Development of two-dimensional MOS2-based nanocomposite free-standing electrodes for energy storage applications

Electrochemical energy storage are systems that can keep electrical energy as a reserve in an environment and convert this stored energy into electrical energy when needed. Increasing the specific capacity and energy density values of the batteries among the energy storage devices is tried to be increased in parallel with the increasing energy demand. The use of two-dimensional materials with highly superior properties also contributes to the development of new generation batteries. In this thesis,MoS2/Graphene nanocomposite free-standing electrodes were produced using graphene oxide produced by the modified hummers method and MoS2 two-dimensional materials exfoliated by electrochemical lithiation method. The produced nanocomposite electrodes were tested as an anode in the range of 0.01-3.0V for lithium-ion batteries and it is tested as an air breathing cathode material in the range of 2.0-4.5V under oxygen gas flow for lithium air batteries. The morphology of the nanocomposites was characterized by using Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (TEM). The elemental distribution of graphene and MoS2 catalysts was studied by energy dispersion spectrometry (EDS). Phase structures were studied using Raman spectroscopy and X-ray diffraction patterns (XRD). Their electrochemical performances were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS),galvanostatic charge-discharge and electrochemical cyclic tests. The optimized MoS2/Graphene nanocomposite anode exhibited 700 mAhg-1 discharge capacity at the end of 100 cycles and 99% capacity retention after the first cycle, and the full discharge capacity reaching 12, 500 mAhg-1 in the MoS2/Graphene nanocomposite cathode material produced for lithium air batteries and It was demonstrated stable capacity behaviour of 50 cycles in 1000 mAhg-1 limited capacity.