Flexible Paper-like Free-Standing Electrodes by Anchoring Ultrafine SnS2 Nanocrystals on Graphene Nanoribbons for High-Performance Sodium Ion Batteries.

Ultrafine SnS2 nanocrystals-reduced graphene oxide nanoribbon paper (SnS2-RGONRP) has been created by a well-designed process including in situ reduction, evaporation-induced self-assembly, and sulfuration. The as-formed SnS2 nanocrystals possess an average diameter of 2.3 nm and disperse on the surface of RGONRs uniformly. The strong capillary force formed during evaporation leads to a compact assembly of RGONRs to give a flexible paper structure with a high density of 0.94 g cm-3. The as-prepared SnS2-RGONRP composite could be directly used as free-standing electrode for sodium ion batteries. Due to the synergistic effects between the ultrafine SnS2 nanocrystals and the conductive, tightly connected RGONR networks, the composite paper electrode exhibits excellent electrochemical performance. A high volumetric capacity of 508-244 mAh cm-3 was obtained at current densities in the range of 0.1-10 A g-1. Discharge capacities of 334 and 255 mAh cm-3 were still kept, even after 1500 cycles tested at current densities of 1 and 5 A g-1, respectively. This strategy provides insight into a new pathway for the creation of free-standing composite electrodes used in the energy storage and conversion.