Physical activation with CO₂ is used to modify the micro-, meso-, and macropore system of commercial, highly branched carbon black (CB) particles. Due to the increased total porosity and high surface area of 1747m²g^-1 the completeness of sulfur infiltration in intra-particle pores of CB is promoted. This is found to not only minimize sulfur agglomeration on the particle surface but also reduce self-discharge, that is, polysulfide leakage. Wrapping the CB/sulfur composite with a poly(ethylene oxide)/poly(vinylpyrrolidone) film further triggers a synergy allowing for faster sulfur conversion with increased reversibility. Thus, an initial capacity of 1238mAhg^-1_S at C/10 and a stable capacity of 1015mAhg^-1_S after 50cycles were obtained, combined with a superior rate capability up to 2C (≈7.5mAcm^-2) and extremely slow self-discharge over 100days (open-circuit voltage>2.30V).