New formulation leads to improved liquid battery

Researchers at MIT have improved a proposed liquid battery system that could enable renewable energy sources to compete with conventional power plants.

PTI| Last Updated: Sep 23, 2014, 18:45 PM IST

Washington: Researchers at MIT have improved a proposed liquid battery system that could enable renewable energy sources to compete with conventional power plants.

The new formula by Donald Sadoway, the John F Elliott Professor of Materials Chemistry at the Massachusetts Institute of Technology (MIT), and colleagues substitutes different metals for the molten layers used in a battery previously developed by the team.

Sadoway says the new formula allows the battery to work at a temperature more than 200 degrees Celsius lower than the previous formulation.

In addition to the lower operating temperature, which should simplify the battery's design and extend its working life, the new formulation will be less expensive to make, he said.

The battery uses two layers of molten metal, separated by a layer of molten salt that acts as the battery's electrolyte (the layer that charged particles pass through as the battery is charged or discharged).

Because each of the three materials has a different density, they naturally separate into layers, like oil floating on water.

The original system, using magnesium for one of the battery's electrodes and antimony for the other, required an operating temperature of 700 degrees Celsius.

But with the new formulation, with one electrode made of lithium and the other a mixture of lead and antimony, the battery can operate at temperatures of 450 to 500 degrees Celsius.

Extensive testing has shown that even after 10 years of daily charging and discharging, the system should retain about 85 per cent of its initial efficiency - a key factor in making such a technology an attractive investment for electric utilities.

Currently, the only widely used system for utility-scale storage of electricity is pumped hydro, in which water is pumped uphill to a storage reservoir when excess power is available, and then flows back down through a turbine to generate power when it is needed.

Such systems can be used to match the intermittent production of power from irregular sources, such as wind and solar power, with variations in demand.

Because of inevitable losses from the friction in pumps and turbines, such systems return about 70 per cent of the power that is put into them.

Sadoway says his team's new liquid-battery system can already deliver the same 70 per cent efficiency, and with further refinements may be able to do better.

The study was published in the journal Nature.