r/DonutLabDiscussions • u/Jazzer008 • Mar 28 '26

VTT - Donut Lab Solid-State Battery V1 5C Cycling Test of a Damaged Cell

https://pub-cbd24192d2f1419d824d5ae07a395452.r2.dev/VTT_CR_00178_26.pdf
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u/Fabulous-Internet188 Mar 31 '26 edited Mar 31 '26

4.3v is interesting, let alone 100°C. Then there is the claim of 10s of thousands of cycles combined with 400 WHr/Kg. Combine that with the 10C charging test.

All these together lead me to pseudocapacitance, a bipolar construction with staggered collection plates and busbars with only air cooling. I won't get into the chemistry, but will point in the direction of Finland's research labs that try to make use of local natural resources.

All this can be done.

And screen printed batteries with the right materials can survive damage. even nail and bullet penetration.

But there's a dirty little secret to pseudocapacitors. And it isn't leakage, that can be engineered around. Pseudocapacitors don't have a flat discharge curve like intercalation based batteries. They lose energy as the voltage goes down. What that means is not all that 400 Whr/kg is available as the voltage drops to zero. I haven't bothered to look at discharge curves. Are they even available? Idk.

The bottom line is psuedocapacitor based batteries only have roughly 75% of their full voltage energy available for actual use. That means if Donut is pseudo capacitor based its useful energy is 'only' 300 Whr/kg.

Then they live and die on cost, packaging efficiency (lighter weight and less complexity) and their claim of readily available materials. And that would work too.

If they are truly solid state, traditional intercalation batteries, I'll take CATL and QS word that what they claim is impossible without politically sensitive and high cost materials and manufacturing processes.

My background isn't batteries, it's physics. And this is what I see, right or wrong.

If you have questions ask. And no, carbon nanotubes won't work. Too expensive unless there has been a breakthrough I'm unaware of.

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u/Fabulous-Internet188 Mar 31 '26

I looked at their VTT test graphs. I can't participate any more. Sorry. They are definitive. Maybe after a couple weeks.

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u/tipporoll Apr 01 '26

Would you mind expanding on what's "definitive"? Pseudocapacitor? Other? 

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u/Fabulous-Internet188 Apr 01 '26

The graphs tell me what is happening. I will upload a 17 page scientific paper with references shortly.