Flow batteries have the potential to help store energy on a large scale, and might be particularly useful to back up renewable energy sources, but there are a few issues still to overcome. Engineers at Stanford have developed a new type of flow battery that might be scalable, safe, efficient and inexpensive, using a metal mixture that remains liquid at room temperature.

In a flow battery, the cathode and anode are in fluid form and are kept in external tanks, to be pumped into the main cell of the battery when needed. There, the two liquids are separated by a membrane that selectively allows them to exchange electrons to either charge or discharge the energy.

These devices may be able to store huge amounts of energy in future, but the chemicals used are often toxic, expensive, and difficult to handle. The Stanford team designed the new flow battery to overcome those problems, using a unique combination of materials.