A Rapid Low-Temperature Method for Direct Recycling of Lithium-Ion Battery Cathodes
Authors: Lee Jiyoung , Lopez Jeffrey 
Published: August 2024

Batteries provide a promising pathway for transitioning from a society heavily reliant on fossil fuels to one that supports sustainable energy generation and transportation. However, the current production of lithium-ion batteries (LIBs) pose a sustainability challenge due to their dependence on energy-intensive and critical mineral-dependent cathode manufacturing which results in high greenhouse gas emissions and global supply chain risk for critical minerals.[1] Moreover, a significant number of retired batteries, with a typical service life of 5–10 years, end up in landfills or oceans, exacerbating environmental concerns.[2] In this respect, cathode recycling has emerged as a potential solution to address the sustainability issues of LIBs, including critical metal availability, battery waste, and the carbon footprint of the LIB manufacturing process. However, current cathode recycling technologies, primarily based on pyrometallurgy and hydrometallurgy methods, are limited to recovering raw metals that necessitate the re-synthesis of cathode materials, leading to significant greenhouse gas emissions and secondary waste streams.[3] As an alternative, direct cathode recycling that utilizes regenerated spent cathode materials in the manufacturing of new batteries, has garnered a great deal of attention.[4] This method eliminates the need for additional purification or resynthesis processes, offering high economic return and environmental benefits. For direct recycling, it is important to replenish consumed Li and restore the structure and chemical state of transition metal atoms (e.g., Ni, Co, and Mn) in cathodes. However, current direct recycling methods, such as solid-state sintering, hydrothermal treatment, and the molten-salt method, still necessitate high energy input due to the requirement for multistep processes and/or thermal annealing at elevated temperatures and pressures for prolonged durations.[1,4] Therefore, it remains a challenge to develop a facile and rapid ambient condition (e.g., 25oC at 1 bar) direct recycling method.

Herein, we propose a rapid room-temperature recycling method for spent LiNi0.5Mn0.3Co2O2 (NMC) cathodes, utilizing a Li-rich solvated electron solution. The low reduction potential of the solution accelerates the regeneration kinetics of spent NMC, allowing a complete recycling reaction in just minutes with no residue remaining for additional active material washing. This direct recycling method results in a regenerated NMC cathode that closely mirrors the crystal structure, composition, and chemical states of pristine materials, and delivers energy capacity and cycle life comparable to the original. Notably, the concentration of Li ions and free electrons in the solution can be quantified, enabling precise restoration of depleted Li and lost capacity with near-perfect stoichiometry, which thus achieves a long-standing goal in the recycling process. Altogether, this work paves the way to a more energy-efficient and feasible direct recycling process for spent LIBs.

References

[1] P. Xu, D. H. Tan, B. Jiao, H. Gao, X. Yu, and Z. Chen, Adv. Funct. Mater., 2213168 (2023).

[2] T. Yang, D. Luo, A. Yu, and Z. Chen, Adv. Mat., 2203218 (2023).

[3] J. Lin, X. Zhang, E. Fan, R. Chen, F. Wu, and L. Li, Energy Environ. Sci., 16 (3), 745-791 (2023).

[4] X. Yu, W. Li, V. Gupta, H. Gao, D. Tran, S. Sarwar, and Z. Chen, Global chall., 6 (12), 2200099 (2022).