电化学活性羰基有机框架化合物的合成及储钠机理和动力学研究

Organic electrode materials draw tremendous attentions owing to their advantages of abundant raw materials, environmentally friendly, low cost and flexible structure design. However, the dissolution of organic materials in organic electrolytes results in the severe decay of battery performance. Herein, our project proposes two-dimensional covalent organic framework (COF) containing the active organic molecules can be employed as a redox platform for sodium storage. The COF can effectively alleviate the dissolution in organic electrolyte and improve the cycle stability of the battery, while the ordered channel of COF also can facilitate the fast transport of large sodium and enhance the rate capability of sodium-ion battery. In addition, battery performance of COF containing different active molecules are compared in order to verify the main factors that influence the capacities and rate capability of battery. Solid-state NMR(ss-NMR) are performed to monitor the evolution of molecular structures of organic compounds during the charge/discharge processes. By use of the calculation studies, we can clearly realize the sodium storage mechanism of organic compounds containing the different active molecules on operations. Furthermore, GITT, EIS, CV and ss-NMR technique are carried out to evaluate the ions diffusion of sodium within the different pore sizes of COF, combined with the diffusion ways of Na+ predicted by simulation, further to clarify the key control factors for the sodium-ion dynamics and rate capabilities of battery. Our studies will provide a theoretical guidance for the design and synthesis of organic compounds for high performance sodium-ion batteries with stable cycling as well as better rate capability.

有机电极材料因其具有原料丰富、环境友好、价格低廉和结构设计灵活等优势而备受人们的关注，但它在有机电解液中的溶解却导致电池性能的衰减。本项目提出利用偶联单元连接有机活性分子形成的有序孔道的有机框架化合物用于电化学储钠，可缓解其在有机电解液中的溶解，提高电池的循环稳定性；而本身具有的序孔道提供较大半径钠离子的快速传输，提升钠离子电池的倍率性能。通过对比不同种类有机框架化合物的储钠性能，发现影响电池比容量和倍率的因素和规律；利用固体核磁共振技术分析有机框架化合物钠化结构在充放电中的演变，并结合量化计算研究含不同种类有机框架化合物储钠机制；利用GITT，EIS及CV等电化学手段和固体核磁技术，测试不同孔径有机框架化合物中钠离子扩散系数。并结合量化计算预测的离子扩散路径，分析影响有机框架化合物储钠动力学特性和倍率性能的控制机制，从而为设计、合成和优化高性能有机框架储钠化合物用于储钠提供理论指导。

有机电极材料因其具有原料丰富、环境友好、价格低廉和结构设计灵活等优势而备受人们的关注，但它在有机电解液中的溶解却导致电池性能的衰减。本项目将电活性醌基活性分子引入有机框架化合物用于电化学储钠，并研究了电活性有机框架化合物离子存储机理和动力学特性。电化学性能研究发现电活性有机框架化合物可有效提高电池的循环寿命(最长达到10,000圈)，而本身具有一维有序孔道结构有利于较大半价的钠离子传输，因此该有机框架化合物显示出较快的离子反应动力学和优异的倍率性能(最高可达到10A g-1)。深入研究发现该有机框架化合物的存储容量主要来源于钠离子与醌基活性基团之间的多电子氧化还原反应所产生，并可获得最高可达280 mAh g-1的存储容量。本研究将为开发廉价高功率、长寿命的有机储能体系提供理论指导和技术支撑。