Energy Storage – Flexible Wood Based Aerogel Batteries

Nanocellulose based battery

Researchers at KTH Royal Institute of Technology in Sweden and Stanford University have developed a flexible, compressible foam-like battery material made from wood pulp.

The elastic high-capacity batteries are based on nanocellulose broken down from tree fibres, around one million times thinner than the original fibre. The nanocellulose is treated so the material does not collapse and is built layer-by-layer (LbL). This results in a material called aerogel, also sometimes referred to as “frozen smoke” due to its lightweight and ghost-like nature.

Any visual resemblance to frozen smoke is lost when a conductive ink is then used to coat the entire surface – inside and out. The full device is a seven-layer structure, including the aerogel substrate wall.

“The result is a material that is both strong, light and soft,” according to Max Hamedi,  a researcher at KTH and Harvard University. “The material resembles foam in a mattress, though it is a little harder, lighter and more porous.”

Aerogel battery

The massive surface area is where the energy storage potential lies. While there are limits to how thin a traditional battery can be, this becomes less relevant in 3D structure and Aerogels have the highest specific surface area among any man-made material. Mr. Hamedi says a single cubic decimeter of the aerogel material would cover most of a soccer pitch.

Test batteries have been able to be reversibly bent to 90° or compressed up to 75% without any observable structural damage. The devices showed a stable cycling behaviour at the 60C rate for 400 cycles and 75% of the initial capacitance was maintained when the charging rate was increased to 160C (22s).

With further development, one of the possible applications for such a material is in the bodies and seats of electric cars; or perhaps even insulation in homes – making the house itself a giant battery; storing electricity produced by solar panels on its rooftop.

A paper on the battery technology has been published in the latest issue of Nature Communications.

“We have shown that fully interdigitated 3D supercapacitors and batteries can be self-assembled inside high-surface area aerogels using a rapid and scalable methodology. The obtained devices show stable operation without short-circuiting, are bendable, compressible and can be made with arbitrary form factors,” state the paper’s authors.

” These results are very promising and show that this LbL-based methodology can produce fully interdigitated 3D devices with a complex structure containing a variety of materials.”

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