Most batteries come off the shelf with everything they need to operate, ready to be added to a circuit. This includes the electrolyte, usually a liquid or gel that carries ions between the battery’s two electrodes to generate electricity. Because the electrolyte is stored inside the cell, batteries require protective packaging to prevent leaks and damage during shipping and storage.
To minimize that risk, researchers have developed a new flexible battery that ships dry, harvesting water from the air to generate its electrolyte (Sci. Adv. 2026, DOI: 10.1126/sciadv.aee2065). The stretchable, moisture-activated battery could provide a lightweight, nontoxic power source for wearable health monitors and Internet of Things (IoT) devices.
“We wanted to avoid toxic electrolytes, and we wanted to have very safe and nonflammable electrolytes,” says Rajaram Kaveti, a materials scientist at North Carolina State University and first author of the study. “The best case is water.”
Previous designs of liquid activated batteries include versions powered by sweat or manually added water. But instead of relying on an external liquid source, the new battery scavenges water vapor from the surrounding air to activate itself, even in relative humidities as low as 10%. If sealed, the dry battery remains inactive until exposed to the atmosphere.
“It combines part of the idea of an energy harvester with a battery,” says Aiman Rahmanudin, a Linköping University materials scientist, who was not involved in the work. “It does not harvest energy from humidity, but it uses humidity to form the electrolyte needed for the battery to work.”
The trick relies on lithium chloride, a hygroscopic salt, which is a material that readily absorbs water vapor from the atmosphere. The battery consists of a magnesium anode, a silver–silver chloride cathode, and a cellulose separator divided into two regions. One lithium chloride–loaded layer captures moisture from the air; then the harvested water is transported into a second, sodium chloride–loaded layer, where it dissolves the salt to form the electrolyte.
“The battery design is clever because they separate the moisture-capture function from the electrochemical function,” Rahmanudin says. Although lithium chloride is excellent at harvesting atmospheric moisture, it also accelerates corrosion of the magnesium anode, reducing battery performance. “We wanted to prevent the lithium chloride from entering into the battery region,” Kaveti says. “It only transports the water, but not the lithium chloride particles,” to the electrolyte.
The researchers paired the moisture-activated chemistry with a bioinspired mechanical design, which was modeled after overlapping pangolin scales, according to Raudel Avila, a mechanical engineer from Rice University and coauthor of the study. The arrangement allows rigid battery cells to be packed densely while remaining flexible enough to bend, twist, and stretch without sacrificing much energy density.
Researchers have integrated a new battery into this wireless environmental gas sensor (left) equipped with a moisture-triggered kill switch. Pressing the device brings harvested water into contact with aluminum and iodine powders, setting off a reaction that destroys the electronics to prevent tampering (right). Credit:
Rajaram Kaveti/North Carolina State University
To demonstrate the battery’s versatility, the researchers used it to power a wireless pulse oximeter, a wearable device that measures blood oxygen saturation, for about 30 h. They also used this water-capturing concept to design a novel device combining a wireless environmental gas sensor with a moisture-triggered kill switch and powered it with the new battery. Pressing on the device brings a water-laden cellulose membrane into contact with a mixture of aluminum and iodine powders, triggering an exothermic reaction that destroys the electronics to prevent tampering.
Although the researchers envision applications ranging from wearable health monitors to field sensors, Rahmanudin says the battery is likely to find its niche in lightweight, single-use electronics, where flexibility, long shelf life, and safe materials matter more than rechargeability.
