Tetrakis(4-sulphophenyl) porphyrin cross-linked polypyrrole network with enhanced bulk conductivity and polysulfide regulation for improved Li-S battery performances

The synergistic mechanisms of chemisorption and catalysis play an important role in developing high-performance lithium–sulfur (Li-S) batteries. To bestow conductive polymer enhanced bulk conductivity, chemisorptions to polysulfides and catalytic activity, herein, 5, 10, 15, 20-tetrakis (4-sulphophenyl) porphyrin (TPPS) cross-linked polypyrrole (PPy) nanocomposites (named PPy-TPPS) is rationally fabricated as an integrated polymeric host by aqueous self-assembly through the interaction between -SO3− and –NH=+. PPy-TPPS nanocomposites exhibit peag-like chain in morphology with hierarchical porous structure and high pore volume. The rigid conjugate TPPS molecules bridge linear PPy chains to extend the conjugate system, construct a multipath electron highway, create a three-dimensional conductive network and greatly reinforce the bulk conductivity of the nanocomposites. The unique structural features expose plenty of N sites to enhance the chemically anchoring polysulfides, suppress polysulfide diffusion, and release the shuttle effect. Both experimental and theoretical calculation confirms the enhanced polysulfide trapping ability. The presence of TPPS also bestows the PPy-TPPS/S cathode catalytic property to promote the Li2S nucleation rate and accelerate the reversible solid–liquid conversion between Li2S and soluble polysulfides. The improved conductivity and enhanced polysulfide affinity with catalytic property render PPy-TPPS nanocomposites improved Li-S battery performances with high specific capacity, high rate capability, and high cycling stability. The PPy-TPPS/S cathode delivers a high initial capacity of 1278 mAh∙g−1 at 0.2 C. The cathode exhibits an initial discharge capacity of 761 mAh∙g−1 at 2 C with residual capacity of 470 mAh∙g−1 after 500 cycles. The present work contributes a novel route to explore low-cost, up-scale producible and high performance polymeric sulfur host for Li-S battery.