There is news speculating about it

 

 

Another ---> https://learn.sparkfun.com/tutorials/nuclear-battery-assembly-guide/all

Unfortunately they only generate microWatts, and would need to be in a backpack to power your cellphone.
Much ado about nothing ...
 

Not even 'good enough for Australia'.
( entertaining blog if you're into electronics )

4 hours ago, Externet said:

There is news speculating about it

!

Moderator Note

In Science News we expect links to actual news

 

If has to be a 'clickable link'  it is :

https://www.world-nuclear-news.org/Articles/Nuclear-battery-Chinese-firm-aiming-for-mass-mark

https://en.wikipedia.org/wiki/Atomic_battery

Atomic batteries (waste from nuclear power plants) are used in space travel. Very low capacity, but long life.

"Atomic batteries usually have an efficiency of 0.1–5%. High-efficiency betavoltaic devices can reach 6–8% efficiency.[5]"

Putting it in your pocket ("the size of a smartphone"), suggesting using it for everyday use is just silly..