A low-surface-energy design to allogeneic sulfide heterostructures anchored on ultrathin graphene sheets for fast sodium storage

Abstract

Metallic sulfides, endowing high electrochemical reactivity, have been regarded as a kind of promising anode materials for sodium-ion batteries (SIB). However, the low inner conductivity, as well as the inevitable structural collapse during long-term services impede their commercial application. Here, we propose a low-surface-energy strategy to fabricate ultrathin MoS2/SnS/rGO nanoflake with multi-dimensional hierarchical electron transport pathway to mitigate the above issues. The lower surface tension of ionic liquid could release the high surface energy of graphene layers and then induces the uniform growth of bimetallic sulfide. Taking advantage of synergy effect among ternary hybrids, the promoted ion/electron transfer capability on heterointerface and the localized π electrons of sp2 carbon guarantee rapid charge transfer and ions diffusion. Meantime, the compact bonding behavior between graphene layers and bimetallic sulfides shapes a stable microstructure. As a result, the MoS2/SnS/rGO exhibits a high conductivity (4.458 S cm−1) and excellent structural robustness, which facilitate the MoS2/SnS/rGO with a high-rate capability and the long lifespan (a capacity of 255.4 mA h g−1 is maintained even after 500 cycles at 5 A g−1). The as-assembled MoS2/SnS/rGO//Na3V2(PO4)2O2F full cell could maintain the specific capacity as high as 366.1 mA h g−1 after 50 cycles at 1 A g−1.