Atomic investigation on reversible and irreversible lithium storage in silicon incorporated with multi-layered graphene

Abstract

Silicon-graphene composites show large lithium capacity and very small volume expansion during charge processes. However, further study on atomic structure-property relationship of the system is very challenging for current experimental technologies. In this work, the lithiation mechanism of silicon-graphene electrode is investigated by first principle calculations. The calculated densities of states indicate that Si/Gra with higher Si concentration is more energetically favorable for Li incorporation. The formation of Si-C bonds near silicon-graphene interface and C-Li bonds near graphene layers is considered as the main origin of irreversible capacity loss, and a reversible capacity is obtained by excluding the Li atoms related to the irreversible atomic structures. The predicted reversible capacity of Si/Gra1 (75.7 wt% Si) is 2383 mAhg−1, which is comparable to reversible capacity of 2497 mAhg−1 for the composite with similar composition (72 wt% Si) in experiment.