In Situ Fragmentation of Bimetallic Sulfides to Construct Ultrafine MoS ₂ /SnS ₂ Heterostructures Embedded in Carbon Frameworks for Enhanced Sodium Storage

Metal sulfide heterostructures have attractive Na+ storage performance because of the subtle synergy; however, current synthesis of heterostructured metal sulfides typically is based on cohydrothermal reactions or mechanical mixing followed by high-temperature sulfidation, often yielding heterostructures with large particle sizes and nonuniform interfaces. In the present study, we designed a novel bimetallic sulfide precursor, Sn(MoS4)2, and embedded it within polyacrylonitrile (PAN) nanofibers. After a simple pyrolysis, the Sn(MoS4)2 confined in the carbon matrix converts to a heterostructure comprising few-layer MoS2 and ultrafine SnS2 nanoparticles with a size <10 nm. This unique structure endows the heterostructure with high electrochemically active surfaces, ultrafast reaction kinetics, and superior structural stability during cycling. Thus, the heterostructure delivers a large capacity of 374 mAh g–1, and at an ultrahigh current density of 10 A g–1, a capacity of 206 mAh g–1 is retained. After 600 cycles, the capacity remains at 306 mAh g–1 with negligible decay.