Scientists Create 3D, High-Capacity Soft Batteries Using Trees

Max Hamedi and Wallenberg Wood Science Center.

Technology is advancing at a mind-boggling rate, but batteries always seem to be lagging behind, often hindering the development of novel devices and gadgets simply due to their bulky size or limited storage capacity. But progress is slowly being made, and scientists may have just taken a significant stride in the field with the development of two novel high-capacity energy-storage devices made from a cheap and renewable material: wood pulp.

Tough yet flexible, these spongy devices can withstand both shock and stress, a feature that many stretchable electronics do not possess. What’s more, the ultralight material they created to build the devices, an aerogel, allowed them to make 3D structures, something that has been pursued for more than a decade. Although some 3D charge-storage devices have been created in the past, they have been limited by the manufacturing processes used to create the complex architecture.

“There are limits to how thin a battery can be, but that becomes less relevant in 3D,” lead researcher Max Hamedi, of KTH Royal Institute of Technology, said in a statement. “We are no longer restricted to two dimensions. We can build in three dimensions, enabling us to fit more electronics in a smaller device.” And cramming more in means that more power can be stored but in less space than conventional batteries would allow, Hamedi explains.

To create their innovative wood-based aerogel material, scientists from KTH Royal Institute of Technology and Stanford University started off by breaking down cellulose, a long chain of sugar molecules found in plant cell walls that bestows wood with its strength. After reducing these fibers to around one-millionth of their original thickness, the resulting “nanocellulose” is then dissolved and freeze-dried to remove moisture. Finally, the substance is put through a processing technique that stabilizes the molecules, preventing the foam-like material from collapsing.

“The result is a material that is both strong, light and soft,” said Hamedi. “The material resembles foam in a mattress, though it is a little harder, lighter and more porous. You can touch it without it breaking.”

The team then coated this spongy material with an ink that conducts electricity within the aerogel, allowing the researchers to ultimately produce their two 3D energy-storage devices: a hybrid battery and a supercapacitor, which is a rapidly charging and discharging device capable of storing huge amounts of electrical charge. Impressively, the latter was so resistant to impact that it retained full function at compressions of up to 75%, the researchers report in Nature Communications.

Although there is much more work to be done before we start to see this material in use, the researchers envisage that the devices could ultimately be used in electric cars, or even in clothing to charge gadgets on the go. 


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