Direct Recycling of Spent Lithium Iron Phosphate via Residual Carbon Reutilization

다국어 초록 (Multilingual Abstract)

The rapid expansion of lithium-ion batteries （LIBs） for energy storage and electric vehicles has intensified interest in LiFePO4 （LFP） cathodes due to their safety, long cycle life, and cost-effectiveness. As end-of-life LFP batteries accumulate, efficient recycling strategies are urgently needed. Unlike Ni/Co-based cathodes, the relatively low economic value of LFP makes direct recycling particularly attractive. However, the role of residual carbon species from coatings, binders, and additives during regeneration remains poorly understood. In this study, it is demonstrated that residual carbon can be reutilized as an intrinsic carbon source to reconstruct conductive networks in regenerated LFP, eliminating the need for complete carbon removal. Under optimized conditions, the regenerated LFP achieves an initial discharge capacity of 99.1% relative to commercial LFP and exhibits superior rate capability. Raman and TEM analyses confirm that the reorganized carbon forms a well-graphitized, uniform coating layer that enhances electron transport. This simplified approach offers a sustainable and cost-effective recycling route by leveraging residual carbon impurities. Notably, while reutilized carbon improves rate performance, complete carbon removal yields superior long-term cycling stability, suggesting that the optimal recycling pathway should be selected according to the target application.

목차 (Table of Contents)

• Ⅰ. Introduction 1
• Ⅱ. Experimental 7
• 2.1 Sample preparation 7
• 2.2 Experimental procedure 9
• 2.3 Carbon removal 10
• 2.4 Physicochemical characterization 11
• 2.5 Electrochemical measurements 12
• III. Results and discussion 14
• 3.1 Morphology and crystallinity analysis of samples 14
• 3.1.1 Morphology, structure, and carbon content analysis of regenerated LFP via route A 22
• 3.1.2 Electrochemical analysis of regenerated LFP via route A 28
• 3.2 Comparison with regenerated LFP via route B and commercial LFP 33
• IV. Conclusions 51
• V. References 54