Controlled oxidation of MXene into amorphous TiO promotes polysulfide adsorption and catalytic conversion for room-temperature sodium-sulfur batteries

Room-temperature sodium‑sulfur (RT Na S) batteries are regarded as promising next-generation rechargeable systems owing to their high theoretical capacity and energy density, but their practical deployment is hindered by issues such as sluggish redox kinetics and polysulfide shuttling. The development of high-performance sulfur cathodes is therefore crucial. This study designs an amorphous titanium oxide (TiO x ) embedded MXene composite material with a three-dimensional open structure as the high-performance sulfur host for RT Na S batteries. Systematic experimental and theoretical studies show that the in-situ grown amorphous TiO x anchored on the MXene substrate provides abundant active sites for strong adsorption and efficient catalysis of sodium polysulfides (NaPSs), thereby leading to excellent electrochemical performance. Moreover, the heterointerface formed between amorphous TiO x and MXene matrix facilitates rapid electron transmission and enhances reaction kinetics. The cell with 3DMX-TiO x /S cathode exhibits a specific capacity of 349 mAh g −1 at 5C and shows a slow capacity fading rate of 0.033% per cycle over 3500 cycles. This work offers a feasible strategy and new insights into the design of MXene-based composite sulfur hosts for high-performance RT Na S batteries. • Amorphous TiO x catalyst is derived by regulating the oxygen on MXene surfaces for RT Na S batteries. • Systematic experiments and DFT calculations elucidate the important roles of the amorphous TiO x catalyst in polysulfide adsorption and catalytic conversion. • Heterointerface between crystal MXene and amorphous TiO x enables rapid Na + /e − transfer and accelerates reaction kinetics. • 3DMX-TiO x /S exhibits excellent stability at 5C over 3500 cycles with a capacity decay below 0.033% per cycle.