In-situ synthesis of graphene nanosheets encapsulated silicon nanospheres by thermal plasma for ultra-stable lithium storage

Abstract

Owing to its high capacity, silicon (Si) is a promising anode for meeting the escalating need for batteries with high energy density. Nonetheless, the substantial volumetric variation generated by lithiation/delithiation often results in the pulverization of Si, which substantially lowers its cycle stability. Graphene/graphene nanosheets (GNSs) with higher electrical conductivity and mechanical strength are anticipated to overcome these obstacles when employed as the coating matrix of silicon. Unfortunately, the majority of Si@graphene composites are not manufactured in situ , so that graphene is hardly to entirely encapsulate Si.The low-quality coating leads to the exposure of Si after cycles, resulting in a short cycle life. Herein, graphene nanosheets encapsulated silicon nanospheres (Si@GNSs) are synthesized in situ using a radio-frequency (RF) thermal plasma system, in which graphene and Si have strong interfacial chemical interactions. Further, free-standing Si@GNSs/reduced graphene oxide (Si@GNSs/rGO) paper was prepared using graphene oxide (GO) as a special ‘binder’. When Si@GNSs/rGO paper is directly used as anode electrodes, it demonstrates a high reversible capacity (2270 mAh g −1 at 0.2 A g −1 ), outstanding rate performance (1569 mAh g −1 at 5.0 A g −1 ) and ultra-stable cycle performance (capacity retention of 98.55% for 2000 cycles at 3.0 A g −1 ). • Si@GNSs composites were prepared in situ by the RF thermal plasma system. • The flexible Si@GNSs/rGO paper is prepared with GO as a special ‘binder’. • Si@GNSs/rGO paper exhibits high capacity of 2250 mAh g −1 at 0.2 A g −1 . • Si@GNSs/rGO paper show excellent rate performance of 1569 mAh g −1 at 5.0 A g −1 . • After 2000 cycles, the capacity of Si@GNSs/rGO paper remains 98.55%.