空位缺陷调控策略构筑高能量密度六方孔洞MXene水系超级电容器

利用碳空位缺陷有序化策略构筑了多层六方孔洞MXene电极材料,在软包超级电容器中实现了高比容量和高能量密度水系钾离子存储。该电极材料具有较大比表面积的三维六方孔洞结构,为储钾提供了更多的活性位点。结合六方孔洞内壁新暴露的钛原子的化合价变化引起的赝电容效应,阐明了多层六方孔洞MXene水系钾离子超级电容器比容量提高的内在原因。通过密度泛函理论计算多层六方孔洞MXene对钾离子的吸附能,并结合电化学储钾性能实验及动力学分析,确定了钾离子被吸附的最佳位置,得出了钾离子的吸附规律。通过定量分析多层六方孔洞 MXene中电子的能带结构和差分电荷密度等电子传输规律,揭示了其水系钾离子超级电容器具有高电导率和良好倍率性能的内在机理。

Construction of high energy density hexagonal hole MXene aqueous supercapacitor by vacancy defect control strategy

The multi-layer hexagonal hole MXene electrode material was constructed by using the carbon vacancy defect ordering strategy, and the energy density of 235.8 Wh·kg^-1 in the soft-pack supercapacitor was realized at the power density of 6 480 W·kg^-1. The electrode material has a structure of three-dimensional hexagonal holes, which increases the contact area with the electrolyte and provides more active sites for potassium ion storage. Combined with the pseudo-capacitance effect caused by the change of valency of newly exposed titanium atoms in the inner wall of the hexagonal hole, the internal reason for the increase of specific capacity of multi-layer hexagonal hole MXene water system potassium ion supercapacitor is explained. The adsorption energy of multi-layer hexagonal porous MXene for potassium ion was calculated by density functional theory, and the optimal position of potassium ion adsorption was determined by electrochemical potassium storage experiment and kinetic analysis, and the adsorption law of potassium ion was obtained. By a quantitative analysis of the band structure and differential charge density of electrons in multi-layer hexagonal hole MXene, the internal mechanism of high conductivity and good magnification performance of the water system potassium ion supercapacitor is revealed.