Rechargeable lithium–sulfur batteries have attracted tremendous scientific attention owing to their superior energy density. However, the sulfur electrochemistry involves multielectron redox reactions and complicated phase transformations, while the final morphology of solid‐phase Li2S precipitates largely dominate the battery's performance. Herein, a triple‐phase interface among electrolyte/CoSe2/G is proposed to afford strong chemisorption, high electrical conductivity, and superb electrocatalysis of polysulfide redox reactions in a working lithium–sulfur battery. The triple‐phase interface effectively enhances the kinetic behaviors of soluble lithium polysulfides and regulates the uniform nucleation and controllable growth of solid Li2S precipitates at large current density. Therefore, the cell with the CoSe2/G functional separator delivers an ultrahigh rate cycle at 6.0 C with an initial capacity of 916 mAh g−1 and a capacity retention of 459 mAh g−1 after 500 cycles, and a stable operation of high sulfur loading electrode (2.69–4.35 mg cm−2). This work opens up a new insight into the energy chemistry at interfaces to rationally regulate the electrochemical redox reactions, and also inspires the exploration of related energy storage and conversion systems based on multielectron redox reactions. A unique triple‐phase interface with synergistic properties of strong chemisorption, large electrical conductivity, and highly active electrocatalysis sites is proposed, which can effectively regulate the electrochemical redox reaction of soluble lithium polysulfides and tune Li2S nucleation and growth, enabling controllable Li2S precipitates on reactive interfaces at high current rates in a working Li–S battery.