The traditional separator plays a significant role in rechargeable lithium-ion batteries due to the customized features that allow ions to transfer freely with low energy barriers. However, in the lithium-sulfur battery, the commercial separator shows feeble ability for promoting the conversion of accumulated long-chain polysulfides to the short-chain polysulfides on the surface of the cathode. In this work, a carbon-intercalated montmorillonite is designed to release the imprisoned capacity of the sulfur cathode by activating the accumulated long-chain polysulfides on the surface of the cathode. Benefiting from the advantages of carbon-intercalated montmorillonite, the lithium-sulfur battery achieves a high discharge capacity of 818 mAh g(-1) over 300 cycles at a current density of 1 mA cm(-2) with a sulfur loading of 2.6 mg cm(-2). The systematic analyses by cyclic voltammetry and AC impedance reveal that the regulation of redox environment on the cathode surface by reducing the accumulated long-chain polysulfides to short-chain sulfides is a scalable solution for constructing the actual lithium-sulfur batteries.