The importance of employing more efficient energy storage systems for high energy density applications such as hybrid cars and portable electronic devices is remarkably growing at an increasing speed. Among proposed structures for Li-ion batteries, lithium/sulfur (Li/S) batteries are a promising candidate due to their very high specific energy density (~2600 W.h.kg-1), abundance in nature, low cost, and environmental friendliness in comparison to the conventional Li-ion batteries. However, fast capacity fading due to shuttling phenomenon, as a drawback in these cells, has hindered their wide application as an efficient energy storage today. Here a rigorous semi-empirical model is developed to predict the capacity fading of Li/S batteries for different nanostructures embedded in the cathode by taking into account the polysulfide (PS) shuttling effect and discharge rates. In our numerical model, capacity fading of the cell is considered to be affected by the concentration of sulfur dissolved into the electrolyte and deposited on the anode as a Solid Electrolyte Interphase (SEI) layer. Our approach considers SEI layer formation as the main factor that dominates capacity fading over initial cycles (50 cycles). The mean value of percentage error between simulation results and experimental capacity in all analyzed structures is less than 5%. According to our model, adding a graphene layer to the separator with using a hollow carbon nanotube structure in the cathode retain >99% of initial capacity over 50 cycles which is promising for more efficient Li-S batteries.