Metal organic frameworks derived CoS2/NiS2 heterostructure toward high-performance sodium storage anode materials

Synergistic effect of different components in the anode material composed of transition metal dichalcogenides with heterostructure could result in high reversible capacity and superior rate performance for sodium ion batteries (SIBs). Herein, CoS2/NiS2 heterostructure is fabricated from Co-based metal organic framework (MOF, ZIF-67) with a co-precipitation process followed by a hydrothermal sulfidation procedure. The obtained CoS2/NiS2 anode delivers a high capacity of 801.5 mA h g−1 at 0.1 A g−1 with an initial Coulombic efficiency of 88.4%. Remarkably, the cyclic stability with a highly reversible capacity of 545.1 mA h g−1 at 5 A g−1 is maintained even within 2000-cycle testing. In addition, the amorphization and conversions of the CoS2/NiS2 heterostructure during the electrochemical process are analyzed by an in-situ X-ray diffraction instrument. Based on density functional theory (DFT) calculations, it is found that energy barrier (0.085 eV) of the sodium ion transport for CoS2/NiS2 is lower than that of CoS2 (0.614 eV), which should be attributed to the outstanding electrochemical performance with rapid reaction kinetics. Such a design concept is expected to be used for building other anode material with heterostructures for SIBs.