Abstract
•Oxygen vacancies (Vo¨) are introduced in Na0.76V6O15/PEDOT (Vo¨-PNVO).•Bridge-oxygen sited Vo¨ are confirmed experimentally and theoretically.•The interplanar space is enlarged and the electrostatic interaction is weakened by Vo¨ for fast reversible Zn2+ diffusion and intercalation.•Vo¨-PNVO based ZIBs exhibit significantly enhanced energy conversion efficiency over 80%.
Aqueous zinc-ion batteries (ZIBs) have received an increasing attention for large-scale energy storage due to its low cost and high safety. However, the sluggish kinetics stemming from the limited Zn2+ diffusion pathway and the strong electrostatic interaction between Zn2+ and the anion sublattice in the host crystal are great challenges for high-efficient Zn2+ storage. To circumvent these hurdles, bridge-oxygen sited oxygen vacancies are introduced in sodium vanadate Na0.76V6O15 (NVO) through the in-situ polymerization of 3,4-ethylenedioxythiophene. In the resultant oxygen-vacancy rich NVO/poly(3,4-ethylenedioxythiophene) (PEDOT) nanocables (noted as Vo¨-PNVO), the interplanar space is enlarged and the electrostatic interaction is weakened by the introduction of “oxygen vacancies” for fast reversible Zn2+ diffusion and intercalation. The conductive PEDOT coating also provides desired electronic conductivity and improves the structural integrity of NVO. Consequently, Vo¨-PNVO based ZIBs exhibit an enhanced specific capacity (355 mA h g−1 at 50 mA g−1), significantly enhanced energy conversion efficiency (>80%), and long lifespan (99% of the initial capacity remained after 2600 cycles).