① What’s the Story
This past August, news broke that the BOHR satellite, carrying U.S.-based City Labs’ tritium-based radioisotope battery (the so-called “nuclear battery”), launched aboard SpaceX’s Transporter-17 mission, becoming the first case to actually pass through the commercial nuclear-satellite review pathway that the U.S. Federal Aviation Administration (FAA) had set up in 2019. Until now, small-satellite power has run on only two pillars — solar panels and chemical batteries — and this reads as a signal that a third option, the “nuclear battery,” has begun actually reaching commercial orbit.
The industry has long regarded radioisotope batteries as an expensive technology confined to deep-space probes or special military missions. In recent years, however, cracks have appeared in this picture. China’s Betavolt drew widespread public attention in 2024 by unveiling its coin-sized, nickel-63-based nuclear battery, the ‘BV100,’ and the United States is pushing the development of nuclear power sources for orbit and the lunar surface to the level of national policy, through an executive order issued in late 2025 and the announcement of the ‘National Space Nuclear Initiative (NSTM-3)’ in April 2026. City Labs’ commercial satellite case can be seen, within this trend, as an event in which a U.S. private company was the first to step into the practical-application stage.
This article looks at how nuclear batteries actually work, and at how U.S. and Chinese companies are each building up IP around this technology right now.
② Basic Principle
The easiest way to understand a radioisotope battery is to compare it to a solar cell. In a solar cell, photons in sunlight strike a semiconductor p-n junction, generating electron-hole pairs, and the flow of these electrons is drawn out as current. The principle behind a betavoltaic nuclear battery is nearly identical. The only difference is that the energy source is not “sunlight” but the “beta particles (high-speed electrons)” emitted as a radioisotope decays; the basic framework, in which a semiconductor receives these particles, generates electron-hole pairs, and converts them into current, resembles that of a solar cell.
Source: reconstructed by the editorial team from the claims of US12094620B2 and CN119207858A
Here, which isotope is used determines safety and lifespan. Tritium (a radioactive isotope of hydrogen, with a half-life of about 12.3 years) and nickel-63 (with a half-life of about 100 years) emit only relatively low-energy beta rays, placing them on the safe end, since most of the radiation can be shielded with something as thin as a sheet of paper. Tritium’s short half-life makes it favorable for small, low-power devices, while nickel-63’s long half-life makes it favorable for ultra-long-life power sources spanning decades.
The two companies’ design philosophies also diverge. City Labs has chosen a “direct conversion” structure that layers a radioisotope onto a semiconductor (gallium arsenide, etc.) to convert beta particles directly into current. BetaVolt, on the other hand, takes a “convert-then-store, two-stage” structure, performing a primary conversion with a diamond semiconductor and then storing that electricity in a separate storage device — a supercapacitor — before releasing it as a larger current at the moment it is needed. To use an analogy, City Labs’ approach is like drawing water straight from a faucet, while BetaVolt’s approach is closer to first filling a water tank from the faucet and then releasing a rush of water when needed.
③ Comparison: The Two Companies’ Nuclear Battery Designs
| Category | City Labs (US12094620B2) | Betavolt (CN119207858A) |
|---|---|---|
| Conversion structure | Single-stage direct conversion via semiconductor (epitaxial liftoff layer) | Two-stage: diamond semiconductor converter + supercapacitor storage |
| Electrode/electrolyte characteristics | Multilayer stack of GaAs, InAlP, InGaP, etc. | Supercapacitor with carbon-nanotube nonwoven-fabric electrodes + aqueous sulfuric acid electrolyte |
| Operating temperature range | No explicit range stated in the published claims (designed for durability in the space environment) | Approx. -70°C to 110°C (claimed to be extended through improvements to the supercapacitor electrolyte) |
| Legal status | Granted (Active), expected to expire 2035-02-17 | Application published (Pending), not yet granted |
| Demonstration stage | Onboard the BOHR satellite, verified in actual orbit via SpaceX Transporter-17 (2026) | BV100 ground-use coin-cell prototype unveiled (2024); space-based demonstration unconfirmed |
Source: compiled by the editorial team from US12094620B2 and CN119207858A (Google Patents public records) and reports on the BOHR satellite launch
What This Table Tells Us: City Labs has already secured both a granted patent and an actual satellite deployment track record, cementing its position as a ‘proven technology,’ whereas BetaVolt remains at the level of an application-stage right and a ground-use prototype — a clear gap exists between the two companies’ technological maturity and IP defensibility.
④ Patent Perspective
In terms of claim scope, City Labs’ US12094620B2 tightly designs its claims around the device configuration itself, in which a semiconductor stack structure (an epitaxial liftoff layer) directly receives the beta particles emitted by the radioisotope and converts them into power. It is also notable that the claim scope is broadened by listing a wide range of semiconductor material combinations (GaAs, InAlP, InGaP, InAlGaP, AlGaAs, and so on). This style of multi-material claiming is a typical defensive strategy that makes it difficult to escape infringement merely by avoiding one particular semiconductor material.
BetaVolt’s CN119207858A remains a pending application (Pending), so its claim scope has not yet been finalized. That said, its claim intent shows a combination of elements — a “diamond semiconductor converter” and a “supercapacitor with carbon-nanotube electrodes and a sulfuric acid electrolyte” — that is fundamentally different from City Labs’ combination, so even if both patents are eventually granted, the likelihood of their claim scopes directly colliding appears relatively low. However, this is only a preliminary assessment based on the currently published claim language, and the conclusion could change if the claim scope is amended during examination.
From a design-around perspective, a latecomer seeking to develop a direct-conversion device (the City Labs type) could effectively sidestep the claim elements by designing a different semiconductor material combination or a different liftoff process altogether. Conversely, a company examining a convert-then-store, two-stage structure (the BetaVolt type) might find it a safer starting point to design the supercapacitor’s electrode material or electrolyte composition outside the claim scope. That said, since no litigation or opposition history has yet been confirmed for either patent, an actual determination of infringement or invalidity is a matter that can only be discussed at the level of possibility, once specific working examples emerge in the future.
⑤ Limitations and Outlook
Nuclear batteries might look like a ‘game changer’ that instantly solves the power problem for small satellites and extreme-environment sensors, but a counterargument is needed here as well. Radioisotope batteries have a power density that is markedly lower than that of solar cells or chemical batteries, making them unsuitable from the outset for missions requiring large amounts of power. In other words, rather than serving as the primary power source driving an entire satellite, it currently looks more likely that they will remain in the role of an ‘auxiliary/emergency power source’ that keeps minimum functions running even when a separate power source is cut off.
As a strategic alternative, a more realistic approach is to design nuclear batteries as one pillar of a hybrid power system, rather than as a full replacement for solar cells and batteries. In particular, BetaVolt’s supercapacitor storage structure — steadily accumulating low power and then releasing it as a large current at once — could have an advantage for communication and sensing missions that need a momentary burst of high current, so it is worth separately tracking IP trends around this kind of combined design.
Action for planning and IP personnel: if your company is reviewing the development of a power module for space or extreme-environment use, set up a system that divides City Labs’ direct-semiconductor-conversion patent cluster and BetaVolt’s convert-then-store patent cluster into separate clusters and monitors new publications on KIPRIS and Google Patents on a quarterly basis.