CHEN Yanhuan , LI Jiaofu , LIU Huibiao ,＊

1 CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing 100190, P. R. China.

2 University of Chinese Academy of Sciences, Beijing 100049, P. R. China.

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 specif i c capacity of graphite. Previous studies have reported that GDY film, bulk GDY, N-doped graphdiyne, and similar materials exhibit high specif i c 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 specif i c 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

1 引言

石墨炔(Graphdiyne)是以sp和sp2两种杂化态形成的二维平面网络结构，具有丰富的碳化学键、大的共轭体系和优良的化学稳定性和半导体性能等，自2010年被发现以来，在国际上引起重要反响，吸引了国际上众多科学家积极参与到该研究领域1–7。石墨炔独特的多孔层状平面结构和良好的导电性使其在电化学能源领域方面展示了优异的性能。理论计算表明石墨炔通过表面吸附锂的方式形成 LiC3，其理论比容量可以达到 744 mAh·g−1，面间扩散能垒在 0.18 到 0.84 eV，具有优异的储锂性能8,9。研究表明可以通过控制石墨炔聚集态结构实现对其储锂性能的调控，如以石墨炔薄膜为负极时在500 mA·g−1充放电电流下循环400圈其可逆比容量最高可达520 mAh·g−19；而石墨炔粉末为负极时在 50 mA·g−1充放电电流下循环200圈其可逆比容量达到了552 mAh·g−110；当把石墨炔制备成纳米粒子时在 50 mA·g−1充放电电流下其可逆比容量增加到了800 mAh·g−111；当石墨炔形成纳米墙之后，在50 mA·g−1充放电电流下其可逆比容量高达 908 mAh·g−112。

氮掺杂是显著提高碳材料的储锂性能13–15的重要途径，石墨炔掺氮研究也得到了研究人员的关注16,17。中国科学院过程工程研究所张光晋研究组16通过高温实现了石墨炔的氮掺杂，并发现氮掺杂石墨炔具有优良的催化氧化性能。最近中国科学院青岛生物能源与过程研究所黄长水研究组以氨气作为氮源通过高温获得的氮掺杂石墨炔有着优异的储锂性能，在200 mA·g−1充放电电流下其比容量由 345 mAh·g−19提高到 785 mAh·g−117。但是，发展新的、更温和的方法制备氮掺杂石墨炔依然是目前该领域的重要挑战。……