Scalable synthesis of N-doped Si/G@voids@C with porous structures for high-performance anode of lithium-ion batteries

The co-utilization of silicon (Si) and graphite (G) has been considered as the preferred strategy to achieve high energy density anode materials, but the effective synergistic integration of Si and graphite is still a challenge and it is necessary to find a scheme to accommodate the large-scale production of Si/graphite anodes. In this work, silicon cutting waste from the photovoltaic industry was used as raw material, mixed with graphite, pitch, and polyvinylpyrrolidone, and subjected to high-energy ball milling. The mixture was then heated in an Ar atmosphere for the carbon coating, and the resulting Si/graphite/carbon (Si/G/C) composite was etched to remove the thicker SiO_x layer formed on the Si surface to allow the pores between the Si and the carbon matrix to obtain Si@voids/G@C. Benefiting from the integrated structural design and the significantly enhanced electronic conductivity, the Si/G@voids@C composite exhibited the first discharge-specific capacity of 2530 mAh·g⁻¹ with an initial coulombic efficiency (ICE) of 86.7%, and the remaining capacity exceeded 1000 mAh·g⁻¹ after 550 cycles at 1.5 A·g⁻¹. Notably, full lithium-ion batteries with a Si/G@voids@C anode and LiFePO₄ cathode delivered a stable capacity of 140 mAh·g⁻¹. The synthesis method is facile and cost-effective, providing an integration strategy for Si and G with a potential scheme for large-scale commercial applications.