The Science Daily site has an intriguing article on the development of a new type of smaller, lighter nuclar battery by researchers at the University of Missouri. While a conventional battery generates energy by a chemical reaction that produces electricity, a nuclear battery derives its energy from a radioactive decay process, typically one producing relatively low-energy beta or alpha emisiions. (Radioisotopes used include tritium, strontium-90, and technetium-99.) Compared to conventional batteries, nuclear batteries have very high energy density and long life.
These characteristics have made nuclear batteries attractive as power sources for miiltary applications and for devices that mst be long-lived, like space probes. However, because even low-energy radioactive emissions are quite energetic in an absolute sense, they can damage the crystal lattice structure of the solid semiconductors used to “harvest” the energy. To provide a battery that can last as long as the radioisotope requires over-engineering it, making it relatively large and heavy. The research team’s principal innovation is the use of liquid semiconductors, which are less susceptible to damage. They claim that they can now produce a usable nuclear battery approximately the size of a penny.