Self-doped N Sponge Carbon as a functional interlayer for high-performance lithium-sulfur batteries

Lithium-sulfur batteries is regarded as one of the most promising battery systems for the next generation because of its high energy density, low cost and environmental friendliness. However, the high solubility of long-chain polysulfides leads to low active sulfur utilization and strong shuttle effect, resulting in a rapid decline in battery capacity and poor cycle performance, which seriously hinders the practical application of lithium-sulfur batteries (LSB). In this work, we devised a simple method to prepare N-doped Sponge Carbon (SC), which has a rich three-dimensional connection structure, high electronic conductivity, and reasonable N-doped composition. Applied as the interlayer of lithium-sulfur batteries, the N-doped Sponge Carbon (SC) can adsorb long-chain LiPSs dissolved in the electrolyte and accelerate the conversion of long-chain LiPSs to short-chain ones, thereby realizing the secondary utilization of dissolved active sulfur and inhibiting the shuttle effect. Therefore, the lithium-sulfur batteries with a supplemental interlayer provided a large reversible capacity of 834.27 mAh g−1 at 0.5 C and maintained the high specific capacity of 804.9 mAh g−1 after 100 cycles, the capacity attenuation rate was as low as 0.035% per cycle. In addition, when the rate increased to 2 C, the discharge-specific capacity of 618.18 mAh g−1 can still be obtained. Most importantly, this Sponge Carbon interlayer may be of great significance for the commercial application of the high-performance lithium-sulfur batteries.