Elastic high-capacity batteries made from wood pulp, which can also withstand shock and stress, have been designed by a team of researchers.
The researchers from KTH Royal Institute of Technology in Sweden and Stanford University in the US produced a stretchable, foam-like battery material using nanocellulose broken down from tree fibres.
“It is possible to make incredible materials from trees and cellulose,” said Max Hamedi, researcher at KTH and Harvard University. “One benefit of the new wood-based aerogel material is that it can be used for 3D structures.”
“There are limits to how thin a battery can be, but that becomes less relevant in 3D,” he said. “We are no longer restricted to 2D. We can build in 3D, enabling us to fit more electronics in a smaller space.”
The 3D structure allows storage of significantly more power in less space than is possible with conventional batteries, he said.
“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 material, tree fibre is broken down, making it roughly one million times thinner. The nanocellulose is dissolved, frozen and then freeze-dried so that the moisture evaporates without passing through a liquid state.
The material then goes through a process in which the molecules are stabilised so that the matrial doesn’t collapse.
“The result is a material that is strong, light and soft,” Hamedi says. “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 aerogel can then be treated with electronic properties, according to the researchers.
“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 with it.”
Applications for the aerogel batteries could be used in electric car bodies or in clothing.