Beta-voltaic and other nuclear batteries have been around for a long time. The issue, at least so far, isn’t technology, it’s mostly just cost and safety. These things cost hundreds and into the thousands per battery last time I checked. And for that they put out less power than a coin cell.
Outside of pacemakers and space probes where a battery change is difficult to impossible, there aren’t a lot of use cases where the cost is justified.
There actually are other isotopes such as Hafnium 178m2 which have the potential to make much more energy and power dense nuclear batteries, but due to safety concerns haven’t been developed yet.
> 178m2Hf has the highest excitation energy of any comparably long-lived isomer. One gram of pure 178m2Hf contains approximately 1330 megajoules of energy, the equivalent in about 300 kilograms (660 pounds) of the explosive TNT. The half-life of 178m2Hf is 31 years
Outside of pacemakers and space probes where a battery change is difficult to impossible, there aren’t a lot of use cases where the cost is justified.
There actually are other isotopes such as Hafnium 178m2 which have the potential to make much more energy and power dense nuclear batteries, but due to safety concerns haven’t been developed yet.
Checkout: https://en.m.wikipedia.org/wiki/Hafnium_controversy
> 178m2Hf has the highest excitation energy of any comparably long-lived isomer. One gram of pure 178m2Hf contains approximately 1330 megajoules of energy, the equivalent in about 300 kilograms (660 pounds) of the explosive TNT. The half-life of 178m2Hf is 31 years