton flow battery” have used liquid electrolytes rather than the solid state proton exchange membrane created by the RMIT team. “The area requiring the most work is getting the protons in,” Andrews says. “We can store more than we can get out at the moment, so we are looking at finding nanostructures for metals that give a reversible reaction.”