Environmental battery made from wood shows promise, say scientists

June 22, 2013 by  
Filed under Solar Energy Tips

A new kind of ecologically friendly battery made out of a sliver of wood coated with tin may provide an answer to large-scale energy needs, according to the authors of a report appearing in the journal Nano Letters. The new energy storage device, which is 1,000 times thinner than a sheet of paper, is efficient, durable, and long-lasting, the scientists say.

According to co-author Liangbing Hu, an assistant professor of materials science at the University of Maryland, the team got their inspiration for the new gizmo from trees. Because wood fibers from trees once absorbed mineral-rich water, they are ideal for storing liquid electrolytes, allowing them to function as both the base and an active part of the battery. The use of sodium rather than lithium makes the device less efficient but more environmentally friendly than the type of rechargeable batteries typically found in cell phones. However, the low cost of production due to the abundance of tin and wood make the battery ideal for storing large amounts of energy, such as in wind or solar power plants, the report says.

Unlike existing batteries made on stiff bases that are too rigid to tolerate the kind of swelling and shrinking that occurs when electrons are stored and expended, a sodium-ion battery made of wood fibers is flexible enough to last more than 400 charging cycles. This makes the mechanism one of the most long-lasting of all sodium-ion nanobatteries.

In testing the battery, lead author Hongli Zhu and his colleagues noticed that the wood wound up wrinkled but intact after charging and discharging it hundreds of times. Computer models demonstrated that the wrinkles were effective in relaxing the stress in the battery during charging and recharging.

“Pushing sodium ions through tin anodes often weaken the tin’s connection to its base material,” team member Teng Li, an associate professor of mechanical engineering, told Phys.org. “But the wood fibers are soft enough to serve as a mechanical buffer, and thus can accommodate tin’s changes. This is the key to our long-lasting sodium-ion batteries,” Li said.

The wood and tin combo is just the latest attempt by scientists to create an eco-friendly battery. For example, Sony has been working on a paper-powered battery and researchers from the City College of New York are investigating how to use a natural red plant dye called purpurin to produce lithium ion batteries that do not harm the environment.

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