I’m not sure how real is this. Some online seller in China is offering a this batteries for $2720. It is said to last 20 years with the need of recharging and they are made from nano-tritium.
“Researchers say that the amount of tritium extracted from 1L of sea water can release the energy equivalent of 300L of gasoline in one complete nuclear fusion.”
The battery is in thumb-sized which is designed for smaller devices such as pacemakers, sensors, and implants. As in today, the nano-tritium based batteries can be found in signs, watches, and some types of glow sticks.