基于CNTs@MXene的钠离子电容器“同源”电极的设计、匹配及耦合机制

开发高能量密度、高功率密度和长循环寿命的钠离子电容器对能源利用具有重要意义。然而电极间材料结构、容量和反应动力学的不匹配限制了钠离子电容器的性能。本项目以实现电极相互匹配为目标，设计制备基于电压窗口较宽的CNTs@MXene的“同源”电极。以在MXene层间原位生长碳纳米管为“柱撑”材料来扩大层间距、防止片层再次堆叠并提高电极导电性。以“同源”正、负极实现电极材料结构的匹配；以表面正电荷改性的CNTs@MXene来促进阴离子存储，提高正极能量密度，实现电极容量的匹配；以CNTs@MXene衍生的碳复合二维层状金属化合物复合碳纳米管为负极，并利用赝电容作用提高负极反应速率，实现电极反应动力学的匹配。通过探究电极的“构-效关系”和储能机理，揭示电极间的匹配规律及耦合机制，建立匹配良好的电极结构和组成的设计原则。研究成果将对拓展钠离子电容器电极设计思路及开发新型高性能离子电容器电极材料提供依据。

The development of sodium-ion capacitors with high energy, high power density and long lifespan is of great importance for energy utilization. However, the electrochemical performance is limited seriously by the mismatch between anode and cathode electrodes in the aspects of material structure, capacity and reaction kinetics. To address this issue, the “homologous” anode and cathode electrodes derived from CNTs@MXene with a wide voltage window will be designed and fabricated in this project. The in-situ grown carbon nanotubes between MXene layers could act as “pillar materials” to expand the layer spacing, prevent the layers from stacking again, and improve the conductivity of the electrodes. The matching of material structure of the electrodes is hopefully to realize by using the same precursor to fabricate both anode and cathode electrodes. Surface modification of the CNTs@MXene with positive charge is used to promote the anion storage and improve the energy density of cathode electrode, helping the matching of capacity between the electrodes. Moreover, the composite of two-dimensional layered metal compounds with carbon and carbon nanotubes derived from CNTs@MXene is used as anode electrode, taking advantage of the pseudocapacitance behavior to improve the reaction rate, then helping the matching of reaction kinetics between the electrodes. By investigating the “structure-performance” relationship and the energy storage mechanism of the electrodes, the matching patterns and the coupling mechanism of anode and cathode electrodes will be further revealed. As such, a guideline for the design of structure and composition of well-matched anode and cathode electrodes will be established. This research is expected to clarify the designing principles of the electrode materials, providing a referential basis for high performance sodium-ion capacitors and other novel ion capacitors.