Graphitic carbon nitride-derived high lithium storage capacity graphite material with regular layer structure and the structural evolution mechanism

A novel graphite anode (Ni-g-C₃N₄) is synthesized by using graphitic carbon nitride as the precursor and nickel (Ni) as the catalyst, which dramatically decreases the reaction temperature to 850 °C. The critical role of Ni in denitrifying g-C₃N₄ to produce high-quality graphite is identified, with the results showing that the nitrogen content decreases from 62.1% to 1.2% and thus leading to greatly enhanced electrical conductivity as well as excellent rate capability, cycle performance and structure integrity. The Ni-g-C₃N₄ exhibits typical low voltage plateau characteristic of graphite anode and the transformation of graphite intercalation compounds are investigated in the in-situ XRD analysis during the discharge/charge process. The capacity retention is as high as 99.3% after 600 cycles at 0.5 A⋅g⁻¹, demonstrating excellent structural stability. Moreover, the evolution from g-C₃N₄ to graphite Ni-g-C₃N₄ is investigated via TG-MS and high-temperature in-situ XRD, which clearly reveals that the catalytic graphitization processes mainly consist of the dissolution, re-precipitation and carbide conversion, along with the formation of intermediate Ni₃C and the release of nitrogen gas. In general, this work not only proposes a novel method to synthesize high performance graphite anode from g-C₃N₄ for lithium ion batteries, but also unravels the catalytic graphitization mechanism.