Some of the most remarkable improvements in the cycle life of Li-S batteries could be achieved by nano-structuring of the sulfur/carbon (SIC) cathode material. Meso- and micro-porous particles, carbon nano tubes, and other sophisticated structures are used to actively retain highly soluble polysulfides which are responsible for capacity fading and a short cycle life. In this article we present a detailed 1+1D continuum model of SIC composite cathodes which is based on an ideal structure where all polysulfides are confined within meso- and micro-porous carbon particles. The model allows to correlate particle properties to cell performance and gives interesting insights for cell operation. Most interestingly we identified an additional overpotential caused by a transport of Li ions against a concentration gradient into the particle. Furthermore, the model can be used to find optimal structural and electrolyte properties such as pore volume, sulfur loading, solubility products, and salt concentration. (C) 2015 Elsevier Ltd. All rights reserved.