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2,6-二氨基蒽醌/還原氧化石墨烯復合材料的制備及在鋰有機電池的應用

Preparation of 2,6-diaminoanthraquinone/reduced graphene oxide-based composites as cathode materials for organic lithium batteries

  • 摘要: 采用水熱合成法和冷凍干燥技術制備了2,6-二氨基蒽醌(2,6-AAQ)/rGO復合材料,通過氨基(—NH2)與羧基(—COOH)形成肽鍵(—CO—NH—)共價鍵,使其在電解液中的溶解問題從本質上得到了解決。SEM和EDS Mapping表明,2,6-AAQ/rGO-3復合材料中的2,6-AAQ呈現出高度的棒狀結構,并且被石墨烯包裹得更緊密。這種獨特的結構提高了2,6-AAQ在鋰化過程中的電子導電性,可有效減少2,6-AAQ的聚集,利于電解質的浸潤。XPS、XRD、FTIR和Raman結果表明,2,6-AAQ和rGO之間發生了水熱輔助化學鍵合,形成了rGO包裹2,6-AAQ的結構。此外,非原位FTIR表征結果驗證了2,6-AAQ/rGO-3具有良好的儲鋰性能,羰基(C=O)為反應位點。同時,紫外-可見光譜測試清楚表明,與2,6-AAQ相比,通過肽鍵連接的2,6-AAQ/rGO-3的溶解度顯著降低,表明電化學性能大大提高。其中2,6-AAQ/rGO-3作為鋰離子電池正極時,在100 mA·g?1電流下,首圈放電容量高達212.2 mA·h·g?1, 在500 mA·g?1電流下循環100周后放電容量仍為184 mA·h·g?1,展現出了優異的循環穩定性和高倍率性能。2,6-AAQ/rGO出色的電化學性能得益于石墨烯的碳骨架對2,6-AAQ的錨定,該結構不僅可以防止2,6-AAQ溶解,還可以為其提供導電網絡,進一步提高電子傳導速率。

     

    Abstract: Organic carbonyl compounds have received great attention as electrode materials because of their fast reduction–oxidation kinetics, environment friendliness, and high theoretical capacity. Especially, the small molecular quinones, such as anthraquinone (AQ), can possess high theoretical (257 mA·h·g?1) and a discharge–charge voltage of 2.2–2.3 V, implying that it has the potential of up to 565 W·h·kg?1 energy density. However, it suffers from high solubility in organic electrolytes and low conductivity, leading to rapid capacity fading and inferior rate performance. Herein, we report 2,6-diaminoanthraquinone (2,6-AAQ) uniform self-assembly into a three-dimensional (3D) porous structure graphene foam, which was successfully fabricated through a gentle hydrothermal synthesis reaction with simultaneous in situ condensation of 2,6-AAQ on the reduced graphene surface, as a high-performance cathode for Lithium-organic batteries. Benefiting from the formation of a covalent bond (—CO—NH—) between the amino group (—NH2) of 2,6-AAQ and the carboxyl group (—COOH) of oxidized graphene, the molecular structure of AQ is uniformly anchored into a 3D graphene foam architecture. The strategy simultaneously solved the high dissolution and low conductivity of AQ. The as-obtained hybrid composites were characterized by various techniques. SEM and EDS mapping images demonstrated that the 2,6-AAQ within the hybrid architecture was not only uniformly anchored on the surface but also tightly wrapped in the interior of graphene foam. This unique architectural structure can improve the electronic conductivity of 2,6-AAQ in the lithiation process and effectively inhibit the dissolution of 2,6-AAQ in electrolytes, which is beneficial to hoist the electrochemical performance of the composite materials. XPS, XRD, FTIR, and Raman results indicated that hydrothermally assisted chemical bonding occurred between 2,6-AAQ and rGO, significantly facilitating the mass electron transformation and ion diffusion from graphene substrate to 2,6-AAQ for the fast reduction–oxidation reaction. Combined with the above results, UV–Vis spectroscopy tests also further disclosed that the 2,6-AAQ and rGO linked by covalent bonds significantly decrease solubility compared with 2,6-AAQ, indicating the greatly increased cycling stability of the hybrid material. Additionally, ex situ FTIR characterization results verified that the composite cathode material with two carbonyls (C=O) active sites has good lithium storage performance. By optimizing the 2,6-AAQ concentration, the 25% 2,6-AAQ in the as-prepared composite was used as the high-performance cathode for the lithium-ion battery. The composite material can display a high initial discharge capacity of 212.2 mA·h·g?1 at 100 mA·g?1 (based on the 2,6-AAQ mass) and a reversible capacity of 184 mA·h·g?1 with a capacity retention of 86.7% after 100 cycles at 500 mA·g?1 current density. This excellent electrochemical performance is attributed to fast lithium-ion diffusion and electric transport between the 2,6-AAQ and the 3D porous structure hybrid architecture, which also proposes a facile strategy for the immobilization of the small molecular quinones to construct advanced organic lithium batteries.

     

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