基于表面氟钝化多孔炭正极和硬炭@石墨烯负极的高性能锂离子电容器研究

Lithium ion capacitors have dual characteristic of both batteries and electric double layer capacitors and possess both high energy and power densities. But, their the energy density and power density need to be further improved. As for “prelithiated carbon/porous carbon” system, improving the working potential of porous carbon cathode and employing a hard carbon anode is an effective way to raise the overall performance of lithium ion capacitors. In this work, controllable fluorination technique will employed to passivate the surface active sites of porous carbons, with the aim to increase the working potential of cathode. The passivation mechanism of the porous carbon surface will be studied and the relations among passivation conditions, carbon surface structure and capacitive properties will be disclosed. Besides, we will also design and synthesize hard carbon@graphene two-dimensional composites anode with controllable thickness, with the aim to improve the rate-performance of the anode. The relationships of the hard carbon type and thickness of composite with its capacitive characteristic will be investigated intensively. Moreover, we will also study the mass and potential matching rules between the prelithiated composite anode and passivated porous carbon cathode, leading to optimized matching strategy between anode and cathode. Thus, the synergy of the cathode and anode will be fully utilized to evidently improve the energy density and power density of lithium ion capacitors at the same time. The smooth implementation of this project will provide a new strategy and theoretical basis to research and development of lithium ion capacitors with high energy and power densities.

锂离子电容器是一种兼具电池和双电层电容器双重特性的高能量大功率储能器件。但，其能量密度和功率密度仍有待进一步提高。对”预锂化碳/多孔炭”体系来说，提高多孔炭正极的工作电势和采用硬炭负极是提升锂离子电容器综合性能的有效途径。本课题拟采用可控氟化技术钝化多孔炭正极表面活性位，以达到提高正极工作电势的目的，研究多孔炭表面的钝化机制，弄清钝化工艺条件、多孔炭表面结构与其电容特性之间的规律；设计合成厚度可控的硬碳@石墨烯二维复合材料作为负极，以提高电池负极的倍率特性，研究硬碳种类、复合材料厚度与其嵌锂特性之间的规律；研究钝化多孔炭正极与预锂化复合材料负极之间的质量、电势匹配规律，得到正、负电极的优化匹配策略，充分发挥所制备正负极材料的协同作用，同时实现锂离子电容器能量密度和功率密度的大幅提升。该项目的顺利实施将会为高能量大功率锂离子电容器的研究和开发提供新的策略和理论依据。

锂离子电容器是一种兼具电池和双电层电容器双重特性的高能量大功率储能器件。但，其能量密度和功率密度仍有待进一步提高。对”预锂化碳/多孔炭”体系来说，提高多孔炭正极的工作电势和采用硬炭负极是提升锂离子电容器综合性能的有效途径。本课题采用可控氟化技术钝化多孔炭正极表面活性位，以达到提高正极工作电势的目的。研究结果表明，2%的低浓度氟气钝化，可以有效减少碳表面的含氧官能团，增加碳表面的碳氟键，大幅提升了碳表面副反应的能垒，使活性炭材料在电解液中的电化学稳定性明显升高，从而大大提高了其工作电位范围。作为超级电容器电极材料，拓宽了器件的电压窗口，从而提升了器件的能量密度。设计合成了厚度可控的硬碳@石墨烯二维复合材料作为负极，以提高电池负极的倍率特性，研究了硬碳种类、复合材料厚度与其嵌锂特性之间的规律。研究结果表明，硬碳@石墨烯二维复合材料厚度为50 nm左右时，负极的容量和倍率特性可以最佳匹配。利用恒电流充放电测试考察了电极材料的比容量、充放电动力学性能及循环耐用性。测试结果表明，采用硬碳@石墨烯二维材料的比容量可达600-800 mAh/g，20C倍率下10000次循环其容量可以保持在90%以上。研究了钝化多孔炭正极与预锂化复合材料负极之间的质量、电势匹配规律，得到了正、负电极的优化匹配策略，充分发挥所制备正负极材料的协同作用，同时实现了锂离子电容器能量密度和功率密度的大幅提升。电化学测试表明，在2.2-4.5 V的电压窗口下，锂离子电容器器件表现出优异的电化学性能。在351和6900 W/kg的功率密度下分别具有121和76 Wh/kg的能量密度。在10000次循环后仍然具有92.6%的容量保持率，表现出良好的综合性能。该项目的顺利实施为高能量、大功率锂离子电容器的研究和开发提供了新的策略和理论依据。