锂离子混合电容器正负电极电化学行为的匹配性研究

The dynamic mismatch of the positive and negative electrode of the lithium ion hybrid capacitor will lead to the poor rate capability and low cycle life of the device. This project will use the distinct characteristics of the metal organic framework compound (MOFs), such as element composition could be fine controlled and adjustable, high specific surface area and variable pore structure and so on, we will firstly start with the scientific design of the molecular structure of MOFs precursor, MOFs derived porous carbon anode and metal compound/carbon composite cathode materials with superior lithium insertion/extraction kinetics will be developed, to make up the difference in the energy storage dynamics between positive and negative electrodes; we will precisely adjust and control the microstructure of the electrode materials and quantify their kinetic characteristics, clarify the structure-function relationship between the microstructure of the electrode materials and their electrochemical properties, and the effect mechanism of the electrochemical behavior compatibilities of electrode materials on the performance of lithium ion hybrid capacitors will be revealed; the inherent correlations between the composition and intrinsic properties of the electrolyte and the electrochemical properties of the electrode will be investigated in detail, reveal the compatibility between the electrolyte and positive and/or negative electrode and its effect on the inosculate and promotion mechanism of the electrochemical properties of positive and negative electrode materials. Through analyzing the results and optimizing the experimental conditions, we can obtain the key techniques for fabricating the advanced Li-ion hybrid supercapacitors with high energy density, high power density, long cycling life and wide temperature range.

锂离子混合电容器正负电极动力学不匹配会直接导致器件倍率性能差和循环寿命低。本项目将利用金属-有机骨架化合物（MOFs）的元素组分精控可调、比表面积高和孔道结构可变等鲜明特性，从MOFs前驱体分子结构的科学设计入手，开发具有良好脱/嵌锂动力学特性的MOFs衍生多孔纳米炭正极和金属化合物/炭复合储锂负极材料，弥补正负电极储能动力学上的差异；精准调控电极材料的微观结构并量化其动力学特性，阐明正负电极材料的微观结构与电化学性能之间的构效关系，揭示正负电极电化学行为的匹配性对锂离子混合电容器性能的影响机制；研究电解液的组成和本征性质对正负电极电化学性能的影响及内在关系，揭示电解液与正负电极的兼容性及其对正负电极材料电化学性能的融合与提升机理；根据实验结果对材料制备和电解液组配工艺进行科学优化，最终获得兼具高能量密度和高功率密度、循环稳定性好且使用温限宽的锂离子混合电容器的关键制备技术。

锂离子电容器拥有电池和电容器的双重特性，有望满足相关军事和民用领域对高性能储能器件的技术要求。然而，锂离子电容器存在重大的瓶颈问题是正负电极的动力学差异大，导致它们很难发挥好协同增进作用。因此，本项目旨在开发高匹配性的正负电极材料和相关金属离子电容器产品，取得的主要结果如下：.（1）分别从MOF、聚苯胺、柠檬酸钠、蜡烛烟灰及乙二胺四乙酸四钠等入手，成功制备出了一些列具有快速储锂/钠/钾动力学特性的碳基复合负极材料，和具有高比容量的电容型炭正极材料；解决了金属离子电容器正负电极材料组分结构合理设计和器件组装工艺控制等问题，设计和构筑出了一系列兼具高能量密度（最高163.5Wh/kg）和高功率密度（最高达21kW/kg）且长循环寿命（1万次循环容量保持率为91.7%）的锂/钠/钾离子混合电容器。.（2）把PP13TFSI离子液体与LiODFB有机锂盐配置成复合电解液，该电解液不仅能适用于硬炭负极、磷酸铁锂正极和活性炭正极，还具有长循环稳定性、高电化学窗口和不易燃的高安全性。.（3）在该项目的资助下，通过向基于LiTFSI锂盐的WIS中加入有机共溶剂和离子液体的方法，制备出了一系列高性能的WIS混合电解液。所得电解液具有2.7V的高电化学窗口，高电导率、高离子迁移率、低粘度、优异的倍率性能、长循环稳定性、不易燃和易操作的特点，所得超级电容器产品的能量密度达78Wh/kg。.（4）组配出了可耐超低温的多元组分电解液，所得超级电容器最低可耐-90℃的超低温，-50℃时器件呈现的最高能量密度为79.3Wh/kg；采用乙腈抑制盐包水电解液盐析的方法提升了超级电容器的低温性能，当环境温度由20℃降低到-50℃时，电位窗口仍高达2.3V,比电容衰减仅13.5%；采用石墨烯薄膜和尖晶石型光-热转化涂层有效提升了超级电容器的实际工作温度（从-50℃提升到-16.5℃，或从-30℃提升到60℃），实现了电化学储能特性从无到有的突变。. 本项目的研究结果为下一代高性能超级电容器的研发提供了可靠的科学依据和理论指导，所得的电极材料及产品技术水平接近国际领先水平。