An improved, high-capacity lithium-sulfur battery employing a Li2S8 polysulfide-added, TEGDME-LiCF3SO3 electrolyte is reported. We show that the beneficial buffering action of the highly soluble polysulfide significantly reduces dissolution of the cathode during cell operation, thus successfully addressing one of the major issues of Li/S batteries. We in fact demonstrate that a battery exploiting this composite electrolyte operates at high C/3 rate delivering a stable capacity of the order of 1,500 mAh g-1S for over 80 cycles.