As the quest continues for new ways to store renewable power, making it a more competitive source of energy on a massive scale, the search for capable storage materials becomes more surreal. In the latest twist in this intriguing story, researchers at the University of Maryland (UMD) have developed a nano-battery that runs on the most unlikely of materials: wood.


On closer inspection, it makes sense, and it was this parallel that inspired the researchers to give it a shot. Trees, which are wood, survive by transporting mineral-rich water from their roots to their leaves. A similar process takes place in batteries, minus the foliage, of course.


With those similarities in mind, the UMD researchers developed and tested a battery with anodes made of tin-coated wood. The material is one thousand times thinner than a piece of paper. The team also employed sodium ions instead of lithium.


The researchers found that the combination offered a number of advantages. For its part, the wood can withstand the swelling and shrinking that comes from the normal charging and discharging of batteries, making it durable and long-lasting. Associate Professor Teng Li, one of the team members, described the wood fibers as “soft enough to serve as a mechanical buffer.” Their flexibility enables them to accommodate the changes that normally take place with tin anodes, making them a better alternative to the typically stiff and brittle bases in most batteries.


Also, the researchers described the use of sodium as an “environmentally benign” alternative to lithium, even though it is not as efficient at storing electrons. Furthermore, it is much more commonly available and less costly.


The team feels that all of these factors make the wood battery an ideal prototype for storing large amounts of renewable energy, such as the electricity generated at large-scale solar facilities.


The Maryland team put its battery through more than 400 charging cycles and found that it wrinkled but remained intact. Their computer models showed that the wrinkles actually served a positive function by relaxing the stress in the battery during charging and recharging.