{"id":10020,"date":"2015-06-13T11:19:01","date_gmt":"2015-06-13T18:19:01","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=10020"},"modified":"2015-06-15T18:22:15","modified_gmt":"2015-06-16T01:22:15","slug":"trees-source-high-capacity-soft-batteries","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/trees-source-high-capacity-soft-batteries\/","title":{"rendered":"High-capacity, Soft Batteries From Trees"},"content":{"rendered":"

This is not pulp fiction, but pulp fact, trees being converted into squishy new nerf-like batteries.<\/p>\n

Researchers at Sweden\u2019s KTH Royal Institute of Technology and Stanford University <\/a>have made elastic, high-capacity batteries from wood pulp.\u00a0 The foam-like battery material can withstand shock and stress, according to the schools.\u00a0 Max Hamedi, a researcher at KTH and Harvard University, says, \u201cIt is possible to make incredible materials from trees and cellulose.\u201d<\/p>\n

\"Raw<\/a>

Raw material for the KTH\/Stanford nanocellulose battery<\/p><\/div>\n

The wood-based aerogel material can be used for three-dimensional structures, important for overcoming certain restrictions imposed by two-dimensional approaches.\u00a0 Hamedi explains, \u201cThere are limits to how thin a battery can be, but that becomes less relevant in 3D.\u00a0 We are no longer restricted to two dimensions. We can build in three dimensions, enabling us to fit more electronics in a smaller space.”<\/p>\n

\"Flexibility<\/a>

Flexibility plus! Wood fiber battery can be squeezed considerably while still storing energy<\/p><\/div>\n

Moving past former obstacle of using three-dimensional, porous materials in crafting electrodes, researchers managed to make this a non-problem.\u00a0 Hamedi adds, \u201cIn fact, this type of structure and material architecture allows flexibility and freedom in the design of batteries,”<\/p>\n

Think of the process as nano-pulping, breaking down tree fibers and making them \u201croughly one million times thinner.\u201d\u00a0 Researchers dissolve, freeze and then free-dry the resulting nanocellulose, with the moisture in the pulp undergoing sublimation \u2013 evaporating without going through a liquid state.<\/p>\n

\"Manufacturing<\/a>

Manufacturing stages in a different kind of wood working<\/p><\/div>\n

In a vaguely worded description, the KTH press release explains, \u201c\u2026The material goes through a process in which the molecules are stabilized so that the material does not collapse.\u201d<\/p>\n

Like Nerf, the resulting material is strong, light and soft, resembling foam in a mattress, \u201cthough a little harder, lighter and more porous.\u00a0 You can touch it without it breaking,\u201d Hamedi notes.<\/p>\n

In a tiny and extremely enclosed space, researchers added conductive ink within the aerogel<\/em>. \u201cYou can coat the entire surface within.”<\/p>\n

Hamedi compared the surface area of the finished material to a pair of human lungs, a cubic decimeter of which would cover most of a football field.\u00a0 All these nano-materials seem to emulate graphene in having incredibly high surface areas \u2013 important to conductivity.<\/p>\n

\"Wood<\/a>

Wood battery ends up having reasonably good electrical characteristics, having survived 400 cycles, but not quite at lithium performance levels – yet. \u00a0It’s a battery that passes the squeeze test<\/p><\/div>\n

“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.”\u00a0 This may lead to the battery\u2019s use in electric car bodies and in clothing \u2013 as long as the garment has a lining \u2013 insulated from electrical as well as temperature fluctuations.\u00a0 The flexible nature of the material may even provide a degree of crashworthiness.<\/p>\n

The Wallenberg Wood Science Center<\/a> at KTH performed the research, under the leadership of KTH Professor Lars W\u00e5gberg, whose work on aerogels is the basis for the invention of soft electronics. \u00a0Professor Yi Cui from Stanford University provided extra input.<\/p>\n

Researchers\u2019 findings are found in the May 29 issue of Nature Communications<\/em> <\/a>under the title, “Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries.\u201d\u00a0 Authors include Gustav Nystr\u00f6m, Andrew Marais, Erdem Karabulut, Lars W\u00e5gberg, Yi Cui and Mahiar M. Hamedi.<\/p>\n

The abstract for their paper provides additional details on the supercapacitor\u2019s fabrication.\u00a0 \u201cTraditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25\u2009<\/span>F\u2009<\/span>g\u22121<\/sup>\u00a0and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices.\u201d<\/p>\n