Ab initio study of lithium diffusion at a layered carbon/amorphous silicon interface

Abstract

Silicon–carbon composites are widely investigated as anode materials for lithium-ion batteries because they offer improved electrochemical performance compared to the respective pristine elements. In this study, we comprehensively examine Li diffusion in model interface systems composed of γ-graphdiyne and amorphous silicon using ab initio molecular dynamics simulations and nudged elastic band calculations. We analyze the structure–property relationships between the Li diffusion coefficient – which is found to be one to two orders of magnitude higher in γ-graphdiyne than in amorphous Si – and the local environment and charge state of Li in both materials. Migration of lithium across the silicon–carbon interface exhibits only moderate energy barriers and therefore does not limit the overall diffusion kinetics of the composite; instead, bulk amorphous Si constitutes the primary kinetic bottleneck. We conclude that nanostructure design should prioritize controlling the size and shape of Si particles rather than targeting the nature of the interface.