After testing various materials, researchers at Murdoch University, in Perth, Australia, have developed a new battery with potential to offer cheap and reliable energy storage using water and sodium ions.

“To provide power at non-generation times, excess energy needs to be stored in batteries, but storage technologies now being considered, such as molten salt or molten sulfur, work at high temperatures, making them expensive and impractical,” said Senior research fellow and project leader Dr Manickam Minakshi. “Our water-based sodium-ion battery has shown excellent potential for affordable, low-temperature storage.”

The team from Murdoch’s School of Chemical and Mathematical Sciences tested various metals and phosphates to produce a cost-effective battery with high energy density made from manganese dioxide and a novel olivine sodium phosphate.

Dr Minakshi says sodium appealed as a key ingredient because, while its chemical properties are similar to lithium, it’s a good deal cheaper and far more abundantly available. The main challenge it presented, he says, was to find material for cathodes and anodes capable of accommodating sodium’s ionic size, which is  2.5 times larger than that of lithium.

“Ions travel out of the cathode and into the anode to form a current. As an imperfect analogy, you can think of them as mesh filters that ions pass through. We had to find materials with larger gaps in their mesh,” Dr Minakshi said. The team eventually found success with manganese dioxide as the cathode, and a olivine sodium phosphate as the anode.

The resulting battery, says Dr Minakshi, is a safe, cost-effective battery with high energy density, with “excellent potential for large-scale use, including storing energy from wind turbines and solar farms for later feeding into local electricity grids, as well as use in industry.”

The battery technology developed by the Murdoch University team isn’t the only water-based battery to be developed. Another water-based battery was developed by Aquion Energy, a company started out of Carnegie Mellon University. Their battery is set to made available for commercial sale in 2013.

As Technology Review has since reported this February , Aquion Energy has this year selected a site for its first (reportedly fully funded) factory – “a sprawling former Sony television factory near Pittsburgh” – and says production capacity will be “hundreds” of megawatt-hours of batteries per year. The company says it initially hopes to make batteries for under $300 per kilowatt-hour, which can be recharged 5,000 times and could last for over a decade in situations in which they’re charged once a day.

The difference between the two water-based batteries is the phosphate-based anode in the Murdoch University version. Their batter also is still in early stages of testing, but can last 12 hours under average current rates. The Murdoch University team is hoping to move toward commercialization as a low-cost source of power.

Read more about the water-based battery technology at RenewEconomy.