MXene encapsulated titanium oxide nanospheres for ultra-stable and fast sodium storage

Abstract

Sodium-ion batteries with high power density present tremendous potential for large-scale energy storage applications. However, it remains a big challenge to develop suitable anode materials for ultrafast and highly reversible sodium ion storage. Herein, for the first time, we report a novel strategy to fabricate highly conductive MXene Ti3C2Tx encapsulated titanium oxide spheres (TiO2@Ti3C2Tx) as an excellent anode material for sodium-ion batteries. The MXene layers significantly improve the electronic conductivity of the whole electrode and protect the structural integrity of the TiO2 spheres from electrochemical pulverization, which hence contributes to the formation of a stable solid-electrolyte interface. Meanwhile, the pseudocapacitance of the as-fabricated TiO2@Ti3C2Tx composites enables high-rate capability and long cycle life in sodium-ion batteries. As a result, the hybrid electrode delivers a high reversible capacity of 116 mAh g-1 at 960 mA g-1 up to 5000 cycles. By coupling with a NaCrO2 cathode, a prototype Na-ion full cell achieved a capacity of 103.4 mAh g-1 at 960 mA g-1 and an excellent cycling performance with 73.5% capacity retention after 1000 cycles.