From Lychee Seeds to Hierarchical Fe3O4/Carbon Composite Anodes for Lithium-Ion Batteries: A High Additional Value Conversion-Based Self-Assembly Strategy

As an abundant agricultural process residue, lychee seeds are generally disposed of as waste because their practical utilization has been limited to a narrow range of low-value items. It is of great interest and highly desirable to explore a new conversion way from waste lychee seeds to high-value materials. Herein, natural polyphenols are directly extracted from waste lychee seeds and utilized as precursors of a state-of-the-art Fe3O4/carbon composite for high-performance lithium-ion batteries. The polyphenols are first extracted from waste lychee seeds and then coordinated with metal ions to assemble an inorganic–organic hybrid coated on a carbon nanotube substrate. After high-temperature carbonization, metal oxide/carbon composites are obtained. The as-prepared Fe3O4/carbon composite possesses a unique hierarchical structure including a distinctively heterogeneous carbonaceous skeleton comprised of a graphitic core and an amorphous shell and an intimate binding at the Fe3O4/carbon interface. Benefiting from the as-constructed beneficial structure, the hierarchical CNT@Fe3O4/C composite, selected as a proof-of-concept product, shows impressive electrochemical performances when used as an advanced anode material of lithium-ion batteries. This work provides a promising sustainable way for converting waste lychee seeds to high additional value materials and as well sheds light on the realization of advanced energy-storage devices besides lithium-ion batteries.