Brewing better batteries: transforming brewed coffee powder into lithium-ion anodes

Renewable and sustainable biomass materials were increasingly explored for diverse emerging applications. Waste from brewed coffee powder was utilized as a sustainable carbon precursor to synthesize a porous biochar-based anode material for lithium-ion batteries. A rapid route was developed to transform brewed coffee powder waste into hierarchical micro–mesoporous activated carbon. The material was prepared by impregnation with 6 M potassium hydroxide, followed by a short 30 min hot-tube thermal evaporation activation treatment at 600–800 °C. The activation temperature was varied to tune the porosity and defect structure of the resulting carbon materials and to evaluate their suitability as anode materials for lithium-ion batteries. The structural and physicochemical properties of the resulting porous carbon materials were characterized using field-emission scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller surface area analysis. Among the samples prepared at activation temperatures of 600, 700 and 800 °C, the electrode activated at 700 °C exhibited the most favourable overall electrochemical performance. At 700 °C, the activated carbon achieved a high specific surface area of 1274.92 m 2 g −1 , with micropores contributing 72.28% of the total pore volume, which provided a porous structure favourable for electrolyte access and lithium-ion transport. It delivered an initial discharge capacity of 638.83 mAh g −1 at a current density of 100 mA g −1 , with a first-cycle coulombic efficiency of 65.87%, indicating substantial reversible lithium-ion storage capability. Electrochemical impedance spectroscopy revealed a charge-transfer resistance of 31.3 Ω, indicating favourable interfacial charge-transfer behaviour. The combination of a high micropore fraction and interconnected mesopores contributed to lithium-ion storage and transport within the porous carbon structure. The findings demonstrated the feasibility of valorizing brewed coffee waste into porous carbon anode materials with promising electrochemical performance for lithium-ion batteries.