In this paper, we discuss some key parameters in design of lithium sulfur batteries with high energy density, in particular carbon/sulfur ratio, sulfur loading density, electrolyte volume and electrode deformability, which directly impact the battery performance in terms of capacity, cycleability, and processibilities, etc. We find that a carbon to sulfur ratio of 1:2 (w/w) in the electrode is good for high specific capacity, giving a capacity of 538 mA h g−1 which is 3 times as high as that of LiCoO2 cathode. The issue of fragileness for electrode at high sulfur loading density is mitigated by replacing carbon black with fine graphite powders. With these optimizations the carbon–sulfur electrode gives an energy density of 5.88 mW h cm−2 which corresponds to 60% of that of the commercial LiCoO2 electrode.