Encapsulating Ultrafine Sb Nanoparticles in Na+ Pre-Intercalated 3D Porous Ti3C2Tx MXene Nanostructures for Enhanced Potassium Storage Performance.

Taking into consideration the advantages of the highly theoretical capacity of antimony (Sb) and abundant surface redox reaction sites of Na+ pre-intercalated 3D porous Ti3C2Tx (Na-Ti3C2Tx) architectures, we elaborately designed the Sb/Na-Ti3C2Tx hybrid with Sb nanoparticles homogeneously distributed in 3D porous Na-Ti3C2Tx architectures through a facile electrostatic attraction and carbothermic reduction process. Na-Ti3C2Tx architectures with more open structures and larger active specific surface area not only could certainly alleviate volume changes and hinder the aggregation of Sb nanoparticles in the cycling process to improve the structural stability but also significantly strengthen the electron-transfer kinetics and provide unblocked K+ diffusion channels to promote ionic/electronic transport rate. Furthermore, the ultrafine Sb nanoparticles could efficiently shorten K+ transport distance and expose more accessible active sites to improve capacity utilization. DFT calculations further indicate that the Sb/Na-Ti3C2Tx anode effectively decreases the adsorption energy of K+ and accelerates the potassiation process. Benefiting from the synergistic effect, it exhibits an outstanding specific capacity of 392.2 mAh g-1 at 0.1 A g-1 after 450 cycles and a stable capacity reservation with a capacity fading rate of 0.03% per cycle at 0.5 A g-1. Our work may encourage further research on advanced MXene-based hybrid materials for high-performance PIBs.