A study on the metal sulfides as high-performance electrodes in the next generation Li-ion batteries

Abstract

Metal sulfide is an attractive material for lithium-ion batteries (LIBs) because of its unique intrinsic properties and rich redox reaction. In particular, two-dimensional metal sulfides are studied as anode material due to the facile diffusion of the lithium-ion through interlayer and low potential. However, their low conductivity by semiconducting property and structural collapse by conversion reaction cause low stability. In addition, it has a significantly lower capacity compared to other anode materials such as Li and Si for next-generation LIB. Thus, in this study, to apply metal sulfide for suitable materials in next-generation LIB, we suggest two strategies. First, to improve the capacity and long-term stability, we prepare micro-sized metal sulfide by a simple chemical method, and it pulverizes into the nanoparticle via electrochemical treatment using the mechanism property. Herein, there are required two conditions; i) fabricating the composite with reduced graphene oxide (r-GO), and ii) containing the excess sulfur in metal sulfide. Besides, the excess sulfur is released during the electrochemical treatment, inducing an increase in the potential above 1.5 V. Hence, as the content of sulfur in metal sulfide increases, the potential of electrode approaches above about 1.5 V and it can be applied as a cathode. On the other hand, to increase the kinetics, we modify the phase of metal sulfide to metallic 1T through the colloidal method. Besides, as partial substitution of Se, metal sulfide has an expansion of interlayer spacing as well as an increase in conductivity, improving accommodation of lithium-ion. To elucidate the effect of modification in metal sulfide, we present the surface (SEM, TEM, XRD, XPS) and electrochemical analyses (Cycling performance, CV, EIS).