The impact of carbon material microstructure on li-ion storage behaviors of Si in Si/C anodes

•The ant's nest-like Si/C composite anode enhances cyclic stability in micron-sized Si/C composites under high mass loading.•Different carbon materials significantly affect the independent charge–discharge behavior of Si within Si/C composites.•In-situ XRD reveals transitions of Si between crystalline and amorphous states during charge/discharge in Si/C anodes.•The use of hard carbon in Si/C composite anodes leads to improved conversion depth of amorphous Si-Li alloys. Due to the demand for high mass loading in industrial application, micron-sized Si/C composites are preferred compared to nanoparticles. Utilizing Al-Si alloy as the raw material, an ant's nest-like porous Si/C composite material was successfully constructed through carbon coating and acid etching techniques, leading to an improvement in the cyclic stability of micron-sized Si/C composites under high mass loading. Furthermore, notable observations were made regarding the influence of carbon material type on the independent charge–discharge behavior of Si within the Si/C composite material, especially during the plateau region of Si-Li conversion processes. In-situ XRD test revealed transitions of Si between crystalline and amorphous states in the Si/C composite material during charge and discharge processes. Additionally, in Si/C composite materials fabricated using hard carbon, the increased lithium-ion transport rate attributed to the highly disordered structure of hard carbon promotes the acquisition of charges during delithiation process. As a result, this decelerates the lithium de-alloying process in Si-Li alloys, leading to an improved conversion depth of amorphous Si-Li alloys and a reduction in electrode capacity decay. This study provides valuable insights into Si conversion processes within Si/C composite materials and offers rational strategies for future material optimization.