Engineering chemical-bonded Ti3C2 MXene@carbon composite films with 3D transportation channels for promoting lithium-ion storage in hybrid capacitors

Lithium-ion capacitors (LICs) are promising energy storage devices because they feature the high energy density of lithium-ion batteries and the high power density of supercapacitors. However, the mismatch of electrochemical reaction kinetics between the anode and cathode in LICs makes exploring anode materials with fast ion diffusion and electron transfer channels an urgent task. Herein, the two-dimensional (2D) Ti3C2 MXene with controllable terminal groups was introduced into 1D carbon nanofibers to form a 3D conductive network by the electrospinning strategy. In such Ti3C2 MXene and carbon matrix composites (named KTi-400@CNFs), the 2D nanosheet structure endows Ti3C2 MXene with more active sites for Li+ ion storage, and the carbon framework is favorable to the conductivity of the composites. Impressively, Ti-O-C bonds are formed at the interface between Ti3C2 MXene and the carbon framework. Such chemical bonding in the composites builds a bridge for rapid electron transportation and quick ion diffusion in the longitudinal direction from layer to layer. As a result, the optimized KTi-400@CNFs composites maintain a good capacity of 235 mA h g-1 for 500 cycles at a current density of 5 A g-1. The LIC consisting of the KTi-400@CNFs//AC configuration achieves high energy density (114.3 W h kg-1) and high power density (12.8 kW kg-1). This paper provides guidance for designing 2D materials and the KTi-400@CNFs composites with such a unique structure and superior electrochemical performance have great potential in the next-generation energy storage fields.Supplementary material is available for this article at 10.1007/s40843-022-2268-9 and is accessible for authorized users.锂离子电容器(LICs)是一种很有前途的储能装置, 因为它们同时具有锂离子电池的高能量密度和超级电容器的高功率密度的特点. 然而, 由于锂离子电容器中阳极和阴极之间电化学反应动力学的不匹配, 使得探索具有快速离子扩散和电子转移通道的阳极材料面临挑战. 在此, 通过静电纺丝策略将具有可控末端基团的二维Ti3C2 MXene引入一维碳纳米纤维中, 形成三维导电网络. 在这种Ti3C2 MXene和碳基复合材料(称为KTi-400@CNFs)中, 二维纳米片结构赋予了Ti3C2 MXene更多Li+存储活性位点, 而碳骨架则有利于提高复合材料的导电性. 更值得一提的是, 在Ti3C2 MXene和碳骨架的界面上形成了Ti-O-C键. 复合材料中的这种化学键为电子的快速传输和离子在层与层之间纵向的快速扩散建立了桥梁. 因此, 优化后的KTi-400@CNFs复合材料在电流密度为5 A g−1的情况下, 500次循环后仍保持235 mA h g−1的良好容量. 由KTi-400@CNFs//AC 组成的锂离子电容器实现了高能量密度(114.3 W h kg−1)和高功率密度(12.8 kW kg−1). KTi-400@CNFs的这种独特结构和优异的电化学性能为二维材料制备提供了参考.