Lithium–sulfur batteries are highly desired because of their characteristics such as high energy density. However, the applications of Li-S batteries are limited because they exist dissolution of polysulfides into electrolytes. This study reports the preparation of sulfur cathodes by using bimodal microporous (0.5nm and 0.8nm to 2.0nm) carbon spheres with high specific area (1992m2 g−1) and large micropore volume (1.2gcm−1), as well as the encapsulation of polysulfides via formation of carbon–sulfur bonds in a sealed vacuum glass tube at high temperature. Given that sulfur and polysulfides are well confined by the SC bond, the shuttle effect is effectively suppressed. The prepared S/C cathodes with a sulfur loading of up to 75% demonstrate high sulfur activity with reversible capacity of 1000mAhg−1 at the current density of 0.1Ag−1 and good cycling stability (667mAhg−1 after 100 cycles).