Pyrolyzing a Crystalline Organic Hybrid Ternary Selenide to a Bimetallic Selenide Heterostructure NiSe₂/SnSe₂@CN for Electrochemical Sodium Storage

Constructing heterostructures in the anode materials of sodium-ion batteries has been regarded as an efficient method to improve the electrochemical sodium storage capability. However, preparing bimetallic chalcogenide heterostructure materials is still challenging. Organic hybrid ternary metal chalcogenides possess two kinds of metal ions in their structures. These materials would be promising precursors to prepare bimetallic chalcogenide heterostructures. However, this concept has never been executed to date. For this purpose, herein, a crystalline organic hybrid ternary selenide [Ni(phen) 3 ]Sn 3 Se 7 ·1.5H 2 O (NPTS) has been first selected as a precursor to prepare the bimetallic selenide heterostructure. After the bulk crystals of NPTS were heated at 400 °C, nanosheets of NiSe 2 /SnSe 2 @CN (CN = nitrogen-doped carbon) containing both Schottky and NiSe 2 –SnSe 2 junctions were formed. The NiSe 2 and SnSe 2 nanosheets were stacked layer by layer, and the surface of the NiSe 2 /SnSe 2 nanosheet was coated by a CN layer. Benefiting from the heterointerfaces among NiSe 2 nanosheets, SnSe 2 nanosheets, and CN layers, NiSe 2 /SnSe 2 @CN can provide a capacity of 357.4 mA h g –1 at 1000 mA g –1 after 2700 cycles, much higher than the sole NiSe 2 nanoparticles and SnSe 2 nanosheets. In addition, the NiSe 2 /SnSe 2 @CN electrode also exhibited superior rate performance, as compared with the previously reported NiSe 2 - or SnSe 2 -based anode materials. This work proved that pyrolysis of organic hybrid ternary metal selenide could be a promising approach to synthesize bimetallic selenide heterostructure materials for electrochemical sodium storage.