Rigid organic molecule pillared TiC towards high rate capability and fast sodium ion storage.

MXenes are promising two-dimensional layered anode materials for rechargeable batteries due to their outstanding electrical conductivity, high specific surface area, and tunable surface functional groups. However, serious self-stacking of the layered structure and the sluggish sodium diffusion kinetics lead to inferior rate capability and cycling stability. Herein, an organic molecular pillaring strategy is reported to enlarge the interlayer spacing of TiC through a dehydration condensation reaction between the -COOH groups of 3,3',4,4'-benzene tetracarboxylic acid (BTCA) molecules and the -NH groups of TiC-NH, which enables rigid organic BTCA molecules to be chemically pillared into the interlayers of TiC (TiC-BTCA). The rigid organic BTCA molecules not only play a dual role of pillar and strain effects in TiC layers, but also expand the interlayer spacing. Therefore, they can significantly enhance the rate capability and cycling stability of TiC. TiC-BTCA exhibits a reversible capacity of 182.3 mA h g at a current density of 0.1 A g after 2000 cycles and maintains a reversible capacity of 77.9%. Moreover, the sodium diffusion coefficient of TiC-BTCA is 6.6 × 10 cm s. TiC-BTCA shows a relatively low sodium diffusion barrier and a high sodium diffusion coefficient compared with TiC. Interlayer engineering based on the organic molecular pillaring strategy is significant and meaningful for expanding the interlayer spacing of TiC. This work provides theoretical guidance and new perspectives for the development of Na storage materials with high-rate capability.