New water-based capacitor survives 60,000 charging cycles without degrading

It turns out that pure water can store electricity.
A new study by the Hamburg University of Technology in Germany reveals that trapping water inside nanometer-sized clay channels creates a supercapacitor capable of efficiently storing and moving electrical charge.
In this work, pure water has been used as an electrolyte to carry electrical charge. This system is dubbed the “Blue Capacitor.”
“Our goal is to develop safer and more sustainable energy-storage technologies based on abundant materials rather than complex chemical compounds,” said Dr. Vasily Artemov from the Cluster of Excellence “BlueMat—Water-Driven Materials” at Hamburg University of Technology.
“The device stores and releases energy efficiently, operates at a comparatively high voltage for a water-based system, and remains stable over tens of thousands of charging cycles,” the lead author added.
Nanometer-sized channels
Pure water is mostly considered a terrible medium for storing power. To conduct electricity, batteries and supercapacitors have always required a chemical cocktail of added salts, acids, or volatile organic solvents. Without them, energy storage simply stalls.
But the research team tried to change this through its functional “Blue Capacitor” technology. It is an energy-storage device made entirely from three of Earth’s most abundant, naturally occurring materials: water, clay, and carbon.
The system has been engineered to confine pure water within microscopic channels, thereby altering the liquid’s fundamental behavior.
The clay minerals were blended with graphene — a highly conductive, ultra-thin form of carbon. When combined, these materials form a dense labyrinth of millions of parallel channels. Each channel measures just one nanometer wide, roughly 100,000 times thinner than a human hair.
“Our results show that nanoconfined water can serve as the active electrolyte in a practical energy-storage device,” noted Artemov.
To actually see this happening, the team had to look more closely than almost anyone has before. They utilized PETRA III at DESY, one of the world’s most powerful particle accelerator research centers.
“Only with DESY’s brilliant X-ray source PETRA III, were we able to visualize the ultra-thin sheets of individual water films within the clay structures,” said Prof. Patrick Huber, co-author of the paper.
Rigorous testing
The new device is a supercapacitor, a type of energy-storage technology that stores energy by separating electrical charges rather than through chemical reactions. Because of this mechanism, supercapacitors feature rapid charging and discharging capabilities, along with exceptionally long operational lifetimes.
In testing, the proof of concept showed promising results.
In rigorous laboratory testing, the Blue Capacitor survived more than 60,000 charge-discharge cycles without degrading. Furthermore, it operated at up to 1.6 volts.
That is an exceptionally high voltage threshold for any water-based system, which typically breaks down into hydrogen and oxygen gases at much lower voltages.
While commercial applications are still years away, the implications of a non-toxic, un-burnable capacitor are massive.
It offers a promising path for future energy storage. Potential applications include managing renewable energy from solar and wind power, stabilizing electrical grids, and powering devices that need rapid, frequent charging cycles.
According to researcher Artemov, understanding the unexpected nanoscale properties of a familiar substance opens the door to the development of entirely new technological applications.
Beyond green power, the discovery opens the door for water-based nanoscale sensors and bio-inspired computing.
The findings were published in the journal Nature Communications.
