Fe Powder Catalytically Synthesized CN toward High-Performance Anode Materials of Lithium-Ion Batteries.

Recently, carbon nitrides and their carbon-based derivatives have been widely studied as anode materials of lithium-ion batteries due to their graphite-like structure and abundant nitrogen active sites. In this paper, a layered carbon nitride material CN consisting of triazine rings with an ultrahigh theoretical specific capacity was designed and synthesized by an innovative method based on Fe powder-catalyzed carbon-carbon coupling polymerization of cyanuric chloride at 260 °C, with reference to the Ullmann reaction. The structural characterizations indicated that the as-synthesized material had a C/N ratio close to 1:1 and a layered structure and only contained one type of nitrogen, suggesting the successful synthesis of CN. When used as a lithium-ion battery anode, the CN material showed a high reversible specific capacity up to 842.39 mAh g at 0.1 A g, good rate capability, and excellent cycling stability attributed to abundant pyridine nitrogen active sites, large specific surface area, and good structure stability. Ex situ XPS results indicated that Li storage relies on the reversible transformation of -C=N- and -C-N- groups as well as the formation of bridge-connected -C=C- bonds. To further optimize the performance, the reaction temperature was further increased to synthesize a series of CN derivatives for the enhanced specific surface area and conductivity. The resulting derivative prepared at 550 °C showed the best electrochemical performance, with an initial specific capacity close to 900 mAh g at 0.1 A g and good cycling stability (94.3% capacity retention after 500 cycles at 1 A g). This work will undoubtedly inspire the further study of high-capacity carbon nitride-based electrode materials for energy storage.