Robots could one day be powered by tree pulp. Researchers at KTH Royal Institute of Technology and Stanford University have developed a method for making elastic high-capacity batteries using nanocellulose from broken down from tree fibres. The battery can be squished, much like foam, and therefore tolerate a lot of physical wear and tear.
“You can press it as much as you want. While flexible and stretchable electronics already exist, the insensitivity to shock and impact are somewhat new,” Max Hamedi, a researcher at KTH and Harvard University said in a statement.
In addition to being able to handle stress and shock the squishy battery has another benfit: it can be used to create three-dimensional structures.
“There are limits to how thin a battery can be, but that becomes less relevant in 3D, ” Hamedi says. “We are no longer restricted to two dimensions. We can build in three dimensions, enabling us to fit more electronics in a smaller space.”
The 3D structure would be able to store more power in less space than conventional batteries, he adds.
“Three-dimensional, porous materials have been regarded as an obstacle to building electrodes. But we have proven that this is not a problem. In fact, this type of structure and material architecture allows flexibility and freedom in the design of batteries,” Hamedi says.
To create the spongey aerogel material, tree fibres are first broken down into extremely thin pieces. one million times thinner. The resulting nanocellulose is then dissolved, frozen and freeze-dried. Next, the molecules of the aerogel are stabilized so that the material does not collapse. “The result is a material that is both strong, light and soft,” Hamedi says.
The aerogel can then be treated with electronic properties. “We use a very precise technique, verging on the atomic level, which adds ink that conducts electricity within the aerogel. You can coat the entire surface within.”