Preparation and properties of polycrystalline silicon seed layers on graphite substrate

Polycrystalline silicon（poly-Si） seed layers were fabricated on graphite substrates by magnetron sputtering. It was found that the substrate temperature in the process of magnetron sputtering had an important effect on the crystalline quality,and 700℃was the critical temperature in the formation of Si（220） preferred orientation. When the substrate temperature is higher than 700℃,the peak intensity of X-ray diffraction（XRD） from Si（220） increases distinctly with the increasing of substrate temperature.Moreover,the XRD measurements indicate that the structural property and crystalline quality of poly-Si seed layers are determined by the rapid thermal annealing （RTA） temperatures and time.Specifically,a higher annealing temperature and a longer annealing time could enhance the Si（220） preferred orientation of poly-Si seed layers.

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 SiOx 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 dischargespecific 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 1.5A·g^(-1).Notably,full lithium-ion batteries with a Si/G@voids@C anode and LiFePO_4 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.