A carbon microsphere-modified ZnS-MnS@C composite anode for Li-ion battery applications

In this study, carbon-coated hetero-structured ZnS-MnS composite was successfully prepared using a simple hydrothermal method. The carbon content in the composite was determined by Raman spectroscopy. The X-ray diffraction patterns confirmed the crystallinity and phase purity of the composite with clear lattice fringes indicating the crystalline nature of the final composition. The nanoparticle morphology of ZnS-MnS@C was determined by scanning electron microscopy and high-resolution transmission electron microscopy. The high surface area of the ZnS-MnS@C composite provided a large contact area for the electrolyte ions. Cyclic voltammetry confirmed the dual dependence (capacitive and diffusion-controlled mechanism) of the charge/discharge process. The lower charge transfer resistance and Warburg resistance of composite are beneficial for the more Li-ion intercalation/de-intercalation process. The first cycle charge/discharge capacities of the carbon microsphere/ZnS-MnS@C composite were 643.6/808.2 mAh g−1 at a current density of 100 mA g−1 with a coulombic efficiency of 79.6% After 500 cycles, the composite exhibited a discharge specific capacity of 563.4 mAh g−1 at a current density of 2000 mA g−1 with 96% of capacity retention. Even at a high current density of 5000 mA g−1, the composite exhibited a discharge-specific capacity of 221.3 mAh g−1. After carbon coating, the hetero-structured ZnS-MnS showed better Lithium-ion storage ability than the ZnS-MnS composite before coating. These results clearly indicate that, the composite is a promising anode material for Li-ion battery applications.