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

Abstract

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 Nb2C through a dehydration condensation reaction between the -COOH groups in 1,3,5-benzenetricarboxylic acid (BTC) molecules and -NH2 groups on the surface of the amino-functionalized Nb2C, which enable the BTC to chemically weld into interlayers of Nb2C (named as Nb2C/BTC). The intercalation of BTC into Nb2C contributes both pillar and strain effects to the 2D-layered Nb2C, rendering its maximum utilization. Such Nb2C/BTC with enlarged interlayer spacing and inhibited volume variation could remarkably promote the rate capability and cycling stability of Nb2C 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 Nb2C/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.