A new way to recycle such batteries can help meet the rapidly growing demand
Lithium ion batteries are at the heart of almost every electric car, laptop and smartphone, and they are crucial for storing renewable energy in the face of climate emergencies. However, at present, all mining industries in the world cannot extract enough lithium and other key minerals to meet the rapidly growing demand for these batteries. Building new mines is an expensive, multi-year effort. Moreover, mining has also caused a series of environmental problems - such as depletion of local water resources and pollution of nearby areas with runoff debris - which have led to protests against new mines.
All this means that the ability to recycle existing batteries is crucial for sustainable changes in the global energy system. But recycling lithium-ion batteries has only recently made commercial progress. Battery manufacturers have been hesitant because they fear that recycled products may be of lower quality than those made from newly mined minerals, which may lead to shortened battery life or internal damage. The consequences can be serious, especially in applications such as electric vehicles.
But the new study, published in Joule, found a more elegant recycling method described by experts, which can refurbish the cathode - this carefully crafted crystal is the most expensive component of lithium-ion batteries and the key to providing the right voltage. The researchers found that the batteries they made with the new cathode recycling technology performed as well as those using cathodes made from scratch. In fact, batteries that use recycled cathodes have longer life and faster charging. Kang Xu, an electrochemist at the U.S. Army Research Laboratory, said the team's methods and successful demonstrations were "very unique and very impressive" and he was not involved in the study.
No longer a joke
Yan Wang, a professor of materials science at Worcester Polytechnic Institute and co-author of the new study, began studying battery recycling 11 years ago. "At that time, some people joked with me that there were not enough batteries for you to recycle," he said Now it seems that this joke is not out of date. The US Department of energy estimates that the battery market may grow tenfold in the next decade. To ease the pressure of market growth, Dave Howell, director of the vehicle technology office of the Ministry of energy, said: "the recycling of lithium batteries -- bringing this material back into the supply chain -- is very important." As part of its large-scale innovation, the U.S. Department of energy has promoted this large-scale recycling of batteries.
When the lithium ion battery is powered, the lithium ion cluster moves from one crystalline "cage" (anode) to another (cathode). The most commonly used methods at present include shredding or dissolving the entire battery and then recycling it. The result is a mass of black matter - which can vary in texture from powder to mucus - from which chemical elements or simple compounds can be recovered. These recycled products can then be manufactured through the same commercial manufacturing process as the cathode made from newly mined elements.
Wang Yan and his colleagues used a very similar process - but their technology is not to completely decompose the battery into its constituent chemical elements, but to keep some key components of the old cathode unchanged. After they chop up the batteries, they physically remove less expensive parts (such as electronic circuits and steel battery shells) and recycle them separately. The rest is mainly cathode materials; They dissolve it in acid and remove impurities. Next, they carefully add some fresh elements that make up the cathode, such as nickel and cobalt, to ensure that the proportion of the components is just right - another difference from ordinary recycling methods. After a few more steps, the result is that the cathode powder is effectively refreshed, which is composed of tiny crystalline particles that can be adhered to the metal strip and placed in the "new" battery.
Since the cathode is made of precise mixing of precious minerals to achieve the specific voltage of the battery, slight changes in its structure or composition will affect its performance. Therefore, most of the value of cathode powder lies in "how did you design these particles first", said Emma Kendrick, a professor of energy materials at the University of Birmingham in England, who was not involved in the new study. If the whole battery is simply melted or dissolved at one time, as in the current recycling method, this value will be lost.
More pores, faster charging
Wang Yan and his colleagues compared the particles in their recycled cathode powder with those in commercially manufactured cathode powder (mainly made of newly mined minerals). They found that the recovered powder particles were more porous, with particularly large voids in the center of each particle. These characteristics provide space for the cathode crystal. When lithium ions are squeezed into it, the cathode crystal can expand slightly, and this swing space makes the crystal not as easy to crack as the cathode made from scratch. Over time, this crack is a major cause of battery degradation.
More pores also mean more exposed surface areas where the chemical reactions necessary to charge the battery can occur - which is why Wang's recycled battery charges faster than its commercially manufactured equivalent. Wang said that the future goal may be to design all cathodes with this superior structure, not just those made of recycled materials.
Linda Gaines, a transportation analyst at Argonne National Laboratory and chief scientist at the recall center, said: "they can make cathodes that are as good or even better than the commercial materials we have been importing. (Gaines is not involved in this new study.) Such imports mainly come from China, which is a world leader in battery recycling. However, this situation means that materials must be shuffled globally before they can be recycled, which increases the carbon footprint of recycled batteries and weakens its temptation as a more sustainable development path. “
The method developed by Wang Yan's team has reduced a large part of international trade and transportation requirements, opening up a potential path for other countries to strengthen domestic battery recycling. At present, ascend elements (formerly battery resources) is expanding the scale of this process, which is a battery recycling company founded by Wang Yan.
