Abstract:

As an electrochemical energy storage technology, the vanadium redox flow battery (VRFB) has attracted much attention due to its advantages of autonomous and controllable resources, no cross-pollution and less susceptible to environmental disturbances. Optimization of electrode materials for VRFB can significantly improve their energy efficiency and stability. In this study, nitrogen-doped graphene aerogels (NGA) were prepared using hydrothermal and freeze-drying techniques using aspartic acid, dopamine, 2-aminopyridine and 2-methylimidazole (2-MI) as nitrogen dopants of different structures, and the nitrogen dopants were bonded with oxygen-containing functional groups on the surface of graphene oxide (GO), a derivative of graphene. The effects of different nitrogen dopants on the nitrogen doping amount, layer spacing, defect degree and electrochemical properties of NGA were investigated by analyzing and comparing the microscopic morphology, defect degree, physical phase composition and electrochemical properties of different NGA. The results showed that the nitrogen dopant selected 2-MI with five-membered heterocyclic structure prepared NGA with higher nitrogen doping (5.16%), layer spacing (0.367nm) and I_D/I_G value (1.12), which provided not only a storage site for V³⁺ but also more active sites for the V²⁺/V³⁺ pair to promote the charge transfer and ion transfer. 2-MI-NGA coated on carbon felt (CF) was used as the anode material of VRFB for single-cell charge/discharge tests and the overpotential was only 10% of that of CF at 80mA/cm², which effectively reduced the polarization of the cell, while the discharge capacity of 2-MI-NGA@CF was increased by 241mA·h. At a current density of 200mA/cm², the energy efficiency of 2-MI-NGA@CF was 16.8% higher than that of CF and remained stable at about 63.5%. This study provided new ideas for the modification of electrode materials for high-performance vanadium redox flow batteries.

Key words: nitrogen-containing organic compounds with different structures, graphene-based aerogel, nitrogen doping, vanadium redox flow battery, electrochemical performance

摘要：

全钒液流电池（VRFB）作为一种电化学储能技术，因其资源自主可控、无交叉污染和不易受环境干扰等优点备受关注。优化VRFB的电极材料可以显著提高其能量效率和稳定性。本文以天冬氨酸、多巴胺、2-氨基吡啶和2-甲基咪唑（2-MI）作为不同结构掺氮剂与石墨烯的衍生物氧化石墨烯（GO）表面的含氧官能团进行键合，采用水热法和冷冻干燥技术制备氮掺杂石墨烯气凝胶（NGA）。通过分析对比不同NGA的微观形貌、缺陷程度、物相组成及电化学性能，探究不同掺氮剂对NGA的氮含量、层间距、缺陷程度及电化学性能的影响。研究结果表明，掺氮剂选用五元杂环结构的2-MI制备NGA具有较高的氮含量（5.16%）、层间距（0.367nm）及I_D/I_G值（1.12），其不仅为V²⁺/V³⁺提供了储存场所，并且为V²⁺/V³⁺电对提供了更多的活性位点促进了电荷转移和离子传递。将2-MI-NGA涂覆在碳毡（CF）上作为VRFB的负极材料进行单电池充放电测试，在80mA/cm²电流密度下，其过电位仅为CF的10%，有效降低了电池极化，同时2-MI-NGA@CF的放电容量相较CF电池增加了241mA·h。在200mA/cm²电流密度下，2-MI-NGA@CF的能量效率相较于CF提高了16.8%，并且始终保持在63.5%左右稳定运行。该研究为高性能全钒液流电池电极材料的改性提供了新思路。

关键词: 不同结构含氮有机物, 石墨烯基气凝胶, 氮掺杂, 全钒液流电池, 电化学性能