Graphene-scroll-sheathed α-MnS coaxial nanocables embedded in N, S Co-doped graphene foam as 3D hierarchically ordered electrodes for enhanced lithium storage

Abstract

One-dimensional (1D) nanomaterials have been recognized as ideal nanoscale building blocks to build multi-dimensional and multi-functional electrode configurations for electrochemical energy storage, owing to their unique structural advantages. Herein, a hierarchical transition-metal-sulfide-based electrode configuration is designed by constructing N, S co-doped 3D graphene foam with embedded 1D ultra-long α-MnS nanowires sheathed within graphene scrolls. This structural engineering strategy relies on forming coaxial nanocables comprising core-sheath α-MnS@graphene scrolls via a hydrothermally-assisted self-scrolling and self-assembly process, coupled with a sulfidation treatment. The coaxial nanocable as the structural unit is able to accommodate the volume expansion of the enclosed α-MnS by external elastic graphene scrolls together with internal void spaces, and thus ensures the interfacial stabilization of the solid electrolyte interphase layer. Meanwhile, N, S co-doped graphene foam with a cross-linked 3D structure offers continuous conductive paths for fast electron transfer, and also helps to maintain the structural and electrical integrity of the electrode. Because of the unique structural merits, the hierarchically ordered electrode delivers remarkably enhanced rate (406 mAh g−1 at 2000 mA g−1) and cycling capability (519 mAh g−1 after 400 cycles at 1000 mA g−1). Such a hierarchical structure design may present rational synthetic strategies to develop durable transition-metal-sulfide-based electrodes.