Synthesis of Graphene-MoS2 composite based anode from oxides and their electrochemical behavior

Abstract High energy storage capacity and longer life span make rechargeable Li-ion batteries the first choice in portable electronics. Here, a graphene-MoS2 composite material is investigated as a potential electrode material which enhances the electrochemical storage ability of the Li-ion batteries (LIBs). Graphene-MoS2 composite is synthesized from graphene oxide (GO), molybdenum trioxide and thiourea via hydrothermal route. Formation of graphene-MoS2 composite (molar ratio 1:2) is confirmed by X-ray diffraction (XRD). The characteristic phonons modes of graphene (D and G bands) and MoS2 (A1g and E2g) are observed in the Raman spectra of the synthesized graphene-MoS2 composite. Fourier- transform infrared (FTIR) spectroscopy showed reduction from GO to graphene in composite due to absence of C = O bond while the peaks observed at 900 cm−1 and 1095 cm−1 of Mo-O and S = O, respectively, supports the formation composite material. To investigate the diffusion rate of Li+ ions for anode material, the electrochemical impedance spectroscopy (EIS) measurements modeled with equivalent circuit has been performed, which showed the high diffusion rate of Li ions but with less cyclic stability due to drastic change in surface film resistance for increased number of cycles. The value of discharge capacity obtained for the first cycle is ~ 975 mAh/g, which dropped to 250 mAh/g after executing 80 cycles. For different cycles, rate capabilities have also been measured at different current densities. At initial current density of 100 mAh/g, the highest discharge capacity of 975 mAh/g is obtained. The current density dropped to 200 mAh/g from the highest current density of 1000 mAh/g after 40 cycles with a retention capacity of 20%. The present study confirmed that composite synthesized from precursors, namely, molybdenum trioxide and thiourea has the potential as an electrode for LIBs.