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

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 VO 2 and poly(3,4-ethylenedioxythiophene) (PEDOT) (designated as VO 2 -PEDOT) are synthesized as cathode materials for the AZIBs. The nanobelts have a thickness below 10 nm, large amount of exposed VO 2 (001) facets and discrete PEDOT conductive layers. Systematic structural and electrochemical assessment reveals that simultaneous proton and Zn 2+ insertion into the VO 2 host is efficient in the Zn(CF 3 SO 3 ) 2 electrolyte due to synergistic effects rendered by unique structure of the VO 2 -PEDOT nanobelts. The Zn/VO 2 -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 VO 2 -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 VO 2 -based cathodes and reveal a new strategy to improve the performance of the AZIBs especially with regard to grid-scale energy storage.