Because wind and solar are variable resources, energy storage has always been part of the long-term conversation about decarbonising the power network — to store electricity when the grid doesn’t need it, and output that stored power when it is needed.

When people think about energy storage, lithium-ion (Li-ion) batteries invariably come to mind. After all, this technology accounts for more than 95% of the global non-hydro energy storage currently hooked up to the grid.

But if you were to design an energy storage technology from scratch, it would not be Li-ion.