Development of bio-graphite from waste coffee grounds via catalytic graphitization for sustainable Lithium ion batteries anodes

This study presents a sustainable approach to synthesizing carbon-based anode materials for lithium-ion batteries (LIBs) using waste coffee grounds. Two types of carbon were prepared: disordered hard carbon (C-HC) via direct carbonization, and highly crystalline graphite-like carbon (C-AG) through iron-catalyzed graphitization at 1500 °C. Structural analysis using X-ray diffraction (XRD) and Raman spectroscopy confirmed the successful transformation from disordered to graphitic carbon. The interlayer spacing decreased from 3.52 Å (C-HC) to 3.36 Å (C-AG), and the I_D/I_G ratio dropped from 1.20 to 0.05, indicating enhanced crystallinity and reduced defect density. C-AG exhibited a high reversible capacity of 286 mAh g⁻¹ and an initial Coulombic efficiency of 85.5 %, attributed to lithium intercalation through the staging mechanism in well-aligned graphene layers. In contrast, C-HC showed a lower capacity of 156 mAh g⁻¹ and an efficiency of 73.9 %, with lithium mainly stored at surface defects and disordered regions. Despite its lower capacity, C-HC demonstrated superior rate performance, retaining 58.0 % of its capacity at 1000 mA g⁻¹, compared to 18.6 % for C-AG. These results reveal a trade-off between structural crystallinity and rate capability, providing insights into the structure-property relationship in biomass-derived carbon anodes. This work demonstrates the feasibility of catalytic graphitization as a pathway to convert biowaste into high-performance graphite materials for energy storage applications.