Rational design of p-ZnS@CN with 3D interconnected hierarchical pore structure through pyrolysis of an organic hybrid zinc thiocyanide for electrochemical lithium storage

3D interconnected porous carbon-coupled metal-sulfide composites have been demonstrated as promising lithium storage materials owing to their large surface areas as well as the acceleration effect to electrochemical kinetics. However, constructing these materials with ordered hierarchical pore structure is still a challenge. To address this issue, we found that the crystals of an organic hybrid zinc thiocyanide [Zn(NCS)2(phen)2] (phen = 1,10-phenanthroline) could become a fluid at 400 degrees C, and during the melting process, the phen ligand was simulatneously carbonized to form nitrogen-doped carbon materials, while the Zn(NCS)2 species were converted into ZnS quantum dots. This property could allow us to employ a hard template strategy for preparation of a porous p-ZnS@CN composite featuring 3D interconnected hierarchical structure, namely employing SiO2 nanospheres as sacrificial template and [Zn(NCS)2(phen)2] as precursor and thermal treatment this mixture at 400 degrees C. The as-obtained p-ZnS@CN (p = porous structure, CN = nitrogen-doped carbon) composite possesses ordered macro-and mesoporous nitrogen-doped carbon structures, where the ZnS quantum dots are embedded in. Due to their structural features, p-ZnS@CN showed a superior lithium storage performance in comparison with ZnS nanoparticles. The well-defined 3D interconnected hierarchical pore structure not only enhances the efficiency of lithium-ion diffusion, but also offers ample void space to buffer the volume expansion during lithiation. Given the diversity of crystalline organic hybrid metal thiocyanates, this work opens a new avenue of preparing 3D interconnected porous carbons-coupled metal-sulfide composites.