Tailoring N skeleton substituted cobalt phthalocyanine/reduced graphene oxide nanostructures for boosting redox kinetics and regulating Li2S nucleation enabled high rate performance of lithium-sulfur batteries

The shuttle and sluggish conversion kinetics of polysulfides (LiPS) significantly hinder the sulfur utilization and cycle performance of Li-S batteries. Herein, reduced Graphene Oxide supported Cobalt phthalocyanines(CoPc/ rGO) and its skeleton Nitrogen substituent Cobalt Tetrapyridinoporphyrazine (CoTAP/rGO), are fabricated using a preform-solid synthesis process. When employed as separator modification, the CoTAP/rGO can capture and electrocatalyze LiPS by the active central Co-N4 units. And the Co-N4 sites are proved that can augment the LiPS redox kinetics especially the oxidation as well as the Li + diffusion rate. The introduced substituent N atoms in the skeleton match the LiPS redox ability and further enhance the Li + diffusion ability. Distribution of relaxation time (DRT) analysis shows that CoTAP nanoparticles can reduce the resistance of LiPS as well as Li + diffusion in Li2S precipitation procedure, accomplishing the loose three dimension deposition on cathode. As a result, the CoTAP/rGO separator exhibits a high initial capacity of 1132.7 mAh g- 1 at 0.2C, excellent rate capacity of 672.5 mAh g- 1 at 5C and superior long-term stability with a low capacity decay of 0.57 %o at 2C after 500 cycles.