Donut Lab’s solid-state battery can barely hold a charge after being damaged

If you remember, during extreme heat testing, the bag surrounding the donut battery lost its vacuum seal. This led researchers at the state-owned VTT Technical Research Center in Finland, which had conducted all previous laboratory tests, to explore whether the cell could still operate under conditions of high pressure and high temperatures. As Donat notes, damage, such as what his pack suffered during heat testing, is known to cause fire or thermal runaway in conventional lithium-ion batteries. The startup wanted to see if its solid-state battery could avoid a similar disaster.

The researchers conducted three tests: a basic five-cycle test at one temperature (26 A); High pressure test for 50 cycles at 5°C (130A); And another final baseline test of 5 cycles at 1°C to measure degradation. After tests, the team observed a sharp drop in power capacity, from 24.7 amp-hours to 11.2 amp-hours, or a loss of approximately 55 percent. They also recorded a decrease in efficiency from 89.6 percent to 83 percent, and observed a 17 percent increase in package thickness.

Given the damage to the packaging, the results should not be surprising. The loss of the vacuum seal certainly accelerated the battery’s deterioration and contributed to its thick, swollen state after testing. However, Donut Lab said this is further proof that its battery can avoid some of the worst outcomes caused by lithium-ion battery damage.

“There are no temperature increases, and there is no risk of fire,” the company said on its website. IDonutBelieve.com. “In this scenario, the donut battery fails well when damaged, and continues to operate safely at low capacity rather than posing a risk to the user.”

But the tests also represent the closest the Donut Lab battery has come to cycle testing, and they were under these damaged conditions. The startup has yet to prove how its package holds up under an aging-accelerating procedure that repeatedly charges and discharges cells to evaluate their long-term performance and safety. Donut has previously claimed that its solid-state battery can last 100,000 cycles, which represents about 270 years of charging and discharging. This would be in numbers greater than the 1,000 to 2,000 full charge and discharge cycles that the average electric vehicle battery can handle before its capacity begins to degrade.

Importantly, Donut has not yet requested independent verification of the energy density it claims is 400 watt-hours per kilogram. This seems like a simple enough test — all you have to do is weigh the cell and measure its output — and it’s not clear why Donut Lab hasn’t asked for this yet.

We’ll have more to say about Donut Lab’s tests and what independent experts are saying about the startup in the coming weeks.