Engineering chemical-bonded Ti(3)C(2) 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) Ti(3)C(2) MXene with controllable terminal groups was introduced into 1D carbon nanofibers to form a 3D conductive network by the electrospinning strategy. In such Ti(3)C(2) MXene and carbon matrix composites (named KTi-400@CNFs), the 2D nanosheet structure endows Ti(3)C(2) 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 Ti(3)C(2) 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. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.1007/s40843-022-2268-9 and is accessible for authorized users.