钴（镍）基MOFs材料设计制备及其阴离子嵌脱机理

As the cathode of dual-ion battery, the graphited carbon has a bottleneck that the lattice channel is smaller than the size of anions, making a big resistance of anion’s migration, less reaction sites within graphite and structure instability, thus inhibiting the practical application of dual-ion battery. In this proposal, the cobalt (nickel) based MOFs are proposed to replace graphited carbon as the cathodes of the dual-ion batteries. The diameter of molecular pores will be controlled by changing the chain length of organic ligand, which will benefit to decrease the resistance of anion migration, mitigate the force in MOFs produced by the insertion of anion, thus increasing the kinetics of anions’ intercalation/deintercalation reaction; The redox groups will be bonded in organic ligand to produce a synergistic reaction with metallic ions, making more anions take part in the intercalation/deintercalation reaction due to the drive of potential, and the molecular pore has the ability of absorbing/desorbing ions to produce capacitance, all of which helps to increase anions’ storage capacity of MOFs. By deeply studying the intercalation/deintercalation performance of anions in MOFs and the influence of electrolyte, such as charge and discharge capacity, rate capability and cycling stability, the relationship between structure and property will be explored, and the mechanism of the anion intercalation/deintercalation in MOFs can be clarified. By studying the changes in constitute and structure of MOFs during the intercalation/deintercalation process of anions with the in-situ spectroscopy and ex-situ morphology observation, the influencing factors of MOFs’ composite and structure can be clarified. The present project will pave the way for the application of MOFs with high capacity and good structural stability in dual-ion batteries.

双离子电池石墨碳正极存在的层间离子通道小于阴离子尺寸的瓶颈导致了阴离子迁移阻力大、嵌脱反应位点少及材料结构稳定性差，制约了双离子电池的应用。本项目提出采用钴（镍）基MOFs材料替代石墨碳作为正极，通过调变有机配体分子链长调控MOFs分子孔道尺寸，降低阴离子迁移阻力以及阴离子嵌入导致的材料内应力，提升阴离子嵌脱反应动力学；并通过有机配体上引入氧化还原基团，协同金属离子进行氧化还原反应，依靠电势驱动更多阴离子进行嵌脱反应，同时结合分子孔道对离子吸脱附的电容效应，提高材料储阴离子容量。重点研究MOFs材料结构与容量、倍率和循环性能等关系，兼顾考虑电解液因素，阐明分子孔道大小和阴离子嵌脱性能之间的“构-效”关系，揭示嵌脱反应机理。通过现场谱学和非现场形貌观察，探究嵌脱反应过程中MOFs组成和结构的可能变化，阐明影响结构稳定性的因素。为比容量高、结构稳定的MOFs材料在双离子电池上应用奠定科学基础。

双离子电池可极大地摆脱锂离子电池对资源型金属原料的高度依赖，代表了当前电池发展的一个重要方向。大尺寸阴离子在正极材料嵌入脱出反应是制约双离子电池性能的关键因素。为解决石墨有限的层间距对阴离子嵌脱反应的约束，项目研究选择具有电子共轭链的六氨基苯及六胺基三亚苯作为配体，利用溶剂热与镍离子（钴离子）反应，制得了具有二维层状镍（钴）MOFs，成功实现了阴离子（锂离子）嵌脱反应。研究显示，提升有机配体的电子共轭能力有助于提高MOFs材料的结构稳定性，从而改善MOFs材料的电化学性能，包括充放电容量、倍率性能和循环稳定性。结合DFT量化模拟、XPS元素结合行为分析，MOFs分子中的有机配体和金属离子都可以进行电子转移反应，从而促使阴离子（或）锂离子在分子结构中进行嵌入/脱出反应，贡献了MOFs材料的充放电容量。研究显示，将Ni2+与六氨基三亚苯的混合溶液以喷雾的形式沉积在铝箔上，形成镍基MOFs的自支撑电极，发挥出了约190 mAh/g的储PF6-容量，这主要源于自支撑电极优异的电子传导、好的体积缓冲性能。项目研究为双离子电池设计高性能的正极材料提供理论借鉴，对推动双离子电池的实用化进程具有重要意义。