A novel “point-to-point” 1,4-phenylenediacetic acid grafting of Ti3CN enhances sodium storage stability

The self-stacking of MXenes-Ti3CN limits the accessibility of nanochannels, reduces the ion diffusion kinetics, and hinders its application in alkali metal ion storage field. This study proposes a point-to-point mortise and tenon joining strategy to fabricate a composite structure of 1,4-phenylenediacetic acid-Ti3CN (1,4-PDEA-Ti3CN) by grafting rigid and flexible 1,4-phenylenediacetic acid (1,4-PDEA) into the amino-functionalized Ti3CN interlayers. The rigid and flexible 1,4-PDEA contributes to a pillar effect in the layered structure of Ti3CN, which is benefit to prevent the self-stacking and maintain a stable 2D layered structure. As a result, the interlayer spacing of Ti3CN is expanded from 1.20 to 1.46 nm and the Na+ diffusion coefficient is improved from 1.16 × 10−6 to 1.99 × 10−6 cm2 s−1 after point-to-point 1,4-PDEA grafting. The 1,4-PDEA-Ti3CN achieves a reversible discharge specific capacity of 202.3 mAh g−1 at a current density of 0.1 A g−1 after 770 cycles. Even at a high current density of 5 A g−1, the 1,4-PDEA-Ti3CN still possesses a reversible discharge specific capacity of 137 mAh g−1 and it still maintains the high specific capacity of 256.1 mAh g−1 when the current density comes back to 0.1 A g−1. This point-to-point mortise and tenon joining strategy provides a novel approach for designing other 2D energy storage materials with long cycle stability and high-rate capability. The rigid and flexible 1,4-PDEA provides the synergistic effects for Ti3CN that expanding the interlayer spacing and pillaring the layered structure, so 1,4-PDEA-Ti3CN achieves excellent the long cycle stability and fast sodium ion diffusion kinetics performance. [Display omitted] •A point-to-point mortise and tenon joining strategy is proposed to stabilize the layered structure of Ti3CN.•The interlayer spacing of Ti3CN is enlarged and sodium ion diffusion barrier is reduced by grafting 1,4-phenylenediacetic.•The mortise and tenon joining of 1,4-PDEA-Ti3CN realizes outstanding sodium ions storage performance.