How to Efficiently Recycle Li-ion Batteries

A research team at Rice University led by James Tour, the T.T. and W.F. Chao Professor of Chemistry and Professor of Materials Science and Nanoengineering, is tackling the environmental issue of efficiently recycling Li-ion batteries amid their increasing use.

The team has pioneered a new method to extract purified active materials from battery waste as detailed recently in the journal Nature Communications. Their findings have the potential to facilitate the effective separation and recycling of valuable battery materials at a minimal fee, contributing to a greener production of electric vehicles (EVs).

“With the surge in battery use, particularly in EVs, the need for developing sustainable recycling methods is pressing,” Tour said.

Conventional recycling techniques typically involve breaking down battery materials into their elemental forms through energy-intensive thermal or chemical processes that are costly and have significant environmental impacts.

The team proposed that magnetic properties could facilitate the separation and purification of spent battery materials.

Their innovation uses a method known as solvent-free flash Joule heating (FJH). This technique devised by Tour involves passing a current through a moderately resistive material to rapidly heat and transform it into other substances.

Using FJH, the researchers heated battery waste to 2,500 Kelvin within seconds, creating unique features with magnetic shells and stable core structures. The magnetic separation allowed for efficient purification.

During the process, the cobalt-based battery cathodes — typically used in EVs and associated with high financial, environmental, and social costs — unexpectedly showed magnetism in the outer spinel cobalt oxide layers, allowing for easy separation.

The researchers’ approach resulted in a high battery metal recovery yield of 98 percent with the value of battery structure maintained.

“Notably, the metal impurities were significantly reduced after separation while preserving the structure and functionality of the materials,” Tour said. “The bulk structure of battery materials remains stable and is ready to be reconstituted into new cathodes.”

Here is an exclusive Tech Briefs interview with Co-Lead Author Weiyin Chen, a graduate student.

Tech Briefs: What was the biggest technical challenge you faced while developing FJH? Biggest technical challenge while performing this work?

Chen: The biggest challenge while developing FJH was designing and testing the reaction setup. This task demands a strong understanding of electrical circuits, which I acquired through the guidance of my colleagues, Carter Kittrell and Lucas Eddy. Achieving precise control over temperature and duration during the FJH process is crucial for its successful implementation.

The biggest challenge in this work has been controlling the formation of outer shells for magnetic separation. Unexpectedly, we discovered that the outer spinel cobalt oxide layers exhibited magnetism in the early stages of the project. This led us to realize that magnetic properties could be effectively utilized to separate cobalt-based cathode active materials from non-active additives. During the FJH process, lower temperatures resulted in incomplete conversion of the outer shell to the magnetic phase, while higher temperatures resulted in overreaction. By adjusting the FJH parameters, we achieved precise control over the magnetic shell thickness (~2 nm) while maintaining the stability of the bulk structure.

Tech Briefs: What are your next steps? Any plans for further research/work/etc.?

Chen: We have filed a patent for this innovative technique and are now collaborating with partners to validate the approach using real spent batteries at the kilogram scale.

Since new generations of cathodes are used in commercial devices after every few years, we are working on the modification of the spent cathode materials during the FJH process to enhance the electrochemical properties. Therefore, we can achieve upcycling, which is beyond the recycling we have achieved.

Tech Briefs: Do you have any advice for researchers aiming to bring their ideas to fruition, broadly speaking?

Chen: I encourage engineers and researchers to think in an interdisciplinary manner and be ready to learn and innovate. While magnetism is a well-known property of iron, cobalt, nickel, and their oxides, it is often overlooked in battery research due to the absence of the proper structure. In our work, we discovered that the selective conversion of layered cobalt-based cathodes to spinel structures introduced magnetism. This straightforward physical phenomenon allows us to effectively separate and purify cathodes. Our group developed the FJH process and constructed most of the equipment. When we have an idea, we quickly acquire the necessary skills and build something new.

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