Enhancing and evaluating surface quality of Si/C composites via dynamic CVD method utilizing mixed gaseous carbon sources C2H2&C3H8

While chemical vapor deposition (CVD) is frequently utilized to carbon-coat Si-based materials, comprehensive investigations regarding the quality of the formed carbon layers remain scarce in literature. In this paper, C2H2, C3H8 and their mixture are used as gas carbon sources to coat Si/C composites, and four indexes are summarized to evaluate their surface quality, including specific surface area, surface silicon content, density, and formation efficiency. The findings revealed that the surface quality of the material prepared by the mixture was consistently superior, exhibiting the lowest carbon augmentation. This characteristic ensures a high initial Coulombic efficiency and high specific capacity. This superiority arises from the combined benefits of the high diffusion coefficient of the small C13H12 molecules produced by C2H2, which effectively infiltrate and fill small defects, and the low diffusion coefficient of the large (C6H5)3CH molecules produced by C3H8, leading to agglomeration and effective coverage of large defects. Furthermore, the sample C2H2&C3H8@Si/C-2 shows a good cycling with a capacity retention rate of 81 % over 500 cycles at 25 °C in cylindrical batteries with ternary cathode. The assessment parameters and techniques used to evaluate the surface quality and the prepared samples offer valuable guidance for the commercial application of Si/C materials.