Performance Analysis of Regenerated Lithium-Ion Batteries in Their Second-Life
Authors: Ramamurthy Jayanth , Thelen Adam , Ojha Mihir , Navidi Sina , Alaei Shervin , Jiao Weimin , Hu Chao , Kingston Todd A. , Pint Cary L. 
Published: December 2024

The electric vehicle market's rapid growth is projected to yield 3 million discarded lithium-ion (Li-ion) batteries by 2040, equating to 125 GWh of energy [1]. Transitioning to a circular economy is essential to address this environmental challenge and reduce reliance on vulnerable supply chains. While lead-acid batteries are efficiently recycled, the lithium-ion industry lags in circular practices. Conventional recycling focuses on valuable element extraction, requiring reprocessing for electrode fabrication. Direct recycling preserves the cathode but damages the microstructure, demanding additional processing and heightening environmental strain [2,3]. In this study we perform a comprehensive study of regenerated batteries using an approach more consistent with a circular economy framework where a separator is layered with benign lithium material that can be activated on-demand to rejuvenate lithium inventory in a battery without electrode material degradation [4]. In this study, a series of commercial Li-ion LFP-Graphite cells were cycled in their first-life to 80% of the nominal capacity under different stress levels, where stress is a composite measure of depth of discharge and charge and discharge rate. These used batteries are then directly rejuvenated by electrochemically activating a coating of lithium oxalate material on the separator until the lithium inventory is fully replenished. The resulting (60+) rejuvenated LFP-graphite cells were subsequently cycled through a second lifetime under different stress conditions to evaluate and understand the performance of the cells in their second-life and the overall influence of first-life cycling conditions on second-life performance outcomes. Our findings support that whereas some conditions lead to almost equivalent cycling durations for the second-life cells, the key variable that dictates the second life performance is the damage accumulation and corresponding increased cell resistance occurring during the first-life. Specifically, cells cycled under higher first-life stress conditions, such as at higher rates, gave more favourable second-life performance than cells cycled under lower first-life stress conditions. The results presented provide detailed insights into the technological approach, challenges, and opportunities for the regeneration of used Li-ion batteries for second-life applications in a manner consistent with circular economy framework.

Acknowledgements

This work was supported by the funding received from Iowa Energy Center [Grant No. 21-IEC-007]

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