基于二维MXene的钠离子电容器负极材料的可控制备与超电容特性研究

Sodium ion capacitors, as a new kind of supercapacitors based on sodium ion insertion reaction, have attracted wide attention in recent years. Developing sodium-ion insertion/deinsertion materials with excellent dynamic performance is vital for kinetics match between negative electrode and positive electrode. This project proposes to use two-dimensional layered MXene as the negative electrode material for sodium ion capacitors. The disadvantages of slow ion diffusion and low electrical conductivity of MXene in organic electrolyte will be regulated by facile exfoliation and surface modification of MXene, and controllable preparation of nanocomposites with carbon nanotubes, graphene and hard carbon materials. The effects of surface properties of MXene, micro/nano-structure of nanocomposites and electrolytes on the kinetics of electrochemical reaction of MXene-based electrodes will be investigated through electrochemical technologies and in-situ/ex-situ characterization. Based on these, high performance sodium ion capacitors will be constructed. The relationship between the supercapacitive properties of sodium ion capacitors (energy density, power density and cycle life, etc.) and structure and preparing routes of MXene-based materials will be studied. The research will provide a theoretical guide for developing high-performance supercapacitors.

作为一种基于钠离子嵌入反应的新型超级电容器，钠离子电容器近年来开始受到人们的关注。制备动力学性能优异的嵌钠负极材料以解决正负极的动力学不匹配问题，对于发展高性能钠离子电容器十分关键。本项目拟从新型二维层状材料MXene出发，针对MXene材料在有机电解液中因其表面基团引起的离子扩散速率减慢以及导电性下降等问题，通过单层或少层MXene材料的高效剥离、表面性质调控以及与碳纳米管、石墨烯及硬碳的复合，可控制备高性能钠离子电容器负极材料，进而利用电化学测试与原位/非原位表征技术，揭示其表面性质、微纳结构以及电解液对电化学反应动力学的影响规律。在此基础上，构建基于MXene基负极材料的钠离子电容器，研究其比能量、比功率以及循环寿命等超电容特性与MXene基负极材料及其制备方法之间的关系，为发展高性能钠离子电容器提供理论指导。

MXene作为一种新型的二维层状材料，导电性好、亲水性高且具有超高的倍率性能和循环稳定性，作为钠离子电容器负极材料具有广阔的应用前景。本课题从MXene材料的表面性质调控以及微纳结构构筑两个方面出发，可控制备了具有高比容量、高导电性和良好动力学特性的MXene基电极材料。发展了多种MXene基复合材料的构筑方式，揭示了MXene材料组分/微纳结构与其电化学储钠性能之间的内在关联，提出了防氧化剥离、高分子表面性质调控、多维纳米材料构建等三种表面与性能优化策略，解决了二维材料MXene易堆叠、易氧化、比容量较低等难题，与此同时，在此研究基础上对正负极材料调控，构建了一种基于离子传输机制的“摇椅式”新型钠离子电容器，避免了传统电池储能过程中电解液消耗的问题，其能量密度和功率密度(基于正负极活性物质总量)分别高达158 Wh kg−1和7000 W kg−1。