Characterizing Structure and Electrochemical Properties of Advanced Si/C Anode Materials

Abstract The increasing commercial interest in silicon-based anode materials for Li-ion batteries has driven the development of advanced structural designs to address the challenges of poor cycling stability. This study examines the structure of commercial silicon/carbon composite materials where nano silicon clusters are embedded within a carbon matrix. The size of silicon and carbon nanoclusters is determined by comparing experimental X-ray diffraction patterns with calculated patterns based on the Debye scattering formalism, as implemented in the program DEBUSSY. The size, morphology, surface areas, and porosities of the carbon matrix and composite are measured, along with their resulting tap and true densities. Their electrochemical performance is also assessed to determine operando stack growth and cycling stability. By restricting silicon cluster sizes to sub-nanometer dimensions within a porous carbon matrix, a low specific surface area can be achieved along with a specific capacity of ~2000 mAh/g. Additionally, this approach results in high tap density values close to 1 g/cc, reduces reversible stack growth, and minimizes irreversible stack growth caused by particle cracking during volume changes, thereby significantly enhancing the overall stability and performance of the anode material.