CES 2026

[Cmaier]

From a post on Reddit, here's the paper on which this may be based. The authors claim an energy density of 418 Wh/kg, a power density of 587 kW/kg, and retention of nearly 100 % of initial capacitance after 100,000 charge/discharge cycles. I'm not knowledgeable enough to say whether this is reasonable, but it may be more promising than it appeared.​

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https://www.sciencedirect.com/science/article/pii/S1359836825000691​

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However, if the Donut battery is truly based on this work, it makes me wonder how this small company collaborated with these researchers and how they were able to "extend this proof of concept to other platforms and develop supercapacitors as versatile electrical energy storage devices" so quickly, since the article was published in April 2025.​

The cycle thing doesn’t surprise me too much. Hot carrier injection doesn’t seem like it would be a thing in the structure described by the paper, so not sure what other mechanism would result in capacity loss in a capacitor.

 

[dada_dave]

From a post on Reddit, here's the paper on which this may be based. The authors claim an energy density of 418 Wh/kg, a power density of 587 kW/kg, and retention of nearly 100 % of initial capacitance after 100,000 charge/discharge cycles. I'm not knowledgeable enough to say whether this is reasonable, but it may be more promising than it appeared.​

​

https://www.sciencedirect.com/science/article/pii/S1359836825000691​

​

However, if the Donut battery is truly based on this work, it makes me wonder how this small company collaborated with these researchers and how they were able to "extend this proof of concept to other platforms and develop supercapacitors as versatile electrical energy storage devices" so quickly, since the article was published in April 2025.​

Hmmm ... indeed ... while I'm all for international cooperation, a small Nordic company partnering with South Korean researchers where no names appear to crossover to industrialize a process just published last year seems unlikely.

 

[mr_roboto]

I have no ability to evaluate the electrochemistry parts of the paper, but I kept wanting (and didn't find) some discussion of leakage, an important parameter if you hope to replace batteries with capacitors.

 

[Yoused]

These do not seem to be literal supercaps, because the article describes an electrochemical process. Supercaps, like regular caps, store charge electrostatically and do not involve ion tranfer across the boundary. This, if it is real, is probably some kind of hybrid.

 

[Yoused]

Here is a rather thorough look into the donut battery, which leaves the viewer squarely on the fence about whether to believe the hype. There is a lot of tech detail and also a look at financing. Videos are not the best way to get information, IMO, but this one does provide a lot of it.

 

[Eric]

Here’s an analysis of the battery claims:

Seems like a fair analysis given what we know and it's easy to understand the skepticism, one thing they don't clearly explain is why not a capacitor if it achieves the desired result, the biggest question is how it handles storage. In any case it appears to be the direction they're going and if this is even partially true it would be a huge leap in this technology.

Also, if you are on the verge of a groundbreaking change like this why would you divulge any of the details? Whether true or not one understand their reasoning behind it.

 

[dada_dave]

Seems like a fair analysis given what we know and it's easy to understand the skepticism, one thing they don't clearly explain is why not a capacitor if it achieves the desired result, the biggest question is how it handles storage. In any case it appears to be the direction they're going and if this is even partially true it would be a huge leap in this technology.

Also, if you are on the verge of a groundbreaking change like this why would you divulge any of the details? Whether true or not one understand their reasoning behind it.

The problem is that usually it takes years of grant funded research to achieve a breakthrough and patents are applied for etc. While there of course may be secret sauce recipes that a company will hide, it is exceedingly rare in this day an age to achieve an order of magnitude or more engineering breakthrough without any kind of paper trail providing some detail as to what the technology is behind it.

The reason why not a capacitor is that typically even supercapacitors have not had the storage density anywhere near a standard battery (also as @mr_roboto points out leakage tends to be worse in capacitors). It isn't that it is wrong to use a capacitor, but this would be a massive leap for using supercapacitors. Basically we're at the "extraordinary claims require extraordinary evidence" stage.

 

[Nycturne]

why not a capacitor if it achieves the desired result

To expand a little bit on this piece. Leakage with capacitors is a big deal. Batteries will self-discharge, but capacitors will tend to self-discharge much faster. A standard capacitor will self-discharge in a matter of minutes.

So this is a claim where they've produced a super capacitor that would need to hold onto charge on the order of months, rather than minutes, and have the energy density better than our current best batteries. Since some types of super capacitors are older than I am, it's not like this is an area that people haven't been playing with. There are other challenges, such as the voltage curve of a super capacitor self-discharging has a much wider voltage drop as it loses charge. So unlike a NiMH that goes from 1.4 to 1.2V from "full" to "empty", or an NMC cell that might go from 4.2V to 3V, these can go from say 3V to 1.5V in a matter of a couple days while still holding onto quite a bit of charge. So it's not just holding onto the charge, but keeping the working voltage high enough to do useful work.

i.e. Take how your electric scooter might feel sluggish as it gets into the lower 20% of the battery. Now imagine a super capacitor with a voltage drop large enough to have the same result at 80% charge.

 

[Yoused]

So this is a claim where they've produced a super capacitor that would need to hold onto charge on the order of months, rather than minutes, and have the energy density better than our current best batteries.

I gave a link in post #25 to a lengthy video that goes into what might be the structure, and it is not a supercap, by their guess. They did a lot of journalistic research (they are not experts but can compile what experts tell them) and have put together what could be a plausible interpretation of the design. Their final take is even money between optimism and skepticism, and may be able to tell us more when they get their motorcycle in 7 or 8 months.