It seems like I've heard this story a lot, some startup made an actually working nuclear battery that is actually doable. But even assuming that this is correct the company really did everything they claim it's certainly not going to power a phone.

The Iphone 15 can output 12.981Wh meaning that if the battery really did output 100mWh you would need 129.8 of those batteries to replace an Iphone battery.

There's plenty of room for technology to improve but it's not exactly like nuclear reactions are a new concept so I am not sure if this would be able to improve like an entirely new technology could.

Maybe someday we can have something more powerful but I wouldn't get my hopes up for 2025 like they claim.