Lithium-ion batteries are at the heart of nearly every electric vehicle, laptop and smartphone, and they are essential to storing renewable energy in the face of the climate emergency. But all the world’s current mining operations cannot extract enough lithium and other key minerals to meet skyrocketing demand for these batteries. Establishing new mines is an expensive, years-long effort. And mining also creates a host of environmental headaches—such as depleting local water resources and polluting the nearby region with runoff debris—that have led to protests against new mines. Lithium-ion batteries are at the heart of nearly every electric vehicle, laptop and smartphone, and they are essential to storing renewable energy in the face of the climate emergency. But all of the world’s current mining operations cannot extract enough lithium and other key minerals to meet skyrocketing demand for these batteries. Establishing new mines is an expensive, years-long effort. And mining also creates a host of environmental headaches—such as depleting local water resources and polluting the nearby region with runoff debris—that have led to protests against new mines. Yan Wang, a material's science professor at Worcester Polytechnic Institute and co-author of the new study, started researching battery recycling 11 years ago. At the time, he says, “some people joked with me, ‘There’s not enough batteries for you to recycle.’” That joke is not aging well. The Department of Energy estimates the battery market may grow 10-fold over the next decade. To ease the market’s growing pains, “recycling of lithium-ion batteries—getting that material back into the supply chain—is critical,” says Dave Howell, director of the DOE’s Vehicle Technologies Office. The DOE funded the new research as part of its massive effort to spur large-scale battery recycling innovations in the U.S. When a lithium-ion battery is providing power, a cluster of lithium ions moves from one crystalline “cage” (the anode) to another (the cathode). The most common methods currently used to recycle these batteries involve dismantling and shredding the whole battery, then either melting it all down or dissolving it in acid. The result is a black mass—with a texture can that can vary from powder to goo—from which chemical elements or simple compounds can be salvaged. Those recovered products can then go through the same commercial manufacturing process that newly mined elements do to make cathodes. Wang and his colleagues use a very similar process—but instead of completely breaking the battery down to its constituent chemical elements, their technique keeps some of the old cathode’s crucial composition intact. After they shred the battery, they physically remove the less expensive bits (such as the electronic circuits and steel battery casing) and recycle them separately. What is left is mainly the cathode material; they dissolve this in acid and then remove impurities. Next, they carefully add just a touch of fresh elements that compose the cathode, such as nickel and cobalt, to ensure the ratio of ingredients is just right—another distinction from common recycling methods. After a few more steps, the result is an effectively refreshed cathode powder, composed of tiny crystalline particles that can be stuck onto a metal strip and placed in a “new” battery.
Because a cathode is crafted from a precise mix of precious minerals to achieve the battery’s specific voltage, slight changes to its structure or composition can compromise its performance. Thus, much of the cathode powder’s value is “in how you’ve engineered the particles [of powder] in the first place,” says Emma Kendrick, a professor of energy materials at England’s University of Birmingham, who was not involved in the new study. That value is lost if the entire battery is simply melted down or dissolved in one fell swoop, as in current recycling methods
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