Lithium-sulfur battery represents one of the most promising candidates for electric vehicles. However, its slow electrochemical kinetics and the shuttling of polysulfides between two electrodes have hindered its practical applications for years. Although numerous materials (e.g., metal oxides, metal sulfides, metal carbides) have been identified as efficient adsorbents or mediators for sulfur cathodes, the fundamental understanding of their working mechanisms is still missing. Based on the electronic structures, we thoroughly studied the interactions between various adsorbents and polysulfides, investigated the working principles of mediators, and rationally designed a hybrid sulfur cathode with fast redox kinetics. This work provides not only an effective strategy to achieve longer cycling lifetime and better rate performance, but also a clear design principle for advanced lithium-sulfur batteries.