The article is all hype.[1] The paper isn't much better. There's a bullshit "Significance" section at the top. Most of the "references" are to generic papers about energy. If there's a watt-hours/kilogram value, the number that matters, I can't find it. Here are Wh/Kg values for known ultracapacitors.[2] Numbers are in the 4 to 15 range. Where is this new thing?

[1] https://www.pnas.org/doi/10.1073/pnas.2304318120

[2] https://en.wikipedia.org/wiki/Supercapacitor