Boosting the alkali metal ions storage performance of layered Nb2C with a molecular welding strategy

MXenes are promising 2D-layered anode materials for rechargeable batteries. However, MXenes suffer from severe volume expansion and sluggish ion diffusion kinetics during ions insertion/extraction, leading to inferior battery performance. Herein, we developed a molecular welding strategy to stabilize layered structure and enlarge interlayer spacing of Nb 2 C through a dehydration condensation reaction between the -COOH groups in 1,3,5-benzenetricarboxylic acid (BTC) molecules and -NH 2 groups on the surface of the amino-functionalized Nb 2 C, which enable the BTC to chemically weld into interlayers of Nb 2 C (named as Nb 2 C/BTC). The intercalation of BTC into Nb 2 C contributes both pillar and strain effects to the 2D-layered Nb 2 C, rendering its maximum utilization. Such Nb 2 C/BTC with enlarged interlayer spacing and inhibited volume variation could remarkably promote the rate capability and cycling stability of Nb 2 C when used as the electrodes of alkali metal ions batteries. A decent Li + /Na + ions storage capacity-retention of 86.6% (0.1 A g -1 )/93.5% (1.0 A g -1 ) can be presented. A much reduced ion diffusion barrier of 0.88 eV is also delivered in Nb 2 C/BTC through DFT theoretical calculations. This work provides a new strategy for broadening the interlayer spacing and inhibiting the severe volume variation of MXenes for enhanced alkali metal ions storage. A novel molecular welding strategy was proposed to broaden the interlayer spacing and simultaneously achieve the excellent structure stability of Nb 2 C MXene, which exhibits superior rate capability and extraordinary cycle stability for alkaline metal ions storage. • A novel and effective molecular welding strategy is proposed to broaden the interlayer spacing and guarantee structural durability of Nb 2 C MXene. • The chemical bonds welding 2D layered Nb 2 C/BTC exhibits enhanced specific capacity, rate capability and cycling stability for Li + /Na + storage. • Theoretical calculation proves that the expanded interlayer spacing effectively reduce the migration barrier of alkali metal ions and remarkably improve ions diffusion kinetics.