title: Regenerative Repair of Anode from Spent Lithium-ion Batteries Towards Sustainable Recycling
Creators: name: Tian, Honghong
Publisher: name: UNSPECIFIED
Year: 2025

description: This thesis focuses on recovering and regenerating of graphitic anode materials from spent lithium-ion batteries (LIBs), providing an in-depth exploration of material-related challenges in this field and proposing new path for a sustainable and profitable reuse of recovered materials. The first section provides a comprehensive overview of the background and current status of recycling spent LIBs. In the second section, emphasis is placed on the recovery and reuse of spent graphite from end-of-life lithium-ion batteries (EoL LIBs) from old laptop, Samsung SDI cells manufactured in January 2007. The state of health (SOH) of all 18650 cylindrical cells is below 80%. Through a comprehensive analysis of the failure mechanisms of spent graphite in EoL LIBs, effective recovery methods combining pyrometallurgy and hydrometallurgy are proposed. The regenerated graphite exhibits outstanding electrochemical performance in both capacity and rate performance as compared to the literature. Although the performance of reconstituted graphite is comparable to that of commercial graphite in all other respects, its low initial coulombic efficiency (RG1 79.81%, RG2 80.06%) somehow limits its broader applicability. This may necessitate prelithiation, a solution that we plan to explore in future research. 
The subsequent section explores the possibilities of secondary utilization of spent graphite, particularly focusing on the preparation of contaminant-free, free-standing porous reduced graphene oxide (rGO) film from recycled graphite. Spent graphite was obtained from another Lenovo pack, with the cells manufactured by Great Power on November 2, 2017. All cells exhibit SOH from 61.1% to 83.2%. These cells are collectively referred to as spent graphite, with an average SOH of 75.2%. Within this framework, the synthesis of graphene oxide hosted Li foil was realized through a capillary adsorption of molten lithium, which effectively facilitates prelithiation in both lithium cobalt oxide||commercial graphite (LCO||CG) and lithium nickel-rich cobalt aluminum oxide||commercial graphite blended with nano-silicon (NCA622||CG-Si) full cells. In-situ synchrotron x-ray diffraction technique was used to monitor the crystallographic parameters in real time, thereby revealing the effective mitigation of lattice parameters (a, b, and c) and volume reduction in nickel-rich NCA after pre-lithiation. This straightforward strategy provides a scalable solution for pre-lithiation and facilitates the recycling of waste graphite, thus achieving dual objectives with a single effort.
Additionally, rGO prepared from spent graphite can function as a carbon coating, enhancing the adhesion of aluminum foil and active cathode material. This addresses challenges such as low conductivity of lithium iron phosphate, poor bonding with binders, and powder shedding during cycling, ultimately reducing the dynamic internal resistance of LIBs. Furthermore, the coating provides basis for a reevaluation of corrosion studies for lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte. LiTFSI salt shows superior stability towards hydrolysis and a higher conductivity in ethylene carbonate/ethyl methyl carbonate (EC/EMC) mixture solvents compared to lithium hexafluorophosphate. It demonstrates a higher thermal stability and Li ion transference number than lithium hexafluorophosphate. However, a debate persists regarding LiTFSI´s ability to passivate aluminum (cathode current collector) with corrosion significantly impacting battery performance. rGO coating Aluminum foil effectively prevents direct contact between Al foil and LiTFSI electrolyte, thereby reducing the risk of Al foil corrosion.
Overall, this thesis provides a deep understanding of the complexities surrounding spent LIBs recycling and reveals practical pathways for the recovery and reuse of valuable materials, contributing to the sustainable management of lithium-ion battery waste.