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Diamond battery is the name of anuclear battery concept proposed by theUniversity of Bristol Cabot Institute during its annual lecture[1] held on 25 November 2016 at theWills Memorial Building. This battery is proposed to run on theradioactivity of wastegraphite blocks (previously used asneutron moderator material ingraphite-moderated reactors) and would generate small amounts of electricity for thousands of years.
The battery is abetavoltaic cell usingcarbon-14 (14C) in the form ofdiamond-like carbon (DLC) as the beta radiation source, and additional normal-carbon DLC to make the necessarysemiconductor junction and encapsulate the carbon-14.[2]
Early prototypes usenickel-63 (63Ni) as their source with diamond non-electrolytes/semiconductors for energy conversion, which are seen as a stepping stone to a14C diamond battery prototype.
In 2016, researchers from the University of Bristol claimed to have constructed one of those63Ni prototypes.[3][4]
From their Frequently Asked Questions (FAQ document[5]), the estimated power of a small C-14 cell is 15 J/day for thousands of years. (For reference, a AA battery of the same size has about 10 kJ total, which is equivalent to 15 J/day for just 2 years.) They note it is not possible to directly replace an AA battery with this technology, because an AA battery can produce bursts of much higher power as well. Instead, the diamond battery is aimed at applications where a low discharge rate over a long period of time is required, such as space exploration, medical devices, seabed communications, microelectronics, etc.
In 2018, researchers from theMoscow Institute of Physics and Technology (MIPT), the Technological Institute for Superhard and Novel Carbon Materials (TISNCM), and the National University of Science and Technology (MISIS) announced a prototype using 2-micron thick layers of63Ni foil sandwiched between 200 10-micron diamond converters. It produced a power output of about 1 μW at apower density of 10 μW/cm3. At those values, its energy density would be approximately 3.3 Wh/g over its 100-yearhalf-life, about 10 times that of conventionalelectrochemical batteries.[6] This research was published in April 2018 in theDiamond and Related Materials journal.[7]
In December 2024, the University of Bristol announced that they had successfully created a battery using14C. The battery functions in a way similar to a photocell, but capturing electrons instead of light within the diamond.[8]
Researchers are trying to improve the efficiency and are focusing on use of radioactive14C, which is a minor contributor to the radioactivity ofnuclear waste.[3]
14C undergoesbeta decay, in which it emits a low-energybeta particle to becomeNitrogen-14, which isstable (not radioactive).[9]
These beta particles, having an average energy of 50 keV, undergoinelastic collisions with other carbon atoms, thus creating electron-hole pairs which then contribute to anelectric current. This can be restated in terms ofband theory by saying that due to the high energy of the beta particles, electrons in the carbonvalence bandjump to itsconduction band, leaving behindholes in the valence band where electrons were earlier present.[10][4]
Ingraphite-moderated reactors, fissileuranium rods are placed insidegraphite blocks. These blocks act as aneutron moderator whose purpose is to slow down fast-moving neutrons so thatnuclear chain reactions can occur withthermal neutrons.[11] During their use, some of the non-radioactivecarbon-12 andcarbon-13isotopes in graphite get converted into radioactive14C bycapturing neutrons.[12] When the graphite blocks are removed during station decommissioning, theirinduced radioactivity qualifies them aslow-level waste requiringsafe disposal.
Researchers at the University of Bristol demonstrated that a large amount of the radioactive14C was concentrated on the inner walls of the graphite blocks. Due to this, they propose that much of it can be effectively removed from the blocks. This can be done by heating them to thesublimation point of 3,915 K (3,642 °C; 6,587 °F) which will release the carbon in gaseous form. After this, blocks will be less radioactive and possibly easier to dispose of with most of the radioactive14C having been extracted.[13]
Those researchers propose that this14C gas could be collected and used to produceman-made diamonds by a process known aschemical vapor deposition using low pressure and elevated temperature, noting that this diamond would be a thin sheet and not of the stereotypicaldiamond cut. The resulting diamond made of radioactive14C would still produce beta radiation which researchers claim would allow it to be used as a betavoltaic source. Researchers also claim this diamond would be sandwiched between non-radioactive man-made diamonds made from12C which would block radiation from the source and would also be used for energy conversion as adiamond semiconductor instead of conventionalsilicon semiconductors.[13]
Due to its very lowpower density, conversion efficiency and high cost, a14C betavoltaic device is very similar to other existingbetavoltaic devices which are suited to niche applications needing very little power (microwatts) for several years in situations where conventional batteries cannot be replaced or recharged using conventionalenergy harvesting techniques.[14][15][16] Due to its longerhalf-life,14C betavoltaics may have an advantage in service life when compared to other betavoltaics usingtritium ornickel. However, this will likely come at the cost of further reduced power density.
In September 2020, Morgan Boardman, an Industrial Fellow and Strategic Advisory Consultant with the Aspire Diamond Group at the South West Nuclear Hub of the University of Bristol, was appointed CEO of a new company calledArkenlight, which was created explicitly to commercialize their diamond battery technology and possibly other nuclear radiation devices under research or development at Bristol University.[17] In September 2024,Arkenlight announced that they had created a14C diamond.[18]