Lithium metal batteries, often called the next big thing in battery technology, have the potential to power our devices and cars far better than today’s lithium-ion batteries.

But they have some big problems: they don’t last long, and they can catch fire.

Now, researchers from KAIST (Korea Advanced Institute of Science and Technology) have made a groundbreaking discovery to solve these issues—with the help of water.

The team, led by Professor Il-Doo Kim from KAIST and Professor Jiyoung Lee from Ajou University, found a way to make lithium metal batteries last about 750% longer.

They used hollow nanofibers, made from a plant-based material, as a special protective layer for the battery’s lithium metal.

Their study, published in Advanced Materials, could pave the way for safer, longer-lasting, and more eco-friendly batteries.

In conventional batteries, protective coatings are added to lithium metal to prevent it from reacting with the battery’s liquid electrolyte.

However, these coatings are expensive to produce, rely on toxic chemicals, and haven’t solved the problem of short battery life.

The new solution is both clever and sustainable.

The researchers developed a protective layer made of hollow nanofibers that stabilize the battery’s lithium metal anode (the part of the battery where lithium ions move in and out).

The nanofibers were created using guar gum—a material extracted from plants—and water as the only solvent. This simple, environmentally friendly process avoids the toxic chemicals used in traditional methods.

The hollow spaces in the nanofibers help control how lithium ions grow and interact with the electrolyte.

This prevents random buildups of lithium, which often lead to short circuits and reduce battery lifespan. The result?

A lithium metal battery that lasts much longer and retains 93.3% of its capacity even after 300 charge-discharge cycles.

Another benefit is that the protective layer is biodegradable. It naturally decomposes within about a month in soil, making it safe for the environment. This eco-friendly feature is particularly important as the world faces growing concerns about the environmental impact of batteries.

Professor Kim explained that the hollow nanofibers work in two ways: physically, by creating a stable structure, and chemically, by controlling how lithium reacts with the electrolyte. Together, these effects suppress the growth of dangerous lithium dendrites (needle-like formations that can cause batteries to fail).

“With battery demand skyrocketing, this water-based, biodegradable method offers a greener path forward,” Professor Kim said. “It’s a major step toward next-generation batteries that are safer, longer-lasting, and better for the planet.”