Atomic battery

An atomic battery, nuclear battery, radioisotope battery or radioisotope generator uses energy from the decay of a radioactive isotope to generate electricity. Like a nuclear reactor, it generates electricity from nuclear energy, but it differs by not using a chain reaction. Although commonly called batteries, atomic batteries are technically not electrochemical and cannot be charged or recharged. Although they are very costly, they have extremely long lives and high energy density, so they are typically used as power sources for equipment that must operate unattended for long periods, such as spacecraft, pacemakers, underwater systems, and automated scientific stations in remote parts of the world.^[1][2][3]

Nuclear batteries began in 1913, when Henry Moseley first demonstrated a current generated by charged-particle radiation. In the 1950s and 1960s, this field of research got much attention for applications requiring long-life power sources for spacecraft. In 1954, RCA researched a small atomic battery for small radio receivers and hearing aids.^[4] Since RCA's initial research and development in the early 1950s, many types and methods have been designed to extract electrical energy from nuclear sources. The scientific principles are well known, but modern nano-scale technology and new wide-bandgap semiconductors have allowed the making of new devices and interesting material properties not previously available.

Nuclear batteries can be classified by their means of energy conversion into two main groups: thermal converters and non-thermal converters. The thermal types convert some of the heat generated by the nuclear decay into electricity; an example is the radioisotope thermoelectric generator (RTG), often used in spacecraft. The non-thermal converters, such as betavoltaic cells, extract energy directly from the emitted radiation, before it is degraded into heat; they are easier to miniaturize and do not need a thermal gradient to operate, so they can be used in small machines.

Atomic batteries usually have an efficiency of 0.1–5%. High-efficiency betavoltaic devices can reach 6–8% efficiency.^[5]