#atomic battery

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Radioactive Power: The Nuclear Battery

If you’re fed up with your phone battery not lasting through the day, there may be a solution in the future: nuclear batteries. These don’t derive their energy from chemical reactions like ordinary batteries; instead, nuclear batteries harness the energy created in radioactive decay.

Before you get freaked out about having a nuclear meltdown in your phone, nuclear batteries don’t actually contain tiny fission reactors. They don’t utilise chain reactions, and they’re actually much more akin to solar cells, but instead of generating electricity from photons, they generate electricity from high-energy electrons that are emitted when radioactive elements decay.

Betavoltaic batteries are one type of nuclear battery, harnessing energy from beta decay. They’re constructed almost exactly like a solar cell, with a piece of semiconductor like silicon sandwiched between two electrodes, so when radiation hits the silicon, a flow of electrons is produced. Since beta radiation can be stopped with just a thin film of aluminium (whereas gamma radiation needs a slab of lead or concrete), betavoltaic batteries are pretty safe.

They’re also not at all new: the first beta cell was demonstrated in 1913, and betavoltaic batteries have been used in the military, satellites, spacecraft and older models of pacemakers for years, because they have an extremely long life. The Curiosity Rover is powered by a nuclear battery containing plutonium-238, which will last it 14 years. Typically, though, they’re quite large because the semiconductor material is damaged by the high-energy particles, so batteries must be built large to last as long as the radioactive isotope. Their size has limited their use, but recently, researchers at the University of Missouri have been developing a nuclear battery the size of a penny that holds a million times more charge than regular batteries.

Led by Associate Professor Jae Wan Kwon, the researchers are using a liquid semiconductor—a water-based solution—instead of a solid one, which minimises the problem of semiconductor damage. Water absorbs the beta radiation from strontium-90 like a buffer, and the radiation also splits up the water molecules to produce free radicals and energy that increase the battery’s efficiency. A titanium dioxide electrode then collects the energy and converts it into electrons.