Octafluoroadipic acid grafted Ti3CN MXene with expended interlayer spacing and absorption capability for enhanced sodium-ion storage

MXenes are considered as the most promising anode materials for sodium-ion storage due to the intriguing merits of exceptional conductivity and ample surface functional groups. However, the application of MXenes are facing huge challenge of serious self-stacking and volume expansion issues. In this work, a novel intercalating agent of octafluoroadipic acid (OA) with high electronegativity is grafted into the interlayer of Ti3CN to enlarge the interlayer spacing, which significantly enhances the sodium ions diffusion kinetics and sodium ions storage capacity. As a result, the D Na + value of Ti3CN-OA (7.07 x 10-7 cm 2 s-1 ) is significantly larger than that of Ti3CN (2.73 x 10-7 cm 2 s-1 ). At the meaning time, the Ti3CN-OA delivered an outstanding specific capacity of 211.6 mAh g-1 at 0.1 A g-1 . Even at and a high current density of 5.0 A g-1 , the Ti3CN-OA still maintained a high specific capacity of 117.0 mAh g-1 , demonstrating its excellent rate capability. Furthermore, the constructed Ti3CN-OA//AC hybrid capacitor could stably work over 1800 cycles at a current density of 1.0 A g-1 with a capacity retention of 71.42 %. This study provides a new strategy for expanding interlayer spacing of MXenes towards high-rate sodium ion storage.