Sustainable Recovery of Graphite from Dead Li-Ion Cells as a Next-Generation Dual Anion Intercalated Cathode for Zn-Ion Cells

With the increasing use of lithium-ion batteries (LIBs) in modern electronics and renewable energy storage systems, the need for sustainable management of battery waste has become crucial. Although graphite accounts for approximately 12–21 wt % of a typical LIB, it is often undervalued and discarded, even though it is classified as a critical raw material and contributes to CO2 emissions during production. In this study, graphite was recovered from spent lithium-iron-phosphate (LFP) cells after cell discharge via alkaline electrolysis with NaOH and manual disassembly. The recovered graphite was subjected to probe sonication under solvent co-diffusion for various durations (5, 10, 30, and 60 min) to study the effect of structural modification on its electrochemical performance. Physical characterizations, including XRD, Raman spectroscopy, TEM, and FE-SEM, were performed on the sonicated graphite samples to analyze the structural changes induced by sonication and solvent co-intercalation. These modified materials were employed as cathodes in Zn-Gr coin cells, with zinc foil serving as the anode. The cells were tested using ZnSO4 and ZnSO4+ KCl mixed electrolytes to understand anion intercalation during cell operation. Comparative electrochemical analysis revealed that 30 min sonicated graphite electrode based cell exhibited better performance in ZnSO4 + KCl electrolyte, delivering a higher reversible charge capacity. Excessive sonication degraded the graphitic layers, thereby adversely affecting cell performance. The Zn∥ZnSO4 + KCl∥Ex-Gr30 exhibits excellent capacity retention, retaining above 99% even after 300 cycles, achieving 100% coulombic efficiency. This study provides a sustainable, low-cost procedure for recovering graphite from spent LIBs. It demonstrates its viability as a cathode in Zn-graphite cells, a newly developed family of aqueous energy storage devices with improved environmental sustainability and safety.