Researchers are beginning to use more natural materials in battery designs in an effort to make them more organic and efficient. For example, a
University of Maryland student team is using a wood base for a nanobattery that could be used one day to store solar and wind energy.
These grad students, working under the tutelage of Dr. Liangbing Hu of the Department of Materials Science and Engineering, have developed a sodium-ion battery whose components are thinner than a piece of paper. The National Science Foundation is supporting the work.
The researchers say that their battery would be more environmentally friendly and easier to produce than the lithium-ion designs used today because of its material structure. It doesn't store energy as efficiently as its lithium-ion counterparts, but it would be ideal for storing large amounts of solar and wind energy at once, making it a candidate for a large-scale renewable battery of the future.
Jiayu Wan, a PhD candidate on the team, told us in an email that it has been developing sodium-ion batteries for about two years and working on the nanobattery project for one year. Sodium is a good candidate to replace lithium, because it's more abundant and easier to obtain. "Lithium is not resourceful in the United States, but sodium is very resourceful -- imagine [all the sodium] in the sea."
The battery itself is made of tin-coated wood fibers, which expand and contract but don't degrade quickly when used for storing liquid electrolytes.
People want to use tin as anode for sodium-ion batteries for it has the highest known capacity and it is cheap; however, the cyclability of tin is poor because when sodium ion inserts into tin, it will form alloy and volume-expand 420 percent. When the sodium ion is taken out at discharge, the volume will shrink back.
In a normal battery template, this type of drastic expanding and contracting will not survive the huge volume cycling, thus leading to poor battery performance. Wood cellulose, on the other hand, expands and contracts to hold mineral-rich water in trees, so it can be used to build a more stable and longer-lasting sodium-ion battery.
We came up with this idea that soft template would help accommodate volume cycling and wood cellulose would be it. Also, wood cellulose naturally transfer sodium ions; that helps the sodium-ion battery charge/discharge faster because it provide alternative ion passways.
In lab experiments, the sodium-ion nanobattery lasted more than 400 charging cycles, which is high for current nanobattery designs. The UMD researchers published a paper in Nano Letters about their work (registration required). They also explain the benefits of the battery and how it works in the video below.
Other projects are focused on batteries that can store renewable energy for large-scale use on a larger scale. Organic materials are at the core of a Harvard project we discussed in December. A startup out of MIT called Ambri has taken the opposite approach by developing a giant liquid-based battery.