As the production of electric vehicles accelerates on a global scale, an inherent consequence will be the continuous increase in the number of decommissioned lithium-ion batteries. Unlike traditional lead-acid car batteries, these batteries are difficult to handle.

A new study led by Cornell University has identified several keys to sustainable management of the influx, focusing on battery chemistry, secondary life applications and recycling.

"How to deal with all these retired electric vehicle batteries will be a huge problem," said Fengqi You, professor of energy systems engineering Roxanne E. and Michael J. Zak, who uses advanced models to study environmental and economic trade-offs. How batteries are manufactured, used and recycled.

The study published on Science Advances on November 5 details life cycle analysis, which considers multiple options for battery materials and technologies.

From the beginning of the battery's life cycle, when its raw materials are mined from the earth, economics determines how to make the battery.

"Lithium-ion batteries are now designed for performance, not for recycling or secondary use," You said, noting that electric car batteries usually last 5 to 12 years before they lose the energy needed to power the car. capacity. "Currently there is little discussion about these environmental dimensions of improving battery design for recycling or reuse."

One finding is that the chemistry of the battery affects its overall environmental impact. For example, cobalt is a common battery material, which consumes a lot of energy when mined and causes damage to the environment. Substituting nickel for cobalt can alleviate these concerns, but most life cycle scenarios show that there are trade-offs.

"The presence of cobalt in the battery cathode, even if the content is relatively small, will bring a less oxidizing environment for other components, extend the life of the battery, and increase the options for second use and material recycling," Joseph Lin Said Lynden Archer. Dean of the Silbert School of Engineering and co-author of the study.

But Archer says that the cost of cobalt-and its association with exploitative child labor-has resulted in this material "traditionally considered to be undesirable in the low-cost batteries needed for the'electricity of everything' in the future."

The analysis also found that if electric car batteries can be reused before recycling, their overall carbon footprint can be reduced by up to 17%. One option for battery reuse is power stations that store wind and solar energy. The demand for such energy storage continues to grow, and retired batteries with reduced energy capacity can be used. As the share of renewable energy in the grid increases, the carbon footprint of re-used batteries is reduced by about a quarter.

Most recycling facilities today have difficulty decomposing highly fortified car batteries and recycling the raw materials. Tao Yanqiu, a co-author of the study and a doctoral student, said that policymakers should consider how to incentivize recycling technologies and optimize the sustainability of batteries.

"In our research, we used commonly used graphite as the negative electrode active material. This material is difficult to recycle and emits carbon dioxide when burned," Tao said. "If policy makers can promote graphite separation or emerging recycling methods, it will reduce the impact on the environment."

Christopher Rahn, associate dean of innovation at the Pennsylvania State University School of Engineering, is also a co-author of the study.

Syl Kacapyr is the Public Relations and Content Manager of the School of Engineering.

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