What the research is about
Many devices around us-such as smartphones, laptop computers, and drones-run on batteries. Among them, lithium-ion batteries are currently the most widely used and highly advanced. However, the amount of electricity they can store is largely determined by the properties of the materials inside them. This means it is not easy to significantly increase their capacity while keeping the battery the same size. As a result, new approaches are needed to meet the growing demand for devices that can operate longer.
One promising alternative is the fuel cell. Unlike conventional batteries, fuel cells do not store electricity in advance. Instead, they generate electricity through a chemical reaction between a fuel-such as hydrogen-and oxygen from the air. As long as fuel is supplied, they can continue producing electricity.
Among various types of fuel cells, solid oxide fuel cells (SOFCs) have attracted particular attention. SOFCs operate at high temperatures, typically above 600°C. At such temperatures, the electrochemical reactions that generate electricity become much more active. This allows SOFCs to produce electricity efficiently not only from hydrogen but also from readily available fuels such as alcohols.
However, these high temperatures also create challenges. Conventional SOFC systems require a long time to reach the temperature needed for stable power generation, and the devices themselves tend to be large. Developing a compact and safe power source that operates at high temperatures has therefore been a long-standing challenge.
To address this problem, a research team led by Assistant Professor Tetsuya Yamada at Institute of Science Tokyo (Science Tokyo) took on the challenge directly. By combining conventional SOFC cells with structural designs that enable rapid heating and highly effective thermal insulation, the team optimized the entire device as a single integrated system. As a result, they successfully developed a compact high-temperature power source that can start up in just five minutes.
Why this matters
The biggest challenge was achieving three difficult requirements at the same time: high temperature, safety, and rapid start-up. While the inside of the device exceeds 600°C, the outer surface must remain safe enough to touch by hand.
Instead of simply making materials stronger, the researchers designed a structure that can relieve thermal stress. They introduced a cantilever structure, in which one side is fixed while the other side can flex. This design helps distribute the strain caused by heat, preventing cracks even at high temperatures.
The team also implemented multilayer thermal insulation, in which multiple layers of insulating materials are stacked together. This allows the device to maintain internal temperatures above 600°C while keeping the outer surface at a safe temperature.
Another important feature is that the system is designed to incorporate commercially available planar SOFC cells. This means the device can potentially be developed as a compact power generation system that builds upon existing SOFC technologies.
Thanks to these innovations, the system can start up in about five minutes and successfully power a motor. The researchers also confirmed an additional safety feature: although the device uses hydrogen and other fuels, if the system is damaged, the temperature quickly drops, reducing the risk of ignition.
Demonstrating a compact high-temperature power source that also incorporates built-in safety measures is a major achievement of this research.
What's next
If this technology continues to advance, it could enable devices to operate much longer than with today's batteries, even with the same size and weight. This could extend the operating time of drones, robots, and AI devices. Because it can be refueled, the system could serve as a reusable power source that can quickly return to operation.
In addition, because the design can utilize existing SOFC technologies, the path toward practical applications and wider adoption becomes more realistic. The technology could also expand new types of power sources for environments without electrical infrastructure, such as remote monitoring systems or field robotics.
Comment from the researcher
We aim to realize a 'small power plant' that can use high-temperature chemical reactions within a palm-sized device. This system could generate electricity for much longer than conventional batteries and may become a power source for next-generation drones, robots, and other technologies-even in places without access to power grids.
（Tetsuya Yamada, Assistant Professor, Laboratory for Future Interdisciplinary Research of Science and Technology, Institute of Integrated Research, Institute of Science Tokyo）
