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Lithium-polysulphide makes for a cheaper flow battery

ESEARCHERS from the US Department of Energy’s (DOE) SLAC National Accelerator Laboratory and Stanford University have designed a lithium-polysulphide flow battery.

The new battery design is low-cost and has a long life, with potential applications in the renewable energy market.

Solar and wind electrical generation methods currently provide intermittent power: to regulate the natural fluctuations, a battery is needed to store the power, and discharge when the input drops.

The battery needs to be economical to make, with cheap and accessible materials, be easy to scale, and still be efficient.

Currently, flow batteries are seen as the energy storage solution of choice for intermittent energy generation systems. Flow batteries pump two different liquids through an interaction chamber where dissolved molecules undergo chemical reactions that store or give up energy. The chamber contains a membrane that only allows ions not involved in reactions to pass between the liquids while keeping the active ions physically separated.

They can be scaled up by simply specifying bigger tanks, pumps and pipes.

The new flow battery developed by the Stanford and SLAC researchers is simplified, less expensive to build, and presents a potentially viable solution for large-scale production. It also overcomes the current weakness of flow batteries: the high cost of the liquids (which tend to carry rare materials such as vanadium), and the membrane, which is very expensive and maintenance-intense.

The new Stanford/SLAC battery design uses only one stream of molecules and does not need a membrane at all. Its molecules mostly consist of the relatively inexpensive elements lithium and sulfur, which interact with a piece of lithium metal coated with a barrier that permits electrons to pass without degrading the metal.

When discharging, the molecules, called lithium polysulfides, absorb lithium ions; when charging, they lose them back into the liquid. The entire molecular stream is dissolved in an organic solvent, which doesn’t have the corrosion issues of water-based flow batteries.


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