Date of Award
2026
Document Type
Open Access Master's Thesis
Degree Name
Master of Science in Chemical Engineering (MS)
Administrative Home Department
Department of Chemical Engineering
Advisor 1
Lei Pan
Committee Member 1
Kulwinder Dhindsa
Committee Member 2
Timothy Eisele
Abstract
Direct recycling of lithium-ion battery cathodes has emerged as a promising alternative to conventional pyrometallurgical and hydrometallurgical recycling routes because it preserves the cathode crystal structure, reduces energy consumption, and minimizes chemical waste. However, aqueous processing steps commonly used during cathode recovery can induce lithium loss and structural degradation, particularly in nickel-rich layered oxide cathodes. Understanding and mitigating these degradation mechanisms is essential for developing scalable and sustainable direct recycling processes. This thesis presents an integrated investigation of water-induced degradation in layered NMC cathodes and explores strategies to mitigate lithium loss during aqueous processing. The first part of this work investigated the recovery of high-purity NMC811 cathode material from black mass using centrifugal gravity separation. Gravity separation effectively removed conductive carbon and polymer binder while preserving the layered crystal structure and particle morphology of the recovered cathode material. However, inductively coupled plasma optical emission spectroscopy (ICP-OES) revealed approximately 15% lithium loss in the recovered concentrate, indicating that chemical degradation occurred during upstream aqueous delamination rather than during physical separation. Motivated by this observation, the second part of the study systematically examined the composition-dependent susceptibility of NMC cathodes to water-induced delithiation and evaluated lithium-rich delamination media as a mitigation strategy. Results showed that lithium loss increased with nickel content, with NMC811 exhibiting approximately 18% lithium depletion compared to 6.8% for NMC622 and 4.0% for NMC532. X-ray diffraction analysis revealed increased Li/Ni cation mixing and lattice contraction following water exposure, while thermogravimetric analysis demonstrated reduced thermal stability and earlier oxygen release in water-treated materials. In contrast, lithium-rich delamination media effectively suppressed lithium loss, preserved structural integrity, and maintained thermal stability across all cathode compositions investigated. Overall, this work demonstrates that while gravity separation is an effective approach for recovering high-purity cathode active materials, aqueous processing can induce significant composition-dependent lithium loss that becomes more severe with increasing nickel content. The implementation of lithium-rich delamination media provides a practical and effective strategy for mitigating water-induced degradation and preserving cathode quality during direct recycling.
Recommended Citation
Ozah, Blessing N., "DIRECT RECYCLING OF NMC CATHODES IN LITHIUM-ION BATTERY: WATER-INDUCED DELITHIATION, MITIGATION STRATEGIES, AND PROCESS DEVELOPMENT", Open Access Master's Thesis, Michigan Technological University, 2026.
https://digitalcommons.mtu.edu/etdr/2192