This would effectively bring high-capacity batteries compliant with the new EU regulations, which require coin cell type batteries in devices like the earphones and watches to be rechargeable and replaceable.
It remains to be seen if the future AirPods or Apple Watch editions will take advantage of the new solid-state battery cells, but TDK explains how it was able to achieve the breakthrough.
As many solid-state battery makers, TDK leveraged an oxide-based solid electrolyte and added lithium alloy anodes. The solid oxide electrolyte is not flammable like its liquid electrolyte counterpart in current Li-ion batteries, so it makes the CeraCharge battery “extremely safe,” but that could be said for basically all batteries done with a solid electrolyte.
Still, battery safety is even more important for wearables that people have on them at all times. TDK now plans to bring the cells to mass production, and will try to increase the capacity of its new solid-state battery further, so that it can provide longer battery life to the earbuds and smartwatches which will carry it.