Beta batteries (also known as betavoltaic cells) use energy from a radioactive source that emits electrons (also known as beta particles). The radioactive hydrogen isotope tritium is often used as the beta source. Most nuclear power sources use radioactivity to generate heat which is then used to generate electricity. This can be either thermoelectric which utilizes a thermocouple to generate electricity from a temperature differential or thermoionic in which heat induces a flow of charge carriers from a surface. Beta batteries do not use heat to generate electricity. Instead, when electrons from radioactive decay move through a semiconductor material, they leave ionizations trail which produces electron-hole pairs which produce usable energy.
The first beta batteries were created over sixty years ago. Because early semiconductor materials were not very efficient for use in beta batteries, high energy, expensive and dangerous radioactive isotopes were used which limited their commercial potential. During the 1970s, some cardiac pace makers employed promethium in a beta battery called the Betacel which was the first commercial beta battery. These batteries were later replaced by cheaper lithium batteries. Eventually better semiconductors were developed and relatively low energy, cheap and safer tritium came into use for beta batteries.
Beta radiation can be easily blocked by a few millimeters of shielding. This means that a properly constructed beta battery will not emit dangerous radiation. Beta cells depend on radioactive materials which produce less and less energy as they age. This means that a beta battery has to be designed to produce a minimum of useful power over its lifespan as power generation falls.
The main use for beta batteries is in remote locations and long-term use. They are popular power sources for space probes that cannot be serviced and usually need to have a more than a decade of reliable power. Recently it has been proposed that beta batteries could be used to trickle-charge conventional batteries in consumer devices such as cell phones and laptop computers.
In 2016, it was proposed that carbon-14 be extracted from nuclear waste and encapsulated in diamond for use in a beta battery. In 2018, a Russian team created a design for a beta battery that would utilize nickel-64 enclosed between ten micro layers of diamond. The prototype has a a power output of about one microwatt with a power density of ten microwatts per cubit centimeter. The half life of the nickel-63 is about a hundred years.
A team of Russian researchers from the National University of Science and Technology, the Institute of Microelectronics Technology and High Purity Materials of the Russian Academy of Sciences, and the Kurchatov Institute National Research Center have announced a breakthrough in anticipating the properties of different designs for beta batteries.
Up until now, the development of beta batteries has had to proceeded by trial and error. The Russian researchers have developed a computer program that can optimized the structure and behavior of proposed beta batteries. This will make it much simpler and cheaper to improve the design of new beta batteries