Official: Donut Labs’ solid-state EV battery fully charges in seven minutes

Well, this is all getting excitingly real. Last month, we brought you news of Donut Labs’ production-ready solid-state battery that it claimed could be recharged from flat to full in five minutes.

Now, the Finnish tech startup says this has been independently verified by the VTT Technical Research Centre of Finland following, erm… scepticism.

In testing, a charge from zero to 80 per cent was achieved in four and a half minutes, with a full charge taking just over seven minutes. That essentially means a C-rate of 11C. What's an 11C? We'll try and keep this as simple as possible here: it's the rate at which the battery can be charged from empty to full in one hour. For example, 1C means one hour, 5C means 12 mins, etc.

For context, traditional lithium-ion batteries typically charge at 1C to 3C with active cooling. Donut says the test proves its solid-state batteries "can withstand astonishing charging rates even without active temperature control".

Indeed, the cell was tested at 1C, 5C and 11C and in two passive cooling configurations. In the first, it was enclosed by two lightly compressed aluminium cooling plates, and in the other it was attached to only one bottom cooling plate.

At a reduced C-rate of 5C, the battery cell reached an 80 per cent state of charge in nine and a half minutes, and a full charge in just over 12.

It’s worth noting, however, that this was just one individual cell, and, says Donut, does not “directly simulate cell behaviour in a battery pack”. But with less cooling required the battery pack architecture can be simpler, smaller, and lighter.

“Unlike other solid-state batteries requiring high compressive pressures and undergoing volume changes of up to 15-20 per cent during recharging cycles, the Donut Battery does not require special compression or more extensive cooling,” said Donut Lab CEO Ville Piippo.

“This greatly simplifies the structure of battery packs and enables solutions that are cost-efficient, powerful, and better than traditional lithium-ion batteries in terms of energy and power density.”

Further results from the research will be released over the coming weeks – more as we have it.