Sandwich-like MXene bridged heterostructure electrode enables anti-aggregation and superior storage for aqueous zinc-ion batteries

Abstract

Severe aggregation and sluggish reaction kinetics are the main research challenges that impair the storage performance of cathode materials for aqueous zinc-ion batteries. In this work, we report the concept of sandwich-like Ti3C2Tx MXene-bridged VO2 heterostructure (VO2/Ti3C2Tx) design to simultaneously relieve the self-aggregation and boost the interfacial storage kinetics. When acting as cathode material, such VO2/Ti3C2Tx electrode can deliver a high specific capacity 415 mAh g−1 at 0.1 A g−1 after 110 cycles, as well as 338 mAh g−1 at 1 A g−1 after 300 cycles, much higher than that of the pure VO2 case. Moreover, such electrode also exhibits remarkably rate capability and cyclic stability, which can retain a specific capacity of 170 mAh g−1 at the high current density of 5 A g−1 after 1500 cycles. The superior storage performance should be mainly benefited from the mixed-dimensional heterogeneous engineering. In addition, the evolution of crystal structure and valence state of electrode upon cycling were investigated, thus a storage mechanism can be revealed. That is, single VO2 phase would be transformed into the VO2 and ZnxV2O5·nH2O mixed phase, with a highly reversible H+/Zn2+ insertion/extraction behavior. Such strategy proposed in this work can be also applied for other kinds of cathode materials and promoting the development of aqueous zinc-ion batteries.