特征性N-掺杂多孔碳正极构建锂离子混合电容器及其储能机理研究

As a burgeoning energy storage system with integration of both high energy and power densities, Li-ion hybrid supercapacitors (Li-HSCs) are highly promising to bridge the gaps amongst currently-available energy storage technologies. Carbon cathode based on capacitive mechanism determines the energy density of whole device, yet the low capacitance is still a crucial handicap to circumvent for Li-HSCs research. Nitrogen-doping is regarded as effective way to increase the performance, but the underlying mechanism and detailed influence in this non-aqueous system lack deep understanding and still needs systematic investigation. This project intends to design a facile sol-gel method to synthesize featured N-doped porous carbons (FNPCs) through altering the nitrogen sources, carbon sources and related ratio, realizing the controllable tuning of N-doping species and corresponding contents. Meanwhile, Electrochemical analysis and structural characterization will be conducted accompanied by the computational simulation of electrode-electrolyte interface raction to cast insight into the electrochemical mechanism as well as advantages of specific N-species in organic systems. Furthermore, the optimized FNPCs with uniquely high performance will pair with the Li-HSCs anode, finally constructing a high-performance Li-HSC full device. This project targets at combing material preparation, mechanism study and computational simulation to shed light on structure-to-performance relation of specific N-species doping as well as the underlying mechanism of their improving effects, thus offering guidelines for the construction and development of next-generation Li-HSCs.

高能量-功率的新型锂离子混合电容器(Li-HSCs)有望填补当今电源技术的储能空白。整体储能器件的能量密度取决于电容式碳正极，但其较低容量一直是目前亟待解决的关键问题。氮掺杂被认为是提高低容量碳材料的有效手段，然而其在有机体系Li-HSCs中电化学反应机制及具体影响尚不明确。本项目拟设计简单易行的溶胶凝胶法，通过系统地改变氮源、碳源及其比例，制备特征性N-掺杂多孔碳材料(FNPCs)，实现N官能团及掺杂量的可控调节。拟对不同FNPCs的电化学分析和电极过程结构的原位表征，同时结合电极/电解液界面反应计算模拟，阐明N-掺杂基团的电化学储能机理。选择最优的赝电容正极与负极匹配，实现高性能Li-HSCs的构筑。本项目旨在结合材料制备、机理探究和计算模拟，探索掺杂可控的FNPCs的通用合成技术路线，阐明不同N-掺杂基团在有机体系中的电化学反应机理和储能优势，继而指导和推动高效Li-HSCs的构筑。

混合电池电容器(Hybrid Batteries Capacitors, HBCs)由于具备电池-电容器复合式机理，实现了高能量-功率的完美结合，突显了填补当前能源体系中储能缺口的广阔前景。本项目基于异质掺杂多孔碳材料(HPCs)及其相应复合物构建高能量-功率密度的钠离子混合电容器(Na-HSCs)。通过简单的溶胶凝胶法制备工艺，实现对掺杂类型和掺杂量的有效调控。结合电化学分析方法和理论计算模拟，阐明不同类型掺杂于Na-HSCs中的电化学反应机理和储能优势。其中，N,S共掺杂类石墨烯（NS-GNS）电极在0.1 A g−1的电流密度下能够提供约300 mAh g−1的可逆电化学储钠容量，稳定循环10000周并未出现容量衰减。将该NS-GNS负极与Na0.5MnO2电池型正极匹配组装钠离子混合电容器，全电池的工作电压范围为1.5-3.5 V，在0.05 A g−1的电流密度下具有近200 mAh g−1的比容量。在此基础上，通过金属离子与有机官能团的螯合作用，以及有机物小分子官能团之间交联反应，得到均匀分散的金属硫化物/掺杂多孔碳的纳米复合材料，包含了硫化钴二维复合材料Co1-xS/FGNs和硫化镍一维核壳结构的Ni3S2@NS-CNTs复合材料。Co1-xS/FGNs电极在0.1 A g−1的电流密度下，能够提供466 mA h g−1相对较高的可逆容量，首周库伦效率为82%，当电流密度增大到10 A g−1时，仍然具有210 mAh g−1的容量。通过核壳设计将Ni3S2包覆于掺杂碳纳米管中的Ni3S2@NS-CNTs复合电极材料在200 mA g−1电流密度下容量可达432 mAh g−1，尤其，该电极在首周库伦效率高达92%的情况下能够稳定循环300周，远远优于其它结构设计的复合物。通过实验和计算结合，N掺杂可以有效提高石墨烯的导电性，增加石墨烯结构缺陷，以提供电化学反应所需的活性位点。而S原子由于其原子半径较大，极大拓宽了碳层之间的间距，更有利于钠离子的嵌入脱出，同时，含S基团提供了大量赝电容反应位点，提升了电极储钠能力。本研究为新型异质掺杂碳材料及其与金属硫化物的纳米复合物的制备提出了一种普适性的低成本绿色化方法，阐明不同掺杂基团在有机体系中的电化学反应机理和储能优势，推动了高性能钠离子混合电容器的研究发展。