Transforming Aquatic Weed (Water Hyacinth) into High-Performance Flake-like Activated Carbon for Application in Lithium-Ion Batteries

Water hyacinth (WH), an invasive plant in freshwater bodies in tropical and subtropical regions, poses a severe threat to the aquatic environment, human health, and the livelihoods of people in the surrounding areas. This study presents a sustainable, easy-to-scale approach to valorize WH by converting its stem into high-performance activated carbon (ACs) for application in lithium-ion batteries. The process involves cleaning, chopping, drying, and carbonizing the stem, followed by chemical activation using KOH. The physicochemical properties revealed that ACs have a high surface area of 1600–2450 m2 g–1 with mesoporous structure, and have ordered graphitic domains as confirmed by XRD and Raman. The microstructure revealed a flake-like configuration of grains, as confirmed by FESEM. The activated carbons obtained using different mass ratios of KOH delivered specific capacities of 209–326 mAh g–1 at 0.2 mA cm–2 against lithium when tested in 2032 lithium-ion cells. The fabricated cells were cycled for more than 250 cycles with variable current densities ranging from 0.2 to 1.4 mA cm–2, exhibiting excellent rate capability, coulombic efficiency (>95%), and capacity retention (>70%). This study thus highlights a scalable, eco-friendly method to transform water hyacinth biomass into valuable carbon materials for energy storage, aligning with the global “Waste to Wealth for Energy” initiative.