氮化铌的赝电容特性研究及其在高性能锂离子混合电容器中的应用

本项目基于本课题组首次发现面心立方氮化铌具有突出赝电容特性的基础上，拟将氮化铌的赝电容特性与N掺杂有序介孔石墨烯优异的双电层电容性能结合起来，设计和构造“氮化铌/N掺杂有序介孔石墨烯—锂离子有机电解液—N掺杂有序介孔石墨烯”锂离子混合电容器体系，用于解决电容器两电极储能机理差异所导致的能量密度与功率密度不匹配和循环稳定性差的问题。首先，从氮化铌的本征结构入手，重点考察氮化铌的结构与其赝电容行为之间的内在关系，从微观层面揭示氮化铌的赝电容形成机理和影响机制，筛选出电容性能最佳的氮化铌材料；其次，将优选的纳米氮化铌与N掺杂有序介孔石墨烯复合制备出高容量、倍率特性和循环性能优异的氮化铌/N掺杂有序介孔石墨烯复合材料；最终，将复合材料与高容量N掺杂有序介孔石墨烯材料科学复配，充分发挥二者在锂离子有机电解液中的赝电容和双电层储能效用，得到兼具高能量密度、高功率密度和优异循环稳定性的锂离子混合电容器。

For the first time, we find that niobium nitride with cubic crystal structure has prominent feature of pseudocapacitive characteristics. Based on this, “niobium nitride/nitrogen-doped ordered mesoporous graphene anode-lithium ion organic electrolytes-nitrogen-doped ordered mesoporous graphene cathode” lithium ion hybrid capacitors will be designed and constructed using the high pseudocapacitance characteristics of NbN and using the assistance of nitrogen-doped ordered mesoporous graphene with excellent double-layer capacitance. This lithium ion hybrid capacitor can solve the mismatch between the energy density and power density of lithium ion hybrid capacitor and the problem of poor cycle stability caused by the imbalance between the kinetics of the two electrodes. In this project, we will firstly study the intrinsic structures of niobium nitride, and mainly focus on the inherent correlations among the intrinsic structure and properties of the pseudocapacitive behaviors. The formation and influencing mechanisms of pseudocapacitance based on niobium nitride-lithium ion organic electrolyte system would be elucidated at the micro-level, and we will optimize nanostructure niobium nitride with excellent pseudocapacitive properties. On this basis, in order to further improve pseudocapacitive properties of this niobium nitride, nano-niobium nitride/nitrogen-doped ordered mesoporous graphene composite material will be synthesized with the high specific capacitance, excellent rate capability and good cycling stability. Subsequently, we will build the advanced lithium ion hybrid capacitors, which comprise as-prepared niobium nitride/nitrogen-doped ordered mesoporous graphene material as anode material and superior nitrogen-doped ordered mesoporous graphene with ultra-high specific capacitance as cathode material matching with lithium ion organic electrolytes, where the pseudocapacitance and the electric double-layer capacitance are able to well take place at the same time. Consequently, the advanced lithium ion hybrid capacitor with superior energy and power densities as well as long cycle life can be obtained.