One-Pot Synthesis of an FeS@GQDs Composite for Lithium Storage with Coal Tar Pitch as ″Natural GQDs″

Graphene quantum dots (GQDs), a newly emerging zero-dimensional material, have achieved widespread interest in energy storage applications. However, the complicated preparation processes of GQDs involving harsh reagents/conditions, cumbersome purification procedures, or costly precursors hinder their practical use. Herein, we reveal a low-cost and eco-friendly solvothermal method to obtain an FeS@GQDs composite, with coal tar pitch (CTP) as ″natural GQDs″. When evaluated as an anode material in lithium-ion batteries (LIBs), this composite delivers an outstanding reversible capacity of 718.7 mAh g^–1 over 200 cycles at 100 mA g^–1; as comparison, the reversible capacity of pure FeS is only 16.3 mAh g^–1 in the same situation. Furthermore, the FeS@GQDs composite shows much better rate performance and higher initial Coulombic efficiency than pure FeS. These prominent electrochemical properties of the FeS@GQDs composite profit from the successful coupling between FeS and GQDs by forming C–S–C, which provides a large specific surface area and well-developed porosity, leading to improved electrical conductivity and enhanced structure stability. In terms of energy storage, this approach is a potential way to prepare GQDs-based composites on a large scale without the expensive precursors, harsh reagents, as well as complex preparation conditions.