Ultrathin hybrid nanobelts of single-crystalline VO2 and Poly(3,4-ethylenedioxythiophene) as cathode materials for aqueous zinc ion batteries with large capacity and high-rate capability

Abstract

Design and fabrication of cathode materials with large capacity and high-rate capability in aqueous zinc ion batteries (AZIBs) are challenging. Herein, ultrathin hybrid nanobelts comprising single-crystalline VO2 and poly(3,4-ethylenedioxythiophene) (PEDOT) (designated as VO2-PEDOT) are synthesized as cathode materials for the AZIBs. The nanobelts have a thickness below 10 nm, large amount of exposed VO2 (001) facets and discrete PEDOT conductive layers. Systematic structural and electrochemical assessment reveals that simultaneous proton and Zn2+ insertion into the VO2 host is efficient in the Zn(CF3SO3)2 electrolyte due to synergistic effects rendered by unique structure of the VO2-PEDOT nanobelts. The Zn/VO2-PEDOT battery that shows a storage mechanism involving two carriers delivers extraordinary performance including a high capacity of 540 mAhg−1 with 36.3% beyond a high operating voltage of 0.7 V at −0.05 Ag−1, high rate capability of 231.2 mAhg−1 at 10 Ag−1, excellent cycling stability up to 1000 cycles with capacity retention of 84.5%. Moreover, the 50 μm thick freestanding electrode consisting of ultrathin VO2-PEDOT nanobelts has a large areal capacity of 1.35 μAhcm−2 at 5 Ag−1. The results provide mechanistic insights into the electrochemistry of VO2-based cathodes and reveal a new strategy to improve the performance of the AZIBs especially with regard to grid-scale energy storage.