[barbegal]

Not comparable to a real battery any time soon based on the paper https://pubs.rsc.org/en/content/articlelanding/2025/cc/d4cc0...

> The perovskite betavoltaic cell achieved impressive parameters, including a short-circuit current density of 15.01 nA cm−2, an open-circuit voltage of 2.75 mV, and an energy conversion efficiency of 1.83%, all of which represent significant improvements over previous works.

[mr_mitm]

Will it ever be comparable to a "real" battery? The energy output has a clear upper limit. Are there materials that produce only beta particles at a high enough rate per gram that could power a cell phone with a half life of more than a few days?

[barbegal]

Assuming you could get these to 10% efficiency (which is theoretically possible) and a phone needs 0.2W of energy to function then you would need a source capable of supplying 2W of energy (of which 1.8W would be dissipated as heat). The phone would be fairly hot all the time but 2W could be dissipated without it overheating in most environments. Strontium 90 generates 0.95 W/g so in theory a few grams of strontium 90 would be enough to power your phone for many decades (the half life is 28 years). But if someone were to accidentally put such a phone into an insulating material it might overheat and become a dangerous radioactive mess!

[Filligree]

If you found such a material, would you want it in your pocket? Or someone else's pocket, where it could break in an accident?