Illustration: ikonaut

4 — For the Internet of Things
This battery will be useful in places where not much energy is needed, but where it has to be ready for use within a short space of time – such as for the Internet of Things. It could be used for sensors in parcels with sensitive contents that need energy to transmit information on their status. They could then be recharged with a solar cell. Or it could be employed in small electronic devices – such as the pen of a computer tablet that can be recharged quickly whenever needed. Its combination of robustness and flexibility means that this battery could also be used in portable devices such as hearing aids.

3 — One-stop layering shop
Applying these fine layers is possible using an existing industrial process that takes place in a vacuum. This means that BTRY can apply all three layers to the film as a powder, one after the other, in a single process. The film has the thickness of roughly a single human hair and is therefore flexible.

2 — Thin layers do the trick
The Empa spin-off BTRY miniaturises energy storage. They apply wafer-thin layers of crystal (yellow), ceramic (blue) and copper (orange) to a metal foil (grey). Everything is so delicate that the lithium ions can pass through even without the aid of any liquid. This solid-state battery can’t leak or catch fire, and it functions at between minus 40 and plus 150 degrees Celsius. What’s more, you can charge and discharge it in just one minute.

1 — Long distances for ions
When you recharge the battery in your smartphone, lithium ions are released from a crystal (yellow) at the positive electrode (grey) and migrate through a salt solution (an electrolyte) across a separating membrane (blue) to a graphite layer (black) at the negative electrode (orange). They remain here until they discharge. These long paths for the ions are the reason for the battery’s correspondingly long charging and discharging times.

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