It's basically common knowledge that when we dispose of batteries, we're not supposed to just throw them in our trash casually. Whether or not we all dispose of them properly is another issue. But why are batteries so bad for the environment?

In a nutshell, batteries, especially rechargeable ones, aren't great for the environment when you throw them out because the heavy metals—cadmium, cobalt, and lead—will degrade and release the toxicity into the air, through the topsoil, into the groundwater, and eventually reach us again—except this time we'll be consuming it.

This is why a team of visiting professors at the University of Maryland decided to look for more sustainable materials to build batteries and hopefully replace the heavy metals. They first tried many other natural materials, including wood fibers, before making an attempt at a leaf. Their goal was to find materials that could absorb and store the sodium and make up the anode of a battery.

There are many benefits to using leaves. As Hongbian Li, one of the lead authors of the paper that published these results, stated,

"Leaves are so abundant. All we had to do was pick one up off the ground here on campus."

Credit: Clip Arts

They also have a carbon structure that can be burnt off to make the sodium more absorbable, they're covered in pores where the sodium electrolytes enter, and they already have the perfect structure to fit the need of a battery. Additionally, Fei Shen, another lead author on the paper, notes that,

"The natural shape of a leaf already matches a battery's needs: a low surface area, which decreases defects; a lot of small structures packed closely together, which maximizes space; and internal structures of the right size and shape to be used with sodium electrolyte."