Enhancing the sodium-ion storage performance of two-dimensional layered Ti3CN with a molecular riveting strategy

Abstract

Adjustable 2D layered MXenes hold considerable promising as anode materials for sodium-ion batteries. However, the serious self-stacking and volume variation during sodium-ions insertion/extraction processes inevitably result in inferior rate capability and terrible cycle stability. Herein, we report a novel and effective “molecular riveting” strategy to simultaneously adjust the interlayer spacing and stabilize layered structure of Ti3CN (TCN), which is realized by riveting L-Aspartic acid/L-Glutamic acid/L-2-Aminoadipic acid (LAA/LGA/L2AA, abbreviated as LXA) molecules into interlayers of TCN (named as LAA-TCN/LGA-TCN/L2AA-TCN and abbreviated as LXA-TCN) to form strong amido (HN-C = O) bonds. The riveted LXA molecules between the interlayer of TCN contribute double effects of pillar and strain, achieving the maximum utilization of the 2D layered TCN. As consequences, the interlayer spacing of TCN can be broadened from 1.04 nm to 1.31 nm via altering the carbon chain length of LXA molecules, and the Na+ migration barrier can be reduced from 0.71 eV to 0.08 eV. Meanwhile, the L2AA-TCN with maximum interlayer spacing exhibits a significantly improved reversible capacity of 121.7 mAh/g (45.0 mAh/g for TCN) at 1.0 A/g. The constructed L2AA-TCN//NVP sodium-ion battery (SIB) displays excellent cycle stability with the capacity-retention of 96.6 % after 200 cycles at 10 C. This work opens a new way to broaden interlayer spacing and hinder enormous volume variation of 2D layered MXenes.