Long-lasting energy storage from trees

Lithium-ion batteries are the standard when it comes to gadgets with rechargeable batteries and electric cars. If we increase the scale of those batteries to the size of a microgrid, they become less efficient, environmentally friendly, and all-around useful. A new type of battery, though, is in development and it could be a solution to these problems.

Many researchers believe sodium-ion batteries are the answer. Sodium is cheap and environmentally benign and sodium-ion batteries would be well-suited for storing large amounts of renewable energy at once. The major obstacle to advancing these batteries has been a very short life due to the swelling of the anode with each charge and discharge of sodium ions, which when using a brittle base, causes the battery to fall apart after only about 20 charge cycles.

Researchers at the University of Maryland  have developed a solution to this problem by using a paper-thin layer of wood fibers coated with conductive carbon nanotubes as the base in a sodium-ion nanobattery. The wood is able to withstand the swelling and contracting of the anode and allows the battery to survive more than 400 charge cycles, which makes it one of the longest lasting nanobatteries.

Because the fibers that make up the wood in trees had at one point held mineral-rich water, they are a good medium for storing liquid electrolytes. They are also much more flexible than metal, or other rigid materials, so they can withstand the swelling that takes place in the charging cycles of a sodium-ion battery.

At the end of the charging cycles, the wood was wrinkled, but still intact. Computer models showed that those wrinkles relaxed the stress in the battery during charging and recharging, creating a flexible and long-lasting battery.

Read more over at Tree Hugger.