Thiomolybdate [Mo₃S₁₃]²⁻ clusters combined with mesoporous carbon spheres are employed as sulfur host. Such structures not only increase overall electrical conductivity via inner carbon capsule, but also enhance the redox kinetics of polysulfides by the bidirectional catalysis of [Mo₃S₁₃]²⁻, thus confining the volume expansion of sulfur and shuttle effect.