Abstract:

Graphdiyne(GDY) is a novel carbon allotrope containing sp-and sp²-hybridized carbon atoms.Because of GDY's special structure, theoretical studies have predicted Li storage as dense as 744 mAh∙g⁻¹ in the form of LiC₃, representing twice the specific capacity of graphite.Previous studies have reported that GDY film, bulk GDY, N-doped graphdiyne, and similar materials exhibit high specific capacity, excellent rate performance, and long cycle life when used as anode materials in lithium ion batteries(LIBs).The flat(sp²-and sp-hybridized) carbon networks endow GDY with extensive π-conjunction and uniformly distributed pores, which allow π–π interactions between GDY and organic conjugated molecules to construct a GDY/organic conjugated molecule hybrid material for high-performance anodes with in LIBs.Anode materials with higher specific capacity, better rate performance, and longer cycle life still present an important challenge in LIBs.Nitrogen doping of GDY is one of the effective ways to improve the performance of LIBs.Nitrogen doping of GDY has been achieved by annealing at high temperature in an ammonia atmosphere.The resulting material shows enhanced electrochemical properties due to the creation of numerous heteroatomic defects and active sites.Herein, we have developed a new method based on supramolecular chemistry for preparing N-doped GDY(graphdiyne/porphine) with π–π interactions between graphdiyne and organic conjugated molecules.As opposed to previously reported graphdiyne films, the as-prepared graphdiyne/porphine film can be used as an anode for LIBs without any binders or conducting agents.The resulting anode delivers a high capacity of 1000 mAh∙g⁻¹ and exhibits excellent performance and cycle stability, suggesting that the high rate capability and long cycle life are due to the large amount of active sites provided by porphine for lithium storage.Galvanostatic measurements were performed for 5 cycles each, and retentions of 915.4, 778.9, 675.9, 553.6, and 375.2 mAh∙g⁻¹ were obtained at current densities of 100, 200, 500, 1000, and 2000 mA∙g⁻¹, respectively.When the current density was reset to 50 mA∙g⁻¹, the capacity reached 900 mA∙g⁻¹, indicating excellent structural stability during the high-rate measurements.Excellent cyclic stability with a retention of 1000 mAh∙g⁻¹ at 50 mA∙g⁻¹ after 50 cycles was obtained for LIB applications, which results from the unique hierarchical porosity due to the presence of butadiyne linkages.The unique hierarchical structure of the GDY/porphine film was not destroyed after 50 charge/discharge cycles at 50 mA∙g⁻¹, which suggested high structural stability.The competitive lithium storage values provide promising potential for the development of high-performance LIBs.This strategy opens an avenue for designing N-doped graphdiyne with tunable electronic properties under mild conditions.

Key words: Graphdiyne, Porphine, π–π interaction, N-doping, Lithium ion battery