Silicon-based anode materials have emerged as leading candidates for next-generation lithium-ion batteries due to their exceptionally high theoretical capacity (up to 4200 mAh/g), low cost, and natural abundance. However, their practical application is hindered by substantial volume expansion (~300%) during lithiation, which leads to mechanical degradation, loss of electrical contact, and rapid capacity fade. To mitigate these issues, silicon-carbon (Si/C) composite anodes have been developed, combining the high capacity of silicon with the mechanical buffering and excellent conductivity of carbon. Despite their promise, the fundamental atomic-scale mechanisms governing lithium diffusion within these composites remain poorly understood, particularly regarding how different structural configurations influence ion transport.
In this study, density functional theory (DFT) combined with ab initio molecular dynamics (AIMD) simulations are employed to investigate lithium diffusion behavior in two representative Si/C composite structures: a mixture mode and a core-shell mode. The mixture mode features randomly dispersed Si and amorphous carbon (a-C) particles, allowing lithium ions to diffuse into either phase freely. In contrast, the core-shell mode consists of Si cores encapsulated by a carbon shell, forcing lithium ions to traverse the carbon layer before reaching the silicon interior. This distinction enables a comparative analysis of how microstructure dictates ion mobility.
The results reveal that the presence of carbon significantly enhances lithium diffusion in silicon, increasing the diffusion coefficient from 7.75 × 10⁻⁵ cm²/s in pure crystalline silicon to 2.097 × 10⁻⁴ cm²/s in the mixture mode—representing a 170% improvement. This enhancement is attributed to the superior electronic and ionic conductivity of carbon, which facilitates charge transfer and provides favorable pathways for lithium migration.PIK3R1 Antibody Autophagy In the mixture mode, the effect is more pronounced due to the availability of multiple diffusion routes, whereas in the core-shell mode, performance becomes highly dependent on the atomic architecture of the carbon layer. Notably, when the carbon layer develops voids or layered structures aligned with the diffusion direction (as observed in Si/C(3)), lithium diffusivity increases significantly. Conversely, layers with perpendicular or disordered structures (e.g., Si/C(4)) act as barriers, reducing overall ion mobility.BTK Antibody Cancer
Structural evolution during lithiation was analyzed using radial distribution functions (RDFs), showing that both Si/Si and Li/Li bonds break while new Si/Li bonds form, indicating a transition from crystalline to amorphous phases. The formation of interfacial Si/C bonds reduces the number of Si/Si bonds, further influencing local atomic environments.PMID:34657161 Volume expansion calculations confirm that thicker carbon layers reduce the extent of silicon expansion, especially in the core-shell configuration, where constraints are stronger. This suggests that core-shell designs offer better mechanical stability under cycling stress.
Mean square displacement (MSD) analysis confirms that lithium diffusion is faster in the mixture mode, but the core-shell structure allows for tunable diffusion through engineered carbon architectures. These findings provide critical insight into the design principles for advanced Si/C anodes, emphasizing that optimal performance requires not only compositional control but also precise architectural engineering at the nanoscale. By understanding how carbon morphology influences lithium transport, researchers can develop smarter, more durable, and higher-energy-density battery systems for future energy storage applications.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com