Defective Graphitic Carbon Nitride Modified Separators with Efficient Polysulfide Traps and Catalytic Sites for Fast and Reliable Sulfur Electrochemistry

The serious shuttle effect of lithium-sulfur batteries limits the efficient realization of high rate charging and discharging under high sulfur loading in practical applications. Herein, this work reports a strong mitigation toward lithium polysulfide (LiPSs) adsorption/catalysis by introducing defective graphite phase carbon nitride (g-C3N4) as an effective additive. Without significant weight increase, the nitrogen deficient g-C3N4, in the form of ultrafine spindle-like nitrogen deficient g-C3N4-x (sCN), can be easily combined with commercial poly-propylene (PP) separators after hydrophilic modification of polydopamine, which corresponds to an ultralow overall weightiness contribution of 0.17 mg cm(-2). Physical/electrochemical characterizations and theoretical studies reveal that sCN exhibits strong electrostatic attraction with LiPSs by nitrogen defects and new formation of cyano groups near edges, thereby maintaining rapid and reliable Li-S electrochemistry. Of particular importance is the chainmail catalyst design with separators that enable magic polysulfides adsorption effect and desirable thermostability/wettability, which guarantees the sCNPP-assembled cells with long and stable durability over 500 cycles at 5.0 C (capacity fading rate: 0.05% per cycle), and a high capability of 476 mAh g(-1) is obtained.

Automated summary

By introducing defective graphite phase carbon nitride as an effective additive, this study successfully mitigated lithium polysulfide adsorption/catalysis effects, enabling high rate charging and discharging in lithium-sulfur batteries. The chainmail catalyst design with separators contributed to the long-term stability and high capacity of the assembled cells, demonstrating excellent cycling performance and durability under high rates.