Fast, Reversible Lithium Storage with a Sulfur/Long‐Chain‐Polysulfide Redox Couple

Abstract The cathodic reactions in Li–S batteries can be divided into two steps. Firstly, elemental sulfur is transformed into long‐chain polysulfides (S 8 ↔Li 2 S 4 ), which are highly soluble in the electrolyte. Next, long‐chain polysulfides undergo nucleation reaction and convert into solid‐state Li 2 S 2 and Li 2 S (Li 2 S 4 ↔Li 2 S) by slow processes. As a result, the second‐step of the electrochemical reaction hinders the high‐rate application of Li–S batteries. In this report, the kinetics of the sulfur/long‐chain‐polysulfide redox couple (theoretical capacity=419 mA h g −1 ) are experimentally demonstrated to be very fast in the Li–S system. A Li–S cell with a blended carbon interlayer retains excellent cycle stability and possesses a high percentage of active material utilization over 250 cycles at high C rates. The meso‐/micropores in the interlayer are responsible for accommodating the shuttling polysulfides and offering sufficient electrolyte accessibility. Therefore, utilizing the sulfur/long‐chain polysulfide redox couple with an efficient interlayer configuration in Li–S batteries may be a promising choice for high‐power applications.