Study on the Interface Characteristics in Si-C Composite Anode Materials

Due to the volume expansion during the lithium intercalation and deintercalation process, the carbon layer of silicon@carbon gradually falls off, exhibiting low capacity or poor cycling stability. The role of Si-C bonding and interface characteristics in Si@C composite materials on material cycling stability is still unclear. Based on the first principle method, the Si-C bonding and lithium intercalation and deintercalation properties of two Si-C alloys with different space group were studied. The results show that the lithium intecalation formation energy of SiC-1 is only 0.158 eV, much lower than the 0.6537 eV of SiC-2. The volume expansion ratio after lithium intercalation is only 38.9064%, which is basically equivalent to graphite. The bonding mode between Li-Si and Li-C determines whether lithium ions can be reversibly released. The bonding strength of Si-C bonds plays a stabilizing role in the lithium intercalation and deintercalation process, which is beneficial for reducing the volume expansion ratio of lithium intercalation.This work has certain guiding significance for the research of silicon carbon anode materials with high capacity and long cycilc life.