Researchers in Sweden and the US have described a method for making elastic high-capacity batteries from wood pulp. Using nanocellulose broken down from tree fibers, the scientists have produced an elastic, foam-like battery material that can withstand shock and stress.

Wood Pulp Nanocellulose Battery.  A closeup of the soft battery, created with wood pulp nanocellulose. Image Credit: Max Hamedi at Wallenberg Wood Science Center KTH Royal Institute.  Click image for the largest view.

Wood Pulp Nanocellulose Battery. A closeup of the soft battery, created with wood pulp nanocellulose.  Image Credit: Max Hamedi at Wallenberg Wood Science Center KTH Royal Institute. Click image for the largest view.

Max Hamedi, a researcher at KTH and Harvard University explained, “It is possible to make incredible materials from trees and cellulose.” One benefit of the new wood-based aerogel material is that it can be used for three-dimensional structures.

“There are limits to how thin a battery can be, but that becomes less relevant in 3D. We are no longer restricted to two dimensions. We can build in three dimensions, enabling us to fit more electronics in a smaller space,” he said. A 3D structure enables storage of significantly more power in less space than is possible with conventional batteries.

“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 said.

The process for creating the material begins with breaking down tree fibers, making them 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,

Then the material goes through a process in which the molecules are stabilized so that the material does not collapse.

“The result is a material that is both 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 finished 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.” The electrodes are a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode.

The result is a three-dimensional energy-storage device based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate.

In terms of surface area, Hamedi compared the material to a pair of human lungs, which if unfurled could be spread over a football field. Similarly, a single cubic decimeter of the battery material would cover most of a football pitch, he said.

“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.”

Hamedi offered that aerogel batteries could be used in electric car bodies, as well as in clothing, providing the garment has a lining.

The research was carried out at the Wallenberg Wood Science Center at KTH. KTH Professor Lars Wågberg also was involved, and his work on aerogels is in the basis for the invention of soft electronics. Another partner is leading battery researcher, Professor Yi Cui from Stanford University.

The team’s research paper has been published in the journal Nature Communications.

The technology would be very beneficial across a very wide range of products. The question remains as usual – Can the technology go to mass production and expand to low cost commercial scale? Lets hope so.


Comments

1 Comment so far

  1. Matt Musson on June 9, 2015 9:04 AM

    Gee Whiz. Neat. Cool.

    But scaling up atomic level processes at a reasonable cost becomes the real challenge.

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