Fast, reversible lithium storage with a sulfur/long-chain-polysulfide redox couple

The cathodic reactions in Li-S batteries can be divided into two steps. Firstly, elemental sulfur is transformed into long-chain polysulfides (S ₈↔Li₂S₄), which are highly soluble in the electrolyte. Next, long-chain polysulfides undergo nucleation reaction and convert into solid-state Li₂S₂ and Li₂S (Li₂S₄↔Li₂S) 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. More juice: The kinetics of the sulfur/long-chain polysulfide redox couple (S ₈↔Li₂S₄; theoretical capacity= 419 mA h g^-1) are experimentally demonstrated to be very fast in the Li-S system. A Li-S battery with a blended-carbon interlayer retains excellent cycle stability and high discharge capacity over 250 cycles at 10 C and 15 C rates. The meso-/micropores in the interlayer are responsible for storing the migrating polysulfides and offering sufficient electrolyte accessibility.