▎ 摘　　要

Two-dimensional layered marcasite (FeS2) is a promising anode electrode material for lithium-ion batteries (LIBs) due to its high specific capacity, excellent structure, and variable chemical valence state. However, the volume changes dramatically during the discharge/charging process, resulting in a rapid decrease in capacity and poor electrochemical performance. Introducing a sulfur vacancy structure into the marcasite (FeS2) anode would be a great help for its electron fast transport, thereby promoting the electrochemical performance of LIBs. Herein, guided by density functional theory (DFT) calculations, these problems were alleviated through FeS2 nanoparticles that were synthesized using the biomolecule L-cysteine as the sulfur source along with the reduction process of GO to rGO sheets by NaBH4, forming an intriguing S-vacancy 3D FeS2/rGO (FSG) composite. S-vacancy FeS2 nanoparticles, with an average size of 100 nm, were formed on the surface of rGO sheets homogeneously. As an anode material for LIBs, the FSG electrode delivers a higher rate capability of 410 mA h g???1 at 5 C (1 C = 900 mA g???1) and a better cyclability of 826 mA h g???1 after 150 cycles at 0.2 C compared to pure FeS2. By DFT calculations and systematic characterization, we show that S-vacancies can modulate the surface electronic structure, thereby enhancing the binding energy and charge-transfer rate of FSG composites. We found that the superior performance of FSG anode materials is due to their prominent 3-D and S-vacancy structures. The FSG composite materials for charge storage promote the reversibility of the conversion reaction. The Li???S bonds break and form ceaselessly, which is why the crystallographic structure is destructed. The results demonstrate that a simple feasible method to construct composites with an S-vacancy structure and high-performance anodes for LIBs could be designed.