基于无粘结剂碳纳米纤维/碳布的高性能锂离子电容器研究

Li-ion capacitors (LICs), as one kind of hybrid asymmetrical supercapacitors, bridge the gap between supercapacitors and Li-ion batteries. They have been recognized as one of major emerging devices in energy storage. To construct high-performance LICs with high energy and power densities, as well as high cycling stability, the key is to design and fabricate novel electrode materials. In this study three-dimensional porous carbon nanofiber (CNF) array will be directly grown on carbon cloth (CC) using thermal chemical vapor deposition technique at low temperature, and then employed as LIC electrodes without any binders. The elimination of binders leads to improved stability of the CNF/CC electrodes. By means of electrode modification (MnOx), material characterization and analysis, as well as electrochemical testing, etc., the intrinsic relationship between the properties of electrode materials (e.g. structure, pore distribution, etc.) and their electrochemical performance will be explored and clarified. In this context, the growth and performance of electrode materials can be controlled. By adjusting the capacitive and kinetic parameters of both positive and negative electrodes, the final goal of this work is to fabricate high-performance LICs, and to build one stand-alone demonstrator with these LICs as power supplies for their practical applications. This work will play an important role in guiding and promoting the development of novel electrode materials with high specific capacity and fast charge-discharge performance, as well as the design and application of high-performance LICs.

锂离子电容器是一种介于超级电容器和锂离子电池的非对称型混合超级电容器,在能量存储领域具有重大应用前景。新型正负极材料的设计和制备是构建出同时具有高能量和高功率密度以及高稳定性的高性能锂离子电容器的关键。本项目计划利用低温热化学气相沉积法在碳布表面直接生长三维多孔阵列碳纳米纤维作为电极材料，避免了粘结剂的使用，可大幅度提高电极稳定性。通过运用电极修饰（MnOx）、材料表征和分析、电化学测试等手段，掌握碳纳米纤维的生长机理，揭示电极材料结构、孔径分布等特征与电极性能之间的内在联系，实现电极材料的生长可控及性能可控。通过调控正负极材料容量和动力学等参数，构建出高性能锂离子电容器，并将其作为电源制造可自主充放电的模型机，实现其实际应用。本项目的研究对于兼具高比容量和快速充放电性能的新型电极材料的开发以及高性能锂离子电容器的设计和应用具有重要的指导意义和积极的促进作用。

超级电容器作为新型电化学能量储存装置在众多领域都具有广阔的应用前景。如何制造出具有高能量和高功率密度的超级电容器，是目前该领域研究的核心问题。非对称型超级电容器（如：锂离子电容器）的构建是解决这一问题的有效途径，而先进电极材料的开发是其中的关键。本项目实现了碳纳米纤维（CNF）以及MnO2的可控生长、探明了其结构等特征与相关电极电化学性能之间的联系。以预锂化MnO2@碳布（CC）为负极，KOH活化后的CNF@CC为正极，LiPF6电解质的碳酸乙酯与碳酸二乙酯（体积比1:1）混合溶液为电解液所构建的非对称型锂离子电容器器件最高能量密度和功率密度分别达到143.9Wh kg-1和5709.5W kg-1。依托CNF及MnO2等过渡金属氧化物基电极材料，项目进行过程中还构建了其他高性能非对称型超级电容器，包括MnO2@CC/Na2SO4+KI//Na2SO4+乙基紫精二溴化物/Fe2O3@CC及Co3O4@硼掺杂金刚石（BDD）/KOH+Fe(CN)63-/4-//KOH+对苯二胺/CNF@BDD。前者最大能量和功率密度分别达到112.1Wh kg-1及3894.4W kg-1。后者电容值达到48.5mF cm-2，相比于基于BDD的超级电容器的电容值（几个µF cm-2）增大了3个数量级别。所构建的器件能量和功率密度可比拟于其它储能设备，所获得的能量密度甚至接近于锂离子电池的，表明了它们在工业上的应用潜力。本项目也成功构建以所设计非对称型超级电容器为电源的便携式可自主充放电样机，用于点亮LED灯。