Nuclear Batteries: How Betavoltaic Cells Could Power Sensors and Pacemakers for Decades

The fundamental problem with conventional batteries is that they run out. A smartphone battery lasts one to two days. A lithium-ion cell in a cardiac pacemaker needs replacement every five to fifteen years — a surgical procedure with its own medical risks. A sensor deployed in a remote pipeline or deep inside industrial equipment eventually requires a maintenance visit, which may cost thousands of dollars and hours of downtime, or may simply be impossible.

Nuclear batteries — devices that harvest energy from radioactive decay — offer a different proposition: energy densities vastly higher than chemical batteries, and operational lifetimes measured not in months but in years, decades, or even centuries. They are not new. But a convergence of materials science advances and manufacturing improvements in 2025-2026 has brought a new generation of betavoltaic devices to practical deployment thresholds that earlier versions never reached.

## How Radioactive Decay Becomes Electricity

Radioactive isotopes decay by emitting particles or radiation. The three principal types — alpha (helium nuclei), beta (electrons), and gamma (high-energy photons) — differ dramatically in their properties and usefulness for energy harvesting.

Gamma radiation is highly penetrating and carries substantial energy, but is difficult to convert to electricity efficiently and requires significant shielding. Alpha particles carry large amounts of energy but have very short ranges (a few centimeters in air, stopped completely by a sheet of paper) and require careful handling of the source material.

Beta particles — high-speed electrons emitted when a neutron in an unstable nucleus converts to a proton — are the basis of betavoltaic cells. Like photovoltaic cells that convert photons from sunlight into electricity using a semiconductor junction, betavoltaic cells use a semiconductor junction to convert the kinetic energy of beta particles into electrical current.

The physical process is analogous to solar cells: incoming beta particles create electron-hole pairs in the semiconductor. These are swept across a p-n junction by the built-in electric field, producing a continuous current. No heat is involved. No moving parts. The output is proportional to the activity of the radioactive source and the conversion efficiency of the semiconductor.

## The Isotope Question: Tritium vs. Nickel-63

Practical betavoltaic design centers on choosing the right radioisotope. The criteria include: half-life (which determines how long the battery lasts and how its power output decays over time), beta particle energy (higher energy means more power but also more radiation management challenges), specific activity (activity per unit mass), and availability and cost.

**Tritium (hydrogen-3)** has a half-life of 12.3 years. It emits low-energy beta particles with a maximum energy of 18.6 keV — low enough to be stopped by a few millimeters of almost any solid material, which makes radiation management straightforward. Tritium is produced in nuclear reactors and is also available from industrial processes. The City University of Hong Kong and Betavolt Technology (a Beijing-based startup) have both published results using tritium in betavoltaic designs. Betavolt announced a coin-sized battery in early 2024 using nickel-63, with a tritium prototype in development.

**Nickel-63** has a half-life of 100.1 years — the longest of any commonly considered betavoltaic isotope. Its beta energy is very low (maximum 66.9 keV), making shielding trivial. The long half-life means power output declines very slowly: a nickel-63 betavoltaic cell designed today would still be producing roughly 50% of its original power in 100 years. The limitation is specific activity: nickel-63 has relatively low activity per gram, requiring thin-film deposition techniques to concentrate enough material in a small volume.

Betavolt's publicly demonstrated nickel-63 battery as of early 2024 produced approximately 100 microwatts from a coin-sized cell — enough to power some IoT sensors, but far from sufficient for high-drain applications.

## The Semiconductor Challenge

The dominant research challenge in betavoltaics is improving semiconductor efficiency. Beta particles create radiation damage in conventional silicon semiconductors over time, degrading the p-n junction and reducing conversion efficiency. Early betavoltaic cells showed significant output degradation within months.

Diamond semiconductors have emerged as the most promising solution. Diamond has exceptional radiation hardness — its crystal lattice is resistant to the displacement damage that degrades silicon. It also has wide band gap properties that match the energy spectrum of common beta emitters. The UK startup Arkenlight and several academic groups have demonstrated diamond betavoltaic cells with dramatically improved stability.

Wide-bandgap semiconductors including silicon carbide (SiC) and gallium nitride (GaN) offer intermediate options: better radiation hardness than silicon, lower cost than diamond, and established manufacturing infrastructure. Several research groups published results in 2025 demonstrating SiC betavoltaic cells with conversion efficiencies of 6-8% and projected operational lifetimes exceeding 10 years with less than 20% power degradation.

## Applications: Where Nuclear Batteries Make Sense

The power output of current betavoltaic cells — microwatts to low milliwatts — places them in a specific application window. They are not suitable for powering smartphones, laptops, or electric vehicles. They are suitable for low-power electronics that require extreme longevity or are deployed in environments where battery replacement is impractical or impossible.

**Cardiac pacemakers** are the historical application. The first cardiac pacemakers to use nuclear batteries in the 1970s used plutonium-238 (a source of heat, not beta particles, powering a thermoelectric generator). These lasted 20+ years in patients, but nuclear regulation and public concern ended their use. Modern betavoltaic cells using tritium or nickel-63 emit far less radiation than those early devices and operate at body temperature without heat generation. Several research groups have demonstrated in-vitro biocompatibility. Regulatory approval for implantable use remains the major barrier.

**Industrial IoT sensors** deployed in hard-to-access locations — inside pipelines, in structural monitoring applications in bridges or dams, in downhole oil and gas sensors — represent a large potential market. A sensor that operates for 20 years without battery replacement changes the economics of remote monitoring dramatically.

**Space applications** have long used radioisotope power sources (the Mars rovers use plutonium-238 thermoelectric generators). Betavoltaic cells offer a lower-power alternative for spacecraft systems requiring low-maintenance, long-duration power in environments where solar power is insufficient.

**Military and defense** applications — tactical sensors, remote monitoring equipment, devices that must operate unattended for years — have driven significant research funding.

## The 2026 Landscape

As of 2026, betavoltaic batteries are transitioning from laboratory curiosities to commercial products, but have not yet achieved broad deployment. Betavolt has announced commercial availability of its first-generation nickel-63 product for industrial IoT applications. Several Western startups are in late-stage development. The power output remains limited relative to chemical batteries of comparable size, and the cost per microwatt is still substantially higher than conventional alternatives.

The path to broader adoption requires: higher conversion efficiencies (the theoretical limit for betavoltaics is around 40-50%, versus current practical levels of 5-10%), lower-cost production of thin-film radioactive sources, demonstrated long-term stability in radiation-hardened semiconductors, and regulatory frameworks for commercial deployment, particularly in medical applications.

None of these is insurmountable. The physics is sound, the materials science is advancing, and the application space — devices that must operate for decades without maintenance — is real and commercially valuable. The nuclear battery is not a technology of tomorrow. It is slowly becoming a technology of today.

Nuclear Batteries: How Betavoltaic Cells Could Power Sensors and Pacemakers for Decades

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