Rational design of three-dimensional interlaced frameworks with 2D MXene-Ti3C2Tx and 2D ZnCo bimetallic hydroxide for enhanced sodium-ion capacitors

Abstract

MXene-Ti3C2Tx is a promising material for next-generation energy storage for sodium-ion capacitors (SICs). However, the attraction between active functional groups and hydrogen bonds on the surface of Ti3C2Tx make the interlayer agglomerate obviously. Herein, we introduce 2D ZnCo bimetallic hydroxide (ZnCo-LDH) to adsorb on Ti3C2Tx nanosheets (Ti3C2Tx/ZnCo-LDH) and form the 3D interlaced porous frameworks, which could stabilize the complex structure and provide flexible ion diffusion channels. The ZnCo-LDH could not only increase the active sites for adsorbing the charges, but also prevent Ti3C2Tx from agglomerating and promote the electron transport kinetics. Benefited from this novel stable structure, Ti3C2Tx/ZnCo-LDH possess a wonderful specific capacitance (644.9 F g−1 at 2 mV s−1) and outstanding rate performance that combine with pseudocapacitance and low resistance. Particularly, the Ti3C2Tx/ZnCo-LDH electrode exhibit an excellent cyclic stability with 95.5% of the initial capacitance after 10000 cycles at 5 A g−1. More significantly, the SICs fabricated with 3D porous Ti3C2Tx/ZnCo-LDH display maximized energy density of 27.2 Wh kg−1 and power density of 7987.5 W kg−1, and an outstanding cycle stability of 95.8% after 10000 cycles. This work could provide an effective strategy for the preparation of MXene and LDH composites as electrode materials for sodium ion capacitors.