It doesn't seem like they've made much progress since this snopes article came out in 2017[0]. I'm also skeptical that they could use these batteries to practic

It doesn't seem like they've made much progress since this snopes article came out in 2017[0]. I'm also skeptical that they could use these batteries to practically power a cellphone. So a cellphone requires about an average power of about 200 mw assuming we deplete the battery once every 24 hours. 1 gram of Carbon-14 experiences about 156*10^9 decays per second, which release at most 156 KeV in the form of beta particles, so carbon 14 has a power density of about 4 mW/g. By itself this is decent, but conversion of these high energy electrons to electricity won't be very efficient. 9.8% efficiency has been attained for diamond films under electron irradiation[1], although because the beta particles emitted have a much larger energy than the bandgap of all the semiconductors we know, the efficiency is likely to be less. So assuming 10% conversion efficiency, we need 500 grams of just C-14. This about twice the mass of the iphone 11 pro max. It is probably not very practical to haul a large brick of radioisotopes around to power a phone. However, in theory it is possible to make a nuclear battery capable of providing this amount of power taking up only a fraction a phone's mass. [3] shows that it is theoretically possible to make nuclear batteries with power densities of 1-50 mW/g. The way they propose to accomplish this is to use the alpha particle emissions from americium to generate power. Alpha particles have on the order of MeV of energy rather than KeV beta particles typically have. Even if the conversion efficiency is low, because there's so much energy available we still attain high power densities. The issue is that because alpha particles have so much energy and are massive they do quite a bit of damage to semiconductors. This means that alphavoltaic batteries do not last very long before they degrade, and it is not expected that alphavoltaic devices can made with current semiconductors that last much longer than month. I've also heard that some alphavoltaic devices have not lasted much longer than an hour. Although, self healing liquid semiconductors appear to be a promising option with one test demonstrating minimal degradation over a 57 day period. [0]https://www.snopes.com/fact-check/radioactive-diamond-batteries-real-thing/ https://www.snopes.com/fact-check/radioactive-diamond-batter... [1]https://aip.scitation.org/doi/full/10.1063/1.4954013 https://aip.scitation.org/doi/full/10.1063/1.4954013 [2]https://www.apple.com/iphone/compare/ https://www.apple.com/iphone/compare/ [3]https://aip.scitation.org/doi/full/10.1063/1.5123163 https://aip.scitation.org/doi/full/10.1063/1.5123163 [4]https://www.nature.com/articles/s41598-018-30815-w https://www.nature.com/articles/s41598-018-30815-w