The development of lithium–sulfur batteries is limited by the poor conductivity of sulfur cathodes and soluble long-chain lithium polysulfides (LPSs), which cause the low utilization of sulfur and the aversive shuttle effect, and further, give rise to self-discharge, rapid reversible capacity fading, and low Coulombic efficiency. In this work, a novel configuration is built for high-performance lithium–organosulfur batteries, in which the organosulfur hybrid material and lithium metal are used as the cathode and the anode, respectively, and are separated by a functional separator decorated with nitrogen and sulfur co-doped reduced graphite oxide. The organosulfur in the cathode prevents the shuttle effect by inhibiting the formation of long-chain LPSs. In addition, the functional separator effectively adsorbs LPSs escaping from the cathode by electrostatic interactions and further restrains the shuttle effect. These effects are confirmed by density-functional theory calculations. As a result, this novel configuration provides a high initial discharge capacity of 1364 mAh g−1 at 0.2 C and a high discharge capacity of 750 mAh g−1 at 1 C after 700 cycles with a very low capacity decay rate of 0.037% per cycle.