Coordination Engineering Based on Graphitic Carbon Nitrides for Long‐Life and High‐Capacity Lithium‐Sulfur Batteries

Lithium‐sulfur (Li‐S) batteries have received tremendous academic and industrial attentions owing to their ultrahigh energy density. However, technical challenges including lithium dendrite formation, polysulfide shuttling and sluggish sulfur reaction kinetics limit their cycle life, rate capability and areal capacity, especially at practically high sulfur loadings. Here, coordination‐engineered graphite carbon nitrides is proposed to effectively address these challenges. On the anode a layer of novel N‐rich graphitic carbon nitride (g‐C3N5) is applied, in which tricoordinated N atoms display strong affinity to Li+, to guide lithium deposition and efficiently inhibit dendrite formation. Besides, a layer of defective g‐C3N5 carrying highly active bicoordinated N vacancies and cyano N atoms is applied on the cathode, which significantly adsorb polysulfides and catalyze the reversible conversion, as well as the nucleation and dissolution of Li2S thereby outcompeting polysulfide shuttling and raising kinetics at high sulfur loading. This coordination‐engineering strategy based on g‐C3N5 enables Li‐S batteries exhibiting high stability and low capacity‐fading‐rate (0.03% per cycle) in 400 cycles at the high current rate of 4 C, as well as Li‐S pouch cells showing a high areal capacity of 11.69 mAh cm−2 at a high sulfur loading of 9.02 mg cm−2, demonstrating the feasibility of Li‐S batteries in practical applications. In this work, a coordination engineering strategy based on graphitic carbon nitrides (g‐C3N5) has been proposed, which can not only guide uniform lithium deposition to inhibit dendrites by tricoordinated N atoms of the pristine g‐C3N5, but also promote sulfur utilization and inhibite the polysulfide shuttle by optimized bicoordinated N vacancy and cyano N atoms of novel defective g‐C3N5.